土壤吸附砷酸盐动力学的初步研究

本研究目的是了解陕西省的几种土壤吸附和解吸附砷酸盐的速率和过程,以及其吸附能量。Kuo和Lotse导出的双常数速率公式拟合试验资料优于一级、二级、三级反应公式,抛物线扩散和Elovich公式等五个公式。用双常数速率公式(C=k·C₀·t^1/m)分两段拟合能进一步提高拟合优度。根据Arrhenius公式计算出的吸附活化能是0.70—3.40千卡/克分子。低的活化能表明,供试土壤对砷酸盐的吸附作用是一种完全不同于真溶液条件化学反应的物理学过程。土壤吸附和解吸附砷酸盐的速度和容量受作用时间、温度、溶液∶土壤比率,加入的砷量和浓度,以及土壤特性的影响。粘土的吸附反应常数(k),吸附量比沙壤土大。而沙壤土有高的解吸附反应速度常数(k_-1^'),砷酸盐容易被解吸附而释放出来。

A PRIMARY STUDY ON KINETICS OF ARSENATE ADSORPTION BY SOILS

The present paper is to inyestigate the rate and process of arsenate adsorption and desorption,and the energy of arsenate adsorption by some soils in Shaangi Province.A two-constant rate equation (C=k·C₀·t^1/m)developed by Kuo and Lotse is better than five equations,i.e.firstrorder reaction,second-order reaction,third-order reaction,parabolic diffusion and the elovich equations used for fitting the experimental data.Sectionally fitting by two-constant rate equation can further improve the goodness of fit.The activation energy of adsorption calculated according to the Arrhenius equation was 0.7-34 kcal/mole.The relatively low activation energy suggests that adsorptian of aasenate in the soils might probably be a physical process,which obviously dffifens from the chemical reaction in true solution.The rate and capacity of adsorption and desorption by soils are affected by incubating time,temperature,ratio of solution and soil,concentration and amount of As added,and soil characteristics.Clay soil has a higher adsorption rate constant (k),and higher adsorption amount than sandy loam.But the sandy loam has a higher desorption rate constant (k_-1),so arsenate is more easily released from soil into solution.