Environ Sci Pollut Res DOI 10.1007/s11356-013-2230-8

REVIEW ARTICLE

Potential of biological materials for removing heavy metals from wastewater Bhupinder Dhir

Received: 4 April 2013 / Accepted: 9 October 2013 # Springer-Verlag Berlin Heidelberg 2013

Abstract Agricultural products/by-products are natural sorbent materials that possess capacity for removing contaminants including heavy metals from wastewaters and hence can be exploited as replacement of costly methods for wastewater treatment. The sorption of heavy metals onto these biomaterials is attributed to constituent's proteins, carbohydrates, and phenolic compounds that contain functional groups such as carboxylate, hydroxyl, and amine. Natural efficiency of these materials for removing heavy metals can be enhanced by treating them with chemicals. The present review emphasizes their use in developing ecofriendly technology for a large-scale treatment of wastewater. Keywords Agricultural residues . Biological materials . Heavy metals . Wastewater

Introduction Conventional techniques for treatment of municipal and industrial wastewaters mainly include physical, chemical, and biological methods. Each wastewater treatment technique has advantages and disadvantages (Table 1). Heavy metals form a major category of contaminants reported to be present in large quantities in wastewaters. Heavy metals are removed from wastewater by conventional techniques such as membrane filtration, chemical precipitation, adsorption, chelation, and ion exchange (Ahluwalia and Goyal 2007; Lin et al. 2008; Lesmana et al. 2009). Most of these techniques, however, are not suitable for developing countries Responsible editor: Philippe Garrigues B. Dhir (*) Department of Genetics, University of Delhi South Campus, New Delhi 110021, India e-mail: [email protected]

as they require huge cost investment in terms of use of chemicals, infrastructure and operation. They have inadequate efficiencies at low metal concentrations, particularly in the range of 1–100 mg L−1 (Ahluwalia and Goyal 2007). Moreover, they have other limitations such as sensitive operating conditions, production of secondary sludge and its disposal (Sud et al. 2008). Many commercial adsorbents such as silica gel, activated alumina, zeolites, anion-exchange resins, and activated carbon have been used for wastewater treatment (Gupta et al. 2009; Bhatnagar and Sillanpaa 2010; Iakovleva and Sillanpää 2013). Most of these adsorbents possess excellent adsorption characteristics such as high surface areas (100 to 750 m2 g−1), polarity, and good efficiency to remove various pollutants such as heavy metals, dyes, and inorganic ions (Bhatnagar and Sillanpaa 2010; Iakovleva and Sillanpää 2013) (Table 2). Many of these adsorbents show better adsorption properties when modified using physical or chemical treatment (Bhatnagar and Sillanpaa 2010). The major drawback of using these adsorbents is their high cost. For example, cost of activated alumina is approximately US $700–800 per metric ton, cost of zeolite is US $400–500 per metric ton, and cost of activated carbon is about US $500–1,800 per metric ton (Kurniawan et al. 2006; Bhatnagar and Sillanpaa 2010). Their modification by chemical or physical treatment processes increases their cost further (Bhatnagar and Sillanpaa 2010). Use of commercial adsorbents adds to environmental problems as some of these adsorbents (such as silica gel) are non-biodegradable. Moreover, the adsorption capacity is affected by physical and chemical factors. For example, the adsorption capacity of most of these adsorbents decreases with increase in temperature. Because of these shortcomings, the interest has been generated in use of activated carbons derived from peat, lignite, coconut shell, hardwoods, and other natural adsorbents. The activated carbons derived from these natural materials possess a

Environ Sci Pollut Res Table 1 Comparison of various wastewater treatment technologies Physical

Chemical

Biological

Definition

Physical processes carried out to strictly improve or treat the wastewater

Use of some chemicals to improve the water quality

Use microorganisms (mostly bacteria) and other biological sources for decomposition of wastewaters to stable end products

Types

SedimentationScreening AerationFiltrationFlotation and skimmingDegasificationEqualization

Chlorination, Ozonation Neutralization Coagulation, Adsorption, Ion exchange

Aerobic Activated sludge treatment Trickling filtration

Materials used Use of sand filters to further remove entrained solids from wastewater

Principle

Settling of solids by gravity allowing the heavier solids to settle

Mechanism

Gravitation

Disadvantages Sludge generated Require huge set up

Advantages

Able to treat large amount of wastewater

highly porous structure and large surface area (600 to 2, 000 m2 g−1) (Demirbas 2009). They have been found to adsorb a variety of contaminants such as metals, dyes, and phenols, therefore have been used effectively for treatment of domestic and industrial wastewaters. Their use is convenient and the operation costs are also comparatively low. However, the high cost of activated carbon and its loss during the regeneration restricts its application (Choudhari et al. 2013). In recent years, the potential of biological means for treatment of wastewaters has been explored. Biological materials such as biomass of microbes (bacteria), yeasts,

Anaerobic Digestion Septic tanks Lagoons

Oxidation ponds Lagoons Aerobic digestion Use of chemicals such as lime, chlorine, Use of microbes, plants, and ferric sulfate) other alternate materials such alum (aluminum sulfate), and other as agricultural residues for coagulants wastewater treatment Additions of acid or base adjust pH levels Conversion of dissolved and to neutrality. suspended substrates into Coagulants form an insoluble end biomass which is separated product that serves and removed from the water to remove substances from the wastewater Oxidation and reduction Adsorption or biosorption process Require huge setup ●Activated-sludge system is Sludge generated in large amount expensive as it requires energy and substantial amount of real estate for operation and maintenance ●Performance of anaerobic processes is limited under tropical climatic conditions Able to treat large amount of wastewater ●Does not require huge setup ●Sludge generated in low quantity ●Materials required are readily available ●Inexpensive and eco-friendly technique ●Operation takes place at ambient temperature ●Saves on energy consumption

algae, fungi, and higher aquatic plants have been evaluated for their potential to adsorb pollutants. Microbes including actinomycetes, cyanobacteria, algae, fungi, yeasts, and higher plant species showed excellent capacity to remove high amounts of heavy metals from wastewaters (Agarwal et al. 2006; Ahluwalia and Goyal 2007; Wan Ngah and Hanafiah 2008; Wang and Chen 2009; Sankaran et al. 2010; Dhankhar and Hooda 2011). Microbes possess advantages such as low investment cost, less space requirement, low energy demand, less sludge production and high treatment efficiencies. At the same time, their use can be restricted because isolation,

Environ Sci Pollut Res Table 2 List of some of the commercial/conventional adsorbents Name

Structure and synthesis

1 Activated Alumina is a synthetic porous crystalline gel. It is alumina manufactured from aluminium hydroxide by dehydroxylating it 2 Zeolites They are crystalline aluminosilicates consisting of a framework of tetrahedral molecules, linked with each other by shared oxygen atoms. They are formed by fusing feldspar, clay, and soda ash 3 Activated Produced from carbonaceous materials such as nutshells, carbon peat, wood, coir, lignite, coal, and petroleum 4 Silica gel

It is prepared by the coagulation of colloidal silicic acid, which results in the formation of granules

5 Bauxite

It is a naturally occurring porous crystalline alumina contaminated with kaolinite and iron oxides in varying proportions

screening, and harvesting of microbes on a large scale is complicated, tedious, and very expensive, and this limits the practical possibility of employing them for large-scale industrial biosorbent applications (Ahluwalia and Goyal 2007). Besides this, microbes also show sensitivity to environmental conditions. Aquatic plants show high biomass production without specific requirements, least energy requirement, and easy disposal. Aquatic plants form a major part of constructed wetlands used for wastewater treatment. These also require energy to pump the wastewater to the entrance of the system but show some limitations such as reduced performance during winter. Evaluating advantages and disadvantages of various techniques and potential of various materials for removing heavy metals from wastewater, low-cost adsorbents were tested for their efficacy to remove heavy metals from wastewater. Low-cost adsorbents require a little bit processing, are abundant in nature, and are a by-product or a waste from an industry or agricultural operation (Kurniawan et al. 2006; Visekruna et al. 2011; Renge et al. 2012). They are inexpensive and have little economic value. These are classified either on basis of their availability or depending on their nature (i.e., inorganic and organic). Depending upon the availability, they are classified as (1) natural materials (such as wood, peat, coal, lignite), (2) agricultural wastes (rice and wheat waste, tea and coffee waste, coconut waste, peanut and groundnut waste, fruit peels, stem, stalk, and seed coat waste), (3) industrial waste (blast furnace slag and sludge, black liquor lignin, fly ash, bagasse, red mud) (Table 3). Low-cost adsorbents and activated carbon prepared from natural conditions have been reported to remove variety of contaminants from mining, domestic, municipal, and industrial wastewaters (Kurniawan et al. 2006; Choudhari et al. 2013) (Table 4). The natural materials are available in bulk quantities and possess large surface area and high cation exchange capacity

Properties

Contaminants removed

It is highly porous material and F, Po43−, As, and Se have large surface area over 200–300 m2 g−1 It is highly porous material and Pb, Al, Fe, Mn, Zn, Cu, Cd, Ni have large surface area

Porous and have high surface Metal ions, anions, dyes, phenols, area ranging from 600 to 2, detergents, pesticides, humic 000 m2 g−1 substances, chlorinated hydrocarbons Porous and have high surface Anions, dyes, phenols, detergents area (ranging from to 250 to 750 m2 g−1) Surface area ranges from 25 to Heavy metals 250 m2 g−1

that are essential requisite for an adsorbent (Bhatnagar and Minocha 2006). They are also cheaper than the other commercial adsorbents. For example, montmorillonite clay has a current market price (US$ 0.04–0.12/kg) which is cheaper than activated carbon (Bhatnagar and Minocha 2006; Crini 2006). The annual worldwide production of crustacean shells has been estimated to be 1.2×106 tonnes, and accordingly high amount of chitin can be recovered from its waste (Crini 2006). Industrial waste can be another replacement for costly conventional methods of removing heavy metal ions from wastewater since they require little processing to increase the adsorptive capacity (Ahmaruzzaman 2011). These materials are locally available in large quantities and are inexpensive. Their availability of industrial wastes is regulated by production of industrial processes that in turn is regulated by demand. Agricultural waste materials are an economical, abundant, renewable, and hence a convincing option for wastewater treatment (Johnson et al. 2008). Agricultural wastes are hard and have low ash content, therefore, can easily be converted into activated carbon which has shown better heavy metal adsorption potential. Agricultural materials have shown good sorption capacity for various pollutants (Sud et al. 2008; Gupta et al. 2009; Lesmana et al. 2009; Farooq et al. 2010; Sharma et al. 2013; Kumar 2013; Choudhari et al. 2013). These agricultural waste materials can be used in their natural form without further processing or after some physical or chemical modification. According to an estimate, agricultural residues can be collected annually in large quantities. For example, in 2012, in the Republic of Serbia, the yield of wheat was around 1.9 million tons, corn was around 3.5 million tons, soybean was around 280,000 tons, barley was around 266,000 tons, and sunflower was 167,000. Approximately, one third of the biomass residue produced annually is assumed to be available for collection and use (Šćiban et al. 2013). Moreover, agricultural waste/by-product is abundantly

Environ Sci Pollut Res Table 3 List of some non-conventional adsorbents Name

Types

Pollutants removed

1 Agricultural wastes

Heavy metals, dyes, inorganic ions

2

Heavy metals, inorganic ions, dyes, phenols, pesticides

3

4 5

Rice and wheat waste, tea and coffee waste, coconut waste, peanut and groundnut waste, fruit peels, stem, stalk and seed coat, pulp Industrial wastes Fly ash ( waste from thermal power plants) Blast furnace slag, dust and sludge (waste from steel industry) Red mud (waste from aluminum industry) Fe(III)/Cr(III) hydroxide (waste from fertilizer industry) Leather industry waste Black liquor (waste from paper industry) Sludge (waste from industrial operations), e.g., chrome sludge (waste from an electroplating industry) Naturally occurring materials Clay Chitin, chitosan Peat Coal Lignin Municipal sewage sludge Wood Zeolite Activated carbon Prepared from agro materials such as pinewood, rice hull, palm shell, Pinus, seed husks, coconut shell palm fruit Biomass Seaweeds, bacteria, fungi, plants

available in rice-producing countries in Asian continent where the annual world rice production is approximately 500 million metric tons, of which 10–20 % is rice husk that can be utilized as an adsorbent for the removal of pollutants (Šćiban et al. 2013). According to an Indian cost estimate, waste bagasse is approximately Rs 60 ton−1 (~US $1.2 ton−1) and the cost after processing (chemical) would be approximately Rs 400 ton−1(~US $8.9 ton−1). This suggested that the adsorbent

Dyes, heavy metals, inorganic ions

Dyes, heavy metals, inorganic ions Dyes, heavy metals, ions

may be a good replacement for commercially available carbon due to its comparable efficiency and a significantly lower cost (Gupta et al. 2009). The present review presents concise information on various agricultural residues that have been studied for their capacity to remove heavy metals from wastewater and hence further emphasizes the exploitation of their potential on a large scale to develop low cost technology for wastewater treatment.

Table 4 Different types of wastewater treated using agricultural residues and byproducts Sample no.

Name of adsorbent

Contaminants

Type of wastewater

Reference

1 2 3

Neem leaf powder Sugar cane bagasse ash Spent tea leaves

Industrial effluent Dye effluent Dye wastewater

Gopalakrishnan et al. (2013) Kanawade et al. (2010) Zuorro et al. (2013)

4

Coconut shell, coconut husk, waste tea Coconut leaves Rice husk, sawdust

Heavy metal (Cr) Dye (Acid Orange-II) Azo dyes (Reactive Green 19, Reactive Violet 5) Heavy metals (Cr, Zn, Ni)

Electroplating effluent

Olayinka et al. (2007)

Heavy metal (Ni) Inorganic ions (Ca, Mg, K, Na) Heavy metals (Mn, Fe, Cu, Zn) Dyes Reactive dyes (RR120, RB15) Dye (Yellow 12) Heavy metals (Zn, Cd, Fe)

Electroplating effluent Hospital effluent

Gowda et al. (2012) Fayemiwo et al. (2013)

Textile wastewaters Textile effluents Textile dye effluent Industrial wastewater

Kyzas (2012) Kannan et al. (2012) Khaled et al. (2009) Osman et al. (2010)

Total suspended solids, inorganic ions (Cl, Mg, Ca)

Textile wastewater

Parihar and Malaviya (2013)

5 6 7 8 9 10 11

Coffee waste Cotton shell, neem bark Orange peel Rice hull, sawdust, sugarcane bagasse, and wheat straw Sawdust

Environ Sci Pollut Res

Potential of agricultural products and by-products Crop residues Various agricultural residues and by-products have been investigated for the capacity to remove heavy metals from

aqueous solutions (Ahluwalia and Goyal 2007; Sudha and Giri Dev 2007; Shareef 2009; Shaban et al. 2009) (Table 5). Chaff, an agricultural by-product, showed capacity to remove Pb and Cu, and metal sorption capacity has been attributed to fiber and protein (Han et al. 2006). Husk of Bengal gram (Cicer arietinum ) and Black gram (Vigna mungo) showed

Table 5 List of natural materials with the potential to be applied as biosorbents to remove heavy metals from aqueous solutions Adsorbent

Heavy metals

Maximum adsorption capacity (m mol g−1)

References

Crop residues Almond shell Groundnut hull Ground nut shell

Cr Pb, Cr Cr

0.42–0.58 3.31, 3.021 0.11

Pehlivan and Altun (2008) Qaiser et al. (2009) Agarwal et al. (2006)

Hazelnut shell Walnut shell Rice bran Rice husk Rice straw Rice hull Wheat bran

Cr Cr Zn Cu, Mn, Pb, Zn, Cr Cr Ni, Cd, Cu, Zn, Pb Cu, Zn, Cr

4.43 0.35–2.98 0.279 0.2175, 0.2503, 0.0667, 0.2114, 0.3 0.061 0.085, 0.125, 0.93, 0.17, 0.2 0.199, 0.239, 0.942

Wheat shell Chaff Husk of Bengal gram Husk of Black gram Maize stalks Tamarindus indica seed Neem (Azadirachta) leaf powder

Cu Cu, Pb Cr Pb, Cd, Zn, Cu, Ni Zn, Cd, Mn Cr Cd, Cr, Pb

0.083 to 0.108 0.031, 0.032 0.916 0.499, 0.399, 0.38, 0.257, 0.195 0.30, 0.18, 0.16 0.0188 1.404, 0.19–1.2, 1.45–3.05

Neem oil cake Fruit residues Coconut copra meal Green coconut shell powder Orange peel Carrot residues Grapefruit peels Lemon peel

Cu,Cd,Pb

0.16, 0.13,0.14

Pehlivan and Altun (2008) Agarwal et al. (2006); Pehlivan and Altun (2008) Wang et al. (2006) Mohan and Sreelakshmi (2008) Gao et al. (2008) Osman et al. (2010) Dupont et al. (2005) Singh et al. (2006b) Singh et al. (2006b) Han et al., (2006) Ahalya et al. (2005) Saeed et al. (2005) El-Sayed et al. (2011) Pehlivan and Altun (2008) Sharma and Bhattacharyya (2004); Athar et al. (2007); Babu and Gupta (2008) Rao and Khan (2007)

Cd As, Cd, Cr, Cr Ni Cu Cd Cd, Mn, Pb

0.015–0.05 1.15, 2.54, 2.30,1.41 15.8 0.937 0.24 0.46, 0.43, 0.869

Eslamzadeh et al. (2004) Schiewer and Patil (2008) Pehlivan and Altun (2008); Arslanoglu et al. (2008)

Lemon resin Olive pomace Olive cores Olive wastes Orange peels Orange barks

Mn, Pb Cd, Cu Cd Cd Cd Cd

0.429, 0.869 0.100, 0.480 0.125 0.0655 0.335 0.3101

Arslanoglu et al. (2008) Gao et al. (2008) Azouaou et al. (2008) Azouaou et al. (2008) Schiewer and Patil (2008); Gönen and Serin (2012) Azouaou et al. (2008)

Pomegranate peel Yellow passion-fruit shell Sugar beet pulp (Beta vulgaris) Tree residues Palm flower

Pb, Cu Cr Cu, Zn

0.732–1.637 0.309, 0.356

El-Ashtoukhy et al. (2008) Jacques et al. (2007) Aksu and Isoglu (2005); Pehlivan et al. (2006)

Cr

Ho and Ofomaja (2006a); Ofomaja and Ho (2007) Pino et al. (2006a, b)

Elangovan et al. (2008)

Environ Sci Pollut Res Table 5 (continued) Adsorbent

Heavy metals

Maximum adsorption capacity (m mol g−1)

References

Palm Tree Leaves Pine bark Pinecone powder Moringa oleifera Birch wood Betula sp Caesalpinia bonducella Rhizophora apiculata Cassia fistula

Zn Cd Pb As(III), As(V) Cu Ni Ni, Cu Ni

0.225 0.2687 0.0607–0.0934 0.0126, 0.0286 0.023 0.0188 0.0725, 0.0695 0.02793–0.03341

Al-Rub, (2006) Argun and Dursun (2008) Ofomaja et al. (2010a) Kumari et al. (2006) Grimm et al. (2008) Gutha et al. (2011) Rozaini et al. (2010) Hanif et al. (2007)

Sunflower stalks Oil palm fibers Oil palm waste P. jezoensis bark Tea waste Bamboo sawdust Ficus religiosa Pine sawdust Bamboo charcoal Bamboo dry powder

Cu, Cd, Zn, Cr Cu Cr, Zn Cd Cu, Pb Zn Cd Cd, Pb Cd Cu, Zn

0.293, 0.4218, 0.3073, 0.2507 0.0189 0.31, 0.163 0.101–0.142 0.755, 0.314 11.12 0.2714 0.0613, 0.108 0.1208 0.74, 0.69

Malik et al. (2005) Low et al. (1993) Seki et al. (1997)

capacity to remove Cr, Pb, Cd, Zn, Cu, and Ni from wastewaters (Ahalya et al. 2005; Dupont et al. 2005; Saeed et al. 2005; Singh et al. 2006a, b). Groundnut hull showed capacity for Pb and Cr biosorption (Shukla and Roshan 2005; Qaiser et al. 2009). Rice hull, sugarcane bagasse, wheat straw, bran, and shell showed potential for removal of Zn, Cd, Pb, Cu, Ni, and Fe from wastewater samples (Farooq et al. 2010; Osman et al. 2010). Rice husk showed capacity to absorb As, Cd, Cr, and Pb (Daifullah et al. 2003; Bishnoi et al. 2004; Shareef Surchi 2011; Ahmaruzzaman and Gupta 2011) while rice bran (by-product of the rice milling process) showed removal of Cr and Zn from synthetic wastewater (Oliveira et al. 2005; Wang et al. 2006). Maize stalks have also shown potential to remove Zn, Cd, and Mn from aqueous solutions (El-Sayed et al. 2011). Vegetable waste has showed potential for heavy metal biosorption (Azouaou et al. 2008). Metal adsorption in most of these materials has been attributed to protein, lignin, cellulose, and hemicellulose via functional groups such as alcohols, ketones, and carboxylic acids. Caesalpinia bonducella seed powder showed Ni removal capacity (Gutha et al. 2011).

Fibers Spruce, coconut coir, kenaf bast, kenaf core, coir, jute, and cotton showed an ability to remove Cu, Ni, Pb, and Zn ions from aqueous solutions (Shukla and Roshan 2005; Lee et al. 2008).

Amarasinghe and Williams, (2007) Sulaiman et al. (2011) Rao et al. (2011) Hidalgo-vázquez et al. (2011) Wang et al. (2010) Slaiman et al. (2010)

Basso et al. (2002) found a direct correlation between heavy metal sorption and lignin content of lignocellulosic material.

Fruit residues Fruit residues showed capacity to absorb Hg, Pb, Cd, Cu, Zn, and Ni (Senthilkumaar et al. 2000) from aqueous solutions. Sugar beet pulp, apple pomace, and citrus peels showed Cd uptake capacities. The metal binding has been attributed to pectin, an anionic plant cell wall polysaccharide. Pectin-rich fruit wastes or citrus peels proved to be superior adsorbent for its high metal uptake (Schiewer and Patil 2008). The metal uptake capacity ranged between 0.5 and 0.9 meq g−1 of dry peel. Sugar beet pulp (Beta vulgaris) showed capacity to remove Cu and Zn (Aksu and Isoglu 2005; Pehlivan et al. 2006). Coconut (Cocos nucifera L.) copra meal (a by-product of coconut oil production), green coconut shell, and shell powder showed capacity to absorb Zn, Cd, Cr, Pb, As, Cd, and Cu from aqueous solutions (Ho and Ofomaja 2006a; Ofomaja and Ho 2007; Okafor et al. 2012). Coconut husk also showed capacity for removing Cd and Pb from wastewater (Osobamiro and Adewuyi 2012). Metal binding is facilitated by lignin acid and cellulose which bear polar functional groups namely carboxylic and phenolic acid groups (Pino et al. 2006a, b; Amuda et al. 2007). Orange mesocarp residue biomass showed capacity of binding metals ions such as Zn, Cu, Pb, Cd, Ni, Mg, arsenate,

Environ Sci Pollut Res

and arsenite. The metal ions were probably adsorbed to the cell walls of the biomass (Annadurai et al. 2003; Ghimire et al. 2003; Ogali et al. 2008). Carrot residues showed removal of Cu, Zn, and Cr from wastewater (Eslamzadeh et al. 2004). Apricot seeds showed capacity to adsorb Cu and Pb from solutions (Kahraman et al. 2008). Yellow passion fruit shell, pinecone powder, and pomegranate peel also showed biosorption capacity for Cr, Pb, and Cu (Jacques et al. 2007; El-Ashtoukhy et al. 2008; Ofomaja et al. 2010a). Agaricus bisporus showed adsorption capacity for removing Cu from synthetic wastewater (Ertugay and Bayhan 2010). Chrysophyllum albidum seeds showed capacity for adsorption of Cu, Ni, Zn, and Pb from industrial wastewater (Oboh et al. 2009). Adsorption of Ni and Cu from aqueous solution by dry leaf powder of Pinus gerardiana and pineapple has also been noted (Mathpala et al. 2011; Weng and Wu 2012). Amaranthus hybridus (African spinach) stalk and Carica papaya seeds showed efficiency for removing Mn and Pb from aqueous solution (Egila et al. 2011). Dry leaves of Pinus gerardiana remove Ni from aqueous solution (Mathpala et al. 2011).

Gupta and Babu. 2006; Athar et al. 2007; Rao and Khan 2007; Babu and Gupta 2008; Gopalakrishnan et al. 2013). Teak leaves showed good sorption potential for Cu (Rathnakumar et al. 2009). Nickel biosorption affinity of Cassia biomass has been reported (Hanif et al. 2007). Tea waste (black and green) showed biosorption potential for removal of Cu, Cd, Ni, Pb, and Cr (Ahluwalia and Goyal 2005; Kumita et al. 2005; Malkoc and Nuhoglu 2005; Amarasinghe and Williams 2007; Zuorro and Lavecchia 2010; Shareef Surchi 2011; Albadarin et al. 2013). Chromiun(VI) ions bound to biomass was reduced to Cr(III) after biosorption at acidic conditions and the electrons for the reduction might have been donated from the biomass (Albadarin et al. 2013). Coffee residues (treated and untreated) have also shown capacity for removal of Cu and Cr from aqueous solutions (Kyzas 2012). Biosorption of Cd and Pb by Ficus religiosa leaf powder has also been noted (Qaiser et al. 2009; Rao et al. 2011).

Wood and tree residues

Almond shell (Prunus dulcis ), Tamarindus indica seed, walnut shell walnut (WNS) (Juglans regia), and hazelnut (HNS) (Corylus avellana ) showed Cr removal capacity (Agarwal et al. 2006; Pehlivan and Altun 2008; Kuchekar et al. 2011). Arundo donax stems, Brazil nutshells, and Prosopis ruscifolia sequestered trace metals Cd or Ni from wastewater. Cassava waste biomass showed Cd, Cu, and Zn biosorption capacity (Horsfall et al. 2006). Peanut shell and peanut hull showed potential to remove Cd, Pb, and Ni (Brown et al. 2000; Wilson et al. 2006). Almond husk activated carbon, hazelnut shell, and activated carbon prepared from them showed capacity for removing Ni and Cr (Hasar et al. 2003; Kobya 2004). Adsorption capacity of 4.89 mg/g for Ni was reported for activated carbon prepared from almond husk, while hazelnut shell activated carbon showed Cr adsorption capacity of 107 mg g−1 at pH 1. Jatropha oil cake and seed coat showed capacity for removing Cr and Cu (Garg et al. 2007; Jain et al. 2008). Moringa (Moringa oleifera) seed powder showed As removal capacity (Kumari et al. 2006). Tamarind hull showed potential for Cr sorption (Verma et al. 2006). Cocoa shells also showed efficiency to remove Pb, Cr, Cd, Cu, Fe, and Zn (Meunier et al. 2003). Adsorbent prepared from Calotropis procera showed adsorption of Zn from wastewaters (Vaishnav et al. 2011). Biosorption of heavy metals by mangrove barks have been noted (Rozaini et al. 2010). Sawdust showed affinity for removal of metal ions such as Cd, Cu, Pb, Cr, Ni, and Zn (Sciban et al. 2007; Ofomaja et al. 2010b; Hidalgo-vázquez et al. 2011). Metal ions bind to functional groups such as COOH and OH of sawdust and release H+ ions. Sciban and Klasnja (2004) have studied the

Sunflower stalks served as adsorbents for the removal of metal ions such as Cu, Cd, Zn, and Cr from aqueous solutions (Malik et al. 2005). The adsorption capacity of metal ions varied according to particle sizes of sunflower stalks and was also regulated by temperature. Low metal adsorption was noted at high temperature, while Cr showed the opposite phenomenon (Sun and Shi 1998). Papaya wood also showed biosorption of Cu, Cd, and Zn (Saeed et al. 2005). Cotton stalks showed adsorption of Cu and Pb from solutions (Kahraman et al. 2008). Cork oak tree biomass showed biosorption capacity of Cu, Zn, and Ni (Chubar et al. 2004). Petiolar felt sheath of palm showed removal of Pb, Ni, Cd, Cr, and Zn (Alfa et al. 2012). Palm fibers showed metal biosorption capacity (Nomanbhay and Palanisamy 2005; Ho and Ofomaja 2006b). Elangovan et al. (2008) noted Cr removal potential of palm flower. Oil palm shell and activated carbon prepared from it showed potential for adsorption of Cr, Zn, and Pb (Issabayeva et al. 2006). Picea abies (Norway spruce) and Picea jezoensis (Yezo spruce) bark and sawdust showed high metal adsorption capacity (Demirbas 2008; Urík et al. 2009). Dried olive husks and olive stone waste showed efficiency to remove Zn, Cu, Ni, Hg, and Cd (pH 5.5 to 6) (Fiol et al. 2006; Malkoc et al. 2006). Dried powder of bamboo showed biosorption of Cu and Zn from aqueous solutions (Sulaiman et al. 2010). Tobacco stems showed capacity to remove Pb from wastewater (Li et al. 2008). Neem (Azadirachta indica) leaf powder and oil cake possess capacity to absorb Cr, Cu, Cd, and Pb (Bhattacharyya and Sharma 2004; Sharma and Bhattacharyya 2004, 2005;

Potential of other agro-based materials

Environ Sci Pollut Res

abilities of different wood sawdusts (sawdust of poplar, willow, fir, oak and black locust wood, pulp, and Kraft lignin) for removing toxic heavy metal ions from water. Hardwood barks also showed adsorption capacities for Cu and Zn, respectively. Apart from conventional agro-based materials, some other materials have also been studied for heavy metal removal potential (Das et al. 2008). Eggshell (duck) showed capacity to remove Pb and Cr. The calcium carbonate of the eggshell possess functional groups, i.e., carboxyl, amine, and sulfate group which help in heavy metal binding (Chojnacka 2005; Arunlertaree et al. 2007). Thiol-functionalized eggshell membrane showed adsorption abilities for Cr, Hg, Cu, Pb, Cd, and Ag (Wang et al. 2013). Arca shell biomass showed removal of Pb, Cu, Ni, and Co (Dahiya et al. 2008). Chitin and chitosan produced from crustacean shell waste was also recognized as excellent metal ligands, forming stable complexes with many metal ions, and serving as effective protein coagulating agents (Zhou et al. 2004). Chitosans also possessed the capacity for chelating metal ions (Hg, Fe, Ni, Pb, Cu, Zn) from industrial wastewater. It also served as an effective coagulating agent in removing proteins from wastewater. Chitosan packed in columns removed more than 98 % of Ni, Cu, Cd, and Ag from aqueous solutions at both 50 and 100 mg L−1 levels of metal ion concentrations (Gamage and Shahidi 2007). Utilization of crab shells, a waste disposed off by seafood industry, showed biosorption of Cu, Co, and Zn (Niu and Volesky 2006; Vijayaraghavan et al. 2006). Fish scales also showed potential for removal of Pb, As, and Cr (El-Sheikh Sweileh 2008; Prabu et al. 2012). Fish scales have also shown capacity to remove heavy metals such as As from wastewater (Mustafiz et al. 2003).

Potential for removing other contaminants Agricultural residues and their by-products could be used as adsorbent materials for ammonia (Liu et al. 2010), dyes (Ho et al. 2005), nitrate (Orlando et al. 2002), phosphate (Eberhardt and Min 2008), and phenol (Mohd Din et al. 2009). Boston ivy leaves and stems, southern magnolia leaves, and poplar leaves showed ammonia adsorption capacity of 6.71, 4.62, 6.07, 5.01, 6.22, and 6.25 mg g−1, respectively, at 30 °C (Liu et al. 2010). The equilibrium data fitted well with both the Langmuir and Freundlich models suggesting that ammonia adsorption might be due to physiosorption. Holocellulose, lignin, and protein present on the surface helped in ammonia adsorption (Liu et al. 2010). Sunflower stalks showed removal of organic dyes and colorants from textile effluents. Sunflower stalks adsorbed two basic dyes (Methylene blue and Basic red 9) and two direct dyes (Congo red and Direct blue 71) in aqueous solutions. The adsorption potential of two basic dyes on sunflower stalks was very high in comparison to two direct

dyes. The maximum adsorption of Methylene Blue and Basic Red 9 was 205 and 317 mg g−1, respectively (Sun and Xu 1997). Coffee waste (untreated coffee residues) from industries also proved to be good low-cost adsorbents for the removal of dyes (reactive and basic) from single-component aqueous solutions (Kyzas et al. 2012). Almond shell (Prunus amygdalus) showed capacity of low-cost adsorbent for methyl orange removal from aqueous media (Deniz 2013). Apple pomace, rice husk, and wheat straw also showed capacity to remove dyes from aqueous solution (Robinson et al. 2002; Abdelwahab et al. 2005). Phoenix tree's leaf, yellow passion fruit (Passiflora edulis), a powder was tested as biosorbent for the removal of a cationic dye and methylene blue, from aqueous solutions (Han et al. 2007; Pavan et al. 2008). The maximum amount of MB adsorbed by passion fruit was 44.70 mg g−1. The activated carbon prepared from agricultural by-products also showed potential to remove dyes from aqueous solutions (Demirbas 2008, 2009). Orange waste immobilized with zirconium (Zr) showed potential to remove phosphate from an aquatic environment. The prepared gel was an effective adsorption gel for phosphate removal with a reasonably high sorption capacity of 57 mg g−1 (Biswas et al. 2008). Orange peel and banana peel showed capacity to remove methylene blue from wastewater (Velmurugan et al. 2011). Spent tea leaves, a solid waste, showed potential for removal of two azo dyes, Reactive Green 19 (RG19) and Reactive Violet 5 (RV5), from contaminated waters (Zuorro et al. 2013). Activated carbons prepared from agricultural waste such as groundnut hull, pea shells, wheat straw, and bagasse have shown potential to remove dyes from wastewater (Demirbas 2009). Aspen wood fibers remove poly aromatic hydrocarbons (PAHs) from the aqueous solution. Removal increased with increasing molecular weight of the PAH. It was noted that barks having high amount of tannins were effective filtration media and hence could find applications in wastewater treatment (Boving et al. 2008). Red soil, horse gram seed powder, orange peel powder, chalk powder, pineapple peel powder, and ragi seed powder have the significant capacity to absorb fluoride from water (Gandhi et al. 2012).

Mechanism of removal of contaminants Metal removal by various biological materials occurs by biosorption. It is a passive process (i.e., metabolismindependent). The process of biosorption involves a solid phase (sorbent) and a liquid phase (solvent) containing a dissolved species to be sorbed. Due to high affinity of the sorbent for the metal ion species, the latter is attracted and bound by rather complex process affected by several mechanisms involving chemisorption, complexation, adsorption on surface and pores, ion exchange, and chelation (Sud et al. 2008). Agricultural residues and by-products remove toxic heavy metals from

Environ Sci Pollut Res

aqueous solutions by adsorption, chelation, and ion exchange (Demirbas 2008; Sud et al. 2008). It is a comparatively fast, cost-effective, reversible, highly efficient, and potential technique for the treatment of wastewater with low concentration of contaminants. Agricultural residues are composed of lignin, cellulose, hemicellulose, pectin, tannins, proteins simple sugars, starches, water, and hydrocarbons. The functional groups present in these materials include alcohols, aldehydes, ketones, carboxylates, phenols, and ethers. These groups have the affinity for metal complexation. These groups contribute to native exchange capacity (Abia et al. 2003; Sud et al. 2008; Lesmana et al. 2009). They bind heavy metals through replacement of hydrogen ions with metal ions in solution or by donation of an electron pair from these groups to form complexes with metal ions in solution (Ofomaja and Ho 2007). Chemically reactive groups chelate, reduce, oxidize, demonstrate ion exchange properties, and aid in removing heavy metals from wastewater streams. Lignin and cellulose are the main constituents of agricultural waste materials and by-products. Cellulosic surface becomes partially negatively charged when immersed in water and, therefore, possess columbic interaction with cationic species in water (Demirbas 2008). The columbic interactions contribute to high binding capacities of cationic species on the adsorbent. Lignocellulosic materials contain polyphenolic compounds, such as tannin and lignin, which are believed to be the active sites for attachment of heavy metal cations (Demirbas 2008). Metal ions compete with hydrogen ions for the active sorption sites on the lignin molecules (Demirbas 2008). Equilibrium and column experiments determine rate, selectivity, and capacity of the agricultural substrates for removal of heavy metal cations. The capacity of the substrates for the majority of the metal ions studied is well above 1 mequiv g−1 of the substrate. Most of these biosorbents are nonselective and bind to a wide range of heavy metals with no specific priority. The adsorption capacity of these materials is influenced by a number of factors, such as adsorbent dose and size, contact time, agitation speed, temperature, pH, nature of adsorbent, and ionic strength of the aqueous solution (Johnson et al. 2008). Generally, adsorption increase with increased adsorbent dose, contact time, and agitation speed. However, favorable conditions may be different for different materials and adsorptions (Pavasant et al. 2006). For each type of material and every metal, there is a favorable pH range in which maximum adsorption was observed. The sorption capacities of coconut shell for Cd, Cr, and As varied according to particle sizes (0.044–0.297 mm), initial metal concentration (0.385– 19.232 mmol L−1), and pH values (2–9) in batch experiments (Lesmana et al. 2009). Adsorption of Cd by Picea jezoensis (Yezo spruce) bark was greatly affected by the pH and the initial Cd concentration of solution. Removal of Cr ions by tamarind seed is significantly reduced with a pH increase, slightly

decreased with ionic strength enhancement and enhanced with rising temperature (Agarwal et al. 2006). A rise of pH from 4 to 9.5 resulted in 11-fold enhancement of metal removal efficiency in neem (Azadirachta indica ) leaf powder (8.8–93.6 %) (Babu and Gupta 2008). Particle sizes of sunflower stalks affected the adsorption of metal ions, the finer size of particles showed better adsorption to the ions (Sun and Shi 1998). The heavy metal adsorption efficiency of dried olive husks increased with increase in initial pH and decrease in particle size (Wan Ngah and Hanafiah 2008). The maximum biosorption capacity of Pb and Cr on groundnut hull was noted at optimum pH of 5 and 2, respectively. The temperature change affected the biosorption capacity. The maximum removal of Pb was achieved at 20 °C, where as maximum uptake of Cr was observed at 40 °C (Qaiser et al. 2007). It is postulated that modifications of the biosorbent surface tend to improve the adsorption capacity of the biosorbents (Xuan et al. 2006; Igwe et al. 2008). This involves pretreatment or modification of the material by physical or chemical methods. Chemical modification is usually performed by adding some chemicals such as acid (Xuan et al. 2006; Babu and Gupta 2008; Martin-Lara et al. 2008), alkali (Khormaei et al. 2007), or other oxidizing and organic chemicals (Argun and Dursun 2008; Martin-Lara et al. 2008) while in the physical method, pretreatment is facilitated by heat, autoclaving, freeze-drying, and boiling. Studies have shown that thiolation of coconut fiber, treatment of pine bark with Fenton reagent, and treatment of olive pomace by phosphoric acid and hydrogen peroxide altered the surface properties hence improving sorption properties of the material (Argun and Dursun 2008; Martin-Lara et al. 2008). The adsorption capacity of neem leaf powder was significantly enhanced by modifying the physical structure and surface chemistry via an activation process (Babu and Gupta 2008). Batch adsorption studies show that the modified rice hull and sawdust treated with 0.1 M HNO3 show a great ability for extracting metallic ions from wastewater samples. In general, treated (HCl, NaOH, and heat) sawdust and rice hull sorbed the maximum amount of ions in all wastewater samples. The removal percentage of Zn, Cd, and Fe by modified rice hull and sawdust was significantly higher in the column procedure than by batch procedure (Osman et al. 2010). H2O2-treated coir fibers showed high metal uptake capacity of 4.33, 7.88, and 7.49 mg g−1 dry wt due to generation of carboxylic groups against unmodified coir fibers which showed lower capacity of 2.51, 1.83, and 2.84 mg g−1 dry wt (Shukla et al. 2006). Modification of rice husk by chemical treatment with NaOH, EDTA, and phosphate enhanced the metal adsorption capacity (Wong et al. 2003; Kumar and Bandyopadhyaya 2006; Mohan and Sreelakshmi 2008). Acid-treated peanut shells and granular activated carbon prepared from peanut shell possessed higher metal (Cd, Cu, Pb, Ni, Zn) adsorption as compared to untreated samples

Environ Sci Pollut Res

(Wafwoyo et al. 1999; Chamarthy et al. 2001; Romero et al. 2004). Orange mesocarp residue bound 56 % Mg, 81 % Zn, 71 % Cu, 73 % Pb, and 85.05 % Cd while modified orange mesocarp residue was able to bind 63.05 % Mg, 37 % Zn, 43.25 % Cu, 33.05 % Pb, and 86.45 % Cd (Ogali et al. 2008). Low-value agricultural by-products such as soybean hull, sugarcane bagasse, peanut shell, rice hull, rice straw, coconut, and bamboo can be made into granular activated carbons (GACs) and oxidized GACs that can absorb higher amounts of Pb, Cu, Ni, Cd, Cr, and Zn (Mohan and Singh 2002; Gaikwad 2004; Gao et al. 2008; Asadi et al. 2008; Wang et al. 2010). If agro wastes possess all the above-mentioned characteristics, then these adsorbents may offer significant advantages over currently available expensive commercially activated carbons, and in addition contribute to an overall waste minimization strategy. Further studies are required to apply the design and simulation model to larger.

Advantages and limitations of using these materials Agricultural residues, products, and by-products are waste materials which need proper disposal, hence can be converted to useful and inexpensive ion exchange or sorbent material, which could remove toxic metal ions from aqueous solutions and serve as value-added products (Kumar 2006). These materials can therefore be used for development of an efficient, clean, and cheap technology for wastewater treatment. Agricultural residues/by-products are porous and lightweight, and possess higher affinity for uptake/binding of heavy metal ions. Vital characteristics that make them valuable enough as an adsorbent include the following: 1. 2. 3. 4. 5. 6. 7. 8.

High adsorption capacity. Available in large quantities at one location. Low economic value and less useful in alternative products. Attached metals can be easily recovered while biosorbent is reusable Minimal amount of chemical and/or biological sludge production No additional requirement of nutrients for their utilization Effective adsorbent for a wide range of solutes and divalent metals cations (Lesmana et al. 2009). Adsorbents can be regenerated by suitable desorption technique.

At the same time, utilization of these materials in industrialscale applications is still some distance from reality because of certain limitations. These include the following: 1. Low exchange or sorption capacity and poor physical stability (i.e., partial solubility).

2. Leaching of color and extracts. For example, peanut skin leaches reddish color into solution on contact with water. The soluble colored compounds were primarily low molecular weight tannins. Also, on prolonged contact with water, peanut skin tends to disintegrate. 3. Availability in large amounts at one location. These wastes should be available in tons per day, which would be the case for middle- to large-scale agricultural or food processing industries. For instance, an abundant amount of yellow passion fruit shell, lemon peel, sour orange residue, ponkan peel, and orange peel can normally be obtained from fruit juice industries, while tea waste can be obtained from tea processing industries. 4. Economic considerations, such as harvesting and material collection of waste along with transportation to a processing area, will make the technology be impractical. These activities requires more economic margin to compensate their existing economic value. 5. Chemical activation of biosorbents is not favorable because that will make the technology non-eco-friendly and costly (Kumar 2006). Unused chemicals entail serious problems and necessitate expensive waste treatment facilities. In order to increase adsorption capacity of neem leaf powder, 1.8 g of concentrated HCl (36.5 %) was added for each gram of neem leaf powder (Babu and Gupta 2008).

Conclusions Advantages such as high adsorption capacity, surplus availability, and low economic value establish these materials (agricultural by-products, agricultural residues, and other industrial waste) as a good alternative to existing commercial materials for removing heavy metals from wastewater. These materials can serve as an alternate to the expensive commercial ion-exchange resins, to remove toxic metals from contaminated water to acceptable safety limits. The appropriate choice of biomass and proper operational conditions need to be standardized to extract their metal removal potential to maximum. Further studies are required to frame protocols wherein these materials can be used for large-scale wastewater treatment. Acknowledgments The financial assistance from Department of Science and Technology is gratefully acknowledged.

References Abdelwahab O, Nemr A, El Sikaily A, Khaled A (2005) Use of rice husk for adsorption of direct dyes from aqueous solution: a case study of direct f. Scarlet Egypt J Aquat Res 31:1–11 Abia AA, Horsfall M, Didi O (2003) The use of chemically modified and unmodified cassava waste for the removal of Cd, Cu and Zn ions from aqueous solution. Bioresour Technol 90:345–348

Environ Sci Pollut Res Agarwal GS, Bhuptawat HK, Chaudhari S (2006) Biosorption of aqueous chromium VI by Tamarindus indicus seeds. Bioresour Technol 97: 949–956 Ahalya N, Kanamadi RD, Ramachandra TV (2005) Biosorption of chromium (VI) from aqueous solutions by the husk of Bengal Gram (Cicer arietinum). Electron J Biotechnol 8:258–264 Ahluwalia SS, Goyal D (2005) Removal of heavy metals by waste tea leaves from aqueous solution. Eng Life Sci 5:158–162 Ahluwalia SS, Goyal D (2007) Microbial and plant derived biomass for removal of heavy metals from wastewater. Bioresour Technol 98: 2243–2257 Ahmaruzzaman M (2011) Industrial wastes as low-cost potential adsorbents for the treatment of wastewater laden with heavy metals. Adv Colloid Interface Sci 166:36–59 Ahmaruzzaman M, Gupta VK (2011) Rice husk and its ash as low-cost adsorbents in water and wastewater treatment. Ind Eng Chem Res 50(24):13589–13613 Aksu Z, Isoglu IA (2005) Removal of copper ions from aqueous solution by biosorption onto agricultural wastes sugar beet pulp. Process Biochem 40:3031–3044 Albadarin AB, Mangwandi C, Walker GM, Allen SJ, Ahmad MN, Khraisheh M (2013) Influence of solution chemistry on Cr(VI) reduction and complexation onto date-pits/tea-waste biomaterials. J Environ Manag 114:190–201 Alfa YM, Hassan H, Nda-Umar UI (2012) Agricultural waste materials as potential adsorbent for removal of heavy metals from aqueous solutions. Int J Chem Res 2:48–54 Al-Rub FAA (2006) Biosorption of zinc on palm tree leaves: equilibrium, kinetics, and thermodynamics studies. Sep Purif Technol 41:3499–3515 Amarasinghe BMWPK, Williams RA (2007) Tea waste as a low cost adsorbent for the removal of Cu and Pb from wastewater. Chem Eng J 132:299–309 Amuda OS, Giwa AA, Bello IA (2007) Removal of heavy metal from industrial wastewater using modified activated coconut shell carbon. Biochem Eng J 36:174–181 Annadurai A, Juang RS, Lee DJ (2003) Adsorption of heavy metals from water using banana and orange peels. Water Sci Technol 47:185–190 Argun ME, Dursun S (2008) A new approach to modification of natural adsorbent for heavy metal adsorption. Bioresour Technol 99:2516–2527 Arslanoglu H, Altundogan HS, Tumen F (2008) Preparation of cation exchange from lemon and sorption of divalent heavy metals. Bioresour Technol 99:2699–2705 Arunlertaree C, Kaewsomboon W, Kumsopa A, Pokethitiyook P, Panyawathanakit P (2007) Removal of lead from battery manufacturing wastewater by eggshell. Songklanakarin J Sci Technol 29:857–868 Asadi F, Shariatmadari H, Mirghaffari N (2008) Modification of rice hull and sawdust sorptive characteristics for remove heavy metals from synthetic solutions and wastewater. J Hazard Mater 154:451–45 Athar M, Farooq U, Hussain B (2007) Azadirachata indicum (neem): an effective biosorbent for the removal of lead(II) from aqueous solutions. Bull Environ Contam Toxicol 79:288–292 Azouaou N, Sadaoui Z, Mokaddem H (2008) Removal of cadmium from aqueous solution by adsorption on vegetable wastes. J Appl Sci 8: 4638–4643 Babu BV, Gupta S (2008) Adsorption of Cr(VI) using activated neem leaves: kinetic studies. Adsorption 14:85–92 Basso MC, Cerrella EG, Cukierman AL (2002) Lignocellulosic materials as potential biosorbents of trace toxic metals from wastewater. Ind Eng Chem Res 41:3580–3585 Bhatnagar A, Minocha AK (2006) Conventional and non-conventional adsorbents for removal of pollutants from water. Ind J Chem Technol 13:203–217 Bhatnagar A, Sillanpaa M (2010) Utilization of agro-industrial and municipal waste materials as potential adsorbents for water treatment—a review. Chem Eng J 157:277–296

Bhattacharyya KG, Sharma A (2004) Adsorption of Pb(II) from aqueous solution by Azadirachta indica (neem) leaf powder. J Hazard Mater B 113:97–109 Bishnoi NR, Bajaj M, Sharma N, Gupta A (2004) Adsorption of Cr on activated rice husk carbon and activated alumina. Bioresour Technol 91:305–307 Biswas BK, Inoue K, Ghimire KN, Harada H, Ohto K, Kawakita H (2008) Removal and recovery of phosphorus from water by means of adsorption onto orange waste gel loaded with zirconium. Bioresour Technol 99:8685–8690 Boving TB, Klement J, Rowell R, Xing B (2008) Effectiveness of wood and bark in removing organic and inorganic contaminates from aqueous solution. Mol Cryst Liq Cryst 483:339–347 Brown P, Jefcoat IA, Parrish D, Gill S, Graham E (2000) Evaluation of the adsorptive capacity of peanut hull pellets for heavy metals in solution. Adv Environ Res 4:19–29 Chamarthy S, Chung WS, Marshall WE (2001) Adsorption of selected toxic heavy metals by modified peanut shells. J Chem Technol Biotechnol 76:593–597 Chojnacka K (2005) Biosorption of Cr ions by egg shells. J Hazard Mater 121:167–173 Choudhari D, Sharma D, Phadnis A (2013) Heavy metal remediation of wastewater by agrowastes. Eur Chem Bull 2(11):880–886 Chubar N, Carvalho JR, Correia N (2004) Heavy metal biosorption on cork biomass: effect of the pre-treatment. Colloid Surf A Physicochem Eng Asp 238:51–58 Crini G (2006) Non-conventional low-cost adsorbents for dye removal: a review. Bioresour Technol 97(9):1061–1085 Dahiya S, Tripathi RM, Hegde AG (2008) Biosorption of heavy metals and radionuclide from aqueous solution by pre-treated Arca shell biomass. J Hazard Mater 150:376–386 Daifullah AAM, Girgis BS, Gad HMH (2003) Utilization of agro residues (rice husk) in small wastewater treatment plants. Mater Lett 57: 1723–1731 Das N, Karthika P, Vimala R, Vinodhini V (2008) Use of natural products as biosorbent of heavy metals: an overview. Nat Prod Radiance 7:133–138 Demirbas A (2008) Heavy metal adsorption onto agro-based waste materials: a review. J Hazard Mater 157:220–229 Demirbas A (2009) Agricultural based activated carbons for the removal of dyes from aqueous solutions: a review. J Hazard Mater 167:1–9 Deniz F (2013) Adsorption properties of low-cost biomaterial derived from Prunus amygdalus L. for dye removal from water. Sci World J 2013:9616–9671 Dhankhar R, Hooda A (2011) Fungal biosorption—an alternative to meet the challenges of heavy metal pollution in aqueous solutions. Environ Technol 32:467–491 Dupont D, Bouanda J, Dumonceau J, Aplincourt M (2005) Biosorption of Cu(II) and Zn(II) onto a lignocellulosic substrate extracted from wheat bran. Environ Chem Lett 2:165–168 Eberhardt TL, Min S (2008) Biosorbents prepared from wood particles treated with anionic polymer and iron salt: effect of particle size on phosphate adsorption. Bioresour Technol 99:626–630 Egila JN, Dauda BEN, Iyaka YA, Jimoh T (2011) Agricultural waste as a low cost adsorbent for heavy metal removal from wastewater. Int J Phys Sci 6(8):2152–2157 Elangovan R, Philip L, Chandraraj K (2008) Biosorption of hexavalent and trivalent chromium by palm flower (Borassus aethiopium). Chem Eng J 141:99–111 El-Ashtoukhy ESZ, Amina NK, Abdelwahab O (2008) Removal of lead(II) and copper(II) from aqueous solution using pomegranate peel as a new adsorbent. Desalination 223:162–173 El-Sayed GO, Dessouki HA, Ibrahiem SS (2011) Removal of Zn, Cd and Mn from aqueous solutions by adsorption on maize stalks. Malays J Anal Sci 15:8–21 El-Sheikh Sweileh JA (2008) Sorption of trace metals on fish scales and application for lead and cadmium pre-concentration

Environ Sci Pollut Res with flame atomic absorption determination. Jordan J Chem 3:87–97 Ertugay N, Bayhan YK (2010) The removal of copper (II) ion by using mushroom biomass (Agaricus bisporus ) and kinetic modeling. Desalination 255:137–142 Eslamzadeh T, Bonakdar N, Zamani A, Esmaail M (2004) Removal of heavy metals from aqueous solution by carrot residues. Iran J Sci Technol Trans A 28:161–167 Farooq U, Kozinski JA, Khan MA, Athar M (2010) Biosorption of heavy metal ions using wheat based biosorbents—a review of the recent literature. Bioresour Technol 101:5043–5053 Fayemiwo KA, Awojide OH, Tolu G (2013) Comparative analysis of two low cost metal adsorbents (rice husk and sawdust). Int J Eng Sci Technol 5:1245–1248 Fiol N, Villaescusa I, Martinez M, Miralles N, Poch J, Serarols J (2006) Sorption of Pb, Ni, Cu and Cd from aqueous solutions by olive stone waste. Sep Purif Technol 50:132–140 Gaikwad RW (2004) Removal of Cd(II) from aqueous solution by activated charcoal derived from coconut shell. Electron J Environ Agric Food Chem 3:702–709 Gamage A, Shahidi F (2007) Use of chitosan for the removal of metal ion contaminants and proteins from water. Food Chem 104:989–996 Gandhi N, Sirish D, Chandra Shekar KB, Asthana S (2012) Removal of fluoride from water and waste water by using low cost adsorbents. Int J Chem Tech Res 4:1646–1653 Gao H, Liu YG, Zeng GM, Xu WH, Li T, Xia WB (2008) Characterization of Cr(VI) removal from aqueous solutions by a surplus agricultural waste—rice straw. J Hazard Mater 150:446–452 Garg UK, Kaur MP, Garg VK, Sud D (2007) Removal of hexavalent Cr from aqueous solution by agricultural waste biomass. J Hazard Mater 140:60–68 Ghimire KN, Inoue K, Yamaguchi H, Makino K, Miyajima T (2003) Adsorptive separation of arsenate and arsenite anions from aqueous medium by using orange waste. Water Res 37:4945–4953 Gönen F, Serin DS (2012) Adsorption study on orange peel: removal of Ni(II) ions from aqueous solution. Afr J Biotechnol 11(5):1250–1258 Gopalakrishnan S, Kannadasan T, Velmurugan S, Muthu S, Vinoth KP (2013) Biosorption of chromium(VI) from industrial effluent using neem leaf adsorbent. Res J Chem Sci 3(4):48–53 Gowda R, Nataraj AG, Rao NM (2012) Coconut leaves as a low cost adsorbent for the removal of nickel from electroplating effluents. Int J Sci Eng Res 2:1–5 Grimm A, Zanzi R, Bjornborm E, Cukierman AL (2008) Comparison of different types of biomass for copper biosorption. Bioresour Technol 99:2559–2565 Gupta S, Babu BV (2006) Adsorption of Cr(VI) by a low-cost adsorbent prepared from neem leaves. Environ Eng Proceedings of National Conference on Environmental Conservation, pp. 175–180. Gupta VK, Carrott PJM, Ribeiro Carrott MML (2009) Low-cost adsorbents: growing approach for wastewater treatment—a review. Crit Rev Environ Sci Technol 39:783–842 Gutha Y, Munagapati VS, Alla SR, Abburi K (2011) Biosorptive removal of Ni(II) from aqueous solution by Caesalpinia bonducella seed powder. Sep Sci Technol 46:2291–2297 Han R, Zhang J, Zou W, Xiao H, Shi J, Liu H (2006) Biosorption of copper(II) and lead(II) from aqueous solution by chaff in a fixed-bed column. J Hazard Mater B 133:262–268 Han R, Zou W, Yu W, Cheng S, Wang Y, Shi J (2007) Biosorption of methylene blue from aqueous solution by fallen phoenix tree's leaves tree's leaves. J Hazard Mater 141:156–162 Hanif MA, Nadeema R, Bhatti HN, Ahmada NR, Ansari TM (2007) Ni(II) biosorption by Cassia fistula (golden shower) biomass. J Hazard Mater B 139:345–355 Hasar H, Cuci Y, Obek E, Fatih-Dilekoglu M (2003) Removal of Zn By activated carbon prepared from almond husks under different conditions. Adsorpt Sci Technol 21:799–808

Hidalgo-Vázquez AR, Alfaro-Cuevas-Villanueva R, Márquez-Benavides L, Cortés-Martínez R (2011) Cadmium and lead removal from aqueous solutions using pine sawdust as biosorbent. J Appl Sci Environ Sanitation 6:447–462 Ho YS, Ofomaja AE (2006a) Biosorption thermodynamics of cadmium on coconut copra meal as biosorbents. Biochem Eng J 30:117–123 Ho Y, Ofomaja AE (2006b) Kinetic studies of copper ion adsorption on palm kernel fibre. J Hazard Mater B137:1796–1802 Ho YS, Chiang TH, Hsueh YM (2005) Removal of basic dye from aqueous solution using tree fern as a biosorbents. Process Biochem 40:119–124 Horsfall MJ, Abia AA, Spiff AI (2006) Kinetic studies on the adsorption of Cd, Cu and Zn ions from aqueous solutions by cassava (Manihot esculenta) tuber bark waste. Bioresour Technol 97:283–291 Iakovleva E, Sillanpää M (2013) The use of low-cost adsorbents for wastewater purification in mining industries. Environ Sci Pollut Res. doi:10.1007/s11356-013-1546-8 Igwe JC, Abia AA, Ibeh CA (2008) Adsorption kinetics and intraparticulate diffusivities of Hg, As and Pb ions on unmodified and thiolated coconut fiber. Int J Environ Sci Technol 5:83–92 Issabayeva G, Aroua MK, Suleiman NMN (2006) Removal of lead from aqueous solution from palm shell activated carbon. Bioresour Technol 97:2350–2355 Jacques RA, Lima EC, Dias SLP, Mazzocato AC, Pavan FA (2007) Yellow passion-fruit shell as biosorbent to remove Cr(III) and Pb(II) from aqueous solution. Sep Purif Technol 57:193–198 Jain N, Joshi HC, Dutta SC, Kumar S, Pathak H (2008) Biosorption of Cu, from wastewater using Jatropha seed coat. J Sci Ind Res 67:154–160 Johnson TA, Jain N, Joshi HC, Prasad S (2008) Agricultural and agroprocessing wastes as low cost adsorbents for metal removal from wastewater. A review. J Sci Ind Res 67:647–658 Kahraman S, Dogan N, Erdemoglu S (2008) Use of various agricultural wastes for the removal of heavy metal ions. Int J Environ Pollut 34: 275–284 Kanawade SM, Gaikwad RW, Misal SA (2010) Low cost sugarcane bagasse ash as an adsorbent for dye removal from dye effluent. Int J Chem Eng Appl 1:309–318 Kannan K, Senthilkumar K, Akilamudhan P, Sangeetha V, Manikandan B (2012) Studies on effectiveness of low cost adsorbents in continuous column for textile effluents. Int J Biosci Biochem Bioinforma 2: 398–402 Khaled A, El Nemr A, El-Sikaily A, Abdelwahab O (2009) Treatment of artificial textile dye effluent containing Direct Yellow 12 by orange peel carbon. Desalination 238:210–232 Khormaei M, Nasernejad B, Edrisi M, Eslamzadeh T (2007) Copper biosorption from aqueous solutions by sour orange residue. J Hazard Mater 149:269–274 Kobya M (2004) Removal of Cr from aqueous solutions by adsorption onto hazelnut shell activated carbon: kinetic and equilibrium studies. Bioresour Technol 91:317–321 Kuchekar SR, Gaikwad VB, Sonawane DV, Lawande SP (2011) Adsorption of Pb(II) ions on Tamarindous indica seeds as a low cost abundantly available natural adsorbent. Chem Sin 2(6):281–287 Kumar U (2006) Agricultural products and by-products as a low cost adsorbent for heavy metal removal from water and wastewater: a review. Sci Res Essay 1(2):33–37 Kumar U (2013) Agricultural products and by-products as a low cost adsorbent for heavy metal removal from water and wastewater: a review. Sci Res Creat 1(1):1–5 Kumar U, Bandyopadhyaya M (2006) Sorption of Cd from aqueous solution using pre-treated rice husk. Bioresour Technol 97:104–109 Kumari P, Sharma P, Srivastava S, Srivastava MM (2006) Biosorption studies on shelled Moringa oleifera lamarck seed powder: removal and recovery of arsenic from aqueous system. Int J Miner Process 78:131–139 Kumita M, Hossain MA, Michigami Y, Mori S (2005) Optimization of parameters for Cr adsorption on used black tea leaves. Adsorption 11:561–568

Environ Sci Pollut Res Kurniawan TA, Chan GYS, Lo W, Babel S (2006) Comparisons of lowcost adsorbents for treating wastewaters laden with heavy metals. Sci Total Environ 366:409–426 Kyzas GZ (2012) Commercial coffee wastes as materials for adsorption of heavy metals from aqueous solutions. Materials 5:1826–1840 Kyzas GZ, Lazaridis NK, Mitropoulos AC (2012) Removal of dyes from aqueous solutions with untreated coffee residues as potential lowcost adsorbents: equilibrium, reuse and thermodynamic approach. Chem Eng J 189–190:148–159 Lee HJ, Lee BG, Shin DY, Park H (2008) Effect of different chemical and physical characteristic having lignocellulosic fibers on heavy metal ion removal from aqueous solution. Mater Sci Forum 569:285–288 Lesmana SO, Febriana N, Soetaredjo FE, Sunarso J, Ismadji S (2009) Studies on potential applications of biomass for the separation of heavy metals from water and wastewater. Biochem Eng J 44:19–41 Li W, Zhang L, Penga J, Li N, Zhang S, Guo S (2008) Tobacco stems as a low cost adsorbent for the removal of Pb(II) from wastewater: equilibrium and kinetic studies. Ind Crops Prod 28:294–302 Lin LC, Li JK, Juang RS (2008) Removal of Cu(II) and Ni(II) from aqueous solutions using batch and fixed-bed ion exchange processes. Desalination 225:249–259 Liu H, Donga Y, Liu Y, Wang H (2010) Screening of novel low-cost adsorbents from agricultural residues to remove ammonia nitrogen from aqueous solution. J Hazard Mater 178:1132–1136 Low KS, Lee CK, Lee KP (1993) Sorption of Cu bye dye treated oil palm fibers. Bioresour Technol 44:109-112 Malik UR, Hasany SM, Sabhani MS (2005) Sorptive potential of sunflower stem for Cr ions from aqueous solutions and its kinetic and thermodynamic profile. Talanta 66:166–173 Malkoc E, Nuhoglu Y (2005) Investigations of Ni removal from aqueous solutions using tea factory waste. J Hazard Mater 127:120–128 Malkoc E, Nuhoglu Y, Dundar M (2006) Adsorption of Cr on pomace— an olive oil industry waste: batch and column studies. J Hazard Mater 138:142–151 Martin-Lara MA, Pagnanelli F, Mainelli S, Calero M, Toro L (2008) Chemical treatment of olive pomace: effect on acid–basic properties and metal biosorption capacity. J Hazard Mater 156:448–457 Mathpala S, Joshi P, Loshali R, Chandra B, Chandra N, Kandpal ND (2011) Usefulness of biomaterial prepared from dry leaves of Pinus gerardiana in the removal of nickel(II) from aqueous solution. J Chem Pharm Res 3(4):452–459 Meunier N, Jerome L, Jean-Francois B, Tyagi RD (2003) Cocoa shells for heavy metal removal from acidic solutions. Bioresour Technol 90: 255–263 Mohan D, Singh KP (2002) Single and multi-component adsorption of Cd and Zn using activated carbon derived from bagasse—an agricultural waste. Water Res 36:2304–2318 Mohan S, Sreelakshmi G (2008) Fixed bed column study for heavy metal removal using phosphate treated rice husk. J Hazard Mater 153:75–82 Mohd Din AT, Hameed BH, Ahmad AL (2009) Batch adsorption of phenol onto physiochemical-activated coconut shell. J Hazard Mater 161:1522–1529 Mustafiz S, Rahaman MS, Kelly D, Tango M, Islam MR (2003) The Application of fish scales in removing heavy metals from energyproduced waste streams: the role of microbes. Energy Sources 25: 905–916 Niu HC, Volesky B (2006) Biosorption of chromate and vanadate species with waste crab shells. Hydrometallurgy 84:28–36 Nomanbhay SM, Palanisamy K (2005) Removal of heavy metal from industrial wastewater using chitosan coated oil palm shell charcoal. Electron J Biotechnol 8:43–53 Oboh IO, Aluyor EO, Audu TOK (2009) Use of Chrysophyllum albidum for the removal of metal ions from aqueous solution. Sci Res Essay 4(6):632–635 Ofomaja AE, Ho YS (2007) Effect of pH on cadmium biosorption by coconut copra meal. J Hazard Mater 139:356–362

Ofomaja AE, Naidoo EB, Modise SJ (2010a) Kinetic and pseudo-secondorder modeling of lead biosorption onto pine cone powder. Ind Eng Chem Res 49:562–2572 Ofomaja AE, Unuabonah EI, Oladoja NA (2010b) Competitive modeling for the biosorptive removal of copper and lead ions from aqueous solution by Mansonia wood sawdust. Bioresour Technol 101:3844–3852 Ogali RE, Akaranta O, Aririguzo VO (2008) Removal of some metal ions from aqueous solution using orange mesocarp. Afr J Biotechnol 7: 3073–3076 Okafor PC, Okon PU, Daniel EF, Ebenso EE (2012) Adsorption capacity of coconut (Cocos nucifera L.) shell for lead, copper, cadmium and arsenic from aqueous solutions. Int J Electrochem Sci 7:12354–12369 Olayinka KO, Alo BI, Adu T (2007) Sorption of heavy metals from electroplating effluents by low-cost adsorbents II: use of waste tea, coconut shell and coconut husk. J Appl Sci 7:2307–2313 Oliveira EA, Montanher SF, Andrade AD, Nobrega JA, Rollenberg MC (2005) Equilibrium studies for the sorption of chromium and nickel from aqueous solutions using raw rice bran. Process Biochem 40(3485–3):490 Orlando S, Baes AU, Nishijima W, Okada M (2002) Preparation of agricultural residue anion exchangers and its nitrate maximum adsorption capacity. Chemosphere 48:1041–1046 Osman HE, Badwy RK, Ahmad HF (2010) Usage of some agricultural by-products in the removal of some heavy metals from industrial wastewater. J Phytol 2:51–62 Osobamiro MT, Adewuyi OO (2012) Biosorption of Cd2+ and Pb2+ ions from waste water using coconut husk and beans chaffs. Cont J Environ Sci 6(3):1–7 Parihar A, Malaviya P (2013) Textile wastewater treatment using sawdust as adsorbent. Intl J Environ Sci 2:110–113 Pavan FA, Lima EC, Dias SLP, Mazzocato AC (2008) Methylene blue biosorption from aqueous solutions by yellow passion fruit waste. J Hazard Mater 150:703–712 Pavasant P, Apiratikul R, Sungkhum V, Suthiparinyanont P, Wattanachira S, Marhaba TF (2006) Biosorption of Cu2+, Cd2+, Pb2+, and Zn2+ using dried marine green macroalga Caulerpa lentillifera. Bioresour Technol 97:2321–2329 Pehlivan E, Altun T (2008) Biosorption of chromium(VI) ion from aqueous solutions using walnut, hazelnut and almond shell. J Hazard Mater 155:378–384 Pehlivan E, Cetin S, Yanik BH (2006) Equilibrium studies for the sorption of Zn aand Cu from aqueous solutions using sugarbeet pulp and fly ash. J Hazard Mater 135:193–199 Pino GH, de Mesquita LMS, Torem ML (2006a) Biosorption of heavy metals by powder of green coconut shell. Sep Sci Technol 4:3141–3153 Pino GH, Mesquita LMS, Torem ML, Pinto GAS (2006b) Biosorption of cadmium by green coconut shell powder. Miner Eng 19:380–387 Prabu K, Shankarlal S, Natarajan E (2012) A biosorption of heavy metal ions from aqueous solutions using fish scale (Catla catla). World J Fish Mar Sci 4(1):73–77 Qaiser S, Saleemi A, Ahmad R, Mahmood M (2007) Heavy metal uptake by agro based waste materials. Electron J Biotechnol 10:409–416 Qaiser S, Saleemi AR, Umar M (2009) Biosorption of lead from aqueous solution by Ficus religiosa leaves: batch and column study. J Hazard Mater 166:998–1005 Rao RAK, Khan NA (2007) Removal and recovery of Cu(II), Cd(II) and Pb(II) ions from single and multimetal systems by batch and column operation on neem oil cake (NOC). Sep Purif Technol 57:394–402 Rao KS, Anand S, Venkateswarlu P (2011) Adsorption of cadmium from aqueous solution by Ficus religiosa leaf powder and characterization of loaded biosorbent. Clean Soil Air Water 39:384–391 Rathnakumar S, Sheeja RY, Murugesan T (2009) Removal of copper(II) from aqueous solutions using teak (Tectona grandis) leaves. World Acad Sci Eng Technol 56:880–884 Renge VC, Khedkar SV, Shraddha V (2012) Removal of heavy metals from wastewater using low cost adsorbents: a review. Sci Rev Chem Commun 2(4):580–584

Environ Sci Pollut Res Robinson T, Chandran B, Nigam P (2002) Removal of dyes from a synthetic textile dye effluent by biosorption on apple pomace and wheat straw. Water Res 36:2824–2830 Romero LC, Bonomo A, Gonzo EE (2004) Peanut shell activated carbon: adsorption capacities for Cu, Zn, Ni and Cr ions from aqueous solutions. Adsorption Sci Technol 22:237–243 Rozaini CA, Jain K, Oo CW, Tan KW, Tan LS, Azraa A, Tong KS (2010) Optimization of nickel and copper ions removal by modified mangrove barks. Int J Chem Eng Appl 1:84–89 Saeed A, Iqbal M, Akhtar MW (2005) Removal and recovery of lead (II) from single and multimetal (Cd, Cu, Ni, Zn) solutions by crop milling waste (black gram husk). J Hazard Mater 117:65–73 Sankaran S, Khanal SK, Jasti N, Jin B, Pometto AL, Van Leeuwen JH (2010) Use of filamentous fungi for wastewater treatment and production of high value fungal byproducts: a review. Crit Rev Environ Sci Technol 40:400–449 Schiewer S, Patil SB (2008) Pectin-rich fruit wastes as biosorbents for heavy metal removal: equilibrium and kinetics. Bioresour Technol 99:1896–1903 Šćiban M, Kukić D, Prodanović J (2013) Potential of agro-based waste materials as adsorbents of heavy metal ions from water. Report Sustain 325–329. Sciban M, Klasnja M (2004) Wood sawdust and wood originate materials as adsorbents for heavy metal ions. Holz Roh Werkst 62:69–73 Sciban M, Radetic B, Keveresan Z, Klasnja M (2007) Adsorption of heavy metals from electroplating wastewater by wood sawdust. Bioresour Technol 98:402–409 Seki K, Saito N, Aoyama M (1997) Removal of heavy metal ions from solutions by coniferous barks. Wood Sci Technol 31:441-447 Senthilkumaar S, Bharathi S, Nithyanandhi D, Subburam V (2000) Biosorption of toxic heavy metals from aqueous solutions. Bioresour Technol 75:163–165 Shaban AM, Kamal MM, Kenawy N, Manakhly HE (2009) Role of interior structure of agro and non-agro materials for industrial wastewater treatment. J Appl Sci Res 5(8):978–985 Shareef KM (2009) Sorbents for contaminant uptake from aqueous solutions. Part 1: heavy metals. World J Agric Sci 5:819–831 Shareef Surchi KM (2011) Agricultural wastes as low cost adsorbents for Pb removal: kinetics, equilibrium and thermodynamics. Int J Chem 3:103–112 Sharma A, Bhattacharyya KG (2004) Adsorption of chromium(VI) on Azadirachta indica (neem) leaf powder. Adsorption 10:327–338 Sharma A, Bhattacharyya KG (2005) Azadirachta indica (neem) leaf powder as a biosorbent for removal of Cd(II) from aqueous medium. J Hazard Mater B 125:102–112 Sharma PK, Ayub S, Tripathi CN (2013) Agro and horticultural wastes as low cost adsorbents for removal of heavy metals from wastewater: a review. Int Refereed J Eng Sci 2:18–27 Shukla SR, Roshan PS (2005) Removal of Pb(II) from solution using cellulose-containing materials. J Chem Technol Biotechnol 80:176–183 Shukla SR, Pai S, Shendarkar AD (2006) Adsorption of Ni, Zn, Fe on modified coir fibers. Sep Purif Technol 47:141–147 Singh KK, Talat M, Hasan H (2006a) Low cost biosorbent ‘wheat bran’ for the removal of Cd(II) from wastewater: kinetic and equilibrium studies. Bioresour Technol 97:994–1001 Singh KK, Talat M, Hasan H (2006b) Removal of Pb from aqueous solutions by agricultural waste maize bran. Bioresour Technol 97: 2124–2130 Slaiman QJM, Haweel CK, Abdulmajeed YR (2010) Removal of heavy metal ions from aqueous solutions using biosorption onto bamboo. Iraqi J Chem Petroleum Eng 11:23–32 Sud D, Mahajan G, Kaur MP (2008) Agricultural waste material as potential adsorbent for sequestering heavy metal ions from aqueous solutions—a review. Bioresour Technol 99:6017–6027 Sudha S, Giri Dev VR (2007) Low cost adsorbents—an overview. Synth Fibres 36:5–9

Sulaiman QJM, Haweel CK, Abdulmajeed YR (2010) Removal of heavy metal ions from aqueous solutions using biosorption on to bamboo. Iraq J Chem Pet Eng 11:23–32 Sulaiman O, Ghani NS, Rafatullah M, Rokiah H (2011) Removal of zinc(II) ions from aqueous solutions using surfactant modified bamboo sawdust. Sep Sci Technol 46:2275–2282 Sun G, Shi W (1998) Sunflower stalks as adsorbents for the removal of metal ions from wastewater. Ind Eng Chem Res 37:1324–1328 Sun G, Xu X (1997) Sunflower stalks as adsorbents for color removal from textile wastewater. Ind Eng Chem Res 36:808–812 Urík M, Littera P, Ševc J, Kolenčík M, Čerňanský S (2009) Removal of arsenic(V) from aqueous solutions using chemically modified sawdust of spruce (Picea abies): kinetics and isotherm studies. Int J Environ Sci Technol 6(3):451–456 Vaishnav V, Chandra S, Daga K (2011) Adsorption studies of Zn(II) ions from wastewater using Calotropis procera as an adsorbent. Int J Sci Eng Res 2:1–6 Velmurugan P, Rathina kV, Dhinakaran G (2011) Dye removal from aqueous solution using low cost adsorbent. Int J Environ Sci 1:1493–1503 Verma A, Chakraborty S, Basu JK (2006) Adsorption study of hexavalent chromium using tamarind hull-based adsorbents. Sep Purif Technol 50:336–341 Vijayaraghavan K, Palanivelu K, Velan M (2006) Biosorption of copper(II) and cobalt(II) from aqueous solutions by crab shell particles. Bioresour Technol 97:1411–1419 Visekruna A, Štrkalj A, Pajc LM (2011) The use of low cost adsorbents for purification wastewater. Holist Approach Environ 1:29–37 Wafwoyo W, Chung WS, Marshall WE (1999) Utilization of peanut shells as adsorbents for selected metals. J Chem Technol Biotechnol 74: 1117–1121 Wan Ngah WS, Hanafiah MAKM (2008) Removal of heavy metal ions from wastewater by chemically modified plant wastes as adsorbents: a review. Bioresour Technol 99:3935–3948 Wang J, Chen C (2009) Biosorbents for heavy metals removal and their future. Biotechnol Adv 27:195–226 Wang XS, Qin Y, Li ZF (2006) Biosorption of zinc from aqueous solutions by rice bran: kinetics and equilibrium studies. Sep Sci Technol 41:747–756 Wang FY, Wang H, Ma JW (2010) Adsorption of cadmium(II) ions from aqueous solution by a new low-cost adsorbent—bamboo charcoal. J Hazard Mater 177:300–306 Wang S, Wei M, Huang Y (2013) Biosorption of multifold toxic heavy metal ions from aqueous water onto food residue eggshell membrane functionalized with ammonium thioglycolate. J Agric Food Chem 61(21):4988–4996 Weng C, Wu Y (2012) Potential low-cost biosorbent for copper removal: pineapple leaf powder. J Environ Eng Spec Issue Adv Res Dev Sust Environ Technol 138:286–292 Wilson K, Yang H, Seo CW, Marshall WE (2006) Select metal adsorption by activated carbon made from peanut shells. Bioresour Technol 97: 2266–2270 Wong KK, Lee CK, Low KS, Haron MJ (2003) Removal of Cu and Pb by tartaric acid modified rice husk from aqueous solution. Chemosphere 50:23–28 Xuan ZX, Tang YR, Li XM, Liu YH, Luo F (2006) Study on the equilibrium, kinetics and isotherm of biosorption of lead ions onto pretreated chemically modified orange peel. Biochem Eng J 31: 160–164 Zhou D, Zhang L, Zhou J, Guo S (2004) Development of a fixed-bed column with cellulose/chitin beads to remove heavy-metal ions. J Appl Polym Sci 94:684–691 Zuorro A, Lavecchia R (2010) Adsorption of Pb(II) on spent leaves of green and black tea. Amer J Appl Sci 7:153–159 Zuorro A, Lavecchia R, Medici F, Piga L (2013) Spent tea leaves as a potential low-cost adsorbent for the removal of azo dyes from wastewater. Chem Eng Trans 32:19–24