氯苯类化合物在沉积物上的非线性吸附行为

Nonlinear Sorption Behaviors of Chlorobenzenes on Sediments

以5种自然沉积物为对象,采用批量平衡法,测定了氯苯、1,4-二氯苯、1,2,4-三氯苯和1,2,4,5-四氯苯在这5种沉积物样品上的吸附等温线,以研究沉积物自然有机质(NOM)的性质对氯苯类化合物(chlorobenzenes,CBs)吸附行为的影响.结果表明,1,2,4-三氯苯在虎门、黄沙、雅岗、三水、长洲5种沉积物中的等温吸附线性因子n都小于1,分别为0.956、0.858、0.872、0.947和0.915,说明所有吸附等温线均为非线性;同时,非线性的程度n与极性指数(O+N)/C呈负相关关系,相关系数R2达0.994 7,表明NOM的聚合度(以极性指数为表征)直接影响着吸附非线性程度;5种沉积物对1,2,4-三氯苯的吸附亲和力(Koc)随沉积物极性指数的增大而减弱,说明NOM聚合度较高的沉积物对1,2,4-三氯苯的吸附亲和力更强;氯苯、1,4-二氯苯、1,2,4-三氯苯、1,2,4,5-四氯苯在同一种沉积物(黄沙)上吸附等温线的线性因子n分别0.755、0.788、0.858、0.949,非线性程度按溶质分子由小到大的顺序依次减弱,说明溶质分子本身的性质也影响着CBs在沉积物上的吸附性能.

Sorption isotherms of chlorobenzene, 1,4-diehlorobenzene, 1,2,4-trichlorobenzene and 1,2,4,5-tetrachlorobenzene on 5 sediments were examined to understand its sorption behavior. All systems examined exhibits nonlinear sorption. All sorption isotherms are nonlinear as evidenced by the Freundlich n values of 5 sediments being between 0.858 to 0.956. Sorption nonlinearity is found to be a function of the polarity index of sediments natural organic matter （NOM） with a high correlative coefficient of 0.994 7, suggesting that the degree of condensation of NOM, characterized by its polarity index, is correlated with the sorption behavior of 1,2,4-trichlorobenzene. In addition, the sorption affinity （Koc） of the sediments for 1,2,4-trichlorobenzene increases with decreasing of NOM polar, indicating that a higher sorption affinity in the sediments is associated with a higher degree of condensation of NOM. The Freundlieh n values of chlorobenzene, 1,4- dicblorobenzene, 1,2,4-trichlorobenzene and 1,2,4,5-tetrachlorobenzene are 0.755, 0.788, 0. 858, 0.949 respectively, indicating that the smaller CBs molecule may result in more significant sorption nonlinearity.