有机修饰改性土对镉离子的吸附及温度效应

主要研究了以不同比例十六烷基三甲基溴化铵(CTMAB)单一修饰和十六烷基三甲基溴化铵 十二烷基磺酸钠(CTMAB SDS)混合修饰的土耕层、黏化层土样对重金属镉离子的吸附。结果表明:吸附量顺序分别为耕层原土(GCK) >CTMAB5 0 %修饰改性土(5 0GCB) >CTMAB10 0 % SDS2 0 %修饰改性土(12 0GCS) >CTMAB10 0 %修饰改性土(10 0GCB)和粘化层原土(NCK) >CTMAB5 0 %修饰改性土(5 0NCB) >CTMAB10 0 %修饰改性土(10 0NCB) >CTMAB10 0 % SDS2 0 %修饰改性土(12 0NCS)的顺序,表明以表面修饰剂修饰土表面,确实存在着使得镉离子吸附能力减弱的趋势,但并未使修饰改性土完全丧失对于镉离子的吸附能力;吸附等温线可以用Langmuir方程描述;热力学参数的研究表明Cd2 吸附反应是熵增控制的自发性过程,但在探讨吸附自发性和最大吸附量关系时应考虑土壤本身的容量性质。机理研究认为,表面修饰剂对土壤表面的修饰改性是不均匀的,阳离子交换吸附和疏水键键合两种机制的竞争性吸附是修饰改性土壤依然具有对镉离子吸附作用的原因。土耕层各改性土样对Cd2 吸附的温度效应明显高于粘化层土样,证实了耕层对镉离子的化学吸附作用强于粘化层的结果

Cd2+ ADSORPTION OF ORGANIC MODIFIED SOILS AND ITS TEMPERATURE EFFECT

A study of Cd 2 adsorption of soil samples gathered from the tillage layer(TLLS)and clay layer of Lou soil(CLLS)modified with cetyltrimethylammonium bromide(CTMAB) at various rates and cetyltrimethylammonium bromide sodium dodecylsulphonate (CTMAB SDS) mixture was carried out. The results show that in terms of amount of Cd 2 adsorbed, a decreasing order of GCK>50GCB>120GCS>100GCB on TLLS and NCK>50NCB>100NCB>120NCS on CLLS, respectively, indicated that the adsorption capacity increased with the rise in temperature; and that a decreasing trend of Cd 2 adsorption was quite obvious on modified soils, but not to the extent that the modified soils completely lost their Cd 2 adsorption capacities. The Langmuir equation can be used to describe the Cd 2 adsorption isotherm. The study of thermodynamic parameters showed that Cd 2 adsorption on modified soils was spontaneously controlled by entropy increment, but the capacity property of the soil must be considered simultaneously in discussing the relationship between the adsorption spontaneity and maximal adsorption capacity of Cd 2 . The analysis of mechanism revealed that modification of the soils was uneven, and that the competition in Cd 2 adsorption between the mechanism of cation exchanging adsorption and the mechanism of hydrophobic bonding resulted in the residual adsorption of Cd 2 on modified soils. The effect of temperature on Cd 2 adsorption was significantly higher in TLLS than in CLLS, indicating that chemical adsorption on TLLS is stronger than that on CLLS.