恒电荷土壤胶体对Cu2+ 、Pb2+ 的静电吸附与专性吸附特征

供试土壤胶体对Cu2 、Pb2 的吸附强度用pH50 值表示 ,其大小次序为 :土 >黄绵土、黑垆土 >黄褐土。离子强度实验和表面络合反应机制证明恒电荷土壤胶体对Cu2 、Pb2 的吸附含有专性吸附 ,n值可作为判断专性吸附与静电吸附比例的特征值 ,低pH值时 ,以水解 -络合吸附为主 ;高pH值时 ,以水解 -络合与沉淀吸附为主。静电吸附和专性吸附的比例与pH有关 ,各土壤胶体专性吸附百分数大小为 :黄褐土 >土 >黑垆土 >黄绵土。不同土壤胶体在同一介质中对Cu2 、Pb2 的固有络合常数logKintM 值及固有络合ΔG m 负值大小次序与吸附强度大小一致。在定pH定浓条件下 ,考虑离子之间的相互作用时 ,土壤胶体对重金属离子的吸附过程可用BDM等温式描述。供试土壤胶体对Cu2 、Pb2 专性吸附ΔG m 的大小与固有络合ΔG m 接近且大小次序也一致。

THE CHARACTERISTICS OF Cu2+ AND Pb2+ ELECTROSTATIC AND SPECIFIC ADSORPTIONS OF CONSTANT CHARGE SOIL COLLOIDS

The strength of Cu²⁺,Pb²⁺ adsorbed by the tested soil colloids could be expressed by pH₅₀ value.The strength of Cu²⁺,Pb²⁺ adsorbed was in sequence of old manured loessal soil>dark cultivated loessal soil>yellow loessal soil>yellow cinamon soil.Cu²⁺,Pb²⁺ adsorption of the tested soil colloids mainly include specific adsorption,and n value was regarded as characteristic value of specific and electrostatic adsorption proportion.The proportion between specific and electrostatic adsorption was related to pH.The percentage of Cu²⁺,Pb²⁺ specific adsorption by the tested soil colloids showed the trend of yellow cinamon soil>old manured loessal soil>dark cultivated loessal soil>yellow loessal soil.At lower pH,adsorbed mechanism was mainly controlled by hydrolysis-complex reaction;at higher pH,it was controlled by hydrolysis-complex and precipitating adsorption.The sequence of Cu²⁺,Pb²⁺ intrinsic complex constant of different soil colloids was consistent in adsorbed strength.If the interaction of metal ions was considered,the adsorption of soil colloids to metal ion could be described through BDM equation. value was expressed as Cu²⁺,Pb²⁺ adsorbed strength by soil colloid,the larger the negative value was,the larger the specific adsorbed strength was.The negative value of in different soil colloids was consistent with the sequence of Cu²⁺,Pb²⁺ intrinsic complex constant and permanent charge density.