-
随着我国工业化水平以及人民生活水平的日益提高,恶臭气体带来的污染逐渐引起了全社会的重视. 我国《恶臭污染物排放标准》(GB 14554-93)中限制排放的恶臭污染物质包括硫化氢、甲硫醚、二甲二硫、甲硫醇、氨、二硫化碳、苯乙烯和三甲胺. 其中甲硫醇来源广泛,污水处理废气[1-2]、污泥处置废气[2-3]、垃圾填埋场废气[4-5]、制药厂废气[6]、造纸厂废气[7]、餐厨垃圾废气[8-9]、炼油废气[10-11]等主要恶臭成分中均含有甲硫醇. 其中,污水处理厂、垃圾填埋场、餐厨垃圾废气中的甲硫醇主要是由于蛋氨酸、甲硫氨酸、胱氨酸、半胱氨酸等含硫氨基酸的降解、巯基的转移以及含硫化合物的甲基化产生的. 甲硫醇是臭味最强的气体之一,其阈值仅为0.045 mg·m−3,且具有毒性和腐蚀性[12-13]. 此外,甲硫醇还属于含硫挥发性有机物,不但具有恶臭污染物的特征,而且具有挥发性有机物的特征[14],能够参与雾霾、光化学烟雾、二次气溶胶等环境污染事件的形成[15]. 因此,甲硫醇气体污染物的治理对我国经济高质量发展以及优美人居环境创建具有重要意义.
目前,广泛研究的甲硫醇治理技术主要包括吸附法[16-17]、生物法[18-19]、氧化法[12, 20]、等离子体法[21-22]、光催化法[23-24]、催化氧化法[13-14]和催化降解法[25-27]等. 其中氧化法和催化氧化法受到了人们的广泛关注,但由于甲硫醇氧化降解过程中生成的含硫化合物易使催化剂失活[13],实际应用过程中氧化法因其设备简单(喷淋洗涤塔、接触反应塔等)、氧化剂选择性多(臭氧、过氧化氢、次氯酸钠、高锰酸钾等)等特点而使用较为普遍,其中臭氧氧化法具有臭氧制备方便、均相反应效率高、脱臭效果好等优点而被广泛应用[28]. 虽然臭氧对甲硫醇臭气具有较好的脱臭效果,但关于臭氧投加剂量、反应条件等因素对甲硫醇去除效果的影响以及甲硫醇的臭氧氧化降解产物的研究鲜见报道. 因此,本文通过对臭氧投加量、接触反应时间、反应温度、湿度等因素的考察,并结合原位红外光谱、气相色谱-质谱联用和离子色谱技术研究了臭氧对甲硫醇的氧化降解性能及主要降解产物,以期为臭氧氧化法在甲硫醇脱臭净化领域的应用提供技术参考.
臭氧对气体中甲硫醇的氧化降解
Oxidative degradation of gaseous methyl mercaptan by ozone
-
摘要: 甲硫醇是主要恶臭污染物之一,研究甲硫醇的降解技术对于恶臭异味的治理具有重要意义. 为了获得臭氧对气体中甲硫醇的氧化降解性能,实验研究了臭氧对气体中甲硫醇的均相氧化过程,考察了氧含量、臭氧投加量、反应时间、温度和湿度等因素的影响. 结果表明,氧气可将甲硫醇部分氧化为二甲二硫. 甲硫醇去除率随臭氧投加量、反应时间的增加而升高,且臭氧对气体中甲硫醇的氧化降解过程符合伪一级动力学反应模型. 甲硫醇的去除率随温度升高而增大,该趋势在温度高于50 ℃时不再明显;氧化反应的最佳相对湿度为45%—62%. 采用原位红外光谱、气相色谱-质谱联用和离子色谱技术对甲硫醇氧化降解过程的研究证明,考察条件下,臭氧不能将全部甲硫醇矿化为二氧化碳和水,而是生成了部分醛类和酮类中间产物,且甲硫醇中硫的主要氧化产物是硫单质. 综合考虑臭氧氧化甲硫醇的最佳反应条件和降解产物,该工艺存在能耗高、易造成二次污染等不足,在实际应用中不建议采用臭氧直接氧化工艺对含甲硫醇臭气进行净化.Abstract: Methyl mercaptan is one of the main odor pollutants, and the research on degradation of methyl mercaptan is of great significance for the treatment of odor pollution. In this study, the homogeneous ozonation of gaseous methyl mercaptan was studied to obtain the performance of the oxidative degradation of gaseous methyl mercaptan by ozone. The effects of oxygen content, ozone dosage, reaction time, temperature and humidity were investigated. The results showed that oxygen can partially oxidize methyl mercaptan to dimethyl disulfide. The removal of methyl mercaptan increased with the increase of ozone dosage and reaction time, and the oxidative degradation process fitted well with the pseudo first-order kinetic reaction model. Moreover, the removal of methyl mercaptan increased firstly with the increase of temperature, and then tended to a constant value above 50 ℃. The optimum relative humidity was 45%—62% for the oxidation reaction. Further study by in-situ infrared spectroscopy, gas chromatography-mass spectrometry and ion chromatography showed that under the investigated conditions, ozone cannot mineralize all methyl mercaptan into carbon dioxide and water. Some aldehydes and ketones intermediates were produced, and the main oxidation product of sulfur in methyl mercaptan was elemental sulfur. Considering the optimal reaction conditions of the ozonation of methyl mercaptan and its degradation products, the process has the disadvantages of high energy consumption and potential secondary pollution. In practical application, direct ozonation process is not recommended to purify the odor containing methyl mercaptan.
-
Key words:
- methyl mercaptan /
- ozone /
- oxidation /
- odor.
-
表 1 吸收前后吸收液中阴离子浓度
Table 1. Anion concentration in absorption solution before and after absorption
吸收液
Absorption solutionF− /(mg·L−1) Cl−/(mg·L−1) NO3− /(mg·L−1) SO42− /(mg·L−1) 吸收前 0.42 3.55 4.96 1.62 吸收后 1.29 3.49 8.54 2.69 -
[1] 桂红艳, 盛彦清, 陈繁忠, 等. 污水处理厂恶臭含硫化合物的研究[J]. 给水排水, 2006, 32(S1): 133-137. GUI H Y, SHENG Y Q, CHEN F Z, et al. Study on odorous sulfur compounds emitted from the wastewater treatment plants[J]. Water & Wastewater Engineering, 2006, 32(Sup 1): 133-137(in Chinese).
[2] 申翰彰. 城市污水处理厂污泥处理过程中恶臭气体排放特征和净化研究[D]. 北京: 北京林业大学, 2020. SHEN H Z. Study on emission characteristics and purification of malodorous gases during sludge treatment in urban sewage treatment plants[D]. Beijing: Beijing Forestry University, 2020(in Chinese).
[3] 杨伟华, 邹克华, 李伟芳, 等. 污水处理厂臭气浓度预测方法及愉悦度评价 [J]. 环境污染与防治, 2018, 40(11): 1306-1309. YANG W H, ZOU K H, LI W F, et al. Odor concentration prediction method and hedonic tone evaluation for sewage treatment plant [J]. Environmental Pollution & Control, 2018, 40(11): 1306-1309(in Chinese).
[4] ORTA de VELASQUEZ M T, MONJE-RAMIREZ I. Combined pre-treatment of coagulation-ozonation for saline-stabilized landfill leachates [J]. Ozone:Science & Engineering, 2006, 28(5): 309-316. [5] WANG Q, ZUO X R, XIA M, et al. Field investigation of temporal variation of volatile organic compounds at a landfill in Hangzhou, China [J]. Environmental Science and Pollution Research, 2019, 26(18): 18162-18180. doi: 10.1007/s11356-019-04917-5 [6] 陶丽霞, 王成端, 李钧. 生物净化器处理制药恶臭废气工程实例 [J]. 中国给水排水, 2007, 23(20): 67-69. TAO L X, WANG C D, LI J. Engineering case of pharmaceutical odor gas treatment by biological purifier [J]. China Water & Wastewater, 2007, 23(20): 67-69(in Chinese).
[7] MOUAMMINE A, OJALA S, PIRAULT-ROY L, et al. Catalytic partial oxidation of methanol and methyl mercaptan: Studies on the selectivity of TiO2 and CeO2 supported V2O5 catalysts [J]. Topics in Catalysis, 2013, 56(9): 650-657. [8] 张妍, 王元刚, 卢志强, 等. 我国餐厨废物生化处理设施恶臭排放特征分析 [J]. 环境科学, 2015, 36(10): 3603-3610. ZHANG Y, WANG Y G, LU Z Q, et al. Odor emission characteristics from biochemical treatment facilities of kichen waste in China [J]. Environmental Science, 2015, 36(10): 3603-3610(in Chinese).
[9] 任连海, 郝艳, 王攀. 改性沸石对餐厨垃圾释放的恶臭气体吸附研究 [J]. 环境科学与技术, 2014, 37(7): 137-140. REN L H, HAO Y, WANG P. Absorption of modified zeolite to odorous gases released from kitchen waste [J]. Environmental Science & Technology, 2014, 37(7): 137-140(in Chinese).
[10] 廖定满, 谭伟红. 炼油厂液化气脱硫醇副产二硫化物废液的利用 [J]. 广州化工, 2014, 42(18): 203-205. doi: 10.3969/j.issn.1001-9677.2014.18.077 LIAO D M, TAN W H. Usage of LPG sweetening disulphide waste liquid [J]. Guangzhou Chemical Industry, 2014, 42(18): 203-205(in Chinese). doi: 10.3969/j.issn.1001-9677.2014.18.077
[11] FENG J J, GAO S, FU Q Y, et al. Indirect source apportionment of methyl mercaptan using CMB and PMF models: A case study near a refining and petrochemical plant [J]. Environmental Science and Pollution Research, 2019, 26(23): 24305-24312. doi: 10.1007/s11356-019-05728-4 [12] YANG S Y, LI Y, WANG L L, et al. Use of peroxymonosulfate in wet scrubbing process for efficient odor control [J]. Separation and Purification Technology, 2016, 158: 80-86. doi: 10.1016/j.seppur.2015.12.010 [13] HE H, HU L L, ZENG J W, et al. Activation of persulfate by CuO-sludge-derived carbon dispersed on silicon carbide foams for odorous methyl mercaptan elimination: Identification of reactive oxygen species [J]. Environmental Science and Pollution Research, 2020, 27(2): 1224-1233. doi: 10.1007/s11356-018-3038-3 [14] ZHAO Y T, HE D D, CHEN D K, et al. Investigating the support effect for catalytic elimination of methyl mercaptan: Role of hydroxyl groups over Cr-based catalysts [J]. Catalysis Letters, 2020, 150(10): 2763-2773. doi: 10.1007/s10562-020-03178-z [15] KAMAL M S, RAZZAK S A, HOSSAIN M M. Catalytic oxidation of volatile organic compounds (VOCs) - A review [J]. Atmospheric Environment, 2016, 140: 117-134. doi: 10.1016/j.atmosenv.2016.05.031 [16] VELLINGIRI K, KIM K H, KWON E E, et al. Insights into the adsorption capacity and breakthrough properties of a synthetic zeolite against a mixture of various sulfur species at low ppb levels [J]. Journal of Environmental Management, 2016, 166: 484-492. [17] YANG C, WANG J, FAN H L. Three-dimensionally ordered macroporous metal oxide-silica composite for removal of mercaptan [J]. Research on Chemical Intermediates, 2017, 43(7): 3847-3858. doi: 10.1007/s11164-016-2853-8 [18] van LEERDAM R C, van den BOSCH P L F, LENS P N L, et al. Reactions between methanethiol and biologically produced sulfur particles [J]. Environmental Science & Technology, 2011, 45(4): 1320-1326. [19] LIU B, ZHAO Y J, WU W F, et al. Biodegradation of methanethiol-laden waste gas stream using a combined bioreactor system [J]. Environmental Engineering Science, 2010, 27(5): 397-402. doi: 10.1089/ees.2009.0304 [20] PETRE C F, PICHÉ S, NORMANDIN A, et al. Advances in chemical oxidation of total reduced sulfur from kraft Mills atmospheric effluents [J]. International Journal of Chemical Reactor Engineering, 2007, 5(1): 1-31. [21] YAN N Q, QU Z, JIA J P, et al. Removal characteristics of gaseous sulfur-containing compounds by pulsed Corona plasma [J]. Industrial & Engineering Chemistry Research, 2006, 45(19): 6420-6427. [22] CUI T, SHEN C Y, XU A L, et al. Use of a novel coupled-oxidation tubular reactor (COTR)/NTP-DBD catalytic plasma in a synergistic electro-catalysis system for odorous mercaptans degradation [J]. Chemosphere, 2019, 216: 533-544. doi: 10.1016/j.chemosphere.2018.10.170 [23] CAI W M, LU G H, HE J, et al. The adsorption feature and photocatalytic oxidation activity of K1−2xMxTiNbO5 (M = Mn, Ni) for methyl mercaptan in methane [J]. Ceramics International, 2012, 38(4): 3167-3174. doi: 10.1016/j.ceramint.2011.12.020 [24] LIU T X, LI X Z, LI F B. AgNO3-lnduced photocatalytic degradation of odorous methyl mercaptan in gaseous phase: Mechanism of chemisorption and photocatalytic reaction [J]. Environmental Science & Technology, 2008, 42(12): 4540-4545. [25] CAO X H, LU J C, ZHENG X Q, et al. Regulation of the reaction pathway to design the high sulfur/coke-tolerant Ce-based catalysts for decomposing sulfur-containing VOCs [J]. Chemical Engineering Journal, 2022, 429: 132473. doi: 10.1016/j.cej.2021.132473 [26] LU J C, LIU J P, ZHAO Y T, et al. The identification of active chromium species to enhance catalytic behaviors of alumina-based catalysts for sulfur-containing VOC abatement [J]. Journal of Hazardous Materials, 2020, 384: 121289. doi: 10.1016/j.jhazmat.2019.121289 [27] LU J C, HAO H S, ZHANG L M, et al. The investigation of the role of basic lanthanum (La) species on the improvement of catalytic activity and stability of HZSM-5 material for eliminating methanethiol-(CH3SH) [J]. Applied Catalysis B:Environmental, 2018, 237: 185-197. doi: 10.1016/j.apcatb.2018.05.063 [28] 方晶晶, 江璐, 徐新宏, 等. 电解式臭氧除臭机对密闭舱室含硫恶臭气体净化效果研究[C]. 2020中国环境科学学会科学技术年会论文集(第一卷). 南京, 2020: 1390-1394.
FANG J J, JIANG L, XU X H, et al . Study on the purification of electrolytic ozone deodorizer on sulfur-containing odorous gases in closed compartments [C]. Proceedings of the 2020 Annual Conference of Science and Technology of the Chinese Society of Environmental Sciences (Volume I). Nanjing, 2020: 1390-1394.[29] 林瑜凡. 离子色谱法同时测定环境空气中的二氧化硫和氮氧化物 [J]. 环境与发展, 2017, 29(3): 205-206. doi: 10.16647/j.cnki.cn15-1369/X.2017.03.111 LIN Y F. Ion chromatography and determination of the sulfur dioxide and nitrogen oxides in air environment [J]. Environment and Development, 2017, 29(3): 205-206(in Chinese). doi: 10.16647/j.cnki.cn15-1369/X.2017.03.111
[30] 宋江燕, 李方鸿, 吴根义, 等. 氯咪巴唑在臭氧降解过程中的影响因素及其降解产物 [J]. 环境科学研究, 2022, 35(2): 478-487. SONG J Y, LI F H, WU G Y, et al. Degradation of climbazole by ozonation: Influencing factors and degradation products [J]. Research of Environmental Sciences, 2022, 35(2): 478-487(in Chinese).
[31] 张佳丽, 魏健, 任越中, 等. 臭氧氧化降解水中青霉素G特性和动力学特征 [J]. 环境科学研究, 2019, 32(7): 1231-1238. ZHANG J L, WEI J, REN Y Z, et al. Degradation characteristics and kinetics of penicillin G in water by ozone oxidation [J]. Research of Environmental Sciences, 2019, 32(7): 1231-1238(in Chinese).
[32] 姜宏斌. 催化臭氧氧化工艺处理芳香族VOCs废气的研究[D]. 大连: 大连理工大学, 2021. JIANG H B. Study on the treatment of aromatic VOCs waste gas by catalytic ozonation process[D]. Dalian: Dalian University of Technology, 2021(in Chinese).
[33] 朱自莹, 顾仁敖, 陆天虹. 拉曼光谱在化学中的应用[M]. 沈阳: 东北大学出版社, 1998. ZHU Z Y, GU R A, LU T H. Application of Raman spectroscopy in chemistry[M]. Shenyang: Northeast University Press, 1998(in Chinese)
[34] LIU Q, KE M, YU P, et al. High performance removal of methyl mercaptan on metal modified activated carbon [J]. Korean Journal of Chemical Engineering, 2018, 35(1): 137-146. doi: 10.1007/s11814-017-0272-1