The simultaneous presence of glyphosate and phosphate at the goethite surface as seen by XPS, ATR-FTIR and competitive adsorption isotherms

The simultaneous presence of glyphosate and phosphate at the goethite surface as seen by XPS, ATR-FTIR and competitive adsorption isotherms
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DOI：
10.1016/j.colsurfa.2016.03.049
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发表时间：
2016-06
期刊：
Colloids and Surfaces A: Physicochemical and Engineering Aspects
影响因子：
--
通讯作者：
Carolina V. Waiman;J. M. Arroyave;Hongfeng Chen;W. Tan;M. Avena;Graciela P. Zanini
Carolina V. Waiman;J. M. Arroyave;Hongfeng Chen;W. Tan;M. Avena;Graciela P. Zanini
中科院分区：
其他
文献类型：
--
作者：
Carolina V. Waiman;J. M. Arroyave;Hongfeng Chen;W. Tan;M. Avena;Graciela P. Zanini

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采用宏观（吸附等温线、电泳）和光谱（XPS、ATR-FTIR）相结合的方法研究了草甘膦和磷酸盐在针铁矿上的同时吸附。吸附等温线与竞争性Langmuir等温线一起间接表明，这两种物质共存于针铁矿表面。磷酸盐的最大吸附量为2.50 μmol/m2，草甘膦的最大吸附量为1.77 μmol/m2。Langmuir吸附常数对磷酸盐为0.15 μM− 1，对草甘膦为0.01 μM− 1。草甘膦XPS信号的形状和位置不因表面磷酸盐的存在而改变，反之亦然。ATR-FTIR的结果相当。因此，光谱学证据表明，草甘膦（形成的内球复合物的类型）的针铁矿表面的结合模式是不修改吸附磷酸盐。这对于平衡条件下和动态条件下的系统都是有效的。研究结果是重要的环境建模，表明表面络合模型可以用来与信心预测形态的双配体系统使用单配体系统获得的吸附参数。
The simultaneous adsorption of glyphosate and phosphate on goethite was studied by combining macroscopic (adsorption isotherms, electrophoresis) and spectroscopic (XPS, ATR-FTIR) techniques. Adsorption isotherms together with the Competitive Langmuir isotherm indirectly show that both substances coexist at the goethite surface. The adsorption maximum for phosphate was 2.50 μmol/m2whereas for glyphosate it was 1.77 μmol/m2. The Langmuir adsorption constant was 0.15 μM−1for phosphate and 0.01 μM−1for glyphosate. The shape and position of the XPS signals of glyphosate did not change by the presence of phosphate at the surface andvice versa. Equivalent results were found with ATR-FTIR. Therefore, spectroscopic evidence indicates that the binding mode of glyphosate (type of inner-sphere complexes formed) to the goethite surface is not modified by adsorbing phosphate. This is valid for systems under equilibrium conditions and under dynamic conditions. The findings are important in environmental modeling, showing that surface complexation models can be used with confidence to predict speciation in double-ligand systems using adsorption parameters obtained with single-ligand systems.