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臭氧混凝耦合工艺(hybrid ozonation-coagulation,HOC)是基于传统污水深度处理工艺“混凝-沉淀-过滤”处理流程长、溶解性有机物去除效果差的问题提出并构建的,具有臭氧氧化与混凝同时进行、溶解性有机物去除率高的特点[1-3]。然而在进行高Br−浓度废水处理时,例如工业盐水、肥料废水等[4-5],HOC工艺中的臭氧和由于臭氧与混凝剂的互促增效反应产生的·OH[6]会将Br−氧化为潜在致癌物质溴酸盐(BrO3−)[7-9],而我国《生活饮用水卫生标准》(GB 5749-2022)规定,饮用水中BrO3−含量不能高于0.01 mg·L−1。
近年来,臭氧氧化过程的BrO3−消毒副产物的控制方法受到国内外相关研究领域学者的广泛重视[10-13]。在臭氧氧化体系中,BrO3−的生成途径主要分为2种[14-15]:臭氧直接氧化和·OH间接氧化,2种氧化途径均伴随着中间产物HBrO/BrO−的生成,因此,HBrO/BrO−的继续氧化是控制Br−转化为BrO3−的重要限制反应[16]。而有研究表明,H2O2能通过与HBrO/BrO−反应阻碍其继续氧化为BrO3−,从而有效地延缓溴酸盐消毒副产物的生成[13]。此外,H2O2能加速臭氧分解生成·OH,控制BrO3−生成的同时可提高有机物的去除效果,但·OH的间接氧化也会促进BrO3−的生成[11, 17]。目前HOC工艺中H2O2控制下的溴酸盐消毒副产物的抑制效能尚未探讨,抑制原理也有待进一步探究。
基于以上研究结果,本研究探究在不同臭氧投加量下HOC工艺的有机物处理效果和BrO3−生成情况,考察H2O2投加量对HOC工艺中BrO3−生成的抑制效能,通过对BrO3−生成贡献率和Br−消耗动力学的分析,明确HOC体系中BrO3−的主要生成途径和H2O2抑制原理。
臭氧混凝耦合体系中H2O2对溴酸盐生成的抑制效果及相关机理
Inhibitory effect and mechanism of bromate formation by H2O2 in the hybrid ozonation-coagulation process
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摘要: 探究了臭氧混凝耦合体系(hybrid ozonation-coagulation,HOC)中H2O2对溴酸盐消毒副产物(BrO3−)的抑制效能,明确了BrO3−的主要生成途径和H2O2对BrO3−生成的抑制原理。结果表明,当n(H2O2):n(O3)>0.5时,H2O2能有效延缓BrO3−的生成。当臭氧投加量为4.5 mg·L−1、n(H2O2):n(O3)=2时,能有效的将BrO3−生成量控制在0.01 mg·L−1以下。通过对BrO3−生成贡献率和Br−消耗动力学的分析,臭氧直接氧化是HOC工艺中BrO3−生成的主要途径,贡献率维持在80%以上。在H2O2抑制条件下,•OH间接氧化贡献率有所提高,但臭氧直接氧化仍然是HOC工艺中BrO3−生成的主要途径,贡献率在60%以上。在H2O2抑制条件下,Br−的消耗反应为先慢速后快速,前期慢速反应阶段Br−的氧化过程被抑制,后期快速反应阶段中残余H2O2的存在减少了体系中活性氧物质的浓度,进而有效抑制了BrO3−的生成。
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关键词:
- 臭氧混凝耦合工艺(HOC) /
- 溴酸盐 /
- 消毒副产物 /
- 动力学分析
Abstract: In this study, the inhibitory effect of H2O2 on bromate disinfection byproducts (BrO3−) formation in the hybrid ozonation-coagulation (HOC) process was investigated, and the main generation pathway of BrO3− and the inhibitory mechanism of BrO3− generation by H2O2 addition were clarified. The results showed that when n(H2O2):n(O3)>0.5, BrO3− formation could be effectively mitigated. When the ozone dosage was 4.5 mg·L−1 and n(H2O2):n(O3)=2, BrO3− production could be effectively controlled below 0.01 mg·L−1. Through the analysis of BrO3− generation contribution rate and Br− consumption kinetics, direct ozone oxidation was the main pathway of BrO3− generation in the HOC process, and the contribution rate maintained above than 80%. With the addition of H2O2, the contribution rate of •OH indirect oxidation increased, while ozone direct oxidation was still the main pathway for BrO3− generation with the contribution rate above 60%. With the addition of H2O2, the consumption reaction of Br− was slow at first and then became fast. The oxidation process of Br− was inhibited during slow reaction at the early stage, and the presence of residual H2O2 during fast reaction at the later stage reduced the concentration of oxidizing substances in the process, thus effectively inhibited the formation of BrO3−. -
表 1 H2O2抑制条件下不同臭氧投加量的溴酸盐生成贡献率
Table 1. Contribution rate of Bromate formation at different ozone dosages with the addition of H2O2
臭氧/(mg·L−1) n(H2O2):n(O3) 不同反应时间下的f(·OH)/f(O3) 0.5 min 0.75 min 1 min 2 min 3 min 5 min 7 min 9 min 15 min 4.5 0 0.16/0.84 0.13/0.87 0.11/0.89 0.10/0.90 0.09/0.91 0.08/0.92 0.08/0.92 0.08/0.92 0.08/0.92 0.5 0.17/0.83 0.13/0.87 0.14/0.86 0.09/0.91 0.08/0.92 0.08/0.92 0.10/0.90 0.11/0.89 0.13/0.87 1 0.25/0.75 0.21/0.79 0.26/0.74 0.17/0.83 0.15/0.85 0.13/0.87 0.13/0.87 0.13/0.87 0.13/0.87 1.5 0.36/0.64 0.28/0.72 0.26/0.74 0.19/0.81 0.18/0.82 0.15/0.85 0.15/0.85 0.15/0.85 0.15/0.85 2 0.34/0.66 0.27/0.73 0.23/0.77 0.20/0.80 0.18/0.82 0.17/0.83 0.16/0.84 0.17/0.83 0.17/0.83 8.0 0 0.12/0.88 0.09/0.91 0.08/0.92 0.05/0.95 0.05/0.95 0.04/0.96 0.03/0.97 0.03/0.97 0.03/0.97 0.5 0.13/0.87 0.10/0.90 0.09/0.91 0.07/0.93 0.06/0.94 0.05/0.95 0.05/0.95 0.05/0.95 0.06/0.94 1 0.15/0.85 0.12/0.88 0.16/0.84 0.09/0.91 0.08/0.92 0.08/0.92 0.08/0.92 0.09/0.91 0.10/0.90 1.5 0.19/0.81 0.14/0.86 0.13/0.87 0.10/0.90 0.09/0.91 0.07/0.93 0.07/0.93 0.07/0.93 0.07/0.93 2 0.24/0.76 0.18/0.82 0.16/0.84 0.11/0.89 0.11/0.89 0.09/0.91 0.09/0.91 0.09/0.91 0.09/0.91 11.3 0 0.08/0.92 0.06/0.94 0.05/0.95 0.03/0.97 0.03/0.97 0.02/0.98 0.02/0.98 0.02/0.98 0.02/0.98 0.5 0.14/0.86 0.11/0.89 0.10/0.90 0.06/0.94 0.05/0.95 0.05/0.95 0.05/0.95 0.05/0.95 0.06/0.94 1 0.20/0.80 0.13/0.87 0.11/0.89 0.07/0.93 0.06/0.94 0.05/0.95 0.05/0.95 0.05/0.95 0.05/0.95 1.5 0.18/0.82 0.24/0.76 0.19/0.81 0.13/0.87 0.10/0.90 0.09/0.91 0.08/0.92 0.08/0.92 0.08/0.92 2 0.21/0.79 0.21/0.79 0.18/0.82 0.11/0.89 0.09/0.91 0.08/0.92 0.09/0.91 0.10/0.90 0.11/0.89 表 2 H2O2抑制条件下的Br-消耗的一级速率常数(kobs)
Table 2. kobs of Br- consumption with the addition of H2O2
n(H2O2):n(O3) 反应时间/min 拟合方程式 k/min-1 R2 0 0~10 y = −0.033 7x−0.019 70 0.033 7 0.985 10~25 y = −0.013 4x−0.234 00 0.013 4 0.976 0.5 0~6 y = −0.022 9x−0.018 86 0.022 9 0.950 6~25 y = −0.020 0x−0.038 59 0.020 0 0.990 1 0~8 y = −0.015 4x−0.011 67 0.015 4 0.955 8~25 y = −0.018 0x+0.011 12 0.018 0 0.990 1.5 0~10 y = −0.011 0x+0.005 83 0.011 0 0.971 10~25 y = −0.017 2x+0.076 27 0.017 2 0.983 2 0~15 y = −0.005 9x+0.003 51 0.005 9 0.991 15~25 y = -0.014 5x+0.135 60 0.014 5 0.983 -
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