有机酸对红壤等温吸附镉的影响

研究了有机酸对红壤等温吸附镉的影响,结果表明: 在有机酸的存在下,土壤对镉离子的吸附都满足Langmuir等温吸附方程,相关系数均在0.98以上,镉离子吸附常数k的大小顺序,在黄筋泥田中为:胡敏酸＞无有机酸＞柠檬酸＞草酸＞乙酸＞酒石酸;在黄筋泥中为:胡敏酸＞酒石酸＞乙酸＞柠檬酸＞无有机酸＞草酸; 最大吸附量b在两种土壤上均是胡敏酸最大,柠檬酸最小.对等温吸附的影响是:加入低分子量有机酸后,吸附量降低,而随着胡敏酸的加入,吸附量却升高.未加有机酸的土壤对镉的吸附大部分是通过静电作用完成的,并保留在低能位上.加入胡敏酸的土壤,低能位和高能位对镉的吸附几乎相等,不是以低能位为主.

Effects of organic acids on adsorption isotherms of cadmium in red soils

Effects of organic acids on adsorption isotherms of cadmium in soils were studied leading to the following results. The adsorption isotherms of cadmium in soils containing organic acids could be fitted into the Langmuir equation with correlation coefficients always above 0. 98. The strengths of influence of different organic acids on adsorption constant k in descending order for red clayey paddy soil were: humic acid > without organic acid > citric acid > oxalic acid > acetic acid > tartaric acid; whereas for in red clayey upland soil were : humic acid > tartaric acid > acetic acid > citric acid > without organic acid > oxalic acid. The cadmium adsorption maximum b was highest in soil supplemented with humic acid, and was least in soil supplemented with citric acid. Most of added cadmium was adsorbed by static electronic force and retained on the sites of low binding energy in soil without supplementing organic acid. However, the amount of cadmium retained on low binding energy site and on high binding energy site was almost the same in soil supplemented with humic acid.