甲氧苄氨嘧啶在黏土矿物上的吸附解吸机理

Adsorption and desorption mechanisms of trimethoprim on clay minerals

以高岭土和蒙脱土为吸附剂,选用Na^(+)和L-赖氨酸(Lys)作为共存组分,通过批实验探究了不同赋存形态的甲氧苄氨嘧啶(TMP)在黏土矿物上的吸附/解吸特征。结果表明:TMP在高岭土和蒙脱土上的吸附均在24 h内达到平衡。蒙脱土对TMP的吸附动力学特征会受到溶液中H^(+)竞争吸附与TMP赋存形态的影响,在pH较低时(如pH=3.0时)尤为明显。TMP在黏土矿物上的主要吸附机理为阳离子交换、静电吸引和分子间力,吸附分配系数受TMP^(+)/TMP0比例和作用力强度两方面影响。在实验条件下(TMP初始浓度为1 mg∙L^(-1),溶液pH为6),由于两种黏土矿物的pH缓冲能力和表面带电性不同,Na^(+)和Lys^(+)共存抑制了TMP在高岭土上的吸附,但促进了其在蒙脱土上的吸附。在解吸实验中,TMP^(+)和TMP0分别为TMP在高岭土和蒙脱土溶液中的主要存在形态,由于阳离子交换作用和静电吸引的结合强度要远强于分子间力,TMP在蒙脱土上的解吸率约为高岭土的4~5倍。

In this study,kaolinite and montmorillonite were used as adsorbents,Na^(+) and L-Lysine(Lys)were selected as coexisting components,and the adsorption/desorption characteristics of different forms of trimethoprim(TMP)on clay minerals were investigated through batch experiments.The results showed that TMP adsorption onto kaolinite and montmorillonite reached equilibrium within 24 h.The adsorption kinetic characteristics of montmorillonite on TMP were affected by the competitive adsorption of H^(+) in solution and the form of TMP.The main adsorption mechanisms of TMP were cation exchange,electrostatic attraction,and intermolecular force,while the adsorption coefficient was affected by the ratio of TMP^(+)/TMP0 and the strength of the sorption interaction.Due to the different pH buffering capacities and surface charges of the two clay minerals,when the initial concentration of TMP was 1 mg∙L^(-1) and the initial solution pH was 6,the coexistence of Na^(+)and Lys^(+) inhibited the adsorption of TMP onto kaolinite but promoted its adsorption onto montmorillonite.In the desorption experiments,TMP^(+) and TMP0 were the main species existing in the kaolinite and montmorillonite systems,respectively.Because the binding strength of cation exchange and electrostatic attraction is much stronger than the intermolecular force,the desorption ratio of TMP from montmorillonite was approximately 4~5 times that of kaolinite.