Bioresource Technology 152 (2014) 457–463
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Packed bed column studies on lead(II) removal from industrial wastewater by modified Agaricus bisporus Yunchuan Long 1, Daiyin Lei 1, Jiangxia Ni, Zhuolin Ren, Can Chen, Heng Xu ⇑ Key Laboratory of Bio-resources and Eco-environment (Ministry of Education), College of Life Science, Sichuan University, Chengdu, Sichuan 610064, China
h i g h l i g h t s Sodium hydroxide modified Agaricus bisporus enhanced lead ion removal. The dynamic behavior of the column was described by an S-shaped breakthrough curve. Several models were used to simulate the continuous sorption. The applicability of biosorbent was tested using industrial wastewater.
a r t i c l e
i n f o
Article history: Received 9 September 2013 Received in revised form 10 November 2013 Accepted 14 November 2013 Available online 23 November 2013 Keywords: Biosorption Agaricus bisporus Packed bed column Modification Industrial wastewater
a b s t r a c t Agaricus bisporus showed best performance in removing Pb(II) with a biosorption capacity of 86.4 mg g1 after modification with NaOH. In this work, the removal of Pb(II) from wastewater has been conducted in column mode. The metal removal was dependent on the flow rate, initial metal concentration, and bed height. The experimental data obtained from the biosorption process was successfully correlated with the Bohart–Adams, Thomas, and Yoon–Nelson models. Five biosorption–desorption cycles yielded 95.34%, 92.27%, 90.13%, 86.75%, and 81.52% regeneration, respectively. Pb(II) could be effectively removed from industrial wastewater; some metal ions and organics were also removed concomitantly, and the obtained effluent had characteristics of better quality. The results confirmed that modified A. bisporus could be applied for the removal of heavy metals from industrial wastewater in a continuous column process. Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction Heavy metals released into the environment have been posing a serious threat to natural ecosystems and public health due to their toxicity, bioaccumulation, and non-biodegradation (Sousa et al., 2010; Wang et al., 2006). Among various metal ions existing in wastewater, Pb(II), a widespread heavy metal, is of high toxicity to the human body with damage to the nervous, reproductive, and blood circulation systems (Cruz-Olivares et al., 2013). Thus, excess heavy metals must be removed from wastewater before being discharged into the aquatic environment. Biosorption can be considered as a feasible technique for Pb(II) removal because of its good performance, minimization of secondary wastes and low-cost materials (Montazer-Rahmati et al., 2011). Therefore, the wastes from industry and agriculture such as green coconut shells (Sousa et al., 2010), sugar cane bagasse (Soliman et al., 2011), cortex fruit wastes (Kelly-Vargas et al., 2012), residue of allspice (Cruz-Olivares ⇑ Corresponding author. Tel.: +86 2885414644; fax: +86 2885418262. 1
E-mail address: [email protected] (H. Xu). The first two authors contributed equally to this paper.
0960-8524/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biortech.2013.11.039
et al., 2013), and agave bagasse (Velazquez-Jimenez et al., 2013) have been reported to be used as biosorbents for removing Pb(II) recently. Mushrooms (fruiting bodies of macrofungi) are considered ideal biosorbents for their rapid growth, wide cultivation, high biosorptive potentials, and special physical characteristics (Vimala and Das, 2009). As in the case of microorganisms, mushrooms are macro in size and tough in texture, which conduce their development as biosorbents without the need for immobilization or deployment of sophisticated reactor configuration (Muraleedharan et al., 1994). Agaricus bisporus (A. bisporus), one of the most commonly and widely consumed mushrooms in the world, is extensively cultivated in China. However, spent A. bisporus, by-product of mushrooms, has no commercial value and increased environmental burden as a result of decay (Cao et al., 2010). Therefore, the effective disposal of spent A. bisporus is a meaningful work for environmental protection and maximum utilization of agricultural residues. Nevertheless, when directly employed as adsorbents, mushrooms, like other agricultural by-products, and wastes, have been confirmed to leach organic substances into aqueous solution
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(Mondal, 2009). To overcome such a problem, chemical pretreatment on these solid adsorbents was employed to reduce the organic substances discharge as well as to increase the adsorption capacity by improving physical and chemical properties. Pretreatment with alkali, chelating agents, and surfactants might enhance the metal binding capacity of biological materials (Vázquez et al., 2012; Jing et al., 2011; Kumar and Gaur, 2011). Spent A. bisporus has been utilized as a low-cost biosorbent for the removal of lead ions, but only in batch experiments (Xu et al., 2013). The column type with continuous flow operations that are more useful in large-scale wastewater treatment has distinct advantages over batch treatment. Continuous column operation is a simpler and lower-cost operation compared with batch treatment, and it can be easily scaled up from a laboratory scale procedure (Kumar et al., 2011). Moreover, the biomass can be used in multiple biosorption–desorption cycles, so the requirement of biosorbent is reduced (Singh et al., 2012). Therefore, this low-cost biosorbent applied in packed bed columns has potential industrial value in the field of wastewater treatment. In this paper, four different chemical agents were used to treat the raw A. bisporus. Fourier Transform Infrared Spectrometry (FTIR) and Scanning Electron Microscope (SEM) were applied to analyze the characterization of NaOH-modified A. bisporus (NAB). The aim of the present work was to investigate the effects of flow rate, initial lead concentration, and bed height on biosorption capacity and Pb(II) removal efficiency by NAB in a packed bed column. Bohart– Adams, Thomas, and Yoon–Nelson models were used to analyze the breakthrough curves. The reusability of the packed column was performed by carrying out five cycles of biosorption and desorption. The applicability of the biosorbent to treat Pb(II) contaminated wastewater, in a packed-bed column, was examined by using industrial wastewater. 2. Methods 2.1. Adsorbent materials and chemicals Fresh A. bisporus was collected from a mushroom production base in the suburbs of Chengdu, Sichuan Province, China. It was washed with generous amounts of ultrapure water, and then dried at 50 °C for two days in an oven. After being ground, the biomass was sieved to pass through 40/60 mesh screen to obtain a uniform particle size between 0.30 and 0.45 mm. All the chemicals and reagents utilized in the study were of analytical grade (Kelong Chemical Reagent Factory, Chengdu, China). The Pb(II) solution was prepared by dissolving appropriate amounts of Pb(NO3)2 in ultrapure water. 2.2. Preparation of modified biosorbents To find out the optimal modifier, four chemical agents (sodium hydroxide (NaOH), ammonium citrate, sodium dodecyl sulfonate (SDS), and dodecyl dimethyl benzyl ammonium bromide) were screened in the study. For modification, 5 g of powdered raw biomass was agitated for 12 h in 50 mL 0.5% surface-modifying reagents at 120 rpm. The resulting biomass was filtered, washed, dried, ground, and sieved following the above-mentioned methods for the later experiments. To evaluate the biosorption efficiency of modified A. bisporus, 0.1 g raw or modified biomass was put into 150 mL Erlenmeyer flasks with 50 mL Pb(II) solution of 150 mg L1 in a shaker incubator (SUKUN, SKY211B) at 150 rpm. After biosorption, Pb(II) concentration was measured by a flame Atomic Absorption Spectrometer (AAS; VARIAN, SpectrAA-220Fs). The Pb(II) biosorption capacity (mg g1), was calculated by the Pb(II) concentration before and after biosorption.
2.3. Characterization of adsorbent The surface morphology features of raw and modified biomass were identified by Scanning Electron Microscopy (SEM) (JSM5900LV, Japan). A Fourier Transform Infrared (FTIR) spectrometer (NEXUS-650, America) was used to determine the main functional groups present on the surface of raw and modified biomass. The surface area of the biosorbent was measured by Brunauer–Emmett–Teller (BET) method (Micromeritics ASAP-2020, America) using nitrogen as the adsorbate. 2.4. Packed bed column studies Packed bed biosorption studies were conducted to evaluate dynamic behavior for Pb(II) removal on NAB. NAB with desired height was packed in a glass column (1.5 cm internal diameter) between two supporting layers of glass wool. A layer of glass beads was placed at the top to provide a uniform inlet flow. The experiments were performed by pumping solution in a down-flow mode using a peristaltic pump at room temperature (298 K) and optimum pH 5.5 (Xu et al., 2013). A series of experiments were carried out to study the effect of bed height (2.0, 4.0, and 6.0 cm), flow rate (1.0, 3.0, and 5.0 mL min1), and initial Pb(II) concentration (20, 50, and 100 mg L1). After column exhaustion, the Pb(II)-loaded NAB was regenerated with 0.1 M HNO3, using a flow rate of 3.0 mL min1. After elution, the biosorbent-bed was washed with ultrapure water, and the regenerated bed was reused in another cycle. The applicability of column in treating industrial wastewater was performed. The industrial effluent was collected from a metal manufacturing factory located in the suburbs of Chengdu, Sichuan, China. The physico-chemical characteristics of the industrial wastewater were analyzed by Dr. Lange method (Laohaprapanon et al., 2013), and the concentration of lead(II), copper(II), nickel(II), cadmium(II), and zinc(II) was analyzed using AAS. 300 mL industrial wastewater adjusted to pH 5.5 was treated through the column at optimum bed height and flow rate. 2.5. Packed bed biosorption process analysis Several experimental parameters, which were calculated for the column sorption process, are very important in the continuous column process. The column capacity, qc (mg), is equal to the area under the plot of the adsorbed Pb(II) concentration Cad (mg L1) versus time (min) and is calculated as follows (Luo et al., 2011):
qc ¼
Q A Q ¼ 1000 1000
Z
t
C ad dt
ð1Þ
0
where Q and A are the flow rate (mL min1) and the area under the breakthrough curve, respectively. The metal removal (%) can be calculated from the ratio of column capacity (qc) to the amount of metal ions sent to the column (m) as:
%R ¼
qc 100 m
ð2Þ
The biosorption capacity q, the weight of Pb(II) adsorbed per unit dry weight of adsorbent (mg/g) can be determined as follows:
q ¼ qc =X
ð3Þ
where X is the total mass of the adsorbent in the column (g). Mass transfer zone (MTZ), which is defined as the length of the biosorption zone in the column, can be calculated from the equation (Nuic´ et al., 2013):
tb MTZ ¼ H 1 ts
ð4Þ
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Y. Long et al. / Bioresource Technology 152 (2014) 457–463 Table 1 Model equations applied for the prediction of the breakthrough curve. Model
Equation
Bohart–Adams
ln CCti
¼ K BA C i T K BA N 0 t
Thomas
lnðCCti
K T q0 m F
Yoon–Nelson
ln
Symbols representation Z
1Þ ¼
Ct C i C t
K T C i V eff F
¼ KYt KYs
Where Ct, Ci, KBA, N0, t, Z were concentration at time t, initial concentration, kinetic constant (L mg1 h1), biosorption capacity(mg L1), linear flow velocity (cm h1), bed height (cm), respectively. Where KT q0 F were rate constant (L mg1 h1), metal uptake capacity (mg g1), flow rate (L h1), respectively. Where KY is the rate constant (h1), s the time required for 50% sorbate breakthrough (h).
where MTZ is the length of the mass transfer zone (cm); H is the height of the biosorbent mixture bed (cm). 2.6. Theoretical models The modeling of the breakthrough curve was done through Bohardt–Adams, Thomas, and Yoon–Nelson models. The Bohart– Adams model proposed by Bohart and Adams (1920) was frequently applied for modeling the breakthrough curves for metal ions sorption (Mishra et al., 2013). The Thomas model (Thomas, 1948) was one of the most widely used models to describe the column performance and predict the breakthrough curve of metal sorption (Mishra et al., 2013). Yoon–Nelson model was based on the assumption that the rate of decrease in the probability of adsorption for each adsorbate molecule was proportional to the probability of adsorbate and the probability of adsorbate breakthrough on the adsorbent (Yoon and Nelson, 1984). Table 1 represents the equation of all the above-mentioned breakthrough models.
Fig. 1. Effect of different modifiers on Pb(II)biosorption. Notations: UW, ultrapure water; NaOH, sodium hydroxide; AC, ammonium citrate; SDS, sodium dodecyl sulfonate; DDBAB, dodecyl dimethyl benzyl ammonium bromide.
2.7. Statistical analysis All biosorption experiments were carried out in triplicate and the mean values were used in data analysis. All statistical analysis was done using Statistical Package for the Social Sciences (SPSS) 17.0 software and error bars representing the standard deviation were provided in figures wherever possible. Microsoft Excel 2010 program was also employed for data processing, and the linear regression method was used to determine the models’ parameters. 3. Results and discussion 3.1. Effect of modification Uptake of Pb(II) by A. bisporus that modified with chemical agents is given in Fig. 1. The biomass pretreated with ultrapure water (64.6 mg g1) enhanced 20.97% compared to the control group (53.4 mg g1) for the Pb(II) biosorption. The result could be attributed to the fact that some soluble organics, making little contribution to the removal of Pb(II), were released into water from native biomass during the treatment (Jing et al., 2011). However, A. bisporus modified with dodecyl dimethyl benzyl ammonium bromide performed worse than the control group. This might be interpreted that the charged sites provided by this cationic surfactant were suitable for the anion’s adsorption. Among the biomass modified with surface modifiers, NaOH-modified A. bisporus (NAB) showed the best performance with a sorption capacity of 86.4 mg g1, while the biosorption capacity of ammonium citrate and SDS were 69.1 mg g1 and 76.8 mg g1, respectively. Possibly, NaOH enhanced alkaline hydrolysis, simultaneously dissolved some components and increased swelling, to facilitate the sorption of Pb(II) onto A. bisporus surface (Vázquez et al., 2012; Velazquez-Jimenez et al., 2013). Higher biosorption efficiency of SDS-modified A. bisporus could be due to electrostatic
Table 2 Reported adsorption capacities (mg g1) for Pb(II) obtained on low-cost adsorbents in the literature. Adsorbent
Adsorption capacity
Reference
Allspice Modified N. zanardini Modifiedagave bagasse Green coconut shells Spirogyra neglecta Lemoncortex Modified A. bisporus Oedogonium sp. Mixture of algae waste and Purolite A-100 resin
16.2 51.83 54.29 54.62 55.71 77.6 86.4 145.0 157.2
Cruz-Olivares et al. (2013) Montazer-Rahmati et al. (2011) Velazquez-Jimenez et al. (2013) Sousa et al. (2010) Singh et al. (2012) Kelly-Vargas et al. (2012) This study Gupta and Rastog (2008) Bulgariu and Bulgariu (2013)
interactions between cationic metal ions and anionic SDS surfactant (Kumar and Gaur, 2011). For ammonium citrate modification, citric acid anhydride combined with the hydroxyl group to form an ester linkage and introduced a carboxyl group to the biosorbent. These additional carboxyl functional groups increased the bindings between modified biomass and positively charged metal ions (Wong et al., 2003). Biomass showed effective removal of Pb(II) after treated by NaOH, which was obtained by other investigators as well (Velazquez-Jimenez et al., 2013). Interestingly, except for Pb(II), modification by NaOH also appeared to enhance sorption capacity for other complexes, such as nickel and methylene blue (Wang et al., 2006). Reported adsorption capacities of low-cost adsorbents in the literature are summarized in Table 2. The Pb(II) adsorption capacity of NAB was 86.4 mg g1, which was superior to many other adsorbents.
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Fig. 2. Effect of flow rate on breakthrough curves (initial Pb(II) concentration: 50 mg L1, bed height: 4.0 cm, pH 5.5).
3.2. Characterization of adsorbents
column. The breakthrough curves at three different flow rates (1.0, 3.0, and 5.0 mL min1) illustrated in Fig. 2 showed that the breakthrough time and saturation time decreased with increasing flow rate (Table 3). The breakthrough time was 977.9, 260.7, and 145.0 min for 1.0, 3.0, and 5.0 mL min1 flow rates, respectively. A short breakthrough time at a high flow rate of metal solution was also reported (Jain et al., 2013; Singh et al., 2012). In this study, the percentage of metal removal decreased with the increase in flow rate; this might be due to less residence time of the solution through the column at a higher flow rate (Bulgariu and Bulgariu, 2013). The sorption capacity was less when the flow rate was high. It was generally considered that at a high flow rate, the residence period of metal ions in the column was very transitory, which cannot lead to the equilibrium of the sorption process (Maiti et al., 2009; Mona et al., 2013). Mass transfer zone (MTZ) increased with increasing flow rate; similar observation was reported by Bulgariu and Bulgariu (2013). Considering the results and the discussions above, the best performance was obtained at the lowest flow rate (1.0 mL min1). However, at this flow rate, the run time (the breakthrough time was up to 977.9 min) and energy costs were very high, so the flow rate of 3.0 mL min1 was chosen for the following experiments.
In order to examine the surface morphology of the biosorbents, SEM micrographs (at magnification 1000) were taken before and after modification. After modification, the biosorbent was characterized by an irregular and porous surface (Fig. S1 of Supplementary material). This might be interpreted that starch, proteins, and sugars from biomaterial were degraded or dissolved in the basification procedure. These irregular and porous surfaces are conducive to increase the specific surface area, thus enhance adsorption efficiency (Sillerova et al., 2013). The FTIR spectra of unmodified A. bisporus and NAB are shown in Fig. S2 of Supplementary material. A broad absorption peak was observed at 3401 cm1 for unmodified A. bisporus, and this was indicative of the presence of –OH groups and –NH groups (Luo et al., 2011). Peak at 2925 cm1 was expressive of stretching of C–H bond of methyl and methylene groups (Saha et al., 2012); The peak at 1652 cm1 represented –NH2 groups (Sillerova et al., 2013); peak at 1028 cm1 could be assigned to stretching vibration of C–OH of alcoholic groups and carboxylic acids (Sillerova et al., 2013). The intensity of transmittance of peaks was relatively more in the case of NAB compared with A. bisporus. The changes of peaks suggested that functional groups such as –NH, –OH, –CH, and –NH2 were involved in the process in modification. According to the BET analysis, NAB had a specific surface area of 1.55 m2 g1 with an average pore diameter of 5.23 nm.
3.3.2. Effect of initial concentration Effect of initial Pb(II) concentration (20, 50, and 100 mg L1) on performance of breakthrough curves at a constant bed height (4.0 cm) and flow rate (3.0 mL min1) is depicted in Fig. 3. The values of the experimental breakthrough parameters summarized in Table 3 indicated that the breakthrough time and exhaustion time were inversely related with influent Pb(II) concentration. In addition, at higher initial Pb(II) concentrations, the breakthrough curves were steeper with a longer MTZ. The steepness of curves is a measure of the efficiency of the column to reach saturation; the steeper the better for the column performance (Naja and Volesky, 2008). Cruz-Olivares et al. (2013) also reported a longer MTZ at higher initial metal concentrations. Nevertheless, many other researchers reported that as influent concentration increased, a shorter MTZ was obtained (Bulgariu and Bulgariu, 2013; Naja and Volesky, 2008). Biosorption capacity increased with increasing Pb(II) initial concentration. This could be explained by the fact that at the greater concentration, gradient caused a faster transport due to an increased diffusion coefficient or mass transfer coefficient (Samuel et al., 2013). These results demonstrated that the higher feed concentration could saturate the sorbent more quickly. Considering the concentration of real industrial wastewater, the concentration of 50 mg L1 was applied to the next experiments.
3.3. Parameters of the breakthrough curves
3.3.3. Effect of bed height The breakthrough profile of Pb(II) biosorption at different bed heights (2.0, 4.0, and 6.0 cm) are given in Fig. 4, and the values of the experimental breakthrough parameters are summarized in Table 3. The breakthrough time increased with the increase in bed
3.3.1. Effect of flow rate The flow rate is an important parameter as it determines the contact time of the sorbate with the biosorbent in a packed bed
Table 3 Parameters obtained from the breakthrough curves of the packed bed column for Pb(II) biosorption. F (mL/min)
H (cm)
Ci (mg L1)
tb (min)
qb (mg/g)
Rb (%)
ts (min)
qs (mg/g)
Rs (%)
MTZ (cm)
3.0 3.0 3.0 3.0 3.0 1.0 5.0
4 4 4 2 6 4 4
20 100 50 50 50 50 50
649 135.1 260.7 128.7 379.6 977.9 145
48.2 50.3 48.2 47.3 46.9 60.8 44.5
99.1 99.3 98.6 98.0 98.8 99.5 98.3
898 232.8 411.5 234.4 565.1 1166.4 245.8
57.6 68.1 62.3 67.0 33.1 66.7 60.2
85.4 78.0 80.7 76.2 46.8 91.5 78.4
1.1 1.7 1.5 0.9 2.0 0.6 1.6
Notations: F, flow rate; H, bed height; tb, ts, the time at breakthrough and saturation point; qb, qs, biosorption capacity at breakthrough and saturation time; Rb, Rs, the removal percent at breakthrough and saturation point; MTZ, the length of mass transfer zone.
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ever, many researchers found a positive correlation between the sorption capacity and bed height (Jain et al., 2013; Kumar et al., 2011). Their explanation was that the longer contact time between metal ions and available biomass in column result in higher sorption capacity. Higher bed height provided a longer residence period of metal ions in the column, thus, a larger volume of metal solution could be treated. Nevertheless, considering the low sorption capacity at a bed height of 6.0, 4.0 cm was chosen as the optimum bed height. 3.4. Modeling of the breakthrough curves The Bohart–Adams model was applied to the initial part (Ct/ Ci = 0–0.5) of the breakthrough curves of Pb(II) sorption, and the values of characteristic parameters are summarized in Table 4. The correlation coefficients (R2) values were found to be above 0.9815 for all breakthrough curves. The biosorption capacity of the bed (N0) increased with increasing initial metal concentration, but decreased with increasing flow rate, and bed height. In addition, the kinetic constant (KBA) decreased with increasing influent metal concentration and bed height; and yet it increased with increasing flow rate. Therefore, under these conditions, for better capacity of the column (N0) and lower kinetic constant (i.e., minimum resistance), the initial Pb(II) concentrations need to be higher while the flow rate should be lower. Bohart–Adams model provides a comprehensive and simple approach to running and evaluating adsorption performance. However, its validity is limited by the range of conditions used. Thomas and Yoon–Nelson models were applied to the breakthrough curves, and the values of characteristic parameters are listed in Table 4. The Thomas rate constant (KT) increased with increasing flow rate, nevertheless; it reduced with increasing flowing metal concentration and bed height. The maximum solid phase concentration (q0) increased with increasing influent metal concentration, but it reduced with increasing bed height and flow rate. The Yoon–Nelson model rate constant (KY) was higher at higher flow rate, higher influent concentration, lower bed height; however, s, the time required for 50% breakthrough, was higher at lower flow rate, lower influent concentration, and higher bed height. In a comparison of values of R2(R2 P 0.9911 for all breakthrough curves) and breakthrough curves, both Thomas and Yoon–Nelson models could be used to describe the behavior of the biosorption of Pb(II) in a packed bed column under different experimental conditions.
Fig. 3. Effect of initial Pb(II) concentration on breakthrough curves (flow rate: 3.0 mL min1, bed height: 4.0 cm, pH 5.5).
Fig. 4. Effect of bed height on breakthrough curves (flow rate: 3.0 mL min1, initial Pb(II) concentration: 50 mg L1, pH 5.5).
height from 102 min (2.0 cm) to 299.5 min (6.0 cm). Similarly, the requirement of metal solution for attaining the breakthrough and saturation point was concomitantly increased with increasing bed height. This might be due to availability of more metal binding sites at taller bed heights for sorption and resulting in a higher MTZ (Jain et al., 2013; Mishra et al., 2013). In the present study, the metal removal efficiency increased with the increase in bed heights, but the sorption capacity was not greatly affected by bed height. This might be due to that metal availability was unlimited in the column (Singh et al., 2012). How-
3.5. Successive cycles of sorption and desorption by column For the sorption process to be viable, efficient regeneration, and reuse of the NAB bed is necessary. It was observed that 0.1 M HNO3 did not obviously affect the structure and metal sorption ability of NAB (Table S1 provided with the Supplementary material).The
Table 4 Bohart–Adams, Thomas and the Yoon–Nelson models parameters for the sorption of Pb(II) by the NAB-packed column. Conditions
Bohart–Adams
Thomas 2
Yoon-Nelson 2
F
H
Ci
KBA
N0
R
KT
q0
R
KY
s
R2
3.0 3.0 3.0 3.0 3.0 1.0 5.0
4 4 4 2 6 4 4
20 100 50 50 50 50 50
0.0455 0.0249 0.0301 0.0444 0.0256 0.0242 0.0470
6173.32 7373.77 6814.00 7420.40 6253.50 6995.72 6633.46
0.9943 0.9948 0.9977 0.9966 0.9929 0.9815 0.992
0.0514 0.0268 0.0344 0.0501 0.0280 0.0265 0.0509
57.72 68.79 63.06 67.72 59.16 66.76 61.05
0.9978 0.9994 0.9995 0.9985 0.9988 0.9911 0.9982
1.0276 2.6796 1.7205 2.5559 1.3981 1.3274 2.5472
12.83 3.06 5.60 3.01 7.89 17.80 3.26
0.9978 0.9994 0.9995 0.9985 0.9988 0.9911 0.9982
Notations: F, flow rate; H, bed height; KBA, Bohart–Adams rate constant (L mg1h1); N0, saturation concentration (mg l1), KT, Thomas rate constant (L mg1 h1); q0, equilibrium metal sorption (mg g1); KY, Yoon–Nelson rate constant (h1); s: the time required for 50% sorbate breakthrough (h).
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Table 5 Characteristics of industrial wastewater before and after passing through NAB-packed column at a flow rate of 3.0 mL min1. Quality parameter (mg/L)
Initial wastewater
Treated wastewater
Maximum permissible concentration
COD BOD Phosphate Nitrate Pb(II) Cu(II) Ni(II) Cd(II) Zn(II) Cr(VI)
1083 725 1.26 17.2 35.15 2.82 1.58 2.25 33.6 3.75
330 187 0.72 9.4 0.23 0.48 0.41 0.03 1.26 0.5
500 300 1.0 20 0.2 0.5 0.5 0.05 1.5 0.2
Acknowledgements This study was financially supported by the Science and Technology Supportive Project of Sichuan Province, China (No. 2013SZ0062), Science and Technology Supportive Project of Chengdu (No. 12DXYB087JH-005) and NSFC (No. J1103518). The authors wish to thank Professor Guanglei Cheng and Dong Yu from the Sichuan University for their technical assistance. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.biortech.2013. 11.039. References
amount of Pb(II) sorbed by the column in the first cycle was 60.8 mg g1 dry weight. Regeneration efficiency (%) decreased with the cycle progress, and yet the desorption of sorbed Pb(II) was still approximately 90% after three cycles. Similar high efficiencies of desorption were reported in other literatures (Gupta and Rastogi, 2008; Samuel et al., 2013). Incomplete desorption of metal ions seems to be an important reason for decrease in metal sorption capacity of the column during successive cycles of sorption and desorption. The biosorbent was put into a biogas digester for fermentation after being exhausted. Heavy metals were extracted from biogas slurry by chemical precipitation and flocculation, and then, the biogas residues containing heavy metals were disposed of via landfill. 3.6. Applicability of column in treating industrial wastewater The characteristics of industrial wastewater before and after passing through the packed bed column are presented in Table 5. More than 99% Pb(II) was removed from 300 mL wastewater, and the concentrations of Cu(II), Ni(II), Cd(II), and Zn(II) were decreased under maximum permissible concentration according to the National Standards of PRC (GB 21900-2008). The results accorded with the findings of Cao, and in a multi-metal system, lead ions could be prior removed from wastewater in the presence of other metal ions (Cu, Cd) (Cao et al., 2010). Overall, the metals of the treated wastewater were in acceptable range except for Cr(VI). This was probably because Cr(VI) mostly exists in its anion form (Jing et al., 2011), but the sites provided by NaOH modified biomass were more suitable for cationic adsorption. In addition, biological oxygen demand (BOD), chemical oxygen demand (COD), phosphate, and nitrate were decreased obviously. The results demonstrated that the NAB could remove multi-metal and organics from wastewater.
4. Conclusion NaOH-modified A. bisporus showed best performance in removing Pb(II) with an adsorption capacity of 86.4 mg g1. FTIR and SEM have been applied to analyze the characterization of A. bisporus and NAB. Pb(II) biosorption performance of the column packed with NAB largely depended on flow rate, influent metal concentration, and bed height. Bohart–Adams, Thomas, and Yoon–Nelson models successfully predicted breakthrough curves obtained under varying experimental conditions. NAB showed good reusability in the bed column during five biosorption–desorption cycles. The NABpacked column could efficiently remove several metal ions and also concomitantly remove some organics from real industrial wastewaters.
Bohart, G., Adams, E., 1920. Some aspects of the behavior of charcoal with respect to chlorine.1. J. Am. Chem. Soc. 42, 523–544. Bulgariu, D., Bulgariu, L., 2013. Sorption of Pb(II) onto a mixture of algae waste biomass and anion exchanger resin in a packed-bed column. Bioresour. Technol. 129, 374–380. Cao, Y.R., Liu, Z., Cheng, G.L., Jing, X.B., Xu, H., 2010. Exploring single and multimetal biosorption by immobilized spent Tricholoma lobayense using multi-step response surface methodology. Chem. Eng. J. 164, 183–195. Cruz-Olivares, J., Pérez-Alonso, C., Barrera-Díaz, C., Ureña-Nuñez, F., ChaparroMercado, M.C., Bilyeu, B., 2013. Modeling of lead(II) biosorption by residue of allspice in a fixed-bed column. Chem. Eng. J. 228, 21–27. Gupta, V.K., Rastogi, A., 2008. Biosorption of lead(II) from aqueous solutions by nonliving algal biomass Oedogonium sp. and Nostoc sp. – a comparative study. Colloids Surf. B: Biointerfaces 64, 170–178. Jain, M., Garg, V.K., Kadirvelu, K., 2013. Cadmium(II) sorption and desorption in a fixed bed column using sunflower waste carbon calcium-alginate beads. Bioresour. Technol. 129, 242–248. Jing, X., Cao, Y., Zhang, X., Wang, D., Wu, X., Xu, H., 2011. Biosorption of Cr(VI) from simulated wastewater using a cationic surfactant modified spent mushroom. Desalination 269, 120–127. Kelly-Vargas, K., Cerro-Lopez, M., Reyna-Tellez, S., Bandala, E.R., Sanchez-Salas, J.L., 2012. Biosorption of heavy metals in polluted water, using different waste fruit cortex. Phys. Chem. Earth 37–39, 26–29. Kumar, D., Gaur, J.P., 2011. Metal biosorption by two cyanobacterial mats in relation to pH, biomass concentration, pretreatment and reuse. Bioresour. Technol. 102, 2529–2535. Kumar, R., Bhatia, D., Singh, R., Rani, S., Bishnoi, N.R., 2011. Sorption of heavy metals from electroplating effluent using immobilized biomass Trichoderma viride in a continuous packed-bed column. Int. Biodeter. Biodegr. 65, 1133–1139. Laohaprapanon, S., Marques, M., Kaczala, F., Hogland, W., 2013. Packed-column of granular activated carbons for removal of chemical oxygen demand from industrial wastewater. Clean – Soil Air Water 41, 244–250. Luo, X., Deng, Z., Lin, X., Zhang, C., 2011. Fixed-bed column study for Cu2+ removal from solution using expanding rice husk. J. Hazard. Mater. 187, 182–189. Maiti, S.K., Bera, D., Chattopadhyay, P., Ray, L., 2009. Determination of kinetic parameters in the biosorption of Cr(VI) on immobilized Bacillus cereus M116 in a continuous packed bed column reactor. Appl. Biochem. Biotechnol. 159, 488–504. Mishra, V., Balomajumder, C., Agarwal, V.K., 2013. Adsorption of Cu(II) on the surface of nonconventional biomass: a study on forced convective mass transfer in packed bed column. J. Waste Manage. 2013, 1–8. Mona, S., Kaushik, A., Kaushik, C.P., 2013. Prolonged hydrogen production by Nostoc in photobioreactor and multi-stage use of the biological waste for column biosorption of some dyes and metals. Biomass Bioenerg. 54, 27–35. Mondal, M.K., 2009. Removal of Pb(II) ions from aqueous solution using activated tea waste: adsorption on a fixed-bed column. J. Environ. Manage. 90, 3266–3271. Montazer-Rahmati, M.M., Rabbani, P., Abdolali, A., Keshtkar, A.R., 2011. Kinetics and equilibrium studies on biosorption of cadmium, lead, and nickel ions from aqueous solutions by intact and chemically modified brown algae. J. Hazard. Mater. 185, 401–407. Muraleedharan, T., Venkobachar, C., Leela, I., 1994. Investigations of fungal fruiting bodies as biosorbents for the removal of heavy metals from industrial processing streams. Sep. Sci. Technol. 29, 1893–1903. Naja, G., Volesky, B., 2008. Optimization of a biosorption column performance. Environ. Sci. Technol. 42, 5622–5629. Nuic´, I., Trgo, M., Peric´, J., Vukojevic´ Medvidovic´, N., 2013. Analysis of breakthrough curves of Pb and Zn sorption from binary solutions on natural clinoptilolite. Microporous Mesoporous Mater. 167, 55–61. Saha, P.D., Chakraborty, S., Chowdhury, S., 2012. Batch and continuous (fixed-bed column) biosorption of crystal violet by Artocarpus heterophyllus (jackfruit) leaf powder. Colloids Surf. B: Biointerfaces 92, 262–270. Samuel, J., Pulimi, M., Paul, M.L., Maurya, A., Chandrasekaran, N., Mukherjee, A., 2013. Batch and continuous flow studies of adsorptive removal of Cr(VI) by adapted bacterial consortia immobilized in alginate beads. Bioresour. Technol. 128, 423–430.
Y. Long et al. / Bioresource Technology 152 (2014) 457–463 Sillerova, H., Komarek, M., Chrastny, V., Novak, M., Vanek, A., Drabek, O., 2013. Brewers draff as a new low-cost sorbent for chromium(VI): comparison with other biosorbents. J. Colloid Interface Sci. 396, 227–233. Singh, A., Kumar, D., Gaur, J.P., 2012. Continuous metal removal from solution and industrial effluents using Spirogyra biomass-packed column reactor. Water Res. 46, 779–788. Soliman, E.M., Ahmed, S.A., Fadl, A.A., 2011. Reactivity of sugar cane bagasse as a natural solid phase extractor for selective removal of Fe(III) and heavy-metal ions from natural water samples. Arab. J. Chem. 4, 63–70. Sousa, F.W., Oliveira, A.G., Ribeiro, J.P., Rosa, M.F., Keukeleire, D., Nascimento, R.F., 2010. Green coconut shells applied as adsorbent for removal of toxic metal ions using fixed-bed column technology. J. Environ. Manage. 91, 1634–1640. Thomas, H.C., 1948. Chromatography: a problem in kinetics. Ann. N Y. Acad. Sci 49, 161–182. Vázquez, G., Mosquera, O., Freire, M.S., Antorrena, G., González-Álvarez, J., 2012. Alkaline pre-treatment of waste chestnut shell from a food industry to enhance cadmium, copper, lead and zinc ions removal. Chem. Eng. J. 184, 147–155.
463
Velazquez-Jimenez, L.H., Pavlick, A., Rangel-Mendez, J.R., 2013. Chemical characterization of raw and treated agave bagasse and its potential as adsorbent of metal cations from water. Ind. Crop. Prod. 43, 200–206. Vimala, R., Das, N., 2009. Biosorption of cadmium(II) and lead(II) from aqueous solutions using mushrooms: a comparative study. J. Hazard. Mater. 168, 376– 382. Wang, S., Soudi, M., Li, L., Zhu, Z.H., 2006. Coal ash conversion into effective adsorbents for removal of heavy metals and dyes from wastewater. J. Hazard. Mater. 133, 243–251. Wong, K.K., Lee, C.K., Low, K.S., Haron, M.J., 2003. Removal of Cu and Pb by tartaric acid modified rice husk from aqueous solutions. Chemosphere 50, 23–28. Xu, H., Chen, Y., Huang, H., Liu, Y., Yang, Z., 2013. Removal of lead(II) and cadmium(II) from aqueous solutions using spent Agaricus bisporus. Can. J. Chem. Eng. 91, 421–431. Yoon, Y.H., Nelson, J.H., 1984. Application of gas adsorption kinetics I. A theoretical model for respirator cartridge service life. Am. Ind. Hyg. Assoc. J. 45, 509–516.
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Packed bed column studies on lead(II) removal from industrial wastewater by modified Agaricus bisporus Yunchuan Long 1, Daiyin Lei 1, Jiangxia Ni, Zhuolin Ren, Can Chen, Heng Xu ⇑ Key Laboratory of Bio-resources and Eco-environment (Ministry of Education), College of Life Science, Sichuan University, Chengdu, Sichuan 610064, China
h i g h l i g h t s Sodium hydroxide modified Agaricus bisporus enhanced lead ion removal. The dynamic behavior of the column was described by an S-shaped breakthrough curve. Several models were used to simulate the continuous sorption. The applicability of biosorbent was tested using industrial wastewater.
a r t i c l e
i n f o
Article history: Received 9 September 2013 Received in revised form 10 November 2013 Accepted 14 November 2013 Available online 23 November 2013 Keywords: Biosorption Agaricus bisporus Packed bed column Modification Industrial wastewater
a b s t r a c t Agaricus bisporus showed best performance in removing Pb(II) with a biosorption capacity of 86.4 mg g1 after modification with NaOH. In this work, the removal of Pb(II) from wastewater has been conducted in column mode. The metal removal was dependent on the flow rate, initial metal concentration, and bed height. The experimental data obtained from the biosorption process was successfully correlated with the Bohart–Adams, Thomas, and Yoon–Nelson models. Five biosorption–desorption cycles yielded 95.34%, 92.27%, 90.13%, 86.75%, and 81.52% regeneration, respectively. Pb(II) could be effectively removed from industrial wastewater; some metal ions and organics were also removed concomitantly, and the obtained effluent had characteristics of better quality. The results confirmed that modified A. bisporus could be applied for the removal of heavy metals from industrial wastewater in a continuous column process. Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction Heavy metals released into the environment have been posing a serious threat to natural ecosystems and public health due to their toxicity, bioaccumulation, and non-biodegradation (Sousa et al., 2010; Wang et al., 2006). Among various metal ions existing in wastewater, Pb(II), a widespread heavy metal, is of high toxicity to the human body with damage to the nervous, reproductive, and blood circulation systems (Cruz-Olivares et al., 2013). Thus, excess heavy metals must be removed from wastewater before being discharged into the aquatic environment. Biosorption can be considered as a feasible technique for Pb(II) removal because of its good performance, minimization of secondary wastes and low-cost materials (Montazer-Rahmati et al., 2011). Therefore, the wastes from industry and agriculture such as green coconut shells (Sousa et al., 2010), sugar cane bagasse (Soliman et al., 2011), cortex fruit wastes (Kelly-Vargas et al., 2012), residue of allspice (Cruz-Olivares ⇑ Corresponding author. Tel.: +86 2885414644; fax: +86 2885418262. 1
E-mail address: [email protected] (H. Xu). The first two authors contributed equally to this paper.
0960-8524/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biortech.2013.11.039
et al., 2013), and agave bagasse (Velazquez-Jimenez et al., 2013) have been reported to be used as biosorbents for removing Pb(II) recently. Mushrooms (fruiting bodies of macrofungi) are considered ideal biosorbents for their rapid growth, wide cultivation, high biosorptive potentials, and special physical characteristics (Vimala and Das, 2009). As in the case of microorganisms, mushrooms are macro in size and tough in texture, which conduce their development as biosorbents without the need for immobilization or deployment of sophisticated reactor configuration (Muraleedharan et al., 1994). Agaricus bisporus (A. bisporus), one of the most commonly and widely consumed mushrooms in the world, is extensively cultivated in China. However, spent A. bisporus, by-product of mushrooms, has no commercial value and increased environmental burden as a result of decay (Cao et al., 2010). Therefore, the effective disposal of spent A. bisporus is a meaningful work for environmental protection and maximum utilization of agricultural residues. Nevertheless, when directly employed as adsorbents, mushrooms, like other agricultural by-products, and wastes, have been confirmed to leach organic substances into aqueous solution
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Y. Long et al. / Bioresource Technology 152 (2014) 457–463
(Mondal, 2009). To overcome such a problem, chemical pretreatment on these solid adsorbents was employed to reduce the organic substances discharge as well as to increase the adsorption capacity by improving physical and chemical properties. Pretreatment with alkali, chelating agents, and surfactants might enhance the metal binding capacity of biological materials (Vázquez et al., 2012; Jing et al., 2011; Kumar and Gaur, 2011). Spent A. bisporus has been utilized as a low-cost biosorbent for the removal of lead ions, but only in batch experiments (Xu et al., 2013). The column type with continuous flow operations that are more useful in large-scale wastewater treatment has distinct advantages over batch treatment. Continuous column operation is a simpler and lower-cost operation compared with batch treatment, and it can be easily scaled up from a laboratory scale procedure (Kumar et al., 2011). Moreover, the biomass can be used in multiple biosorption–desorption cycles, so the requirement of biosorbent is reduced (Singh et al., 2012). Therefore, this low-cost biosorbent applied in packed bed columns has potential industrial value in the field of wastewater treatment. In this paper, four different chemical agents were used to treat the raw A. bisporus. Fourier Transform Infrared Spectrometry (FTIR) and Scanning Electron Microscope (SEM) were applied to analyze the characterization of NaOH-modified A. bisporus (NAB). The aim of the present work was to investigate the effects of flow rate, initial lead concentration, and bed height on biosorption capacity and Pb(II) removal efficiency by NAB in a packed bed column. Bohart– Adams, Thomas, and Yoon–Nelson models were used to analyze the breakthrough curves. The reusability of the packed column was performed by carrying out five cycles of biosorption and desorption. The applicability of the biosorbent to treat Pb(II) contaminated wastewater, in a packed-bed column, was examined by using industrial wastewater. 2. Methods 2.1. Adsorbent materials and chemicals Fresh A. bisporus was collected from a mushroom production base in the suburbs of Chengdu, Sichuan Province, China. It was washed with generous amounts of ultrapure water, and then dried at 50 °C for two days in an oven. After being ground, the biomass was sieved to pass through 40/60 mesh screen to obtain a uniform particle size between 0.30 and 0.45 mm. All the chemicals and reagents utilized in the study were of analytical grade (Kelong Chemical Reagent Factory, Chengdu, China). The Pb(II) solution was prepared by dissolving appropriate amounts of Pb(NO3)2 in ultrapure water. 2.2. Preparation of modified biosorbents To find out the optimal modifier, four chemical agents (sodium hydroxide (NaOH), ammonium citrate, sodium dodecyl sulfonate (SDS), and dodecyl dimethyl benzyl ammonium bromide) were screened in the study. For modification, 5 g of powdered raw biomass was agitated for 12 h in 50 mL 0.5% surface-modifying reagents at 120 rpm. The resulting biomass was filtered, washed, dried, ground, and sieved following the above-mentioned methods for the later experiments. To evaluate the biosorption efficiency of modified A. bisporus, 0.1 g raw or modified biomass was put into 150 mL Erlenmeyer flasks with 50 mL Pb(II) solution of 150 mg L1 in a shaker incubator (SUKUN, SKY211B) at 150 rpm. After biosorption, Pb(II) concentration was measured by a flame Atomic Absorption Spectrometer (AAS; VARIAN, SpectrAA-220Fs). The Pb(II) biosorption capacity (mg g1), was calculated by the Pb(II) concentration before and after biosorption.
2.3. Characterization of adsorbent The surface morphology features of raw and modified biomass were identified by Scanning Electron Microscopy (SEM) (JSM5900LV, Japan). A Fourier Transform Infrared (FTIR) spectrometer (NEXUS-650, America) was used to determine the main functional groups present on the surface of raw and modified biomass. The surface area of the biosorbent was measured by Brunauer–Emmett–Teller (BET) method (Micromeritics ASAP-2020, America) using nitrogen as the adsorbate. 2.4. Packed bed column studies Packed bed biosorption studies were conducted to evaluate dynamic behavior for Pb(II) removal on NAB. NAB with desired height was packed in a glass column (1.5 cm internal diameter) between two supporting layers of glass wool. A layer of glass beads was placed at the top to provide a uniform inlet flow. The experiments were performed by pumping solution in a down-flow mode using a peristaltic pump at room temperature (298 K) and optimum pH 5.5 (Xu et al., 2013). A series of experiments were carried out to study the effect of bed height (2.0, 4.0, and 6.0 cm), flow rate (1.0, 3.0, and 5.0 mL min1), and initial Pb(II) concentration (20, 50, and 100 mg L1). After column exhaustion, the Pb(II)-loaded NAB was regenerated with 0.1 M HNO3, using a flow rate of 3.0 mL min1. After elution, the biosorbent-bed was washed with ultrapure water, and the regenerated bed was reused in another cycle. The applicability of column in treating industrial wastewater was performed. The industrial effluent was collected from a metal manufacturing factory located in the suburbs of Chengdu, Sichuan, China. The physico-chemical characteristics of the industrial wastewater were analyzed by Dr. Lange method (Laohaprapanon et al., 2013), and the concentration of lead(II), copper(II), nickel(II), cadmium(II), and zinc(II) was analyzed using AAS. 300 mL industrial wastewater adjusted to pH 5.5 was treated through the column at optimum bed height and flow rate. 2.5. Packed bed biosorption process analysis Several experimental parameters, which were calculated for the column sorption process, are very important in the continuous column process. The column capacity, qc (mg), is equal to the area under the plot of the adsorbed Pb(II) concentration Cad (mg L1) versus time (min) and is calculated as follows (Luo et al., 2011):
qc ¼
Q A Q ¼ 1000 1000
Z
t
C ad dt
ð1Þ
0
where Q and A are the flow rate (mL min1) and the area under the breakthrough curve, respectively. The metal removal (%) can be calculated from the ratio of column capacity (qc) to the amount of metal ions sent to the column (m) as:
%R ¼
qc 100 m
ð2Þ
The biosorption capacity q, the weight of Pb(II) adsorbed per unit dry weight of adsorbent (mg/g) can be determined as follows:
q ¼ qc =X
ð3Þ
where X is the total mass of the adsorbent in the column (g). Mass transfer zone (MTZ), which is defined as the length of the biosorption zone in the column, can be calculated from the equation (Nuic´ et al., 2013):
tb MTZ ¼ H 1 ts
ð4Þ
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Y. Long et al. / Bioresource Technology 152 (2014) 457–463 Table 1 Model equations applied for the prediction of the breakthrough curve. Model
Equation
Bohart–Adams
ln CCti
¼ K BA C i T K BA N 0 t
Thomas
lnðCCti
K T q0 m F
Yoon–Nelson
ln
Symbols representation Z
1Þ ¼
Ct C i C t
K T C i V eff F
¼ KYt KYs
Where Ct, Ci, KBA, N0, t, Z were concentration at time t, initial concentration, kinetic constant (L mg1 h1), biosorption capacity(mg L1), linear flow velocity (cm h1), bed height (cm), respectively. Where KT q0 F were rate constant (L mg1 h1), metal uptake capacity (mg g1), flow rate (L h1), respectively. Where KY is the rate constant (h1), s the time required for 50% sorbate breakthrough (h).
where MTZ is the length of the mass transfer zone (cm); H is the height of the biosorbent mixture bed (cm). 2.6. Theoretical models The modeling of the breakthrough curve was done through Bohardt–Adams, Thomas, and Yoon–Nelson models. The Bohart– Adams model proposed by Bohart and Adams (1920) was frequently applied for modeling the breakthrough curves for metal ions sorption (Mishra et al., 2013). The Thomas model (Thomas, 1948) was one of the most widely used models to describe the column performance and predict the breakthrough curve of metal sorption (Mishra et al., 2013). Yoon–Nelson model was based on the assumption that the rate of decrease in the probability of adsorption for each adsorbate molecule was proportional to the probability of adsorbate and the probability of adsorbate breakthrough on the adsorbent (Yoon and Nelson, 1984). Table 1 represents the equation of all the above-mentioned breakthrough models.
Fig. 1. Effect of different modifiers on Pb(II)biosorption. Notations: UW, ultrapure water; NaOH, sodium hydroxide; AC, ammonium citrate; SDS, sodium dodecyl sulfonate; DDBAB, dodecyl dimethyl benzyl ammonium bromide.
2.7. Statistical analysis All biosorption experiments were carried out in triplicate and the mean values were used in data analysis. All statistical analysis was done using Statistical Package for the Social Sciences (SPSS) 17.0 software and error bars representing the standard deviation were provided in figures wherever possible. Microsoft Excel 2010 program was also employed for data processing, and the linear regression method was used to determine the models’ parameters. 3. Results and discussion 3.1. Effect of modification Uptake of Pb(II) by A. bisporus that modified with chemical agents is given in Fig. 1. The biomass pretreated with ultrapure water (64.6 mg g1) enhanced 20.97% compared to the control group (53.4 mg g1) for the Pb(II) biosorption. The result could be attributed to the fact that some soluble organics, making little contribution to the removal of Pb(II), were released into water from native biomass during the treatment (Jing et al., 2011). However, A. bisporus modified with dodecyl dimethyl benzyl ammonium bromide performed worse than the control group. This might be interpreted that the charged sites provided by this cationic surfactant were suitable for the anion’s adsorption. Among the biomass modified with surface modifiers, NaOH-modified A. bisporus (NAB) showed the best performance with a sorption capacity of 86.4 mg g1, while the biosorption capacity of ammonium citrate and SDS were 69.1 mg g1 and 76.8 mg g1, respectively. Possibly, NaOH enhanced alkaline hydrolysis, simultaneously dissolved some components and increased swelling, to facilitate the sorption of Pb(II) onto A. bisporus surface (Vázquez et al., 2012; Velazquez-Jimenez et al., 2013). Higher biosorption efficiency of SDS-modified A. bisporus could be due to electrostatic
Table 2 Reported adsorption capacities (mg g1) for Pb(II) obtained on low-cost adsorbents in the literature. Adsorbent
Adsorption capacity
Reference
Allspice Modified N. zanardini Modifiedagave bagasse Green coconut shells Spirogyra neglecta Lemoncortex Modified A. bisporus Oedogonium sp. Mixture of algae waste and Purolite A-100 resin
16.2 51.83 54.29 54.62 55.71 77.6 86.4 145.0 157.2
Cruz-Olivares et al. (2013) Montazer-Rahmati et al. (2011) Velazquez-Jimenez et al. (2013) Sousa et al. (2010) Singh et al. (2012) Kelly-Vargas et al. (2012) This study Gupta and Rastog (2008) Bulgariu and Bulgariu (2013)
interactions between cationic metal ions and anionic SDS surfactant (Kumar and Gaur, 2011). For ammonium citrate modification, citric acid anhydride combined with the hydroxyl group to form an ester linkage and introduced a carboxyl group to the biosorbent. These additional carboxyl functional groups increased the bindings between modified biomass and positively charged metal ions (Wong et al., 2003). Biomass showed effective removal of Pb(II) after treated by NaOH, which was obtained by other investigators as well (Velazquez-Jimenez et al., 2013). Interestingly, except for Pb(II), modification by NaOH also appeared to enhance sorption capacity for other complexes, such as nickel and methylene blue (Wang et al., 2006). Reported adsorption capacities of low-cost adsorbents in the literature are summarized in Table 2. The Pb(II) adsorption capacity of NAB was 86.4 mg g1, which was superior to many other adsorbents.
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Fig. 2. Effect of flow rate on breakthrough curves (initial Pb(II) concentration: 50 mg L1, bed height: 4.0 cm, pH 5.5).
3.2. Characterization of adsorbents
column. The breakthrough curves at three different flow rates (1.0, 3.0, and 5.0 mL min1) illustrated in Fig. 2 showed that the breakthrough time and saturation time decreased with increasing flow rate (Table 3). The breakthrough time was 977.9, 260.7, and 145.0 min for 1.0, 3.0, and 5.0 mL min1 flow rates, respectively. A short breakthrough time at a high flow rate of metal solution was also reported (Jain et al., 2013; Singh et al., 2012). In this study, the percentage of metal removal decreased with the increase in flow rate; this might be due to less residence time of the solution through the column at a higher flow rate (Bulgariu and Bulgariu, 2013). The sorption capacity was less when the flow rate was high. It was generally considered that at a high flow rate, the residence period of metal ions in the column was very transitory, which cannot lead to the equilibrium of the sorption process (Maiti et al., 2009; Mona et al., 2013). Mass transfer zone (MTZ) increased with increasing flow rate; similar observation was reported by Bulgariu and Bulgariu (2013). Considering the results and the discussions above, the best performance was obtained at the lowest flow rate (1.0 mL min1). However, at this flow rate, the run time (the breakthrough time was up to 977.9 min) and energy costs were very high, so the flow rate of 3.0 mL min1 was chosen for the following experiments.
In order to examine the surface morphology of the biosorbents, SEM micrographs (at magnification 1000) were taken before and after modification. After modification, the biosorbent was characterized by an irregular and porous surface (Fig. S1 of Supplementary material). This might be interpreted that starch, proteins, and sugars from biomaterial were degraded or dissolved in the basification procedure. These irregular and porous surfaces are conducive to increase the specific surface area, thus enhance adsorption efficiency (Sillerova et al., 2013). The FTIR spectra of unmodified A. bisporus and NAB are shown in Fig. S2 of Supplementary material. A broad absorption peak was observed at 3401 cm1 for unmodified A. bisporus, and this was indicative of the presence of –OH groups and –NH groups (Luo et al., 2011). Peak at 2925 cm1 was expressive of stretching of C–H bond of methyl and methylene groups (Saha et al., 2012); The peak at 1652 cm1 represented –NH2 groups (Sillerova et al., 2013); peak at 1028 cm1 could be assigned to stretching vibration of C–OH of alcoholic groups and carboxylic acids (Sillerova et al., 2013). The intensity of transmittance of peaks was relatively more in the case of NAB compared with A. bisporus. The changes of peaks suggested that functional groups such as –NH, –OH, –CH, and –NH2 were involved in the process in modification. According to the BET analysis, NAB had a specific surface area of 1.55 m2 g1 with an average pore diameter of 5.23 nm.
3.3.2. Effect of initial concentration Effect of initial Pb(II) concentration (20, 50, and 100 mg L1) on performance of breakthrough curves at a constant bed height (4.0 cm) and flow rate (3.0 mL min1) is depicted in Fig. 3. The values of the experimental breakthrough parameters summarized in Table 3 indicated that the breakthrough time and exhaustion time were inversely related with influent Pb(II) concentration. In addition, at higher initial Pb(II) concentrations, the breakthrough curves were steeper with a longer MTZ. The steepness of curves is a measure of the efficiency of the column to reach saturation; the steeper the better for the column performance (Naja and Volesky, 2008). Cruz-Olivares et al. (2013) also reported a longer MTZ at higher initial metal concentrations. Nevertheless, many other researchers reported that as influent concentration increased, a shorter MTZ was obtained (Bulgariu and Bulgariu, 2013; Naja and Volesky, 2008). Biosorption capacity increased with increasing Pb(II) initial concentration. This could be explained by the fact that at the greater concentration, gradient caused a faster transport due to an increased diffusion coefficient or mass transfer coefficient (Samuel et al., 2013). These results demonstrated that the higher feed concentration could saturate the sorbent more quickly. Considering the concentration of real industrial wastewater, the concentration of 50 mg L1 was applied to the next experiments.
3.3. Parameters of the breakthrough curves
3.3.3. Effect of bed height The breakthrough profile of Pb(II) biosorption at different bed heights (2.0, 4.0, and 6.0 cm) are given in Fig. 4, and the values of the experimental breakthrough parameters are summarized in Table 3. The breakthrough time increased with the increase in bed
3.3.1. Effect of flow rate The flow rate is an important parameter as it determines the contact time of the sorbate with the biosorbent in a packed bed
Table 3 Parameters obtained from the breakthrough curves of the packed bed column for Pb(II) biosorption. F (mL/min)
H (cm)
Ci (mg L1)
tb (min)
qb (mg/g)
Rb (%)
ts (min)
qs (mg/g)
Rs (%)
MTZ (cm)
3.0 3.0 3.0 3.0 3.0 1.0 5.0
4 4 4 2 6 4 4
20 100 50 50 50 50 50
649 135.1 260.7 128.7 379.6 977.9 145
48.2 50.3 48.2 47.3 46.9 60.8 44.5
99.1 99.3 98.6 98.0 98.8 99.5 98.3
898 232.8 411.5 234.4 565.1 1166.4 245.8
57.6 68.1 62.3 67.0 33.1 66.7 60.2
85.4 78.0 80.7 76.2 46.8 91.5 78.4
1.1 1.7 1.5 0.9 2.0 0.6 1.6
Notations: F, flow rate; H, bed height; tb, ts, the time at breakthrough and saturation point; qb, qs, biosorption capacity at breakthrough and saturation time; Rb, Rs, the removal percent at breakthrough and saturation point; MTZ, the length of mass transfer zone.
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ever, many researchers found a positive correlation between the sorption capacity and bed height (Jain et al., 2013; Kumar et al., 2011). Their explanation was that the longer contact time between metal ions and available biomass in column result in higher sorption capacity. Higher bed height provided a longer residence period of metal ions in the column, thus, a larger volume of metal solution could be treated. Nevertheless, considering the low sorption capacity at a bed height of 6.0, 4.0 cm was chosen as the optimum bed height. 3.4. Modeling of the breakthrough curves The Bohart–Adams model was applied to the initial part (Ct/ Ci = 0–0.5) of the breakthrough curves of Pb(II) sorption, and the values of characteristic parameters are summarized in Table 4. The correlation coefficients (R2) values were found to be above 0.9815 for all breakthrough curves. The biosorption capacity of the bed (N0) increased with increasing initial metal concentration, but decreased with increasing flow rate, and bed height. In addition, the kinetic constant (KBA) decreased with increasing influent metal concentration and bed height; and yet it increased with increasing flow rate. Therefore, under these conditions, for better capacity of the column (N0) and lower kinetic constant (i.e., minimum resistance), the initial Pb(II) concentrations need to be higher while the flow rate should be lower. Bohart–Adams model provides a comprehensive and simple approach to running and evaluating adsorption performance. However, its validity is limited by the range of conditions used. Thomas and Yoon–Nelson models were applied to the breakthrough curves, and the values of characteristic parameters are listed in Table 4. The Thomas rate constant (KT) increased with increasing flow rate, nevertheless; it reduced with increasing flowing metal concentration and bed height. The maximum solid phase concentration (q0) increased with increasing influent metal concentration, but it reduced with increasing bed height and flow rate. The Yoon–Nelson model rate constant (KY) was higher at higher flow rate, higher influent concentration, lower bed height; however, s, the time required for 50% breakthrough, was higher at lower flow rate, lower influent concentration, and higher bed height. In a comparison of values of R2(R2 P 0.9911 for all breakthrough curves) and breakthrough curves, both Thomas and Yoon–Nelson models could be used to describe the behavior of the biosorption of Pb(II) in a packed bed column under different experimental conditions.
Fig. 3. Effect of initial Pb(II) concentration on breakthrough curves (flow rate: 3.0 mL min1, bed height: 4.0 cm, pH 5.5).
Fig. 4. Effect of bed height on breakthrough curves (flow rate: 3.0 mL min1, initial Pb(II) concentration: 50 mg L1, pH 5.5).
height from 102 min (2.0 cm) to 299.5 min (6.0 cm). Similarly, the requirement of metal solution for attaining the breakthrough and saturation point was concomitantly increased with increasing bed height. This might be due to availability of more metal binding sites at taller bed heights for sorption and resulting in a higher MTZ (Jain et al., 2013; Mishra et al., 2013). In the present study, the metal removal efficiency increased with the increase in bed heights, but the sorption capacity was not greatly affected by bed height. This might be due to that metal availability was unlimited in the column (Singh et al., 2012). How-
3.5. Successive cycles of sorption and desorption by column For the sorption process to be viable, efficient regeneration, and reuse of the NAB bed is necessary. It was observed that 0.1 M HNO3 did not obviously affect the structure and metal sorption ability of NAB (Table S1 provided with the Supplementary material).The
Table 4 Bohart–Adams, Thomas and the Yoon–Nelson models parameters for the sorption of Pb(II) by the NAB-packed column. Conditions
Bohart–Adams
Thomas 2
Yoon-Nelson 2
F
H
Ci
KBA
N0
R
KT
q0
R
KY
s
R2
3.0 3.0 3.0 3.0 3.0 1.0 5.0
4 4 4 2 6 4 4
20 100 50 50 50 50 50
0.0455 0.0249 0.0301 0.0444 0.0256 0.0242 0.0470
6173.32 7373.77 6814.00 7420.40 6253.50 6995.72 6633.46
0.9943 0.9948 0.9977 0.9966 0.9929 0.9815 0.992
0.0514 0.0268 0.0344 0.0501 0.0280 0.0265 0.0509
57.72 68.79 63.06 67.72 59.16 66.76 61.05
0.9978 0.9994 0.9995 0.9985 0.9988 0.9911 0.9982
1.0276 2.6796 1.7205 2.5559 1.3981 1.3274 2.5472
12.83 3.06 5.60 3.01 7.89 17.80 3.26
0.9978 0.9994 0.9995 0.9985 0.9988 0.9911 0.9982
Notations: F, flow rate; H, bed height; KBA, Bohart–Adams rate constant (L mg1h1); N0, saturation concentration (mg l1), KT, Thomas rate constant (L mg1 h1); q0, equilibrium metal sorption (mg g1); KY, Yoon–Nelson rate constant (h1); s: the time required for 50% sorbate breakthrough (h).
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Table 5 Characteristics of industrial wastewater before and after passing through NAB-packed column at a flow rate of 3.0 mL min1. Quality parameter (mg/L)
Initial wastewater
Treated wastewater
Maximum permissible concentration
COD BOD Phosphate Nitrate Pb(II) Cu(II) Ni(II) Cd(II) Zn(II) Cr(VI)
1083 725 1.26 17.2 35.15 2.82 1.58 2.25 33.6 3.75
330 187 0.72 9.4 0.23 0.48 0.41 0.03 1.26 0.5
500 300 1.0 20 0.2 0.5 0.5 0.05 1.5 0.2
Acknowledgements This study was financially supported by the Science and Technology Supportive Project of Sichuan Province, China (No. 2013SZ0062), Science and Technology Supportive Project of Chengdu (No. 12DXYB087JH-005) and NSFC (No. J1103518). The authors wish to thank Professor Guanglei Cheng and Dong Yu from the Sichuan University for their technical assistance. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.biortech.2013. 11.039. References
amount of Pb(II) sorbed by the column in the first cycle was 60.8 mg g1 dry weight. Regeneration efficiency (%) decreased with the cycle progress, and yet the desorption of sorbed Pb(II) was still approximately 90% after three cycles. Similar high efficiencies of desorption were reported in other literatures (Gupta and Rastogi, 2008; Samuel et al., 2013). Incomplete desorption of metal ions seems to be an important reason for decrease in metal sorption capacity of the column during successive cycles of sorption and desorption. The biosorbent was put into a biogas digester for fermentation after being exhausted. Heavy metals were extracted from biogas slurry by chemical precipitation and flocculation, and then, the biogas residues containing heavy metals were disposed of via landfill. 3.6. Applicability of column in treating industrial wastewater The characteristics of industrial wastewater before and after passing through the packed bed column are presented in Table 5. More than 99% Pb(II) was removed from 300 mL wastewater, and the concentrations of Cu(II), Ni(II), Cd(II), and Zn(II) were decreased under maximum permissible concentration according to the National Standards of PRC (GB 21900-2008). The results accorded with the findings of Cao, and in a multi-metal system, lead ions could be prior removed from wastewater in the presence of other metal ions (Cu, Cd) (Cao et al., 2010). Overall, the metals of the treated wastewater were in acceptable range except for Cr(VI). This was probably because Cr(VI) mostly exists in its anion form (Jing et al., 2011), but the sites provided by NaOH modified biomass were more suitable for cationic adsorption. In addition, biological oxygen demand (BOD), chemical oxygen demand (COD), phosphate, and nitrate were decreased obviously. The results demonstrated that the NAB could remove multi-metal and organics from wastewater.
4. Conclusion NaOH-modified A. bisporus showed best performance in removing Pb(II) with an adsorption capacity of 86.4 mg g1. FTIR and SEM have been applied to analyze the characterization of A. bisporus and NAB. Pb(II) biosorption performance of the column packed with NAB largely depended on flow rate, influent metal concentration, and bed height. Bohart–Adams, Thomas, and Yoon–Nelson models successfully predicted breakthrough curves obtained under varying experimental conditions. NAB showed good reusability in the bed column during five biosorption–desorption cycles. The NABpacked column could efficiently remove several metal ions and also concomitantly remove some organics from real industrial wastewaters.
Bohart, G., Adams, E., 1920. Some aspects of the behavior of charcoal with respect to chlorine.1. J. Am. Chem. Soc. 42, 523–544. Bulgariu, D., Bulgariu, L., 2013. Sorption of Pb(II) onto a mixture of algae waste biomass and anion exchanger resin in a packed-bed column. Bioresour. Technol. 129, 374–380. Cao, Y.R., Liu, Z., Cheng, G.L., Jing, X.B., Xu, H., 2010. Exploring single and multimetal biosorption by immobilized spent Tricholoma lobayense using multi-step response surface methodology. Chem. Eng. J. 164, 183–195. Cruz-Olivares, J., Pérez-Alonso, C., Barrera-Díaz, C., Ureña-Nuñez, F., ChaparroMercado, M.C., Bilyeu, B., 2013. Modeling of lead(II) biosorption by residue of allspice in a fixed-bed column. Chem. Eng. J. 228, 21–27. Gupta, V.K., Rastogi, A., 2008. Biosorption of lead(II) from aqueous solutions by nonliving algal biomass Oedogonium sp. and Nostoc sp. – a comparative study. Colloids Surf. B: Biointerfaces 64, 170–178. Jain, M., Garg, V.K., Kadirvelu, K., 2013. Cadmium(II) sorption and desorption in a fixed bed column using sunflower waste carbon calcium-alginate beads. Bioresour. Technol. 129, 242–248. Jing, X., Cao, Y., Zhang, X., Wang, D., Wu, X., Xu, H., 2011. Biosorption of Cr(VI) from simulated wastewater using a cationic surfactant modified spent mushroom. Desalination 269, 120–127. Kelly-Vargas, K., Cerro-Lopez, M., Reyna-Tellez, S., Bandala, E.R., Sanchez-Salas, J.L., 2012. Biosorption of heavy metals in polluted water, using different waste fruit cortex. Phys. Chem. Earth 37–39, 26–29. Kumar, D., Gaur, J.P., 2011. Metal biosorption by two cyanobacterial mats in relation to pH, biomass concentration, pretreatment and reuse. Bioresour. Technol. 102, 2529–2535. Kumar, R., Bhatia, D., Singh, R., Rani, S., Bishnoi, N.R., 2011. Sorption of heavy metals from electroplating effluent using immobilized biomass Trichoderma viride in a continuous packed-bed column. Int. Biodeter. Biodegr. 65, 1133–1139. Laohaprapanon, S., Marques, M., Kaczala, F., Hogland, W., 2013. Packed-column of granular activated carbons for removal of chemical oxygen demand from industrial wastewater. Clean – Soil Air Water 41, 244–250. Luo, X., Deng, Z., Lin, X., Zhang, C., 2011. Fixed-bed column study for Cu2+ removal from solution using expanding rice husk. J. Hazard. Mater. 187, 182–189. Maiti, S.K., Bera, D., Chattopadhyay, P., Ray, L., 2009. Determination of kinetic parameters in the biosorption of Cr(VI) on immobilized Bacillus cereus M116 in a continuous packed bed column reactor. Appl. Biochem. Biotechnol. 159, 488–504. Mishra, V., Balomajumder, C., Agarwal, V.K., 2013. Adsorption of Cu(II) on the surface of nonconventional biomass: a study on forced convective mass transfer in packed bed column. J. Waste Manage. 2013, 1–8. Mona, S., Kaushik, A., Kaushik, C.P., 2013. Prolonged hydrogen production by Nostoc in photobioreactor and multi-stage use of the biological waste for column biosorption of some dyes and metals. Biomass Bioenerg. 54, 27–35. Mondal, M.K., 2009. Removal of Pb(II) ions from aqueous solution using activated tea waste: adsorption on a fixed-bed column. J. Environ. Manage. 90, 3266–3271. Montazer-Rahmati, M.M., Rabbani, P., Abdolali, A., Keshtkar, A.R., 2011. Kinetics and equilibrium studies on biosorption of cadmium, lead, and nickel ions from aqueous solutions by intact and chemically modified brown algae. J. Hazard. Mater. 185, 401–407. Muraleedharan, T., Venkobachar, C., Leela, I., 1994. Investigations of fungal fruiting bodies as biosorbents for the removal of heavy metals from industrial processing streams. Sep. Sci. Technol. 29, 1893–1903. Naja, G., Volesky, B., 2008. Optimization of a biosorption column performance. Environ. Sci. Technol. 42, 5622–5629. Nuic´, I., Trgo, M., Peric´, J., Vukojevic´ Medvidovic´, N., 2013. Analysis of breakthrough curves of Pb and Zn sorption from binary solutions on natural clinoptilolite. Microporous Mesoporous Mater. 167, 55–61. Saha, P.D., Chakraborty, S., Chowdhury, S., 2012. Batch and continuous (fixed-bed column) biosorption of crystal violet by Artocarpus heterophyllus (jackfruit) leaf powder. Colloids Surf. B: Biointerfaces 92, 262–270. Samuel, J., Pulimi, M., Paul, M.L., Maurya, A., Chandrasekaran, N., Mukherjee, A., 2013. Batch and continuous flow studies of adsorptive removal of Cr(VI) by adapted bacterial consortia immobilized in alginate beads. Bioresour. Technol. 128, 423–430.
Y. Long et al. / Bioresource Technology 152 (2014) 457–463 Sillerova, H., Komarek, M., Chrastny, V., Novak, M., Vanek, A., Drabek, O., 2013. Brewers draff as a new low-cost sorbent for chromium(VI): comparison with other biosorbents. J. Colloid Interface Sci. 396, 227–233. Singh, A., Kumar, D., Gaur, J.P., 2012. Continuous metal removal from solution and industrial effluents using Spirogyra biomass-packed column reactor. Water Res. 46, 779–788. Soliman, E.M., Ahmed, S.A., Fadl, A.A., 2011. Reactivity of sugar cane bagasse as a natural solid phase extractor for selective removal of Fe(III) and heavy-metal ions from natural water samples. Arab. J. Chem. 4, 63–70. Sousa, F.W., Oliveira, A.G., Ribeiro, J.P., Rosa, M.F., Keukeleire, D., Nascimento, R.F., 2010. Green coconut shells applied as adsorbent for removal of toxic metal ions using fixed-bed column technology. J. Environ. Manage. 91, 1634–1640. Thomas, H.C., 1948. Chromatography: a problem in kinetics. Ann. N Y. Acad. Sci 49, 161–182. Vázquez, G., Mosquera, O., Freire, M.S., Antorrena, G., González-Álvarez, J., 2012. Alkaline pre-treatment of waste chestnut shell from a food industry to enhance cadmium, copper, lead and zinc ions removal. Chem. Eng. J. 184, 147–155.
463
Velazquez-Jimenez, L.H., Pavlick, A., Rangel-Mendez, J.R., 2013. Chemical characterization of raw and treated agave bagasse and its potential as adsorbent of metal cations from water. Ind. Crop. Prod. 43, 200–206. Vimala, R., Das, N., 2009. Biosorption of cadmium(II) and lead(II) from aqueous solutions using mushrooms: a comparative study. J. Hazard. Mater. 168, 376– 382. Wang, S., Soudi, M., Li, L., Zhu, Z.H., 2006. Coal ash conversion into effective adsorbents for removal of heavy metals and dyes from wastewater. J. Hazard. Mater. 133, 243–251. Wong, K.K., Lee, C.K., Low, K.S., Haron, M.J., 2003. Removal of Cu and Pb by tartaric acid modified rice husk from aqueous solutions. Chemosphere 50, 23–28. Xu, H., Chen, Y., Huang, H., Liu, Y., Yang, Z., 2013. Removal of lead(II) and cadmium(II) from aqueous solutions using spent Agaricus bisporus. Can. J. Chem. Eng. 91, 421–431. Yoon, Y.H., Nelson, J.H., 1984. Application of gas adsorption kinetics I. A theoretical model for respirator cartridge service life. Am. Ind. Hyg. Assoc. J. 45, 509–516.
