pH、离子强度和介电常数对低分子量有机酸在红壤中吸附行为的影响

Effects of pH,Ionic Strength and Dielectric Constant on Adsorption of Low Molecular Weight Organic Acids in Variable Charge Soil

通过一次平衡法考察了pH、离子强度和溶剂介电常数对红壤吸附低分子量有机酸的影响。研究结果表明,随着溶液pH值的升高有机酸的吸附量降低,其中草酸和酒石酸的吸附量在pH3.5～5.0范围内随着pH值的升高而急剧下降,之后缓慢下降（pH5.0～7.0）。柠檬酸、酒石酸和苹果酸的吸附量在1～2mmol/L初始浓度范围内随着离子强度的增加没有明显变化,但在2～20mmol/L初始浓度范围内却随着离子强度的增加而增加。红壤对草酸、柠檬酸、酒石酸和苹果酸的吸附量均随着溶剂介电常数的减小而增加。当溶剂中含6%的乙醇时,草酸、柠檬酸、酒石酸和苹果酸的吸附量分别是对照（不含乙醇）的1.05、1.05、1.11和1.31倍。

The effects of pH, ionic strength and dielectric constant on adsorption of low molecular weight organic acids in a variable charge soil were investigated by a batch equilibrium method. The results indicated that the adsorption amount of organic acids declined with the increase of solution pH. And the adsorption amount of oxalic and tartaric acids declined sharply with pH increasing from 3.5 to 5.0 and then decreased slowly （.oH 5.0 ~ 7.0）. When the initial concentrations of organic acids ranged from 1 to 2 mmol/L, the ionic strength had little influence on the adsorption of organic acids, but increased significantly with an increase of ionic strength when the initial concentrations ranged from 2 to 20 mmol/L. In addition, the adsorption amount of organic acids increased with a decrease of dielectric constant of the solvent. When 6% ethyl alcohol was contained in the solvent, the adsorption amount of oxalic, citric, tartaric and malic acids were 1.05, 1.05, 1.11 and 1.31 times respectively of those in the absence of ethyl alcohol.