Chen Yong, Wu Feng, Lin Yixin, Deng Nansheng, Bazhin Nikolai, Glebov Evgeni
School of Resources and Environmental Science, Wuhan University, Wuhan 430079, PR China.
J Hazard Mater. 2007 Sep 5;148(1-2):360-5. doi: 10.1016/j.jhazmat.2007.02.044. Epub 2007 Feb 23.
The photoinduced degradation of glyphosate (GLP) in the ferrioxalate system was investigated under irradiation with a 250W metal halide lamp (lambda>/=365nm). The efficiency of orthophosphates release, representing the photodegradation efficiency of GLP, increased with decreasing the initial concentrations of GLP and Fe(III)/oxalate ratios. At acidic pH value in the range of 3.5-5.0, higher efficiency of orthophosphates release up to 60.6% was achieved, while the efficiency dropped to 42.1% at pH 6.0. The photochemical process mainly involved the predominant species of iron(III), namely Fe(C(2)O(4))(2)(-) and Fe(C(2)O(4))(3)(3-), which lead to the formation of hydroxyl radicals in the presence of dissolved oxygen under UV-vis irradiation. Also, the complexation of GLP with Fe(III) obviously increased the light absorption of GLP and facilitated its degradation by direct photolysis. The ninhydrin test for primary amines showed that the GLP was attacked by hydroxyl radicals with CN cleavage to yield aminomethylphosphonic acid (AMPA) and CP cleavage to yield sarcosine. The photodegradation may be enhanced by the decomposition of reactive radicals produced through ligand-to-metal charge transfer (LMCT) of ferric-GLP complexes.
在250W金属卤化物灯（波长≥365nm）照射下，研究了草酸铁体系中草甘膦（GLP）的光致降解。代表GLP光降解效率的正磷酸盐释放效率随GLP初始浓度和Fe(III)/草酸盐比例的降低而增加。在3.5 - 5.0的酸性pH值范围内，正磷酸盐释放效率更高，可达60.6%，而在pH 6.0时效率降至42.1%。光化学过程主要涉及铁(III)的主要物种，即Fe(C₂O₄)₂⁻和Fe(C₂O₄)₃³⁻，它们在紫外-可见光照下在溶解氧存在下导致羟基自由基的形成。此外，GLP与Fe(III)的络合明显增加了GLP的光吸收，并通过直接光解促进其降解。对伯胺的茚三酮试验表明，GLP受到羟基自由基攻击，通过碳氮键断裂生成氨甲基膦酸（AMPA），通过碳磷键断裂生成肌氨酸。通过铁-草甘膦络合物的配体到金属电荷转移（LMCT）产生的活性自由基的分解可能会增强光降解。
