土壤对重金属离子的竞争吸附

COMPETITIVE ADSORPTION OF HEAVY METALS BY SOILS

本文研究了理化性质不同的黄棕壤、红壤和砖红壤对Zn、Ni、Co的竞争吸附。采用含有不同重金属离子量的0.05molL^(_1)Ca(NO_3)_2溶液平衡,pH为5.5。结果表明,其吸附量的顺序:黄棕壤>砖红壤>红壤。对各离子的选择性为:Zn>Ni≥Co。竞争吸附的机制与非竞争吸附有明显的不同。其特征首先表现在吸附量上,竞争吸附要比非竞争吸附高得多。特别明显的,土壤去掉游离氧化铁后其吸附量不但不降,反而有不同程度的增加,Zn^(2+)表现尤为突出;影响吸附量很大的陪伴阴离子作用受到严重抑制;反映土壤与重金属离子间作用能力大小的pH_(50)的变化符合吸附等温线的特点。其次根据土壤对重金属离子的吸附和解吸的情况,可以认为,红壤胶体表面吸附位数量远不及黄棕壤和砖红壤,但高能吸附位的比例高。

The competitive adsorption of Zn,Ni and Co frOm 10^(-4)-10^(-2) molLu^(-2) heavy metal ions solution containing 0.05/molL^(-1) Ca(NO_3)_2 (pH 5.5)by three soils with different physical and chemical properties was irivestigated.The regults obtained showed that the amount of heavy metals adsorbed bv soils was in the sequence:Yellow brown carth>Latosol>Red earth.The order of ion selectivity was:Zn>Ni≥Co.obviouslv,the mechnism of competitive adsorption differed from that of non-cmpetitive adsorption.Firstly,the quantity of competitive adsorption exceeded that of non-competitive adsorption. Most of all,the heavy metal ions,especially Zinc, adsorbed by the samples in which free iron oxide was removed increased to varying degrees instead of decreasing.Obvionsly,the effect of accompanying anion on the quantities of heavy metals adsorbed was greatly inhibited.The change of pH_(50) which could reflect the interaction between soil and heavy metal ionsw was in consistent with the characterisrics of adsorption isothirm.Secondly,according to the characteristics of adsorption and desorption of heavy metal ions,it might be considered that the adsorption sites on colloid stirface in red earth were less than those in yellow brown earth and latosol,but red earth had a higher proportion of high energy adsorption sites than yellow btown earth and latosol.