西北旱田黄土对Pb(Ⅱ)和氯吡硫磷复合污染的共吸附机制研究

Study on the Co-Adsorption Mechanism of Pb (Ⅱ) and Chlorpyrifos on Arid Loess in Northwestern China

通过静态批次实验研究旱田黄土对Pb(Ⅱ)和氯吡硫磷的共吸附行为,使用SEM,FTIR,XRD和理论分析揭示共吸附机制。实验结果发现:黄土对Pb(Ⅱ)和氯吡硫磷的共吸附符合Langmuir等温线方程,经计算得出的理论吸附容量qm分别为12.5和0.64mg.g-1,准二级动力学方程能更好地描述反应行为。吸附反应后,黄土表面形貌变化很小,FTIR图谱中的某些波峰红移、消失或强度减弱,综合XRD图谱及理论分析,认为:旱田黄土对Pb(Ⅱ)的吸附为表面配位络合和范德华力的作用,以化学吸附为主;而氯吡硫磷的去除涉及到黄土有机质对氯吡硫磷大分子的截留作用,以及氢键、范德华力的作用,以物理吸附为主,兼有化学吸附的贡献。旱田黄土有机质对Pb(Ⅱ)和氯吡硫磷的吸附有重要贡献。

The co-adsorption characteristics of Pb （Ⅱ） and chlorpyrifos on arid loess were investigated with batch adsorption procedures,and the co-adsorption mechanism was studied with approaches of SEM,FT-IR,XRD and theoretical analysis.The experimental results indicated that the adsorption process of Pb （Ⅱ） and chlorpyrifos on loess fit better the Langmuir isotherm,the maximum adsorption capacity of qmis 12.5and 0.64mg . g -1 for Pb （Ⅱ） and chlorpyrifos on loess,respectively,and the reaction could be illustrated with pseudo-second order kinetic equation.The SEM micrograph of loess surface varies little after the adsorption process of Pb （Ⅱ） and chlorpyrifos,and certain wave peaks of FTIR spectra red-shift,disappears or intensity-decrease,with the XRD pattern and theoretical analysis,the adsorption mechanism is described as follows ： the adsorption of Pb （Ⅱ） on arid loess is the chemical-effect of coordination-complexation and Van der Waals force ; the physical-adsorption on chlorpyrifos involves the interception function,hydrogen bonds and Van der Waals force,and chemical adsorption effect to some extent.The organic matter in arid loess plays an important role in Pb （Ⅱ） and chlorpyrifos adsorption.