The presence of carbonate and alkaline oxides leads to the strong acid buffering capacity and high pHof municipal solid waste incineration (MSWI) fly ash, hindering the removal of heavy metals (HMs)during electrokinetic remediation (EKR). Acid pretreatment offers the possibility to solve this problem.In this study, four pretreatment solutions (deionized water, HNO3, HCl and HAc) were investigated withthe aim of lowering the high acid buffering capacity of MSWI fly ash. A series of laboratory scale EKRexperiments were conducted with different pretreatment conditions and operating parameters. Theexperiment with HCl pretreatment showed the best removal of HMs. Then, an orthogonal experimentwas designed to explore the optimum EKR conditions based on acid pretreatment. The results showedthat the best leaching efficiencies of Pb (94.23%), Zn (89.09%), Cu (88.21%) and Cd (84.97%) wereobtained after 15 d, at a voltage gradient of 2 V/cm and with the addition of 0.05 mol/L citric acid to thecatholyte every day. The carbonate and alkaline oxides in fly ash were significantly reduced after theEKR treatment, as confirmed by XRD analysis. Sequential extraction of Pb, Zn, Cu and Cd indicatedthat the oxidizable and reducible states were converted to a more stable compound after treatment..
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