贵州典型黄壤土中有机质和碳酸钙对Cd2+吸附解吸特征的影响

Effect of Organic Matter and Calcium Carbonate on Absorption-Desorption Characteristics of Cd2+in Guizhou Yellow Loam Soil

为了研究去除有机质及碳酸钙前后黄壤土对Cd^(2+)的吸附解吸特性,采用序批平衡法进行原土、去有机质土及去碳酸钙土对Cd^(2+)的吸附解吸试验,用Langmuir和Freundlich型吸附等温方程对试验吸附数据进行拟合,研究有机质和碳酸钙对Cd^(2+)吸附解吸的影响。结果表明,3种土壤对Cd^(2+)吸附量均随平衡溶液中Cd^(2+)质量浓度的增加而增加,Cd^(2+)吸附率随Cd^(2+)初始质量浓度的增加呈先升高后降低的趋势,且Cd^(2+)吸附量和吸附率均呈现出原土>去碳酸钙土>去有机质土的趋势。去有机质土和去碳酸钙土中Cd^(2+)吸附等温线不适合用Langmuir方程描述,而Freundlich方程可较好地描述3种土壤对Cd^(2+)的等温吸附过程。黄壤中Cd^(2+)解吸量和解吸率均随Cd^(2+)初始质量浓度的升高而增大,且Cd^(2+)解吸量和解吸率均呈现出去有机质土>去碳酸钙土>原土的趋势。黄壤中Cd^(2+)解吸量与吸附量均呈极显著正相关(P<0.01)。当Cd^(2+)吸附量一定时,3种土壤中Cd^(2+)解吸量表现为去有机质土>去碳酸钙土>原土。由此可见,在贵州偏酸性典型黄壤中,有机质对Cd^(2+)吸附解吸行为的影响明显大于碳酸钙。

In order to understand absorption-desorption characteristics of Cd^(2+)before and after removal of organic matter and calcium carbonate,the laboratory batch experiments were conducted to study the absorption-desorption characteristics of Cd^(2+)in three soils including raw soil,soil with organic matter removed and soil with calcium carbonate removed.Langmuir and Freundlich equations were used to describe the adsorption data,and to analyze the effects of organic matter and calcium carbonate on the absorption-desorption characteristics of Cd^(2+).The results showed that the absorption capacity of Cd^(2+)in three soils increased with the increase of Cd^(2+)concentration in the equilibrium solution.The adsorption rate of Cd^(2+)increased firstly and then decreased with the increase of initial Cd^(2+)concentration.The absorption capacity and adsorption rate of Cd^(2+)followed the order:raw soil>soil with calcium carbonate removed>soil with organic matter removed.The adsorption data of the soils could be well described by Freundlich equation,but not the Langmuir equation in three soils.The desorption capacity and desorption rate of Cd^(2+)increased with the increase of initial Cd^(2+)content.The desorption capacity and desorption rate of Cd^(2+)followed the order:soil with organic matter removed>soil with calcium carbonate removed>raw soil.The desorption capacity was positively related to the adsorption capacity(P<0.01).When the adsorption capacity was constant,the desorption capacity of Cd^(2+)followed the order:soil with organic matter removed>soil with calcium carbonate removed>raw soil.It can be concluded that the effect of organic matter on the absorption-desorption characteristics of Cd^(2+)is greater than calcium carbonate in the typical acidic yellow loam soil in Guizhou.