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標題: | 探討溴離子存在下對苯並三唑自由餘氯光降解及三溴甲烷生成之影響 Effect of bromide on benzotriazole degradation and tribromomethane formation during solar irradiation/free chlorine treatment |
作者: | 朱奕宣 Yi-Hsuan Chu |
指導教授: | 林郁真 Yu-Chen Lin |
關鍵字: | 自由餘氯太陽光解,消毒副產物,溴離子,活性鹵素物種,氯化海水, Solar/free chlorine,Disinfection byproducts,Bromide,Reactive halogen species,Seawater chlorination, |
出版年 : | 2022 |
學位: | 碩士 |
摘要: | 為了去除水中致病菌及微生物,戶外海水游泳池普遍使用自由餘氯(free chlorine, FC)作為消毒劑。然而在消毒的過程中,因海水富含大量的溴離子 (Br-),可能會產生比氯化消毒副產物更具毒性的溴化消毒副產物。此主要歸咎於戶外海水游泳池中可能含有微量有機物,當這些微量有機物同時遇到FC與Br-並進行太陽光照(Solar/FC with Br-),就可能導致溴化消毒副產物生成。 至今為止,微量有機物於Solar/FC with Br-系統中的降解及後續消毒副產物生成的機制尚未被深入研究,因此本研究旨在探討Solar/FC with Br-系統中的反應物種,如溴物種(bromine species)、羥基自由基(hydroxyl radical, HO•)及活性鹵素物種(reactive halogen species, RHS)等,對抗鏽蝕劑──苯並三唑(benzotriazole, BT)的降解及後續溴化消毒副產物形成之影響。研究結果顯示,1 mM Br- 存在會加速BT在氯化(chlorination)及Solar/FC系統中的降解,且其降解趨勢符合擬一階動力方程式(BT於Chlorination with Br-與Solar/FC with Br-下之擬一階反應速率(k’obs)分別為7.2±0.1 × 10–2 min–1 及 2.3±0.06 × 10–1 min–1)。造成BT反應加速的原因在於bromine species、HO•及RHS的產生。在pH為 8.0時,Solar/FC with Br-下bromine species及RHS是主要降解BT的活性物種,其中RHS的降解貢獻會隨pH值上升而增加,當pH從8.0提升至11.0時,RHS的降解貢獻從56.0%上升至84.4%。除此之外,BT的降解亦受到FC及Br-濃度影響,當增加FC劑量(1.0-10.0 mg/L)時,k’obs從5.6±0.9 × 10–2 min–1 提升至 9.7±0.3 × 10–1 min–1 ; 而當提升Br-濃度(0-2.0 mM)時,k’obs由 1.14±0.001 × 10–1 min–1提升至 2.73±0.005 × 10–1 min–1。 儘管Solar/FC with Br-系統可以促進BT的降解,但同時有毒的三溴甲烷(tribromomethane, TBM)也會大量的生成,並在第15分鐘時檢測出最高濃度(83.3 μg/L),這些結果表明RHS對TBM生成具重大影響。除此之外,增加FC亦會促進TBM生成。綜上所述,雖然Solar/FC with Br-系統能更有效地去除微量污染物,但在室外的海水游泳池中,仍需顧及溴化消毒副產物之生成及其對大眾健康之風險。 The coexistence of free chlorine (FC) and bromide (Br-) under solar irradiation (solar/FC with Br-) is inevitable in outdoor seawater swimming pools, and the formation of brominated disinfection byproducts (DBPs) could increase and become more toxic than solar/FC in the absence of Br-. However, the mechanisms of solar/FC with Br- treatment in the degradation of micropollutants and the possibility of forming harmful brominated DBPs are unclear. This study is the first to investigate the role of reactive species (e.g., bromine species, HO•, and reactive halogen species) in the degradation of selected target compounds (benzotriazole, BT) and the formation of brominated DBPs during the solar/FC with Br- process. The results indicated that the presence of Br- (1 mM) enhanced BT degradation under chlorination and solar/FC processes and followed pseudo first-order kinetics. With the presence of Br-, the degradation rate of BT under chlorination was 7.2±0.1 × 10–2 min–1 and was 2.3±0.06 × 10–1 min–1 under the solar/FC process. The enhanced removal through the solar/FC with Br- process could be attributed to the generation of bromine species, HO•, and reactive halogen species (RHS). Bromine species and RHS predominantly accounted for BT degradation during solar/FC with Br- at pH 8.0, and the RHS contribution increased from 56.0% to 84.4% with increasing from 8.0 to 11.0. The degradation rates were further increased with higher free chlorine dose (1.0 to 10.0 mg/L) as well as Br- concentration (0 to 2.0 mM). Under relatively high FC doses, the degradation rates increased from 5.6±0.01 × 10–2 min–1 to 9.7±0.3 × 10–1 min–1; when the system was under relatively high Br- concentrations, the degradation rates increased from 1.14±0.001 × 10–1 min–1 to 2.73±0.005 × 10–1 min–1. Despite the fact that the solar/FC with Br- process enhanced BT degradation, the reaction also enhanced tribromomethane (TBM) formation. A high concentration (83.3 μg/L) of TBM was detected at 15 minutes in the solar/FC with Br- process, which was due to the formation and reaction of RHS. Furthermore, the concentration of TBM increased when the free chlorine dose increased, indicating the formation potential of harmful DBPs in chlorinated seawater swimming pools. In conclusion, solar/FC with Br- may achieve good removal efficiency of micropollutants; however, the formation of brominated-trihalomethanes under this mechanism requires careful consideration, especially in outdoor seawater swimming pools. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/83582 |
DOI: | 10.6342/NTU202202760 |
全文授權: | 未授權 |
顯示於系所單位: | 環境工程學研究所 |
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