红壤中低分子量有机酸的吸附特征

Adsorption Characteristics of Low Molecular Weight Organic Acids in Red Soil

应用平衡法研究了红壤对草酸、柠檬酸、酒石酸和苹果酸的吸附行为。结果表明:红壤对有机酸的吸附量随着有机酸平衡溶液浓度的增加而增加,有机酸种类不同,吸附量也不同。有机酸在红壤中的吸附行为均可以很好地用Langmuir、Freundlich和Temkim方程描述,其中以Langmuir方程的拟合效果最好。红壤对有机酸均具有较高的吸附率,在0.5～20mmolL-1初始浓度范围内,草酸、柠檬酸、酒石酸和苹果酸的吸附率最大分别可达89.2%、77.5%、67.4%和47.1%。红壤对柠檬酸、酒石酸和苹果酸的吸附率均随着有机酸初始浓度的增加先急剧下降(<5mmolL-1),之后缓慢下降至趋于平稳;草酸的吸附率则随着初始浓度的增加而增加,在3mmolL-1左右时达到最大,随后降低至趋于平稳。

This research investigated the adsorption behaviours of oxalic,citric,tartaric and malic acids in red soil by a batch equilibrium method.The results indicated that the adsorption amount increased with the increase of equilibrium concentration,and the adsorption amount was different with the different type of organic acids.The adsorption characteristics of oxalic,citric,tartaric and malic all could be well described by Langmuir,Freundlich and Temkim equations,and the Langmuir equation was the best one.The adsorption ratios of organic acids in red soil were all high.When the initial concentrations ranged from 0.5 to 20 mmol L-1,the maximum adsorption ratio of oxalic,citric,tartaric and malic acids could reach 89.2%,77.5%,67.4% and 47.1%,respectively.The adsorption ratios of citric,tartaric and malic acids in red soil all dramatically decreased with the increasing initial concentrations of organic acids（ 5 mmol L-1）,and then decreased slowly to be steady with the further increase of initial concentrations.The adsorption ratio of oxalic acid increased first with the increase of its initial concentration and reached the maximum concentration of 3 mmol L-1,then decreased until the steady status.