多组分重金属复合体系在高岭土中的吸附差异

Adsorption of heavy metals in multi-metal systems on kaolinite clay

重金属环境污染问题日趋严重。针对利用黏土矿物高岭土治理多组分重金属环境污染的问题,本文研究了三种重金属离子镉(Cd^(2+))、铅(Pb^(2+))和铜(Cu^(2+))在土壤中广泛存在的高岭土于不同理化条件下(包括吸附时间、pH值、离子强度、重金属离子初始浓度)的吸附行为特性,以及两相与三相多组分重金属之间的竞争吸附行为。研究结果表明:在恒温条件下吸附达平衡后,高岭土对Pb^(2+)、Cd^(2+)和Cu^(2+)的吸附率均大于70%;当反应体系pH>7.0时,高岭土对这三种离子的吸附率可达90%以上;而当离子强度大于0.05 mol/L时,吸附率降低近一半。在复合体系中,不同重金属离子在高岭土表面的竞争吸附作用使高岭土对各重金属离子的吸附量小于单一组分,其中,高岭土对三种重金属离子的吸附能力大小为Cu^(2+)<Cd^(2+)<Pb^(2+)。研究结果表明,高岭土对Pb^(2+)、Cd^(2+)和Cu^(2+)都具有良好的吸附能力,其吸附量受pH值、离子强度和竞争吸附作用的影响较大。

Heavy metal pollution has been an increasingly serious issue,and using clay minerals to remediate the heavy metal contaminated environment is one of the hot research fields.The adsorption of Pb^(2+),Cu^(2+)and Cd^(2+)onto the surface of naturally occurring clay,kaolinite,was investigated by means of performing experiments and modeling under various conditions such as time,pH,ionic strength and the initial concentration of heavy metals.Additionally,experiments were carried out to investigate the competitive adsorption of each two and three heavy metals on kaolinite.Results show that kaolinite can uptake more than 70%of heavy metal cations at equilibrium at constant temperature.More than 90%of each heavy metal was adsorbed on kaolinite when the pH was larger than 7.0.However,the amount of metal adsorbed was reduced by about a half when the ionic strength of the solution exceeded 0.05 mol/L.In addition,the competitive adsorption between heavy metals resulted in less adsorption for each heavy metal in a multi-metal system than that in a single metal system.The capacities of kaolinite adsorbing heavy metals were in the order of Cu^(2+)<Cd^(2+)<Pb^(2+).Kaolinite therefore can be an applicative absorbent for Pb^(2+),Cu^(2+),and Cd^(2+).The solution pH,ionic strength and competitive adsorption significantly influence the adsorption of metal cations onto kaolinite.