苯噻草胺光催化和直接光解影响因素和降解途径研究

Photocatalytic and Direct Photolytic Degradation of Mefenacet:Investigation of Environmental Influencing Factors and Degradation Pathway

采用微波辅助光催化降解和直接光解实验方法,研究了苯噻草胺在光催化和直接光解两种体系下的降解情况,并考察了初始pH值、腐植酸浓度以及阿特拉津对其光催化降解和直接光解的影响。结果表明,在光照4min内,苯噻草胺直接光解效率为93.3%,较光催化降解效率高出28.9%;初始pH值从1.88增加至10.28时,苯噻草胺光催化和光解速率常数分别提高了250%和58.6%;添加腐植酸对苯噻草胺的直接光解和光催化均具有抑制效应,并且抑制效应随着腐植酸浓度的增加而增加,当腐植酸浓度增加至40mg·L-1时,直接光解和光催化降解速率分别降低了51.8%和47.5%;10mg·L-1的阿特拉津抑制了苯噻草胺的前期降解,整体直接光解速率降低了46.3%,但整体光催化降解速率没有减小。此外,采用GC-MS对苯噻草胺两种降解体系下的主要中间产物进行鉴定,并提出了主要的光降解途径。

Degradation of mefenacet in both microwave assisted photocatalysis and direct photolysis system was investigated in this study and the effects of initial pH value, humic acid and atrazine on both photodegradation systems were also explored. The results showed that 93.3% of mefenaeet could be directly photodecomposed within 4 rain, which was 28.9% higher than that of photocatalytie degradation. The photocatalytic and photolytic degradation rate constants were enhanced by 250% and 58.6%, respectively, when the initial pH value rose from 1.88 to 10.28, The presence of humic acid had displayed retardation effect on photocalytic and photolytic degradation of mefenacet and the retardation effect became more evident as the concentration of humic acid increased. When the concentration of humic acid increased to 40 mg·L^-1, the direct photolytic and photocatalytic degradation rates reduced by 51.8% and 47.5%, respectively. Photocalytic and photolytic degradation of mefenacet in the initial stage were suppressed significantly due to the presence of atrazine, and the whole direct photolytic degradation rate decreased by d6.3% while the whole photocatalytic degradation rate remained unaffected. Besides, the main intermediates during two photocomposition systems were identified by GC-MS technique and the primary photodegradation pathways for mefenacet were proposed.