The Occurrence Forms and Toxic Leaching Characteristics of Trace Elements in Desulfurization by Products of Coal-fired Power Plants
The by-products of coal-fired power plants,such as desulfurization gypsum and sludge,can adsorb trace elements into the environment again during rainwater or solid waste processing,causing secondary pollution.Three typical coal-fired power plants with ultra-low emissions were selected in Anhui Province,and the occurrence forms of Cr,As,Cd,and Pb in desulfurization sludge and gypsum were determined using the European Community Bureau of Referenee(BCR)stepwise extraction method.The leaching toxicity of desulfurization gypsum was determined using the toxicity characteristic leaching procedure(TCLP)standard toxicity leaching method,and the potential environmental impact of Cr,As,Cd,and Pb in desulfurization by-products was analyzed.The results show that the mass concentration of elements in desulfurization sludge was significantly higher than that in desulfurization gypsum.The stability of Cr and As in desulfurization gypsum is higher,and the effective states of Cd and Pb elements account for more than 50％with stronger migration ability and potential risks to the ecological environment.The migration ability of Cr,Cd,and As is stronger in desulfurization sludge,and their environmental risk is higher.Cr is unstable in oxidizing environments,Cd is more easily leached in acidic environments,and As is unstable in both oxidizing and reducing environments.pH and solid-liquid ratio have important effects on the leaching of heavy metals in gypsum,and there are significant differences between different elements.The leaching rates of Pb,Cr,and As increase with the decrease of pH,increase with the liquid-solid ratio,and gradually reach equilibrium.The maximum leaching rate of Cd is lower than the other three elements,and the correlation between leaching rate and pH and solid-liquid ratio is weak.When pH is 4.47,the leaching rate is higher.The results can provide the reference for disposal and reuse of desulphurization byproducts in coal-fired power plants.
wet desulfurizationdesulfurization by-productstrace elementsEuropean Community Bureau of Reference(BCR)toxicity characteristic leaching procedure(TCLP)
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