The influence of pH on the leaching behaviour of inorganic components from municipal solid waste APC residues |
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| Authors: | Margarida J Quina João CM Bordado Rosa M Quinta-Ferreira |
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| Institution: | 1. GERSE – Group on Environment, Reaction and Separation Engineering, Department of Chemical Engineering, FCTUC, University of Coimbra, Polo II – Rua Sílvio Lima, 3030-790 Coimbra, Portugal;2. Department of Chemical and Biological Engineering, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal;1. Graduate School of Engineering, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka 819-0395, Japan;2. Department of Urban and Environmental Engineering, Faculty of Engineering, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka 819-0395, Japan;1. State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China;2. Xi''an Thermal Power Research Institute Co. Ltd. (Suzhou Branch), Suzhou, Jiangsu, 215153, China;3. School of Power and Energy Engineering, Changsha University of Science and Technology, Changsha, Hunan, 410114, China;1. College of Environmental Science and Engineering, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092, China;2. Key Laboratory of Yangtze River Water Environment, Ministry of Education, Tongji University, Shanghai 200092, China;1. College of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao 266033, PR China;2. Xinjiang Key Laboratory of Environmental Pollution and Bioremediation, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, PR China;3. Qingdao MSW Management & Treatment Co. Ltd., Qingdao 266041, PR China |
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| Abstract: | The influence of pH on the leaching behaviour of air pollution control (APC) residues produced in municipal solid waste incineration (MSWI) is addressed in this study. The residue is considered hazardous waste, and in accordance with their chemical properties, the leaching of contaminants into the environment is the main concern. Several leaching tests can be used for research studies or regulatory purposes, where a wide variety of conditions may be tested. Our work deals mainly with the leaching behaviour of toxic heavy metals (Pb, Cd, Zn, Cr, Ni, Cu) and inorganics associated with soluble salts (Na, K, Ca, Cl). The main goal is to obtain an overview of the leachability of APC residues produced in a Portuguese MSWI process. Among the different variables that may have influence on the leaching behaviour, pH of the leachant solution is the most important one, and was evaluated through pH static tests. The acid neutralization capacity (ANC) of the residue was also determined, which is in the range of 6.2–6.8 meq g?1 (for pH = 7) and 10.1–11.6 meq g?1 (for pH = 4). The analysis of the leaching behaviour is particularly important when the leaching is solubility controlled. The amphoteric behaviour of some elements was observed, namely for Pb and Zn, which is characterized through high solubilization at low and high pH and moderate or low solubility at neutral or moderate high pH. The solubility curves for Pb, Cd, Zn, Cr, Ni and Cu as a function of pH were obtained, which are very useful for predicting the leaching behaviour in different scenarios. The solubility of K and Na reveals to be nearly independent of the solution pH and the released amount is mainly availability-controlled. Moreover, the pH static test showed that Cl? is the most pH-independent species. The APC residue turns out to be a hazardous waste because of the high leaching of lead and chloride. On the other hand, leaching of elements like cadmium, nickel and copper is limited by the high pH of the residue, and as long as the waste keeps its ANC, the risk of mobilization of these elements is low. |
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