光电催化氧化处理中各类活性物质的氧化机理
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摘要
为了深入研究其中各类活性物质氧化机理,以难降解的3,4-二甲基苯胺(3,4-DMA)废水作为研究对象,通过研究不同抑制剂条件下的动力学规律,并以贡献度(kf/K)来量化各活性物质的作用效果,得出氯类活性物质的贡献度为89.03%,羟基自由基(·OH)的贡献度为6.24%,而空穴和阳极直接氧化贡献度可以忽略.采用三聚氰胺法、二甲亚砜(DMSO)法和DPD法定性定量测定了空穴、·OH和自由氯的含量,结果表明:较高浓度的氯化钠降低了空穴和·OH的贡献度;·OH的产量符合零级动力学规律,其产生速率为0.106mg/(L·min);自由氯的累积浓度分为3个阶段,第3阶段累积速率为0.159mg/(L·min).自由氯仅占氯类活性物质氧化体系的一小部分,其他含氯氧化物质和氯类自由基的氧化占重要地位.通过GC-MS、UV-vis和TOC检测,发现在反应10.0min前,主要通过氯类活性物质对侧链的快速攻击,使3,4-DMA转化为苯甲醛等易分解的苯环类物质;10.0min后,主要通过·OH对苯环大π键的攻击,使苯环类物质转化为小分子物质,然后继续被·OH氧化直到矿化.
Refractory 3,4-dimethylaniline wastewater was studied for the oxidation mechanisms of various active substances generated in the HPECO process and the contribution degree(k_f/K) based on kinetics was utilized to evaluate the oxidation effect of each active substance. The results showed that the contribution degrees of active chlorines and hydroxyl radicals were respectively 89.03% and 6.24% and the contribution of hole and anode direct oxidation was negligible. The holes, hydroxyl radicals and free chlorine were determined respectively by the ways of melamine, dimethylsulfoxide and DPD and the results showed that the contribution degrees of holes and ·OH were decreased due to high concentration of sodium chloride and ·OH yield followed the zero-order kinetic law with the rate of 0.106 mg/(L·min). Moreover, the cumulative concentration regulation of free chlorine was divided into three stages with the rate of 0.159 mg/(L·min) in the third stage. Free chlorine only accounted for a small portion in active chlorines, while the oxidation of other chlorinated oxides and chlorinated free radicals played important roles. By GC-MS,UV-vis and TOC determination, it showed that in the initial 10.0 min, the active chlorines attacked the side chains rapidly, so that 3,4-DMA could be converted into benzaldehyde and other benzene derivatives. After 10.0 min, the benzene derivatives were attacked towards the π bonds by·OH and transformed into small molecules which could be finally mineralized.
Refractory 3,4-dimethylaniline wastewater was studied for the oxidation mechanisms of various active substances generated in the HPECO process and the contribution degree(k_f/K) based on kinetics was utilized to evaluate the oxidation effect of each active substance. The results showed that the contribution degrees of active chlorines and hydroxyl radicals were respectively 89.03% and 6.24% and the contribution of hole and anode direct oxidation was negligible. The holes, hydroxyl radicals and free chlorine were determined respectively by the ways of melamine, dimethylsulfoxide and DPD and the results showed that the contribution degrees of holes and ·OH were decreased due to high concentration of sodium chloride and ·OH yield followed the zero-order kinetic law with the rate of 0.106 mg/(L·min). Moreover, the cumulative concentration regulation of free chlorine was divided into three stages with the rate of 0.159 mg/(L·min) in the third stage. Free chlorine only accounted for a small portion in active chlorines, while the oxidation of other chlorinated oxides and chlorinated free radicals played important roles. By GC-MS,UV-vis and TOC determination, it showed that in the initial 10.0 min, the active chlorines attacked the side chains rapidly, so that 3,4-DMA could be converted into benzaldehyde and other benzene derivatives. After 10.0 min, the benzene derivatives were attacked towards the π bonds by·OH and transformed into small molecules which could be finally mineralized.
引文
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[2] Hurwitz G, Pornwongthong P, Mahendras, et al. Degradation of phenol by synergistic chlorine-enhanced photo-assisted electrochemical oxidation[J]. Chemical Engineering Journal, 2014,240(4):235-243.
[3]沙爽,周少奇,张小娜,等.Pr-N共掺杂TiO2光电催化降解孔雀石绿动力学[J].环境科学,2012,33(4):1267-1271.Sha S, Zhou S Q, Zhang X N, et al. Photoelectrocatalytic degradation kinetics of malachite green by Pr-N codoped TiO2 photocatalyst[J],Environmental Science, 2012,33(4):1267-1271.
[4]党聪哲,李一兵,王彦斌,等.K2S2O8强化g-C3N4薄膜电极光电催化降解Cu(CN)32-并同步回收Cu[J].环境科学,2018,39(1):145-151.Dang C Z, Li Y B, Wang Y B, et al. Enhanced photoelectrocatalytic oxidation of Cu(CN)32-and synchronous cathodic deposition of Cu by peroxydisulfate[J]. Environmental Science, 2018,39(1):145-151.
[5]李蒋,王雁,张秀芳,等.Co3O4/BiVO4复合阳极活化过一硫酸盐强化光电催化降解双酚A[J].环境科学,2018,39(8):3713-3718.Li J, Wang Y, Zhang X F et al Enhancement of photoelectrocatalytic degradation of bisphenol A with peroxymonosulfate activated by a Co3O4/BiVO4 composite photoanode[J]. Environmental Science,2018,39(8):3713-3718.
[6] Li G Y,An T C,Chen J X,et al. Photoelectrocatalytic degradation of oilfield wastewater with high content of chlorine[J]. Research of Environmental Sciences,2006,19(1):30-34.
[7] Simond O,Comninellis C Anodic oxidation of organics on Ti/IrO2,anodes using Nafion(?), as electrolyte[J]. Electrochimica Acta,1997,42(13/14):2013-2018.
[8] Li A, Zhao X, Liu H, et al. Characteristic transformation of humic acid during photoelectrocatalysis process and its subsequent disinfection byproduct formation potential[J]. Water Research, 2011,45(18):6131-6140.
[9]杨晓芬,赵美萍,李元宗,等.水中苯胺类化合物的分光光度法测定[J].分析化学,2002,30(5):540-543.Yang X F, Zhao M P, Li Y Z, et al. Spectrophotometric methods for the determination of aniline in water[J]. Chinese Journal of Analytical Chemistry,2002,30(5):540-543.
[10]刘婷,尤宏,陈其伟,等.光助非均相芬顿体系中羟基自由基的荧光光谱法测定与影响因素研究[J].环境科学,2009,30(9):2560-2564.Liu T, You H, Chen Q W, et al. Detection of hydroxyl radical in heterogeneous photo-fenton system using the fluorescence technique and influencing factor Study[J]. Environmental Science, 2009,30(9):2560-2564.
[11]邰超,韩丹,阴永光,等.二甲亚砜捕获-高效液相色谱测定天然水体中羟基自由基的光化学生成[J].环境化学,2015,(2):212-218.Tai C, Han D, Yin Y G, et al. Determination of photogenerated hydroxyl radicals in natural water by high performance liquid chromatography after trapping with dimethyl sulfoxide[J].Environmental Chemistry, 2015,34(2):212-218.
[12] HJ 586-2010水质游离氯和总氯的测定[S].HJ 586-2010 Determination of free chlorine and total chlorineSpectrophotonetric method using N,N-diethyl-1,4-phenylenediamine[S].
[13]郑铭华,陈前进.高效液相色谱法测定美耐皿餐具中三聚氰胺迁移量[J].中国检验检测,2018,26(2):34-37.Zheng M H, Chen Q J. Determination of the migration quantity of melamine in melamine tableware by HPLC[J]. China Inspection&Laboratory, 2018,26(2):34-37.
[14] And T H, Nosaka Y. Properties of O2·-and OH·formed in TiO2 aqueous suspensions by photocatalytic reaction and the influence of H2O2 and some ions[J]. Langmuir,2002,18(18):3247-3254.
[15]杨世迎.TiO2光催化降解有机污染物的初始步骤机理研究[D].杭州:浙江大学,2005.Yang S Y. Initial processes in TiO2-assissted photodegradation of organic pollutants[D]. Hangzhou:Zhejiang university, 2005.
[16] Moreira F C, Boaventura R a R, Brillas E, et al. Electrochemical advanced oxidation processes:A review on their application to synthetic and real wastewaters[J]. Applied Catalysis B:Environmental,2017,202:217-261.
[17] Maurino V, Minella M, Sordello F, et al. A proof of the direct hole transfer in photocatalysis:The case of melamine[J]. Applied Catalysis A General, 2016,521:57-67.
[18] Fujishima A. TiO2 Photocatalysis and Related Surface Phenomena[C]//the 60th annual meeting of the international society of electrochemistry. 2009:515-582.
[19] Comninellis C, Nerini A. Anodic oxidation of phenol in the presence of NaCl for wastewater treatment[J]. Journal of Applied Electrochemistry, 1995,25(1):23-28.
[20] Yang Y, Pignatello J J, Ma J, et al. Comparison of halide impacts on the efficiency of contaminant degradation by sulfate and hydroxyl radical-based advanced oxidation processes(AOPs)[J]. Environmental Science&Technology, 2014,48(4):2344.