电解质及曝气条件对酸性铁电絮凝成矿及其固载重金属的影响

Impacts of supporting electrolyte and aeration conditions on Fe mineral formation and heavy metal immobilization in Fe-electrocoagulation at acidic pH

本文针对酸性重金属废水开展了一系列铁电絮凝实验,重点考察不同电解质种类以及曝气与否对形成铁矿物种类和絮凝性能的影响.研究发现,酸性电絮凝过程可分为铁积累阶段和成矿阶段,积累阶段主要是Fe(Ⅱ)/Fe(Ⅲ)的生成与富集,矿物形成和重金属去除主要发生在成矿阶段.使用NaNO_(3)作为电解质易使铁阳极钝化,导致低成矿量和重金属去除率;在无曝气条件下NaCl、Na_(2)SO_(4)、NaH_(2)PO_(4)电解质体系产生的主要铁矿物分别为磁铁矿、绿锈和蓝铁矿;曝气条件下NaCl、Na_(2)SO_(4)体系产生氢氧化铁,NaH_(2)PO_(4)体系产生磷酸铁.重金属固载实验结果表明,磁铁矿和绿锈对Cd(Ⅱ)、Cu(Ⅱ)和Ni(Ⅱ)均表现出优异的吸附效果,但磁铁矿对于Cd(Ⅱ)的吸附效率高于绿锈;蓝铁矿和磷酸铁对Cu(Ⅱ)和Cd(Ⅱ)吸附效果优异,对Ni(Ⅱ)较差;氢氧化铁絮体对4种重金属的固载效果均较差.浸出实验说明磁铁矿和绿锈对重金属固载稳定性优于其他铁矿物.研究结果为铁电絮凝技术应用于酸性重金属废水处理提供重要证据.

In this study,a series of experiments on Fe-electrocoagulation were conducted to treat acidic heavy metal wastewaters.The effects of the type of supporting electrolyte and aeration on the performance of electrocoagulation and the species of Fe minerals were investigated.The results of the research showed that the acidic electrocoagulation process can be divided into two stages:Fe accumulation stage and Fe mineralization stage.The accumulation stage mainly involves the generation and enrichment of Fe(Ⅱ)/Fe(Ⅲ),while mineral formation and immobilization of heavy metals mainly occur in the latter stage.The use of NaNO_(3)as the supporting electrolyte resulted in the passivation of Fe anodes,leading to a low mineralization rate and heavy metal removal efficiency.Without aeration,Fe-electrocoagulation systems with NaCl,Na_(2)SO_(4),and NaH_(2)PO_(4)as supporting electrolytes generated magnetite,green rust,and vivianite,respectively.Under aeration conditions,iron hydroxide was formed in NaCl and Na_(2)SO_(4)electrolyte systems,while iron phosphate was produced in the NaH_(2)PO_(4)electrolyte system.Magnetite and green rust were found to have high adsorption efficiencies for the heavy metals Cd(Ⅱ),Cu(Ⅱ),and Ni(Ⅱ),with magnetite demonstrating a higher adsorption efficiency for Cd(Ⅱ)than green rust.Meanwhile,vivianite and iron phosphate effectively fixed Cu(Ⅱ)and Cd(Ⅱ),while Ni(Ⅱ)had poor adsorption on both minerals.The adsorption efficiencies of the four types of heavy metals for iron hydroxide were low.The results of leaching experiments showed that the adsorption stability of heavy metals on magnetite and green rust was better than that on vivianite,iron hydroxide,and iron phosphate.Overall,the findings of this study provide important evidence for the potential use of Fe-electrocoagulation as an effective method for treating acidic heavy metal wastewaters.