Abstract: 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 ( FeOAsO₃H^1.5- and FeOAsO(H₂O)₂^0.5-), 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 FeOHCd^1.5+ with binding constant of 31.05 and the amount of this complex decreased with rising pH.

Key words: ferric chloride, mechanism of arsenic and cadmium, CD-MUSIC

摘要： 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（FeOAsO₃H^1.5-、FeOAsO（H₂O）₂^0.5-）的表面配合物，结合常数分别为63.04、66.50；而 Cd（Ⅱ）则以 FeOHCd^1.5+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。

关键词: 三氯化铁, 砷、镉去除机理, 电荷分布多位络合模型