O3/H2O2降解水中致嗅物质2-MIB的效能与机理

Efficiency and mechanism of degradation of 2-MIB by O_3/H_2O_2 in water

采用O3/H2O2工艺对水中致嗅物质二甲基异莰醇(2-methy lisoborneol,2-MIB)的去除效能与机理进行了研究,探讨了H2O2与O3的投加方式、摩尔比以及溶液pH值和水质等因素对2-MIB降解的影响,并通过GC-MS对2-MIB的氧化降解中间产物进行了分析.实验结果显示,H2O2能明显促进O3对水中2-MIB的氧化降解,单独臭氧氧化20min时2-MIB的降解率为38.7%;在同样体系中加入适量的H2O2后2-MIB的降解率最大能提高到89.2%,H2O2与O3最佳投加摩尔比为0.6左右.低浓度(0.5mg·L-1)腐殖酸对O3/H2O2体系2-MIB的降解速率有比较明显的促进作用,高浓度的腐殖酸则会产生较明显的抑制作用;自由基捕获剂叔丁醇对O3/H2O2体系中2-MIB氧化降解具有明显的抑制作用.鉴定出2-MIB的氧化降解产物有4-羟基—1,7,7-三甲基双环[2,2,1]庚烷—2-酮、1,7,7-三甲基双环[2,2,1]庚烷—2,4-二酮、1,7,7-三甲基双环[2,2,1]庚烷—2-酮等,并对2-MIB氧化机制和降解的可能途径进行了推导.

The efficiency and mechanism of the degradation of 2-methylisoborneol （2-MIB） by O3/H2O2 in aqueous solution is investigated. The effects of molar ratio of hydrogen peroxide to ozone, method of addition of hydrogen peroxide and ozone, pH value and water quality on the degradation of 2-MIB during the 03/H2O2 oxidation process are discussed. Hydrogen peroxide highly enhanced the removal efficiency of 2-MIB in water. The removal efficiency is only 38.7% by ozonation alone, but it reaches 89.2% after 20 minutes with the addition of H2O2. The optimum molar ratio of H2O2/O3 was about 0.6. The presence of humic substances （HS） with concentration lower than 0.5 mg· L^-1 enhanced the removal efficiency of 2-MIB from the water. But high concentrations of HS inhibit the removal of 2-MIB by O3/H2O2. Tert-butanol, a typical free radical inhibitor significantly inhibited the removal of 2-MIB, The intermediate oxidation products of 2-MIB were identified by GC-MS and include 4-hydroxy-1,7,7-trimethylbicyclo [ 2,2,1 ] heptan-2-one, 1, 7,7-trimethylbicyclo[ 2,2,1 ] heptane- 2,5-dione, and 1,7,7-trimethylbicyclo [ 2,2, 1 ] heptan- 2 -one. Based on these results, the mechanism and possible degradation pathway for 2-MIB are proposed.