三氯化铁除砷和镉的机理

摘要

The mechanism of arsenic and cadmium removal withferric chloride was studied by analysis of residue samples with CD-MUSIC, XPS, FTIR and Zeta potential. There was interference between As and Cd by competing the active site on iron oxide in the range of pH at 3-7. Nevertheless, in the range of pH at 7-10, Cd(Ⅱ)was mainly removed by precipitation as Cd(OH)2, which could increase As removal by co-precipitation. According to the results simulated with CD-MUSIC, As(Ⅴ) was mainly removed by forming monodentate uninuclear surface complexes (FeOAsO3H1.5- and FeOAsO(H2O)20.5-), with binding constants of 63.04 and 66.50 respectively. Besides, Cd(Ⅱ) was combined on the surface of ferriferrous oxide with the formation of FeOHCd1.5+ with binding constant of 31.05 and the amount of this complex decreased with rising pH.%采用电荷分布多位络合模型模拟（CD-MUSIC）、XPS、FTIR和Zeta电位分析的方法研究了三氯化铁去除As(Ⅴ)、Cd(Ⅱ)的机理。结果表明：在pH 3～7范围内，砷、镉通过竞争铁氧化物表面的有效作用位点而相互抑制；而在pH 7～10范围内，Cd(Ⅱ)主要以Cd(OH)2沉淀的方式得以去除，并通过共沉淀作用促进砷的去除。根据CD-MUSIC 模拟结果，As(Ⅴ)主要形成单齿单核质子化（ FeOAsO3H1.5-、FeOAsO(H2O)20.5-）的表面配合物，结合常数分别为63.04、66.50；而 Cd(Ⅱ)则以 FeOHCd1.5+形态结合在铁氧化物的表面，结合常数为31.05，其含量随着pH的升高逐渐减少。