3种低分子量有机酸对紫色土吸附菲的影响

Influence of Three Low-Molecular-Weight Organic Acids on the Adsorption of Phenanthrene in Purple Soil

采用静态吸附实验,研究了3种低分子量有机酸(柠檬酸、苹果酸和草酸)对紫色土吸附菲的影响.结果表明紫色土吸附菲的动力学过程符合二级动力学模型,3种低分子量有机酸(LMWOAs)均能显著降低紫色土吸附菲的速率常数;线性吸附模型很好地描述了紫色土对菲的吸附热力学过程是以分配作用为主.当加入的3种LMWOAs浓度低于5 mmol·L^(-1)时,促进紫色土吸附菲;当LMWOAs浓度≥10 mmol·L^(-1)时,抑制紫色土吸附菲,抑制作用随LMWOAs浓度的增加而加强.当LMWOAs浓度为20 mmol·L^(-1)时,其抑制作用能力表现为柠檬酸>草酸>苹果酸,这与3种LMWOAs的分子结构和酸性强弱有关.与对照相比,随着LMWOAs浓度的增加,紫色土溶出的溶解性有机质(DOM)含量呈现先降低后升高的趋势,紫色土对菲的吸附量与土壤溶出的DOM含量呈负相关.

The effects of three low-molecular-weight organic acids（ citric acid,malic acid and oxalic acid） on the adsorption of phenanthrene in purple soil were studied by static adsorption experiment. The results showed that the adsorption kinetic process of phenanthrene in purple soil could be described by the second-order kinetic model,and the adsorption rate constant would significantly decrease in the presence of the three low-molecular-weight organic acids（ LMWOAs）. The adsorption thermodynamic process could be well described by linear adsorption model,which was dominated by distribution role. The three LMWOAs could promote the adsorption of phenantherene in purple soil when their concentrations were less than 5 mmol·L^（-1）,whereas inhibit the adsorption when their concentrations were more than 10 mmol·L^（-1）,and the inhibition would increase with increasing concentrations. Moreover,the inhibitory ability displayed a decreasing order of citric acid,oxalic acid,and malic acid when their concentrations were 20 mmol·L^（-1）,which is related to the molecular structure and acidity of the three LMWOAs. Compared with the control,the content of dissolved organic matter（ DOM） released from purple soil showed a trend of first decrease and then increase with increasing LMWOAs concentration,and the adsorption capacity of phenanthrene in purple soil was negatively related to DOM content.