有机修饰塿土对苯胺的吸附

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)混合修饰塿土耕层和粘化层土样,从吸附实验和热力学角度研究修饰土样对苯胺的吸附特征和机理。结果表明,供试土样对苯胺吸附均呈现100CB>50CB>120CS>CK的高低顺序,耕层修饰后对苯胺的平衡吸附量增大了4.5￣8.57倍,粘化层土样增大了6.0￣18.33倍;温度为40℃时耕层未修饰土样对苯胺的吸附量高于粘化层未修饰土样,20℃时则低于粘化层原土土样,而修饰土样则均呈现粘化层修饰土样对苯胺的吸附高于塿土耕层修饰土样的结果;耕层土样随温度升高苯胺平衡吸附量升高,而粘化层土样则表现出降温有利于苯胺吸附的现象,修饰剂对土样的修饰对苯胺的吸附具有"感温钝化"效应;Henry模型适用于描述苯胺的吸附;修饰土样对苯胺的吸附自由能变均为ΔG<0,属于自发反应,粘化层各土样对苯胺吸附为放热熵减过程,吸附自发性由焓减控制,耕层各土样对苯胺吸附为吸热熵增过程,其吸附自发过程为熵增控制过程;疏水吸附是修饰土样对苯胺吸附的主要机理,但修饰剂对于土壤表面的修饰是不均匀修饰,粘化层土样以物理吸附机制为主,耕层土样则存在化学吸附的机制。

Adsorption of Aniline on an Organic Modified Lou Soil

Two soil layer samples, tillage layer (TLLS) and clay layer (CLLS), collected from a lou soil area, were modified by addition of cetyltrimethylammonium bromide (CTMAB) alone at different rates as well as by the mixture of cetyltrimethylammonium bromide and sodium dodecylsulphonate (CTMAB+SDS), and the adsorption characteristics, thermodynamics and mechanism of aniline were studied simultaneously. Results show that the equilibrium adsorption amount (EAA) of aniline on both samples were in the order of 100CB (100%CTMAB modified soils) > 50CB (50%CTMAB modified soils) > 120CS (100%CTMAB + 20%SDS modified soils) > CK (unmodified soils). The EAA of aniline on the modified TLLS was 4.5-8.57 times higher than that on the unmodified TLLS, while the EAA of aniline on the modified CLLS was 6.0-18.33 times higher than that on the unmodified CLLS. The EAA of aniline on the unmodified TLLS was higher at 40 ℃, but was lower at 20 ℃ than that on the unmodified CLLS respectively, while the EAA of aniline on the modified CLLS was higher than that on modified TLLS at both temperature. The EAA of aniline increased on modified TLLS, but, in contract, decreased on the modified CLLS with the increase of temperature, and the modification treatment could decrease the effects of temperature on the adsorption of aniline. Henry equation was used to describe the aniline adsorption isotherm. The thermodynamic parameters show that aniline adsorption for the modified soil was spontaneous (ΔG<0). The adsorption of CLLS is a process of both enthalpy decrease and entropy decrease, its spontaneity being controlled by enthalpy decrease, while that of TLLS is a process of both enthalpy increase and entropy increase, its spontaneity being controlled by entropy increment. The hydrophobic adsorption is the primary mechanism of aniline adsorption on the modified soils, but the organic modifiers are distributed on soil surface with an uneven characteristics. The adsorption of aniline is physical mechanism in CLLS, while the chemical adsorption is in TLLS.