Degradation solution was owed at 8 mL/min via column, then dried in high vacuum for 30 min. The column was eluted with CH 2Cl 2 and. The eluant was and condensed to 1 mL at 45 C under nitrogen gas for GC MS measurement. 2. 3. Analyses and measurement The concentration of pretilachlor in solution was analyzed by HPLC. The UV detected wavelength was set as 210 nm, CH 3CN/H 2O with 1 mL min 1 was used as ow phase, and amount of sample injection was 20 _L. GC MS coupled with an HP 5MS column was used to analyze the intermediates during the degradation of pretilachlor. Helium gas was used as carrier gas at a ow rate of 1. 0 mL min 1. The oven temperature started at 50 C and held for 2 min, increased to 300 C at the heating rate of 8 C min 1 and held for 1 min. Inlet temperature was 250 C.

Test was progressed by EI as ion source, temperature of 230 C, electro energy of 70 eV and interface tem perature of 280 C. The concentration of small organic acids in the degradation solution PF299804 was analyzed by HPLC. The UV detected wavelength was set as 210 nm, H PO /H O injection was 10 _L. It has been reported that the increasing current density would enhance the electron transfer rate of organic compounds on elec trode surface and hence accelerated the direct oxidation rate. Meanwhile, the increasing current density also enhanced the gen eration rate of hydroxy radical as indirect oxidation reagency and hence increased the degradation and mineralization of pretilachlor.

However, with the increasing of current density, the proba bility and reaction rate of side reaction on anode were also greatly increased, resulting in the decreasing of mineralization current effi ciency and increasing of energy PF299804 consumption. Under various current densities, mineralization current efficiency of degradation of pretilachlor was shown in Fig. 1. Therefore, we synthetically considered the in uence of cur rent density on TOC removal, MCE and energy consumption during degradation of pretilachlor. In order to ensure the effective removal of the pretilachlor and TOC, enhance mineralization current effi ciency and reduce energy consumption, the preferable current density is 20 mA cm 2 under the present experimental conditions. 3. 2. Intermediates in the electrocatalysis oxidation process of pretilachlor 3. 2. 1.

UV spectrum during degradation of pretilachlor Results of UV scans of the solution sample under different degra dation time with the concentration diluted by 10 times were shown in Fig. 2. The absorption peaks of pretilachlor were at 210 nm and 270 nm. The peak at 270 nm was weak and the peak at 210 nm was the maximum absorption peak. With CDK the increase of degradation time, the maximum absorption peak at 210 nm rapidly decreased and finally disappeared after 60 min. In addition, an absorption band in the range of 250 nm and 400 nm appeared and its inten sity was increased initially and then decreased with the reaction time. The appearance of new peak indicated that some intermedi ates which were more difficult to degrade than pretilachlor were formed. Therefore, it was more important to analyze the structures and degradability of these intermediates. 3. 2. 2.

Analysis of small organic acids during the electrocatalysis oxidation of pretilachlor During electrocatalysis oxidation CFTR of pretilachlor, the value of pH changed greatly from 8. 14 to 4. 38 after 60 min, which showed that small organic acids were generated during degradation of preti lachlor. These organic acids were identified and quantitated, which was showed in Fig. 3. It could be found that along with degradation of pretilachlor acetic and propionic acids were immediately gen erated and then they increased continuously with reaction time, even when pretilachlor was almost removed after 60 min. There fore it could be presumed that acetic and propionic acids were generated from degradation of pretilachlor and its intermediates.

VEGF In addition, another part of acetic and propionic acids came from Na 2SO 4 solution with and without pretilachlor obtained at a scan rate of 50 mV/s. cleavage of benzene ring. Li et al. proposed that the benzene ring cleavage could occur during the degradation of aromatic ring by electrocatalysis oxidation and acetic acid as well as oxalic acid were generated. Monochloroacetic acid might originate from the oxidation of chloroacetyl group coming off from the pretilachlor and its inter mediates. It could be also found that the concentration of oxalic acid increased gradually with the decrease of monochloroacetic acid and acetic acid, which might be due to that monochloroacetic acid and acetic acid were converted into oxalic acid. Therefore oxalic acid was the ultimate carboxylic acid.