含铁复配药剂钝化土壤中砷和锑的效果及机理

Passivation of As and Sb in Soil with Iron-containing Amendments and Its Mechanism

以矿渣、钢渣、脱硫石膏和氢氧化钙为主要原料,复配硫酸铁盐制备含铁复配药剂,考察其对土壤中砷和锑的钝化效果,研究土壤中砷、锑和铁的形态分布,土壤物相组成及砷、锑价态的变化,探究砷和锑的钝化机理。结果表明,当含铁复配药剂掺加15%(质量分数)的硫酸亚铁,使用量为20%,搭配质量浓度为2%的过氧化氢使用,砷和锑的浸出浓度分别从69.72和172.67μg/L下降到6.95和1.61μg/L。钝化处理后,土壤中砷和锑的非特异性吸附态(F1)分别降低了7.3%和11.7%,特异性吸附态(F2)分别降低了2.7%和0.9%,有效态砷、锑转变成铁/铝氧化物结合态和残渣态;土壤中无定形和结晶态铁氧化物含量显著增加,出现针铁矿和水铁矿相,部分砷由As(Ⅲ)转变成As(Ⅴ),钝化修复后土壤中砷、锑生成Fe-As、Fe-Sb和Ca-Sb沉淀。

Applying blast furnace slag,steel slag,desulfurization gypsum and calcium hydroxide as main raw materials,iron-containing amendments were prepared by further adding iron sulfate.The passivation of As and Sb in co-contaminated soil was investigated by using iron-containing amendments.The passivation mechanisms were revealed by investigating the changes of As,Sb and Fe fractions,mineral compositions of soil and chemical states of As and Sb.The results show that the leaching concentrations of As and Sb can be significantly reduced from 69.7 and 172.67μg/L to 6.95 and 1.61μg/L respectively,while the dosage of iron-containing amendments with 15%FeSO_(4) is 20%and H_(2)O_(2) solution with 2% concentration is used to replace pure water.After passivation,the nonspecifically absorbed As and Sb reduce by 7.3% and 11.7% respectively,and the specifically absorbed As and Sb reduce by 2.7% and 0.9% respectively.Available As and Sb are transformed to Fe/Al hydrous oxide-bound and residual As and Sb species.New phases of goethite and ferrihydrite are generated in passivated soils,and the contents of amorphous/crystal Fe oxides in soils rise remarkably after passivation.Besides,some As(Ⅲ)species are transformed to As(Ⅴ).The results reveal that Fe-As,Fe-Sb and Ca-Sb species might be generated after As and Sb in soil are passivated by iron-containing amendments.