Chemosphere 111 (2014) 18–23
Contents lists available at ScienceDirect
Chemosphere journal homepage: www.elsevier.com/locate/chemosphere
Influence of mixture ratio and pH to solidification/stabilization process of hospital solid waste incineration ash in Portland cement Elzbieta Sobiecka a,⇑, Andrzej Obraniak b, Blanca Antizar-Ladislao c a
Lodz University of Technology, Institute of General Food Chemistry, ul. Stefanowskiego 4/10, 90-924 Lodz, Poland Lodz University of Technology, Faculty of Process and Environmental Engineering, ul. Wolczanska 213, 90-924 Lodz, Poland c The University of Edinburgh, Institute for Infrastructure and Environment, School of Engineering, Mayfield Road, Edinburgh EH9 3JL, United Kingdom b
h i g h l i g h t s Two solidification/stabilization processes of hospital solid waste incinerator ash were compared. The influence of ratio mixture to the products stabilization was investigated. The Influence of pH solution to chemical stability of immobilized hazardous waste was sought. Cement hydration process, equal mixture of waste and Portland cement and weak alkaline pH favoured the treatment.
a r t i c l e
i n f o
Article history: Received 17 January 2013 Received in revised form 6 March 2014 Accepted 15 March 2014
Handling Editor: Klaus Kümmerer Keywords: Physico-chemical waste utilization Ash from hospital incinerator Metal leachability Metal immobilization
a b s t r a c t Solidification/stabilization (S/S) is an established utilization technology to treat hazardous wastes. This research explored the influence of pH (3–12) on the immobilization of heavy metals present in five mixtures of hospital solid waste incinerator ash and Portland cement, following two different processes of waste solidification/stabilization (cement hydration and granulation). In general, cement hydration process resulted in more stable products than granulation process. A high ash content in the mixture with Portland cement (60 wt%) resulted in the highest immobilization of Pb2+ and Cu2+, while a low ash content in the mixture (10 wt%) resulted in the lowest leachability of Zn2+. When ash and Portland cement was mixed in equal proportions (50 wt%) the highest encapsulation was observed for Ni2+, Cd2+ and Cr3+. Neutral and weak alkaline pH values within the range pH = 7–8 resulted in the lowest leachability of the monitored heavy metals. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction The main purpose of the hazardous waste management is to minimize their environmental impact. This kind of the research is very important in Poland and other countries of this European region where the landfill still dominates in the national strategy of waste management. Solidification/stabilization (S/S) is an established utilization technology to treat hazardous wastes. Solidification and stabilization are each distinct technologies: solidification refers to processes that encapsulate a waste to restrict contaminant migration and can be accomplished by a chemical reaction between a waste and binding (solidifying) reagents or by mechanical processes; and stabilization refers to processes that involve chemical reactions that reduce the leachability of a waste (Adaska et al., 1991). Typical ⇑ Corresponding author. Tel.: +48 42 6313416; fax: +48 42 6362860. E-mail address: [email protected] (E. Sobiecka). http://dx.doi.org/10.1016/j.chemosphere.2014.03.057 0045-6535/Ó 2014 Elsevier Ltd. All rights reserved.
binders include, but are not limited to, cement, thermoplastic materials, organic polymers and lime (Roy et al., 1992; Ilic and Polic, 2005). Portland cement – the main component used in the process of concrete production to obtain chemically and physically stable product – has commonly used to treat more contaminated wastes (Lombardi et al., 1998; Shi and Spence, 2004; Genazzini et al., 2005; Batchelor, 2006; Gidarakos et al., 2009). S/S is one of the physico-chemical pre-landfill treatment processes that can be used for hospital solid waste incinerator (HSWI) ash, which requires a special utilization as the hazardous waste listed in the European Catalogue on Hazardous Waste (European Commission Decision, 2000), codes 10.01.16 and 19.01.13. This criteria and related procedures were forced in 2003, European Council Decision 2003/33/EC (2003). Prior studies have focused on the characteristics of waste materials and the products and potential harmful effect to the environment. Special attention has been given to the chemical stabilization of the products, and in particular the leachability of
19
E. Sobiecka et al. / Chemosphere 111 (2014) 18–23
heavy metals under different pH values (Aubert et al., 2007; Cetin et al., 2012). The effect of pH is important as the environment surrounding landfill area influences the natural biodiversity and has its origin in leachability of collected waste. The monitoring of the end products behaviour in different pH solutions allows estimating the most advantageous condition for the waste storage. It would be also useful in set up the proper composition of the raw material to obtain the highest effect of waste immobilisation (Ibáñez et al., 2000). The overall aim of the study was to investigate the efficiency of S/S technology to treat HSWI ash. The objectives were twofold: firstly, to investigate the effect of ratio of Portland cement to ash on the chemical stabilization of the final products using two solidification processes, cement hydration (S1) and granulation (S2); and secondly, to investigate the effect of pH on the encapsulation of heavy metals listed in Council Decision (2003)/33/EC (2003) and stabilization of the final products.
2.3.2. Leachability Leaching tests were conducted according to European Standards, method 14429 (2005). The concentration of heavy metals in the waste samples and associated stabilized waste products obtained following processes S1 and S2, respectively, was measured after 48 h of exposure to water. Leaching tests were conducted with each sample with natural water solutions at constant pH values ranging from pH = 3 to pH = 12. Three replicates were conducted for each leaching test.
2. Material and methods
2.4. Data analysis
2.1. Ash samples
The effect of the mixture ratio of HSWI ash to Portland cement and pH on heavy metals’ leachability of S/S treated samples using two different stabilization process was investigated using a oneway ANOVA analysis with Microsoft Excel 2003.
The ash used in this study was collected from a hospital waste incineration plant in the Province of Lodz, central Poland. The collected samples were grate ashes and chimney filter fly ashes.
and water was 0.5. The samples were then exposed during 48 h to air at 25 °C. A disc granulator was used to prepare waste samples used for S2, set up with the following parameters: rotational velocity of the granulator disc, n = 10 r.p.m.; angle of the granulator disc axis inclination, a = 50°; mass of loose material 500 g; liquid volume of flow rate, Q = 3,6 ml/min; granulation wetting time, t = 15 min.
3. Results and discussion 2.2. Chemical analyses 2.2.1. Hospital ash composition The concentration of heavy metals present in HSWI ash was determined by Atomic Absorption Spectrometer GBC 932 Plus (air-acetylene flame), according to European Standard 12457 (2002). Carbon, hydrogen and sulphur in HSWI ash was determined by EA 1108 CHNS-O Analyzer Fisons Instrument equipped with an auto-sampler and Thermal Conductive Detector (TCD); the instrument was calibrated with a 2,5-Bis-(5-tert-butyl-benzoxazol-2-yl)-thiophen standard (BBOT; CAS Number: 7128-64-5). 2.2.2. X-ray diffraction analysis X-ray diffraction (XRD) studies were carried out on powdered samples by PANalytical Model X’Pert PRO MPD using Cu Ka radiation source in the 2h range from 5° to 90° at 40 kV and 40 mA. Crystalline phases were identified according to the International Centre of Diffraction Data PDF-2. 2.2.3. Metals analysis Metal concentrations of natural water extracts at pH solutions with the range pH = 3–12, were measured by Atomic Absorption Spectrometer GBC 932 Plus (air-acetylene flame) according to European Standard 12457 (2002). 2.3. Experiments 2.3.1. Solidification Commercially available Portland cement I 42.5 R (Cement Lafarge S.A., Poland) was used as binder for the purpose of this study. Five different mixtures of HSWI ash and Portland cement were prepared (samples A–E), with the following ash load (percentage given in dry weight): sample A, 10 wt%; sample B, 20 wt%; sample C, 40 wt%; sample D, 50 wt%; sample E, 60 wt%. The residual composition of the samples was the Portland cement only. The final products were prepared using two different solidification processes: cement hydration (S1) and a granulation (S2). Waste samples used for S1 consisted of HSWI fly ash, Portland cement and water. The ratio of the solid part of the initial mixture
Migration of toxic substances in the subsoil, following extreme whether events, such as storms or rainfalls is of current concern. The presence of various aggressive agents, i.e. sulphates, chlorides, etc. in the subsoil is common, and may result in pH changes of solutions surrounding contaminated sites or landfill sites, which will initiate numerous chemical reactions (Rendell and Jauberthie, 1999). S/S is an environmental technology that can be used to improve the stabilization of hazardous wastes once stored in landfill sites. Prior research has indicated that the composition of wastes treated using S/S has a major impact in the properties of the final product (Hong and Glasser, 1999). The chemical analyses of the HSWI ash used in this study showed that silica, calcium, and aluminium were present at the highest concentrations (Table 1). The oxide forms of these three constituents made up ca. 75 wt% dry mass (d.m.) of the total mass of the HSWI ash. These results were confirmed by XRD analysis (Fig. 1).
Table 1 Chemical composition of HSWI ash and Portland cement. Compound
HSWI ash (wt% d.m.)
Portland cement (wt% d.m.)
SiO2 Al2O3 CaO Fe2O3 K2O MgO Na2O ZnO MnO CuO PbO BaO CrO NiO CoO CdO Ctotal S H
48.60 16.80 10.10 4.11 1.07 0.99 0.73 0.58 0.18 0.03 0.02 0.02 0.02 0.01 0.01 0.01 8.60 4.30 0.63
18.9 5.3 62.7 2.7 – 1.5 0.73 – – – – – – – – – – 1.25 –
E. Sobiecka et al. / Chemosphere 111 (2014) 18–23
Intensity (counts)
20
Anhydrite CaSO4
4000
3000
Quartz SiO2 Calcite CaCO3
2000
Halite NaCl Tricalcium aluminate Ca3Al2O6 1000
0
10
20
30
40
50
60
70
Fig. 1. XRD analysis of HSWI ash.
These results suggested that the HSWI ash used in this study it can be classified as a pozzolan, which is one of two main components used in the production of concrete (Poon et al., 2003). The other component used in the production of concrete is cement, and for the purpose of this study commercially available Portland cement (Table 1) was used as a binder. Once HSWI and Portland cement were characterized, the effect of Portland cement addition to HSWI ash on the stabilization of heavy metals in the S/S process was then investigated. Both solidification processes used in this study resulted in the production of a calcium silicate hydrate (C–S–H) gel created on the surface of the stabilized samples, similarly to what would occur and would influence the stability of minerals under environmental conditions (Tiruta-Barna et al., 2004). This C–S–H gel generated at the surface acts as a barrier between the immobilized solid wastes and the surrounding liquids, and controls the potential adsorption of ions present in the liquids onto the surface of the solid wastes as well as the immobilization of heavy metals in the resulting products (Glasser, 1997). These processes are influenced by chemical reactions which are dependent of the pH of the surrounding liquids and the Ca/Si ratio in the HSWI ash and Portland cement (Asavapist et al., 1997). Based on the chemical composition of HSWI ash and Portland cement (Table 1), Ca/Si ratios were calculated for the different mixtures prepared in this study (samples A to sample E, with HSWI ash loads ranging from 10 wt% to 60 wt%, respectively), and the values obtained were: sample A, 3.0; sample B, 2.3; sample C, 1.4; sample D, 1.1; and sample E, 0.9. These values indicated that the higher the HSWI ash content, the lower the Ca/Si ratio. It is well known that in order to obtain stable products, chemical reactions should be minimized, which occurs when the surface charge of C–S–H gel generated at the surface of the products is ca. zero and this is achieved at a Ca/Si ratio ca. 1.2 (Glasser, 1993; Maschio et al., 2011). Sample D, with a HSWI ash loading of 50 wt% presented a Ca/Si ratio of 1.1, and therefore a low chemical activity was expected on the surface of these samples. Samples A, B, C presented a higher Ca/Si ratio (>1.2), and with a positive surface charge suggested that anions could adsorbed onto the surface of these samples. Samples E, with a lower Ca/Si ratio (0.9), with a negative surface charge suggested that cations could be adsorbed onto the surfaces of these samples. Six heavy metals ions, Pb2+, Cu2+, Cd2+, Zn2+, Cr3+ and Ni2+ monitored in the HSWI ash, Portland cement and stabilized waste
(Council Decision 2003/33/EC). These cations may go under complex chemical reactions under different environmental conditions. In general, they all can form sulphites, hydroxides (alkaline solutions) (Kern and Gale, 2000). Additionally, Cu2+, Cd2+, Ni2+, can be present as simple cations in both, acidic and strong alkaline solutions; Zn2+, Cr3+ and Pb2+ are ampholytic elements and they can be present as simple cations in acidic solution or they can form complex ions, e.g., ZnO22 , CrO2 , PbO22 , in strong alkaline solutions (Valls and Vázquez, 2000; Batchelor, 2006; Galiano et al., 2010). As the liquid phase surrounding the products of S/S technology once deposited in a landfill site can penetrate the pore structure of the solidified waste, various chemical reactions may occur (Li et al., 2001; Glasser and Zhang, 2001), resulting in the leaching of heavy metals, which generally is defined as the extraction of soluble components of a solid mixture by percolating a solvent through it (Daintith, 1996). The results of leaching tests conducted in this study (Table 2) indicated that the higher the load of HSWI ash in the mixtures the higher the concentration of Zn2+ and Cd2+ in the leachate; the opposite occurred for the rest of the heavy metals under investigation. The chemical stabilization of wastes treated by S/S is affected by the presence of aggressive reagents, further influenced by pH changes in surrounding solutions. It has been reported that chemical immobilization of the pollutants in both solidification and stabilization processes depends on the crystalline phase of a binder matrix (Glasser, 1997; Zheng et al., 2010). It is suggested that Portlandite, a naturally occurring mineral (Ca(OH)2) present in the Portland cement used in this study at high concentrations (Table 1) acted as a buffer at the surface of the waste, and influenced the leaching of heavy metals in this study. In fact, prior studies have indicated that Portlandite limited the chemical interactions between the contaminants and the surface of the stabilized waste, resulting in a significant reduction of leachability of heavy metals in a weak alkaline solution (Shi and Fernández-Jiménez, 2006). The effect of pH solutions on the leachability of heavy metals (i.e., stability) in samples A through E, solidified wastes using two processes: cement hydration (S1) and a granulation (S2) is presented in Figs. 2 and 3. Table 3 has compiled the probability value (p-value) for each metal in the stabilized forms prepared in processes S1 or S2. The results of this study indicated that, in general, wastes solidified using S1 process were more stable chemically than the same
21
E. Sobiecka et al. / Chemosphere 111 (2014) 18–23 Table 2 Leachability of heavy metals from different composition of mixtures of wastes. Analyzed metal
Leachability of heavy metals from different composition of mixtures of wastes liquid to solid ratio = 10 (mg kg HSWI ash
Zn Pb Cu Ni Cd Cr
440.94 18.34 22.46 10.15 9.17 10.43
Portland cement
1
d.m)
Mixtures of HSWI ash and Portland cement
97.33 27.33 34.67 19.67 4.00 34.33
A
B
C
D
E
131.69 26.43 33.45 18.72 4.52 31.94
166.05 25.53 32.23 17.76 5.03 29.55
234.78 23.74 29.78 15.86 6.07 24.77
269.14 22.84 28.56 14.91 6.59 22.38
303.50 21.94 27.34 13.96 7.10 19.99
Note: Load of the HSWI ash in the mixture: sample A, 10 wt%; sample B, 20 wt%; sample C, 40 wt%; sample D, 50 wt%; sample E, 60 wt%; HSWI ash, 100 wt%; Portland cement, 0 wt%.
Zn (S2)
Pb (S2) A
D E
50
20
B
15
C D
10
E
4
5
6
7
8
9 10 11 12
3
pH
B
15
C D
10
E
0
0 3
20
5
5
0
4
5
6
7
Zn (S1)
8
9 10 11 12
3
pH
4
5
6
7
Pb (S1)
150
25
A
B
20
B
C 100
D E
50
8
9 10 11 12
pH
Cu (S1)
A
C [mg/kg d.m.]
200
C [mg/kg d.m.]
A
A
C
15
D 10 E
15
A B
C [mg/kg d.m.]
C [mg/kg d.m.]
C 100
C [mg/kg d.m.]
B
150
Cu (S2) 25
25
C [mg/kg d.m.]
200
10
C D
5
E
5
0
0
0 3
4
5
6
7
8
9 10 11 12
pH
3
4
5
6
7
8
9 10 11 12
pH
3
4
5
6
7
8
9 10 11 12
pH
Fig. 2. Leachability of Zn, Pb and Cu from the samples of hydration (S1) and granulation (S2) processes.
wastes solidified using S2. Statistical analysis (Table 3) indicated that the HSWI ash to Portland cement mixture ratio had no significant effect on the leaching of Zn2+, Ni2+, Pb2+ and Cd2+ (p-value < 0.05). However, using the solidification process S2 indicated that the HSWI ash to Portland cement mixture ratio had a significant effect (p-value > 0.05). The leaching of Cr3+ and Cu2+ was comparable in the wastes solidified using S1 and S2 processes, and depended on the ratio composition of waste material and the binder. The influence of pH on the stability of solidified wastes using processes S1 and S2 was systematically investigated. The results of this research indicate that solidification S1 results in products more chemically stable and less influenced by pH changes than products obtained using solidification S2 (Figs. 2 and 3). For both solidification processes, low pH values resulted in a lower immobilization of heavy metals, while the highest immobilization was observed for pH values within the range pH = 7–8. Higher pH values (alkaline solution) resulted in an increased leachability. These results indicated that at low pH values (acidic solution) metals ions exist as soluble forms, when pH increases and reaches neutral to low alkaline values, insoluble hydroxides are formed with results in a higher immobilization of the heavy metals. As the pH increases to higher values, in the alkaline range, heavy metals form complex ions which are leached back from the solidified forms of waste into
solution. Waste solidified using process S2 indicated that samples with at HSWI ash to Portland cement of 60 wt% presented the highest leachability, indicating the influence that mixing ratios might have on the chemical stability of a final product. It was hypothesised that the addition of Portland cement to HSWI ash influences the stability of the solidified product. From the chemical composition of Portland cement (Table 1) it was observed that calcium was present at high concentration levels, and it is known that calcium is one of two main elements responsible for the C–S–H gel appearance on the surface of the solidified waste. In sample E (60 wt%), Ca/Si ratio was 0.9 which would result in a negative charge of the surface area, active to chemical reactions. In an alkaline solution, positive charged heavy metals encapsulated in the solidified waste migrated through the porous structure to the surface, and subsequently leached out to the surrounding solution as hydroxide ions. In an acidic solution, a negative charged C–S–H gel surface reacted with the ions in the surrounded solution. Subsequently the C–S–H gel barrier between the surrounding solution and the solid phase shrank and caused a reduction of the solidified waste stability, resulting in leaching out of heavy metals. Following both stabilization processes, best results were obtained for mixtures with a HSWI ash to Portland cement of 10 wt% HSWI ash (and 90 wt% Portland cement). At pH level within the range pH = 7–8 best immobilization results were obtained.
22
E. Sobiecka et al. / Chemosphere 111 (2014) 18–23
Ni (S2)
C
10
D 5
E
0 3
4
5
6
7
8
9 10 11 12
A
8 C [mg/kg d.m.]
B 6
C
4
D E
2 0
pH
A
3
4
5
6
7
Ni (S1)
8
9 10 11 12
6
C D
4
3
2 0 8
4
5
6
7
9 10 11 12
pH
8
9 10 11 12
pH
Cr (S1)
B
2
C D 1
E
7
E
A C [mg/kg d.m.]
B
6
D
15
A
8
5
C
10
0
pH
3
4
B
Cd (S1)
10
3
15
5
A C [mg/kg d.m.]
C [mg/kg d.m.]
B
20
C [mg/kg d.m.]
A 15
C [mg/kg d.m.]
Cr (S2)
Cd (S2) 10
20
B
10
C D
5
E
0
E 0
3
4
5
6
7
8
9 10 11 12
pH
3
4
5
6
7
8
9 10 11 12
pH
Fig. 3. Leachability of Ni, Cd and Cr from the samples of hydration (S1) and granulation (S2) processes.
study has also shown that pH of surrounding solutions significantly affect the leachability of six heavy metals investigated. The lowest leachability values were observed at pH values within the range pH = 7–8.
Table 3 P-value of the experiments. Metal
P-value S1
Zn Pb Cu Ni Cd Cr
5.39 10 7.60 10 0.26 2.60 10 3.65 10 0.64
S2 6 11
5 11
0.12 1.10 10 0.48 0.59 0.18 0.96
5
Overall, this systematic experimental research provides relevant information regarding effective strategies for storage of hazardous materials. In particular, the obtained results identified operational parameters (i.e., mixture rate, pH value, solidification process) which have a significant influence in the effectiveness of S/S utilization technology. The results also showed an influence of the solidified process type to the immobilization of HSWI ash and the chosen heavy metals as well as the chemical composition impact of the raw materials to the final products stabilization. 4. Conclusions This study has shown that HSWI ash, classified as hazardous waste by the European Commission, can be effectively treated by solidification/stabilization utilization technology. The addition of Portland cement to HSWI ash increased the stability of the mixture. Using two solidification/stabilization processes, hydration and granulation, it has been shown that more stable products were formed using a cement hydration process. The HSWI ash to Portland cement mixture rate resulted in the stabilization of the solidified product. The calcium silicate hydrate (C–S–H) gel was a principal reaction product generated on the surface of the stabilized samples. The C–S–H gel properties depended on the HSWI ash to Portland cement mixture ratio, and the most stable products were produced for the mixture with 50 wt% HSWI ash content. This
Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.chemosphere. 2014.03.057. References Adaska, W.S., Tresouthick, S.W., West, P.B., 1991. Solidification and Stabilization of Waste Using Portland Cement, first ed. Portland Cement Association, Skokie, IL. Asavapist, S., Fowler, G., Cheeseman, C.R., 1997. Solution chemistry during cement hydration in the presence of metal hydroxide wastes. Cem. Concr. Res. 27, 1249–1260. Aubert, J.E., Husson, B., Sarramone, N., 2007. Utilization of municipal solid waste incineration (MSWI) fly ash in blended cement. Part 2. Mechanical strength of mortars and environmental impact. J. Hazard. Mater. 146, 12–19. Batchelor, B., 2006. Overview of waste stabilization with cement. Waste Manag. 26, 689–698. Cetin, B., Aydilek, A.H., Li, L., 2012. Experimental and numerical analysis of metal leaching from fly ash-amended highway bases. Waste Manag. 24, 183–191. Council Decision, 2003. Council Decision 2003/33/EC establishing criteria and procedures for the acceptance of waste at landfill pursuant to Article 16 of an Annex II to Directive 1999/31/EC. Daintith, J. (Ed.), 1996. A dictionary of Chemistry. Oxford University Press, Oxford, p. 292. European Commission Decision, 2000. European Commission Decision 94/3/EC establishing a list of wastes pursuant to Article 1(a) of Council Directive 75/442/ EEC on waste and Council Decision 94/904/EC establishing a list of hazardous waste pursuant to Article 1(4) of Council Directive 91/689/EEC on hazardous waste. European Standard 12457, 2002. Characterization of waste – leaching – compliance test for leaching of granular waste materials and sludge – part 4. European Standard 14429, 2005. Leaching behaviour tests – influence of pH on leaching with initial acid/base addition. Galiano, Y.L., Fernandez Pereira, C., Vale, J., 2010. Stabilization/solidification of a municipal solid waste incineration residue using fly ash-based geopolymers. J. Hazard. Mater. 185, 373–381. Genazzini, C., Giaccio, G., Ronco, A., Zerbino, R., 2005. Cement-based materials as containment systems for ash from hospital waste incineration. Waste Manag. 25, 649–654.
E. Sobiecka et al. / Chemosphere 111 (2014) 18–23 Gidarakos, E., Petrantonaki, M., Anastasiadou, K., Schramm, K.-W., 2009. Characterization and hazard evaluation of bottom ash produced from incinerated hospital waste. J. Hazard. Mater. 172, 935–942. Glasser, F.P., 1993. Chemistry of cement solidified waste forms. In: Spencer, R.D. (Ed.), Chemistry and Microstructure of Solidified Waste Form, vol. 1. Lewis publishers, New York. Glasser, F.P., 1997. Fundamental aspects of cement solidification and stabilization. J. Hazard. Mater. 52, 151–170. Glasser, F.P., Zhang, L., 2001. High-performance cements matrices based on calcium sulfoaluminate–belite compositions. Cem. Concr. Res. 31, 1881–1886. Hong, S.-Y., Glasser, F.P., 1999. Alkali binding in cement pastes. Part I. The C–S–H chase. Cem. Concr. Res. 29, 1893–1903. Ibáñez, R., Andrés, A., Viguri, J.R., Ortiz, I., Irabien, J.A., 2000. Characterisation and management of incinerator wastes. J. Hazard. Mater. A79, 215–227. Ilic, M.R., Polic, P.S., 2005. Solidification/Stabilization Technologies for the Prevention of surface and Ground Water Pollution from Hazardous Wastes. in: Springer-Verlag (Eds.). Handbook Environmental Chemistry. vol. 5. Part F Vol. 3. Berlin Heidelberg, pp 159–189. Kern Jr., F.W., Gale, G.W., 2000. Surface preparation. In: Nishi, Y., Dering, R. (Eds.), Handbook of Semiconductor Manufacturing Technology. Marcel Dekker Inc., New York, pp. 87–104. Li, X.D., Poon, C.S., Sun, H., Lo, I.M.C., Kirk, D.W., 2001. Heavy metals speciation and leaching behaviours in cement based solidified/stabilized waste materials. J. Hazard. Mater. 82, 215–230. Lombardi, F., Mangialardi, T., Piga, L., Sirini, P., 1998. Mechanical and leaching properties of cement solidified hospital solid waste incinerator fly ash. Waste Manag. 18, 99–106.
23
Maschio, S., Tonello, G., Piani, L., Furlani, E., 2011. Fly and bottom ashes from biomass combustion as cement replacing components in mortars production: rheological behaviour of the pastes and materials compression strength. Chemosphere 85, 666–671. Poon, C.S., Qiao, X.C., Lin, Z.S., 2003. Pozzolanic properties of reject fly ash in blended cement pastes. Cem. Concr. Res. 33, 1857–1865. Rendell, F., Jauberthie, R., 1999. The deterioration of mortar in sulphate environments. Constr. Build. Mater. 13, 321–327. Roy, A., Eaton, H.C., Cartledge, F.K., Tittlebaum, M.E., 1992. Solidification/ stabilization of hazardous waste: evidence of physical encapsulation. Environ. Sci. Technol. 26, 1349–1353. Shi, C., Fernández-Jiménez, A., 2006. Stabilization/solidification of hazardous and radioactive wastes with alkali-activated cements. J. Hazard. Mater. B 137, 1656– 1663. Shi, C., Spence, R., 2004. Designing of cement-based formula for solidification/ stabilization of hazardous, radioactive and mixed wastes. Crit. Rev. Environ. Sci. Technol. 34, 391–417. Tiruta-Barna, L., Imyim, A., Barna, R., 2004. Long-term prediction of the leaching behaviour of pollutants from solidified waste. Adv. Environ. Res. 8, 697–711. Valls, S., Vázquez, E., 2000. Stabilisation and solidification of sewage sludges with Portland cement. Cem. Concr. Res. 30, 1671–1678. Zheng, L., Wang, W., Shi, Y., 2010. The effects of alkaline dose and Si/Al ratio on the immobilization of heavy metals in municipal solid waste incineration fly ashbased geopolymer. Chemosphere 79, 665–671.
Contents lists available at ScienceDirect
Chemosphere journal homepage: www.elsevier.com/locate/chemosphere
Influence of mixture ratio and pH to solidification/stabilization process of hospital solid waste incineration ash in Portland cement Elzbieta Sobiecka a,⇑, Andrzej Obraniak b, Blanca Antizar-Ladislao c a
Lodz University of Technology, Institute of General Food Chemistry, ul. Stefanowskiego 4/10, 90-924 Lodz, Poland Lodz University of Technology, Faculty of Process and Environmental Engineering, ul. Wolczanska 213, 90-924 Lodz, Poland c The University of Edinburgh, Institute for Infrastructure and Environment, School of Engineering, Mayfield Road, Edinburgh EH9 3JL, United Kingdom b
h i g h l i g h t s Two solidification/stabilization processes of hospital solid waste incinerator ash were compared. The influence of ratio mixture to the products stabilization was investigated. The Influence of pH solution to chemical stability of immobilized hazardous waste was sought. Cement hydration process, equal mixture of waste and Portland cement and weak alkaline pH favoured the treatment.
a r t i c l e
i n f o
Article history: Received 17 January 2013 Received in revised form 6 March 2014 Accepted 15 March 2014
Handling Editor: Klaus Kümmerer Keywords: Physico-chemical waste utilization Ash from hospital incinerator Metal leachability Metal immobilization
a b s t r a c t Solidification/stabilization (S/S) is an established utilization technology to treat hazardous wastes. This research explored the influence of pH (3–12) on the immobilization of heavy metals present in five mixtures of hospital solid waste incinerator ash and Portland cement, following two different processes of waste solidification/stabilization (cement hydration and granulation). In general, cement hydration process resulted in more stable products than granulation process. A high ash content in the mixture with Portland cement (60 wt%) resulted in the highest immobilization of Pb2+ and Cu2+, while a low ash content in the mixture (10 wt%) resulted in the lowest leachability of Zn2+. When ash and Portland cement was mixed in equal proportions (50 wt%) the highest encapsulation was observed for Ni2+, Cd2+ and Cr3+. Neutral and weak alkaline pH values within the range pH = 7–8 resulted in the lowest leachability of the monitored heavy metals. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction The main purpose of the hazardous waste management is to minimize their environmental impact. This kind of the research is very important in Poland and other countries of this European region where the landfill still dominates in the national strategy of waste management. Solidification/stabilization (S/S) is an established utilization technology to treat hazardous wastes. Solidification and stabilization are each distinct technologies: solidification refers to processes that encapsulate a waste to restrict contaminant migration and can be accomplished by a chemical reaction between a waste and binding (solidifying) reagents or by mechanical processes; and stabilization refers to processes that involve chemical reactions that reduce the leachability of a waste (Adaska et al., 1991). Typical ⇑ Corresponding author. Tel.: +48 42 6313416; fax: +48 42 6362860. E-mail address: [email protected] (E. Sobiecka). http://dx.doi.org/10.1016/j.chemosphere.2014.03.057 0045-6535/Ó 2014 Elsevier Ltd. All rights reserved.
binders include, but are not limited to, cement, thermoplastic materials, organic polymers and lime (Roy et al., 1992; Ilic and Polic, 2005). Portland cement – the main component used in the process of concrete production to obtain chemically and physically stable product – has commonly used to treat more contaminated wastes (Lombardi et al., 1998; Shi and Spence, 2004; Genazzini et al., 2005; Batchelor, 2006; Gidarakos et al., 2009). S/S is one of the physico-chemical pre-landfill treatment processes that can be used for hospital solid waste incinerator (HSWI) ash, which requires a special utilization as the hazardous waste listed in the European Catalogue on Hazardous Waste (European Commission Decision, 2000), codes 10.01.16 and 19.01.13. This criteria and related procedures were forced in 2003, European Council Decision 2003/33/EC (2003). Prior studies have focused on the characteristics of waste materials and the products and potential harmful effect to the environment. Special attention has been given to the chemical stabilization of the products, and in particular the leachability of
19
E. Sobiecka et al. / Chemosphere 111 (2014) 18–23
heavy metals under different pH values (Aubert et al., 2007; Cetin et al., 2012). The effect of pH is important as the environment surrounding landfill area influences the natural biodiversity and has its origin in leachability of collected waste. The monitoring of the end products behaviour in different pH solutions allows estimating the most advantageous condition for the waste storage. It would be also useful in set up the proper composition of the raw material to obtain the highest effect of waste immobilisation (Ibáñez et al., 2000). The overall aim of the study was to investigate the efficiency of S/S technology to treat HSWI ash. The objectives were twofold: firstly, to investigate the effect of ratio of Portland cement to ash on the chemical stabilization of the final products using two solidification processes, cement hydration (S1) and granulation (S2); and secondly, to investigate the effect of pH on the encapsulation of heavy metals listed in Council Decision (2003)/33/EC (2003) and stabilization of the final products.
2.3.2. Leachability Leaching tests were conducted according to European Standards, method 14429 (2005). The concentration of heavy metals in the waste samples and associated stabilized waste products obtained following processes S1 and S2, respectively, was measured after 48 h of exposure to water. Leaching tests were conducted with each sample with natural water solutions at constant pH values ranging from pH = 3 to pH = 12. Three replicates were conducted for each leaching test.
2. Material and methods
2.4. Data analysis
2.1. Ash samples
The effect of the mixture ratio of HSWI ash to Portland cement and pH on heavy metals’ leachability of S/S treated samples using two different stabilization process was investigated using a oneway ANOVA analysis with Microsoft Excel 2003.
The ash used in this study was collected from a hospital waste incineration plant in the Province of Lodz, central Poland. The collected samples were grate ashes and chimney filter fly ashes.
and water was 0.5. The samples were then exposed during 48 h to air at 25 °C. A disc granulator was used to prepare waste samples used for S2, set up with the following parameters: rotational velocity of the granulator disc, n = 10 r.p.m.; angle of the granulator disc axis inclination, a = 50°; mass of loose material 500 g; liquid volume of flow rate, Q = 3,6 ml/min; granulation wetting time, t = 15 min.
3. Results and discussion 2.2. Chemical analyses 2.2.1. Hospital ash composition The concentration of heavy metals present in HSWI ash was determined by Atomic Absorption Spectrometer GBC 932 Plus (air-acetylene flame), according to European Standard 12457 (2002). Carbon, hydrogen and sulphur in HSWI ash was determined by EA 1108 CHNS-O Analyzer Fisons Instrument equipped with an auto-sampler and Thermal Conductive Detector (TCD); the instrument was calibrated with a 2,5-Bis-(5-tert-butyl-benzoxazol-2-yl)-thiophen standard (BBOT; CAS Number: 7128-64-5). 2.2.2. X-ray diffraction analysis X-ray diffraction (XRD) studies were carried out on powdered samples by PANalytical Model X’Pert PRO MPD using Cu Ka radiation source in the 2h range from 5° to 90° at 40 kV and 40 mA. Crystalline phases were identified according to the International Centre of Diffraction Data PDF-2. 2.2.3. Metals analysis Metal concentrations of natural water extracts at pH solutions with the range pH = 3–12, were measured by Atomic Absorption Spectrometer GBC 932 Plus (air-acetylene flame) according to European Standard 12457 (2002). 2.3. Experiments 2.3.1. Solidification Commercially available Portland cement I 42.5 R (Cement Lafarge S.A., Poland) was used as binder for the purpose of this study. Five different mixtures of HSWI ash and Portland cement were prepared (samples A–E), with the following ash load (percentage given in dry weight): sample A, 10 wt%; sample B, 20 wt%; sample C, 40 wt%; sample D, 50 wt%; sample E, 60 wt%. The residual composition of the samples was the Portland cement only. The final products were prepared using two different solidification processes: cement hydration (S1) and a granulation (S2). Waste samples used for S1 consisted of HSWI fly ash, Portland cement and water. The ratio of the solid part of the initial mixture
Migration of toxic substances in the subsoil, following extreme whether events, such as storms or rainfalls is of current concern. The presence of various aggressive agents, i.e. sulphates, chlorides, etc. in the subsoil is common, and may result in pH changes of solutions surrounding contaminated sites or landfill sites, which will initiate numerous chemical reactions (Rendell and Jauberthie, 1999). S/S is an environmental technology that can be used to improve the stabilization of hazardous wastes once stored in landfill sites. Prior research has indicated that the composition of wastes treated using S/S has a major impact in the properties of the final product (Hong and Glasser, 1999). The chemical analyses of the HSWI ash used in this study showed that silica, calcium, and aluminium were present at the highest concentrations (Table 1). The oxide forms of these three constituents made up ca. 75 wt% dry mass (d.m.) of the total mass of the HSWI ash. These results were confirmed by XRD analysis (Fig. 1).
Table 1 Chemical composition of HSWI ash and Portland cement. Compound
HSWI ash (wt% d.m.)
Portland cement (wt% d.m.)
SiO2 Al2O3 CaO Fe2O3 K2O MgO Na2O ZnO MnO CuO PbO BaO CrO NiO CoO CdO Ctotal S H
48.60 16.80 10.10 4.11 1.07 0.99 0.73 0.58 0.18 0.03 0.02 0.02 0.02 0.01 0.01 0.01 8.60 4.30 0.63
18.9 5.3 62.7 2.7 – 1.5 0.73 – – – – – – – – – – 1.25 –
E. Sobiecka et al. / Chemosphere 111 (2014) 18–23
Intensity (counts)
20
Anhydrite CaSO4
4000
3000
Quartz SiO2 Calcite CaCO3
2000
Halite NaCl Tricalcium aluminate Ca3Al2O6 1000
0
10
20
30
40
50
60
70
Fig. 1. XRD analysis of HSWI ash.
These results suggested that the HSWI ash used in this study it can be classified as a pozzolan, which is one of two main components used in the production of concrete (Poon et al., 2003). The other component used in the production of concrete is cement, and for the purpose of this study commercially available Portland cement (Table 1) was used as a binder. Once HSWI and Portland cement were characterized, the effect of Portland cement addition to HSWI ash on the stabilization of heavy metals in the S/S process was then investigated. Both solidification processes used in this study resulted in the production of a calcium silicate hydrate (C–S–H) gel created on the surface of the stabilized samples, similarly to what would occur and would influence the stability of minerals under environmental conditions (Tiruta-Barna et al., 2004). This C–S–H gel generated at the surface acts as a barrier between the immobilized solid wastes and the surrounding liquids, and controls the potential adsorption of ions present in the liquids onto the surface of the solid wastes as well as the immobilization of heavy metals in the resulting products (Glasser, 1997). These processes are influenced by chemical reactions which are dependent of the pH of the surrounding liquids and the Ca/Si ratio in the HSWI ash and Portland cement (Asavapist et al., 1997). Based on the chemical composition of HSWI ash and Portland cement (Table 1), Ca/Si ratios were calculated for the different mixtures prepared in this study (samples A to sample E, with HSWI ash loads ranging from 10 wt% to 60 wt%, respectively), and the values obtained were: sample A, 3.0; sample B, 2.3; sample C, 1.4; sample D, 1.1; and sample E, 0.9. These values indicated that the higher the HSWI ash content, the lower the Ca/Si ratio. It is well known that in order to obtain stable products, chemical reactions should be minimized, which occurs when the surface charge of C–S–H gel generated at the surface of the products is ca. zero and this is achieved at a Ca/Si ratio ca. 1.2 (Glasser, 1993; Maschio et al., 2011). Sample D, with a HSWI ash loading of 50 wt% presented a Ca/Si ratio of 1.1, and therefore a low chemical activity was expected on the surface of these samples. Samples A, B, C presented a higher Ca/Si ratio (>1.2), and with a positive surface charge suggested that anions could adsorbed onto the surface of these samples. Samples E, with a lower Ca/Si ratio (0.9), with a negative surface charge suggested that cations could be adsorbed onto the surfaces of these samples. Six heavy metals ions, Pb2+, Cu2+, Cd2+, Zn2+, Cr3+ and Ni2+ monitored in the HSWI ash, Portland cement and stabilized waste
(Council Decision 2003/33/EC). These cations may go under complex chemical reactions under different environmental conditions. In general, they all can form sulphites, hydroxides (alkaline solutions) (Kern and Gale, 2000). Additionally, Cu2+, Cd2+, Ni2+, can be present as simple cations in both, acidic and strong alkaline solutions; Zn2+, Cr3+ and Pb2+ are ampholytic elements and they can be present as simple cations in acidic solution or they can form complex ions, e.g., ZnO22 , CrO2 , PbO22 , in strong alkaline solutions (Valls and Vázquez, 2000; Batchelor, 2006; Galiano et al., 2010). As the liquid phase surrounding the products of S/S technology once deposited in a landfill site can penetrate the pore structure of the solidified waste, various chemical reactions may occur (Li et al., 2001; Glasser and Zhang, 2001), resulting in the leaching of heavy metals, which generally is defined as the extraction of soluble components of a solid mixture by percolating a solvent through it (Daintith, 1996). The results of leaching tests conducted in this study (Table 2) indicated that the higher the load of HSWI ash in the mixtures the higher the concentration of Zn2+ and Cd2+ in the leachate; the opposite occurred for the rest of the heavy metals under investigation. The chemical stabilization of wastes treated by S/S is affected by the presence of aggressive reagents, further influenced by pH changes in surrounding solutions. It has been reported that chemical immobilization of the pollutants in both solidification and stabilization processes depends on the crystalline phase of a binder matrix (Glasser, 1997; Zheng et al., 2010). It is suggested that Portlandite, a naturally occurring mineral (Ca(OH)2) present in the Portland cement used in this study at high concentrations (Table 1) acted as a buffer at the surface of the waste, and influenced the leaching of heavy metals in this study. In fact, prior studies have indicated that Portlandite limited the chemical interactions between the contaminants and the surface of the stabilized waste, resulting in a significant reduction of leachability of heavy metals in a weak alkaline solution (Shi and Fernández-Jiménez, 2006). The effect of pH solutions on the leachability of heavy metals (i.e., stability) in samples A through E, solidified wastes using two processes: cement hydration (S1) and a granulation (S2) is presented in Figs. 2 and 3. Table 3 has compiled the probability value (p-value) for each metal in the stabilized forms prepared in processes S1 or S2. The results of this study indicated that, in general, wastes solidified using S1 process were more stable chemically than the same
21
E. Sobiecka et al. / Chemosphere 111 (2014) 18–23 Table 2 Leachability of heavy metals from different composition of mixtures of wastes. Analyzed metal
Leachability of heavy metals from different composition of mixtures of wastes liquid to solid ratio = 10 (mg kg HSWI ash
Zn Pb Cu Ni Cd Cr
440.94 18.34 22.46 10.15 9.17 10.43
Portland cement
1
d.m)
Mixtures of HSWI ash and Portland cement
97.33 27.33 34.67 19.67 4.00 34.33
A
B
C
D
E
131.69 26.43 33.45 18.72 4.52 31.94
166.05 25.53 32.23 17.76 5.03 29.55
234.78 23.74 29.78 15.86 6.07 24.77
269.14 22.84 28.56 14.91 6.59 22.38
303.50 21.94 27.34 13.96 7.10 19.99
Note: Load of the HSWI ash in the mixture: sample A, 10 wt%; sample B, 20 wt%; sample C, 40 wt%; sample D, 50 wt%; sample E, 60 wt%; HSWI ash, 100 wt%; Portland cement, 0 wt%.
Zn (S2)
Pb (S2) A
D E
50
20
B
15
C D
10
E
4
5
6
7
8
9 10 11 12
3
pH
B
15
C D
10
E
0
0 3
20
5
5
0
4
5
6
7
Zn (S1)
8
9 10 11 12
3
pH
4
5
6
7
Pb (S1)
150
25
A
B
20
B
C 100
D E
50
8
9 10 11 12
pH
Cu (S1)
A
C [mg/kg d.m.]
200
C [mg/kg d.m.]
A
A
C
15
D 10 E
15
A B
C [mg/kg d.m.]
C [mg/kg d.m.]
C 100
C [mg/kg d.m.]
B
150
Cu (S2) 25
25
C [mg/kg d.m.]
200
10
C D
5
E
5
0
0
0 3
4
5
6
7
8
9 10 11 12
pH
3
4
5
6
7
8
9 10 11 12
pH
3
4
5
6
7
8
9 10 11 12
pH
Fig. 2. Leachability of Zn, Pb and Cu from the samples of hydration (S1) and granulation (S2) processes.
wastes solidified using S2. Statistical analysis (Table 3) indicated that the HSWI ash to Portland cement mixture ratio had no significant effect on the leaching of Zn2+, Ni2+, Pb2+ and Cd2+ (p-value < 0.05). However, using the solidification process S2 indicated that the HSWI ash to Portland cement mixture ratio had a significant effect (p-value > 0.05). The leaching of Cr3+ and Cu2+ was comparable in the wastes solidified using S1 and S2 processes, and depended on the ratio composition of waste material and the binder. The influence of pH on the stability of solidified wastes using processes S1 and S2 was systematically investigated. The results of this research indicate that solidification S1 results in products more chemically stable and less influenced by pH changes than products obtained using solidification S2 (Figs. 2 and 3). For both solidification processes, low pH values resulted in a lower immobilization of heavy metals, while the highest immobilization was observed for pH values within the range pH = 7–8. Higher pH values (alkaline solution) resulted in an increased leachability. These results indicated that at low pH values (acidic solution) metals ions exist as soluble forms, when pH increases and reaches neutral to low alkaline values, insoluble hydroxides are formed with results in a higher immobilization of the heavy metals. As the pH increases to higher values, in the alkaline range, heavy metals form complex ions which are leached back from the solidified forms of waste into
solution. Waste solidified using process S2 indicated that samples with at HSWI ash to Portland cement of 60 wt% presented the highest leachability, indicating the influence that mixing ratios might have on the chemical stability of a final product. It was hypothesised that the addition of Portland cement to HSWI ash influences the stability of the solidified product. From the chemical composition of Portland cement (Table 1) it was observed that calcium was present at high concentration levels, and it is known that calcium is one of two main elements responsible for the C–S–H gel appearance on the surface of the solidified waste. In sample E (60 wt%), Ca/Si ratio was 0.9 which would result in a negative charge of the surface area, active to chemical reactions. In an alkaline solution, positive charged heavy metals encapsulated in the solidified waste migrated through the porous structure to the surface, and subsequently leached out to the surrounding solution as hydroxide ions. In an acidic solution, a negative charged C–S–H gel surface reacted with the ions in the surrounded solution. Subsequently the C–S–H gel barrier between the surrounding solution and the solid phase shrank and caused a reduction of the solidified waste stability, resulting in leaching out of heavy metals. Following both stabilization processes, best results were obtained for mixtures with a HSWI ash to Portland cement of 10 wt% HSWI ash (and 90 wt% Portland cement). At pH level within the range pH = 7–8 best immobilization results were obtained.
22
E. Sobiecka et al. / Chemosphere 111 (2014) 18–23
Ni (S2)
C
10
D 5
E
0 3
4
5
6
7
8
9 10 11 12
A
8 C [mg/kg d.m.]
B 6
C
4
D E
2 0
pH
A
3
4
5
6
7
Ni (S1)
8
9 10 11 12
6
C D
4
3
2 0 8
4
5
6
7
9 10 11 12
pH
8
9 10 11 12
pH
Cr (S1)
B
2
C D 1
E
7
E
A C [mg/kg d.m.]
B
6
D
15
A
8
5
C
10
0
pH
3
4
B
Cd (S1)
10
3
15
5
A C [mg/kg d.m.]
C [mg/kg d.m.]
B
20
C [mg/kg d.m.]
A 15
C [mg/kg d.m.]
Cr (S2)
Cd (S2) 10
20
B
10
C D
5
E
0
E 0
3
4
5
6
7
8
9 10 11 12
pH
3
4
5
6
7
8
9 10 11 12
pH
Fig. 3. Leachability of Ni, Cd and Cr from the samples of hydration (S1) and granulation (S2) processes.
study has also shown that pH of surrounding solutions significantly affect the leachability of six heavy metals investigated. The lowest leachability values were observed at pH values within the range pH = 7–8.
Table 3 P-value of the experiments. Metal
P-value S1
Zn Pb Cu Ni Cd Cr
5.39 10 7.60 10 0.26 2.60 10 3.65 10 0.64
S2 6 11
5 11
0.12 1.10 10 0.48 0.59 0.18 0.96
5
Overall, this systematic experimental research provides relevant information regarding effective strategies for storage of hazardous materials. In particular, the obtained results identified operational parameters (i.e., mixture rate, pH value, solidification process) which have a significant influence in the effectiveness of S/S utilization technology. The results also showed an influence of the solidified process type to the immobilization of HSWI ash and the chosen heavy metals as well as the chemical composition impact of the raw materials to the final products stabilization. 4. Conclusions This study has shown that HSWI ash, classified as hazardous waste by the European Commission, can be effectively treated by solidification/stabilization utilization technology. The addition of Portland cement to HSWI ash increased the stability of the mixture. Using two solidification/stabilization processes, hydration and granulation, it has been shown that more stable products were formed using a cement hydration process. The HSWI ash to Portland cement mixture rate resulted in the stabilization of the solidified product. The calcium silicate hydrate (C–S–H) gel was a principal reaction product generated on the surface of the stabilized samples. The C–S–H gel properties depended on the HSWI ash to Portland cement mixture ratio, and the most stable products were produced for the mixture with 50 wt% HSWI ash content. This
Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.chemosphere. 2014.03.057. References Adaska, W.S., Tresouthick, S.W., West, P.B., 1991. Solidification and Stabilization of Waste Using Portland Cement, first ed. Portland Cement Association, Skokie, IL. Asavapist, S., Fowler, G., Cheeseman, C.R., 1997. Solution chemistry during cement hydration in the presence of metal hydroxide wastes. Cem. Concr. Res. 27, 1249–1260. Aubert, J.E., Husson, B., Sarramone, N., 2007. Utilization of municipal solid waste incineration (MSWI) fly ash in blended cement. Part 2. Mechanical strength of mortars and environmental impact. J. Hazard. Mater. 146, 12–19. Batchelor, B., 2006. Overview of waste stabilization with cement. Waste Manag. 26, 689–698. Cetin, B., Aydilek, A.H., Li, L., 2012. Experimental and numerical analysis of metal leaching from fly ash-amended highway bases. Waste Manag. 24, 183–191. Council Decision, 2003. Council Decision 2003/33/EC establishing criteria and procedures for the acceptance of waste at landfill pursuant to Article 16 of an Annex II to Directive 1999/31/EC. Daintith, J. (Ed.), 1996. A dictionary of Chemistry. Oxford University Press, Oxford, p. 292. European Commission Decision, 2000. European Commission Decision 94/3/EC establishing a list of wastes pursuant to Article 1(a) of Council Directive 75/442/ EEC on waste and Council Decision 94/904/EC establishing a list of hazardous waste pursuant to Article 1(4) of Council Directive 91/689/EEC on hazardous waste. European Standard 12457, 2002. Characterization of waste – leaching – compliance test for leaching of granular waste materials and sludge – part 4. European Standard 14429, 2005. Leaching behaviour tests – influence of pH on leaching with initial acid/base addition. Galiano, Y.L., Fernandez Pereira, C., Vale, J., 2010. Stabilization/solidification of a municipal solid waste incineration residue using fly ash-based geopolymers. J. Hazard. Mater. 185, 373–381. Genazzini, C., Giaccio, G., Ronco, A., Zerbino, R., 2005. Cement-based materials as containment systems for ash from hospital waste incineration. Waste Manag. 25, 649–654.
E. Sobiecka et al. / Chemosphere 111 (2014) 18–23 Gidarakos, E., Petrantonaki, M., Anastasiadou, K., Schramm, K.-W., 2009. Characterization and hazard evaluation of bottom ash produced from incinerated hospital waste. J. Hazard. Mater. 172, 935–942. Glasser, F.P., 1993. Chemistry of cement solidified waste forms. In: Spencer, R.D. (Ed.), Chemistry and Microstructure of Solidified Waste Form, vol. 1. Lewis publishers, New York. Glasser, F.P., 1997. Fundamental aspects of cement solidification and stabilization. J. Hazard. Mater. 52, 151–170. Glasser, F.P., Zhang, L., 2001. High-performance cements matrices based on calcium sulfoaluminate–belite compositions. Cem. Concr. Res. 31, 1881–1886. Hong, S.-Y., Glasser, F.P., 1999. Alkali binding in cement pastes. Part I. The C–S–H chase. Cem. Concr. Res. 29, 1893–1903. Ibáñez, R., Andrés, A., Viguri, J.R., Ortiz, I., Irabien, J.A., 2000. Characterisation and management of incinerator wastes. J. Hazard. Mater. A79, 215–227. Ilic, M.R., Polic, P.S., 2005. Solidification/Stabilization Technologies for the Prevention of surface and Ground Water Pollution from Hazardous Wastes. in: Springer-Verlag (Eds.). Handbook Environmental Chemistry. vol. 5. Part F Vol. 3. Berlin Heidelberg, pp 159–189. Kern Jr., F.W., Gale, G.W., 2000. Surface preparation. In: Nishi, Y., Dering, R. (Eds.), Handbook of Semiconductor Manufacturing Technology. Marcel Dekker Inc., New York, pp. 87–104. Li, X.D., Poon, C.S., Sun, H., Lo, I.M.C., Kirk, D.W., 2001. Heavy metals speciation and leaching behaviours in cement based solidified/stabilized waste materials. J. Hazard. Mater. 82, 215–230. Lombardi, F., Mangialardi, T., Piga, L., Sirini, P., 1998. Mechanical and leaching properties of cement solidified hospital solid waste incinerator fly ash. Waste Manag. 18, 99–106.
23
Maschio, S., Tonello, G., Piani, L., Furlani, E., 2011. Fly and bottom ashes from biomass combustion as cement replacing components in mortars production: rheological behaviour of the pastes and materials compression strength. Chemosphere 85, 666–671. Poon, C.S., Qiao, X.C., Lin, Z.S., 2003. Pozzolanic properties of reject fly ash in blended cement pastes. Cem. Concr. Res. 33, 1857–1865. Rendell, F., Jauberthie, R., 1999. The deterioration of mortar in sulphate environments. Constr. Build. Mater. 13, 321–327. Roy, A., Eaton, H.C., Cartledge, F.K., Tittlebaum, M.E., 1992. Solidification/ stabilization of hazardous waste: evidence of physical encapsulation. Environ. Sci. Technol. 26, 1349–1353. Shi, C., Fernández-Jiménez, A., 2006. Stabilization/solidification of hazardous and radioactive wastes with alkali-activated cements. J. Hazard. Mater. B 137, 1656– 1663. Shi, C., Spence, R., 2004. Designing of cement-based formula for solidification/ stabilization of hazardous, radioactive and mixed wastes. Crit. Rev. Environ. Sci. Technol. 34, 391–417. Tiruta-Barna, L., Imyim, A., Barna, R., 2004. Long-term prediction of the leaching behaviour of pollutants from solidified waste. Adv. Environ. Res. 8, 697–711. Valls, S., Vázquez, E., 2000. Stabilisation and solidification of sewage sludges with Portland cement. Cem. Concr. Res. 30, 1671–1678. Zheng, L., Wang, W., Shi, Y., 2010. The effects of alkaline dose and Si/Al ratio on the immobilization of heavy metals in municipal solid waste incineration fly ashbased geopolymer. Chemosphere 79, 665–671.
