渗滤液浸沥下稳定化飞灰中重金属的浸出行为

Leaching characteristics of heavy metals by landfill leachate from stabilized MSWI fly ash

稳定化飞灰与生活垃圾混合填埋过程中,在渗滤液浸沥作用下,存在稳定化飞灰中重金属溶出的风险.为探究渗滤液浸沥环境下稳定化飞灰中重金属的浸出行为,基于浸提实验,以填埋场早期、晚期渗滤液为浸提剂,研究了不同液固比(10:1、20:1、30:1、50:1、100:1、150:1、200:1)条件下磷酸稳定化飞灰、螯合剂稳定化飞灰中重金属(Cd、Cu、Zn、Pb、Cr、Ni)的浸出行为.结果表明:随着液固比的增加,浸出液中Cd、Cu和Zn浓度先上升后下降,在液固比20:1时达到最大值,Pb的浸出浓度随液固比的升高整体呈现缓慢增加的趋势,Cr、Ni浸出浓度变化较小,液固比对其影响不显著;Cd和Cu在早期渗滤液浸沥环境下更容易浸出,Zn、Pb、Cr、Ni在早期、晚期渗滤液浸沥环境下差别不大.在两种渗滤液浸沥环境下,螯合剂稳定化飞灰比磷酸稳定化飞灰具有更好的稳定性.

In the process of stabilized fly ash co-landfilled with municipal solid waste(MSW),the leaching risk of heavy metal from stabilized fly ash by landfill leachate might exist.Based on batch leaching experiments,the research investigated the leaching behavior of heavy metals(Cd,Cu,Zn,Pb,Cr,Ni)in chelating agent-stabilized fly ash and phosphoric acid-stabilized fly ash with various liquid to solid(L/S)ratios(10:1,20:1,30:1,50:1,100:1,150:1,200:1)by using fresh and matured leachate as extracting agent.The results showed that the leaching trends of Cd,Cu and Zn were similar,which increased at first and then decreased with the increase of L/S ratio;and their respective maximum leaching concentrations were occurred at the same L/S ratio of 20:1.The leaching concentration of Pb increased slowly with the increase of L/S ratio.The change trend in the leaching of Cr and Ni varied little,indicating that the impact of L/S ratio on the leaching of Cr and Ni was not significant.Cd and Cu were more easily leaching out with fresh leachate compared with matured leachate;however,there was no significant difference in the leaching concentration of Zn,Pb,Cr,and Ni with fresh or matured leachate.Overall,the chelating agent-stabilized fly ash showed a better stability than the phosphoric acid(H3PO4)-stabilized fly ash when leached with fresh and matured leachate.