pH-dependent contribution of chlorine monoxide radicals and byproducts formation during UV/chlorine treatment on clothianidin
UV/염소공법을 통한 clothianidin의 처리에서 pH에 따른 chlorine monoxide 라디칼의 기여와 분해생성물 발생에 관한 연구
- 주제(키워드) Clothianidin , UV/chlorine , Reactive chlorine species , Solution pH , Degradation kinetics
- 주제(DDC) 628
- 발행기관 아주대학교
- 지도교수 이창구
- 발행년도 2022
- 학위수여년월 2022. 2
- 학위명 석사
- 학과 및 전공 일반대학원 환경공학과
- 실제URI http://www.dcollection.net/handler/ajou/000000031440
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
Combining UV and free chlorine (UV/chlorine) is an efficient advanced oxidation process for the abatement of recalcitrant organic compounds in drinking water and wastewater. This study investigated the degradation of a neonicotinoid insecticide, clothianidin (CTD), by UV/chlorine treatment. The free chlorine concentration was optimized at 160 μM, and 90.1 ± 0.4% of 40 μM CTD was degraded after 300 s of treatment. Radical quenching tests using tert-butyl alcohol, Cl-, HCO3- , and N3- indicated that chlorine monoxide (ClO•) was the main radical species for CTD degradation. The second-order rate constants of CTD reacting with ClO• (kClO•,CTD = 7.3 ± 0.1 × 109 M-1 s-1) was 4.3 times higher than that for •OH (k•OH,CTD = 1.7 ± 0.2 × 109 M-1 s-1). The presence of humic acid inhibited CTD degradation by filtering UV and scavenging ClO•. The pH was optimized at 7, and the overall reaction rate constant (k′) was 2.35 ± 0.02 × 10-1 s-1 (half-life = 0.49 min). Degradation products identified during the UV/chlorine treatment were 1-methyl-3-nitroguanidine ([M + H]+ = 118.9), nitroguanidine ([M + H]+ = 105.1), methylguanidine ([M + H]+ = 74.3), and clothianidin urea ([M + H]+ = 206). The detailed time dependent concentrations of the generated products under different pH conditions were also provided. The results suggest that the UV/chlorine treatment can be an efficient strategy for CTD degradation.
more목차
I. Introduction １
2. Materials and methods ４
2.1 Chemicals ４
2.2 Experimental procedure ５
2.3 Analytical method ９
3. Results and discussion １０
3.1. Synergistic CTD degradation by UV/chlorine combination １０
3.2. Contribution of different radical species １７
3.3. Reactivity of ClO• and •OH toward CTD ２３
3.4. Effect of natural organic matter (NOM) ２８
3.5 Effect of pH on the kinetics of reactive species ３２
3.6. Transformation products of CTD ４１
4. Conclusions ４９
Recommendations ５０
References ５２
국문 초록 ５９
