污泥生物淋滤过程中黄铁矾对重金属离子的吸附与共沉淀作用的模拟研究

生物淋滤处理可加速污泥中重金属(Zn,Cu和Cr)的溶出.但在淋滤后期,约有31%的已溶出的Cu2 被重新固持.并且,Cu2 浓度的再次下降与Fe3 沉淀形成黄铁矾的反应在时间上具有同步性.为阐明Cu2 固持机理,文章利用氧化亚铁硫杆菌的生物催化氧化作用,模拟生物淋滤环境在纯体系合成了黄铁矾.吸附试验表明,在pH 2.0～2.5的范围内(污泥生物淋滤过程中重金属溶出范围),黄铁矾对10 mg·L-1Cu2-(该浓度与供试污泥生物淋滤中的Cu2 浓度相近)的吸附率低于9%,不能完全解释Cu2 的重新固持现象.共沉淀试验表明,Cu容易与黄铁矾形成共沉淀而掺入矿物的晶格.当Cu2 为10 mg·L-1时,约有44.6%的Cu2 与黄铁矾产生共沉淀而进入固相.可以认为,Cu与黄铁矾的共沉淀效应,是导致污泥生物淋滤后期Cu2 浓度再次下降的主要原因,黄铁矾对Cu2 的吸附只起极小的作用.

Adsorption and Coprecipitation of Dissolved Metals with Jarosite under Conditions Simulating Sewage Sludge Bioleaching

The inoculation of Acidithiobacillus ferrooxidans and the addition of Fe2+ as their substrates accelerated the solubilization of Zn, Cu and Cr from sewage sludge. However, a decrease in Cu removal from 91% to 60% with time elapse could be observed in the late process, which appeared simultaneously with the formation of jarosite resulting from hydrolysis of Fe3+. The tested jarosite was synthesized by using bacterial oxidation of Fe2+ by resting A. ferrooxidans in acid solution (pH 2.5) under conditions stimulating sludge bioleaching. Adsorption edge measurement showed that only less than 9% of Cu2+ was adsorbed onto jarosite in the pH range of 2.0-2.5, indicating that adsorption mechanism could not explain fully re-sorption of Cu2+ (about 31%) in the anaphase of bioleaching process. In the coprecipitation studies, when jarosite was precipitated in the presence of Cu2+ (10 mg x L(-1)), a significant amount of Cu (44.6%) was incorporated into the precipitate. Coprecipitation of jarosite with Cu2+ was the predominant process by which soluble Cu was partially re-sorpted by jarosite in the anaphase of bioleaching process.