State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, 163, Xianlin Ave., Nanjing, 210023, PR China; Department of Environmental Science and Engineering, Nanjing University Jinling College, 8, Xuefu Road, Nanjing, 210089, PR China.
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, 163, Xianlin Ave., Nanjing, 210023, PR China.
Sci Total Environ. 2016 Aug 1;560-561:123-30. doi: 10.1016/j.scitotenv.2016.03.239. Epub 2016 Apr 17.
The adsorption of glufosinate (GLU), a widely used herbicide similar to glyphosate (GLY), onto goethite was investigated as a function of the pH, ionic strength, background cations and anions, heavy metal ions and fulvic acids (FAs) by using batch adsorption experiments. In situ ATR-FTIR spectroscopy and density functional theory (DFT) calculations were carried out to characterize the molecular interactions between GLU and goethite surfaces. The macroscopic results indicated that an increasing pH exerted an adverse effect on GLU adsorption because of the electrostatic repulsion, and the adsorption was not sensitive to ionic strengths or background cation types, indicating that an inner-sphere surface complex was involved. GLU adsorption can be considerably depressed by PO4(3-), SO4(2-), and a high level of FA because of the competitive effect, while being enhanced by Cu(2+) with a maximum adsorption at approximately pH5 because of the metal ion bridging effect. Other examined divalent metal cations (Cd(2+), Zn(2+), and Pb(2+)) showed almost no effect on GLU adsorption, indicating weak interaction between them. ATR-FTIR spectra and the DFT calculations further proved that GLU was bonded to goethite surfaces through the formation of a monodentate mononuclear inner-sphere complex between the phosphinic moiety and surface Fe(III) centers under an acidic condition. The results showed that GLU had a similar adsorption mechanism to that of GLY onto goethite, but with a lower adsorption affinity, possibly exerting higher mobility and risk in soils.
作为一项功能，研究了草甘膦（GLY）类似的广泛使用的除草剂草铵膦（GLU）在针铁矿上的吸附，这取决于 pH 值、离子强度、背景阳离子和阴离子、重金属离子和腐殖酸（FA）。通过批量吸附实验进行了原位 ATR-FTIR 光谱和密度泛函理论（DFT）计算，以表征 GLU 与针铁矿表面之间的分子相互作用。宏观结果表明，由于静电排斥作用，pH 值的升高对 GLU 的吸附产生了不利影响，而吸附对离子强度或背景阳离子类型不敏感，表明涉及内球表面络合物。由于竞争效应，PO4(3-)、SO4(2-)和高浓度的 FA 会极大地抑制 GLU 的吸附，而 Cu(2+)会由于金属离子桥接效应而在大约 pH5 时增强吸附。其他研究的二价金属阳离子（Cd(2+)、Zn(2+)和 Pb(2+)）对 GLU 吸附几乎没有影响，表明它们之间相互作用较弱。ATR-FTIR 光谱和 DFT 计算进一步证明，在酸性条件下，GLU 通过膦酸部分与表面 Fe(III)中心之间形成单齿单核内球络合物与针铁矿表面结合。结果表明，GLU 与 GLY 具有相似的吸附机制，但吸附亲和力较低，可能在土壤中具有更高的迁移性和风险。
