乙二胺改性壳聚糖微球对Pd和Pt的双组分吸附

Bicomponent Adsorption of Pd and Pt Complex Anions on Ethylenediamine Modified Chitosan Microspheres

制备了乙二胺改性壳聚糖微球(ECS)。考察了Pd和Pt双组分体系中,ECS于最优pH(pH=2)下对Pd和Pt的吸附性能。实验结果表明,ECS中氨基的质量摩尔浓度为6.05mmol/g;酸性介质中ECS吸附Pd和Pt的主要机理为质子化氨基与金属络合阴离子之间的静电引力;当n(Pd)∶n(Pt)分别为0.5,1.0,1.5时,ECS吸附Pd的最大吸附容量分别为1.23,1.73,2.09mmol/g,吸附Pt的吸附容量分别为1.68,1.22,0.96mmol/g;Pd和Pt间存在竞争吸附,ECS对Pd的亲合性优于Pt,在吸附后期,原先被吸附的Pt部分被Pd取代;Biot数大于1 000,表明吸附为内扩散控制;用0.5mol/L的硫脲溶液脱附Pd和Pt,脱附率均大于65%,但5mol/L氨水对Pd的脱附选择性最好;经过连续3次吸附-脱附实验,提高了ECS对Pd的吸附-脱附选择性。

Ethylenediamine modified chitosan microspheres （ECS） were prepared for adsorption of metallic complex anions of Pd and Pt. Adsorptions of anions from bicomponent mixture on ECS at optimal pH （ pH = 2 ） were investigated. Concentration of amine group on ECS was 6.05 mmoL/g. The adsorption on ECS in acidic medium was because of electrostatic attraction between metallic complex anions and protonated amine groups. When n（Pd） ： n（Pt） are 0.5,1.0, 1.5, the maximum adsorption capacity of ECS are 1.23,1.73, 2.09 mmoL/g for Pd, and 1.68,1.22, 0.96 mmoL/g for Pt, respectively. The adsorbed Pt on ECS can be partially displaced by Pd due to greater affinity of the latter with ECS and competitive adsorption between the two kinds of ions. The Biot value is above 1 000, which indicates that the adsorption is internal diffusion control. Desorption rates of both Pd and Pt complex anions from ECS are more than 65 % with 0.5 moL/L thiourea as eluant. However 5 moL/ L ammonia is better. The selectivity of adsorption and desorption is improved by combining three adsorption - desorption eycles.