铁盐与铝盐混凝去除EDTA土壤淋洗废液中砷、锑效果对比

实验以三氯化铁和三氯化铝作为混凝剂,对比研究了混凝去除EDTA土壤淋洗废液中砷、锑的效果,重点探讨了反应终点pH、EDTA浓度、Fe/Al投加量以及共存重金属离子对砷、锑去除效果的影响。结果表明:1)对于EDTA土壤淋洗废液中As(Ⅴ)、Sb(Ⅴ)的去除,铝盐比铁盐效果更优;2)EDTA的存在不仅降低了铁盐/铝盐混凝对As(Ⅴ)、Sb(Ⅴ)的吸附去除效果,同时抑制了砷酸铁、锑酸铁等物质的生成,削弱了铁盐对As(Ⅴ)、Sb(Ⅴ)的沉淀去除。EDTA导致铁盐混凝过程中生成粒径较大、表面活性较低的稳定结晶态絮体;3)当c(EDTA)=0.05 mol/L时,在pH=5、ρ(Al)=2000 mg/L的条件下,铝盐对EDTA土壤淋洗废液中As(Ⅴ)、Sb(Ⅴ)的去除率分别高达98.00%和93.09%;4)共存重金属离子通过与EDTA络合,增加了絮体Al(OH)₃的生成量,促进了As(Ⅴ)、Sb(Ⅴ)去除。由此表明,铝盐能够有效实现EDTA土壤淋洗废液中As(Ⅴ)、Sb(Ⅴ)的去除,对于推动基于EDTA的土壤淋洗技术的广泛应用具有重要意义。

COMPARATIVE STUDY ON REMOVAL OF ARSENIC AND ANTIMONY FROM SPENT EDTA SOIL WASHING SOLUTION BY IRON/ALUMINUM COAGULATION PROCESS

In the experiment, the removal efficiencies of As(Ⅴ) and Sb(Ⅴ) by coagulation process were comparatively studied when ferric chloride (FeCl₃) and aluminum chloride (AlCl₃) were used as coagulant separately, while the effects of the reaction endpoint pH, EDTA concentration, Fe/Al dosage and the coexistence of heavy metals on removal of As(Ⅴ) and Sb(Ⅴ) from spent EDTA soil washing solution were mainly discussed. The results showed that: 1) aluminum salt was more effective than iron salt in the removal of As(Ⅴ) and Sb(Ⅴ) from spent EDTA washing solution by coagulation process; 2) the presence of EDTA not only reduced the removal of As(Ⅴ) and Sb(Ⅴ) by the adsorption of iron/aluminum flocs, but also inhibited the formation of iron arsenate, iron antimonite precipitates, in which the removal of As(Ⅴ) and Sb(Ⅴ) decreased simultaneously. Larger size and quantity of stable crystalline precipitate was formed during iron coagulation process with EDTA; 3) when c(EDTA)=0.05 mg/L, the removal efficiency of As(Ⅴ) and Sb(Ⅴ) in the spent EDTA washing solution by aluminum coagulation was up to 98.00% and 93.09%, respectively, with pH=5 and ρ(Al)=2000 mg/L; 4) the formation of Al(OH)₃ flocs was enhanced to promote the removal of As(Ⅴ) and Sb(Ⅴ) when the coexisting heavy metals complexed with EDTA. The effective removal of As(Ⅴ) and Sb(Ⅴ) from spent EDTA soil washing solution by iron/alumiaum coagulation will promote the development and application of EDTA-based soil washing technologies.