草甘膦在高指{201}二氧化钛表面的吸附去除

The removal of glyphosate by adsorption on high-index {201} TiO_2

有机磷农药草甘膦(PMG)的广泛使用和环境残留严重威胁人体健康,其去除治理是环境领域面临的一大挑战.本文研究了草甘膦在高指{201}晶面二氧化钛(TiO_2)上的吸附行为,探讨了吸附时间、溶液pH和草甘膦浓度对吸附效率的影响,并通过Zeta电位表征和电荷分布多位点络合(CD-MUSIC)模型考察了草甘膦在二氧化钛上的络合结构.结果表明,{201}TiO_2对草甘膦的吸附在40 min内即可达到吸附平衡,吸附动力学符合准二级动力学方程.吸附等温线符合Langmuir方程,说明其吸附过程主要是近似单分子层的化学吸附.pH对吸附效率影响较大,酸性条件有利于草甘膦的吸附去除.Zeta电位的表征结果表明,草甘膦吸附后TiO_2表面等电点从5.6向左偏移至4.2,说明形成带负电的内层配合物,进一步的红外光谱结果表明草甘膦以P—O—Ti的络合形式与TiO_2表面结合.CD-MUSIC模型拟合结果表明草甘膦与TiO_2表面可能形成单齿单核或双齿双核的内层络合结构.本研究结果对深入理解草甘膦的微观界面行为及去除具有重要意义.

The widespread use of glyphosate（PMG） and its environmental residues pose a potential threat to human health,and its removal presents a great challenge.In this study,the adsorption mechanism of PMG on high-index {201} faceted titanium dioxide（TiO2） was explored.The effects of reaction time,initial pH of solution,and concentration of PMG on adsorption efficiency were studied,and the surface complexation structure of PMG on TiO2 was investigated via the zeta potential analysis and charge distribution multi-site complexation（CD-MUSIC） model.The results show that the adsorption of PMG on TiO2 reached equilibrium within 40 min.The adsorption kinetics conforms to the pseudo-second order kinetics.The adsorption isotherm fits well with the Langmuir model,indicating its single layer chemical adsorption nature.The pH has a great influence on the adsorption efficiency,and the acidic condition favors the removal of PMG.The results of zeta potential show that the point of zero charge of TiO2 shifted from 5.6 to 4.2 upon PMG adsorption,suggesting the formation of negatively charged inner-sphere complexes.FTIR results confirm that PMG formed surface complex on TiO2 via P—O—Ti bond.The CD-MUSIC model integrating a monodentate mononuclear（MM） or bidentate binuclear（BB） surface complexes well describes the adsorption behavior.The results of this study are of great significance to understand the microscopic interfacial behavior and removal of PMG.