不同有机螯合剂对飞灰中重金属的稳定化效果及环境风险评估

STABILIZATION EFFECT AND ENVIRONMENTAL RISK ASSESSMENT OF HEAVY METALS IN MSWI FLY ASH BY DIFFERENT ORGANIC CHELATING AGENTS

对比考察了不同剂量哌嗪类螯合剂(TS300)和二甲基二硫代氨基甲酸盐(SDD)对生活垃圾焚烧飞灰中重金属的稳定化效果。结果表明:TS300添加量为3%、SDD添加量为5%时,飞灰螯合产物重金属浸出浓度可满足GB 16889—2008《生活垃圾填埋场污染控制标准》的标准限值。然而,飞灰螯合产物在放置28 d后,3%TS300组的Cd、5%SDD组的Pb和Cd的浸出浓度超过标准限值。此外,螯合稳定化处理可将飞灰中重金属从不稳定的可还原态转化为较稳定的可氧化态,同时还可拓宽飞灰稳定存在的pH值范围(即在该pH范围内重金属浸出浓度达标)。环境风险评估指数分析结果表明:3%TS300处理组,目标重金属在考察时间范围内(0~28 d)均对环境无风险,而5%SDD处理组飞灰螯合产物中Pb、Zn和Cd在放置28 d后会造成潜在环境风险。因此,就研究所用飞灰的重金属稳定效果而言,TS300优于SDD。

The stabilization effects of heavy metals in municipal solid waste incineration fly ash stabilized by piperazine chelating agent(TS300)and dimethyl dithiocarbamate(SDD)at different dosages were compared.The results showed that the leaching concentrations of heavy metals in chelated fly ash met the standard limit of GB 16889—2008,when the dosage of TS300 and SDD was 3%and 5%,respectively.However,the leaching concentrations of Cd in the 3%TS300 group,and Pb and Cd in the 5%SDD group,all exceeded the standard limit after the chelated fly ash was placed for 28 days.In addition,chelation stabilization treatment can transform heavy metals in fly ash from unstable reducible fractions to more stable oxidizable fractions,and it can also broaden the range of pH value for stable existence of fly ash(the leaching concentrations of heavy metals met the standard within this pH range).The analysis results of the environmental risk assessment code showed that the target heavy metals in the 3%TS300 group posed no risk to the environment within the inspection time range(0 to 28 days),while the Pb,Zn and Cd in the 5%SDD group posed potential environmental risks after being placed for 28 days.Therefore,TS300 is superior to SDD,in terms of heavy metal stabilization effect of fly ash in this study.