有机修饰塿土中铬酸根吸附热力学特征及机理

Adsorption thermodynamic characteristics and mechanism of chromate in organic modified lou soil

研究了以十六烷基三甲基溴化铵(CTMAB)单一修饰和CTMAB+十二烷基磺酸钠(SDS)混合修饰的塿土耕层和黏化层土样对CrO42-的吸附热力学特征及机理.结果表明,Langmuir模型是描述两层次修饰土对CrO42-吸附等温线的最佳模型,供试土样吸附亲和力(bL)和最大吸附量(qmL)大小具有相同的变化趋势,同时与实验结果具有较好的一致性;热力学研究结果表明,修饰后塿土两土层各土样吸附CrO42-的表观吸附自由能变(?G)均为负值,属自发性反应,同一层次土壤中,各修饰土样-?G基本上呈现100CB>120CS>50CB的顺序,表明-?

The thermodynamic characteristics and mechanism of CrO4^2- adsorption on soil samples gathered tom the tillage layer （TLLS） and clay layer （CLLS） of lou soil modified singlely with cetyltrimethylammonium bromide （CTMAB） and modified mixedly with cetyltrimethylammonium bromide ＋ sodium dodecylsulphonate （CTMAB＋SDS） were studied. Langmuir model was the best one in describing CrO4^2- adsorption isotherms on two layer modified soils; in the test samples, the size of adsorption affinity （b^L） possessed same variation tendency with maximum adsorption amount （qm^L）, and was same relatively with the test results. The results of study of thermodynamics showed that the apparent adsorption free energy change（△G） of each modified soil sample adsorpted CrO4^2- was all negative value, belonging to spontaneous reaction. In the same layer soil, each modified soil sample -△G appeared basically the size order of 100CB〉120CS〉50CB, which showed the same sequence among -△G, b^L ,qm^L and equilibrium adsorption amount. The studies on the mechanism confirmed that the CrO4^2- adsorption of two layer lou soil was a physical and chemical coexist adsorption mechanism; organic modification of soil surface possessed the action of strengthening the physical adsorption but weakening the chemical adsorption.