Instituto de Química de Araraquara, UNESP -Univ Estadual Paulista, CP 355, 14801-970 Araraquara, SP, Brazil.
Water Res. 2010 Jun;44(12):3745-53. doi: 10.1016/j.watres.2010.04.025. Epub 2010 Apr 29.
The complexation of iron ions with the herbicide tebuthiuron (TBH), during a solar photo-Fenton process, was investigated using cyclic voltammetry with a glassy carbon electrode. An oxidation peak was observed at +0.64 V after addition of Fe(NO(3))(3) to TBH solution, indicating the formation of a Fe-TBH complex, which was not observed in the presence of ferrioxalate or citrate complexes. This complexation hinders photoreduction of Fe(III), and consequently TBH degradation. The main degradation route, in the presence or absence of citric acid (in the latter case with Fe(NO(3))(3) only), is initiated by the hydroxylation of a terminal methyl group of the urea, indicating an identical degradation mechanism. Hydroxylation of the central methyl of urea, and of the tert-butyl group, was also observed after extended irradiation periods in the presence of citric acid, but was not observed in the presence of Fe(NO(3))(3), due to a slower degradation rate in the absence of the citrate complex. No intermediate, generated from opening of the thiadiazole ring, was identified under the various different conditions.
在太阳光芬顿过程中，利用玻碳电极的循环伏安法研究了铁离子与除草剂特丁津（TBH）的络合作用。向 TBH 溶液中添加 Fe(NO3)3 后，观察到+0.64 V 处出现氧化峰，表明形成了 Fe-TBH 络合物，而在存在草酸盐或柠檬酸盐络合物时则未观察到。这种络合作用阻碍了 Fe(III)的光还原，从而阻碍了 TBH 的降解。在存在或不存在柠檬酸的情况下（在后一种情况下仅使用 Fe(NO3)3），主要的降解途径是通过尿素末端甲基的羟化作用引发的，表明存在相同的降解机制。在存在柠檬酸的情况下，延长辐照时间后还观察到了尿素的中央甲基和叔丁基的羟化作用，但在不存在柠檬酸络合物的情况下未观察到，因为在没有柠檬酸络合物的情况下降解速度较慢。在各种不同的条件下，均未鉴定出来自噻二唑环开环的中间产物。
