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苯系物[1](苯、甲苯、乙苯和二甲苯,BTEX),作为单环芳烃类物质,主要存在于石油化工产品中,具有“致癌、致突变、致畸”等危害。在化工搬迁场地[2]、废加油站[3]以及钢铁焦化企业[4]的土壤中BTEX污染严重;另外,近年来国内发生多起BTEX泄露事故,泄露后污染物会扩散、渗透、残留在土壤的毛细孔道中,若处理不当会引发紧急公共安全事件[5-6]。因此,研究土壤环境中BTEX的原位修复技术具有重要的理论价值和应用前景。
工业上降解处理BTEX的传统技术有吸附法、吸收法、冷凝法等,近年来新发展的技术包括化学氧化法、低温等离子体法等[7]。其中,化学氧化法具有去除效率高、易操作、施工工期短等优点,常用氧化剂包括过硫酸钠、高锰酸钾、过氧化氢、Fenton试剂、类Fenton试剂等[8]。然而,采用化学氧化法降解处理土壤中有机物时,氧化剂费用在成本核算时所占比例过高,部分工程案例该项支出甚至在50%以上。这是由于在施工过程中,为保证污染物降解完全,防止因污染物不达标而返工,氧化剂用量往往过量很多,造成氧化剂浪费,且多余氧化剂可能会破坏土层结构及有机质含量等相关性质。前人曾研究用化学氧化法处理水中的苯系物[9-15],发现高锰酸钾、过氧化氢、Fenton试剂、类Fenton试剂及活化过硫酸盐氧化苯系物可以达到良好的处理效果。赵丹[16]等比较研究了Fenton试剂、类Fenton 试剂、高锰酸钾以及活化过硫酸钠4种常用的化学氧化剂对焦化工业污染场地中苯系物的去除效果,但考察的污染物浓度较低,最高BTEX含量仅有18.1 mg·kg−1,限制了该研究在焦化场地以外工况中的参考使用。
综合上述问题,本研究选择了5种常见的低成本氧化剂,在密闭顶空瓶中对人工污染的苯系物(浓度最高可达约1000 mg·kg−1)土壤进行处理,采用正交实验法探索最佳氧化条件和显著影响因素,分析对比氧化剂种类对各类苯系物的降解效果,确定氧化剂和苯系物间的最佳匹配关系。
不同氧化剂氧化降解土壤中的苯系物
Study on degradation of volatile benzenes in soil by different oxidants
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摘要: 化学氧化修复技术是处理土壤中有机污染物的一种有效方法,但在施工过程中,氧化剂添加往往过量很多,造成氧化剂浪费,且多余氧化剂还会破坏土层结构及有机质含量。目前采用化学氧化法处理苯系物大多针对于地下水环境,面对复杂工况时的土壤苯系物污染,氧化处理缺少相应的系统数据支持。据此,本研究采用正交实验的方法研究了活化过硫酸钠、高锰酸钾、过氧化氢、Fenton试剂和类Fenton试剂氧化不同苯系物的最佳条件和显著影响因素。结果表明,氧化时间是对降解率影响较大的因素,但是降解不同苯系物所采用的氧化剂、氧化条件及显著影响因素有所不同。整体来看,苯系物中乙苯和二甲苯比较容易被氧化;对于氧化剂来说,过氧化氢、高锰酸钾和过硫酸钠氧化效果更好。研究结果可为实际工程上处理不同种类、不同浓度及不同比例的苯系物时,在氧化剂的选择以及氧化剂、活化剂、络合剂的浓度和反应时间等参数设置上提供基础数据支持。Abstract: Chemical oxidation technology is regarded to be an effective method for the oxidative degradation of organic pollutants in soil remediation. However, excessive amounts of oxidants tend to be employed in the process of operation, which resulting in the waste of oxidant, also destroying the layer structure of soil and its content of organic compound due to the residual oxidant. At present, chemical oxidation technology is mainly used in the degradation treatment of benzene, toluene, ethylbenzene, o-xylene and p-xylene (BTEX) in groundwater environment, but less research is carried out in soil environment. Therefore, chemical oxidative degradation of BTEX in soil was systematacially studied in this thesis. The optimum conditions and significant influencing factors for BTEX degradation were investigated with sodium persulfate, potassium permanganate, hydrogen peroxide, Fenton reagent and Fenton-like reagent as oxidants through orthogonal experiments method. The results showed that the oxidation time had a great influence on the degradation rate, but the effect seems to be different for the degradation of different BTEX compounds if it wholly taking into account of the oxidants, oxidation conditions and significant influencing factors. On the whole, ethylbenzene and xylene in BTEX are founded to be easier being oxidized. As for oxidizing agents, hydrogen peroxide, potassium permanganate and sodium persulfate are discovered to show better oxidation performance. In general, the research can provide basic data supporting for the selection of oxidants, activators and complexing agents and the reaction condition when it dealing with BTEX pollutants with different types, concentrations and proportions in soil remediation.
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Key words:
- BTEX /
- sodium persulfate /
- potassium permanganate /
- hydrogen peroxide /
- Fenton reagent /
- Fenton-like reagent
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表 1 苯-乙苯和甲苯-二甲苯土壤污染量的理论值及实际值
Table 1. The theoretical and actual values of benzene - ethylbenzene and toluene -xylene in soil
设定比
Setting ratio of benzene/ethylbenzene理论值/(mg·kg−1)
Theoretical value老化后实际值/(mg·kg−1)
Actual value after aging苯/乙苯 1/1 175/175 152.1/100.4 1/4 70/280 53.8/115.85 1/6 50/300 28.1/129.1 1/9 35/315 29.7/185.5 甲苯-二甲苯 2/0.5/0.5 1600/400/400 973.3/310.1/309.7 1/0.5/0.5 1200/600/600 773.7/510.9/501.5 3/2.5/2.5 900/750/750 588.0/608.8/580.0 1/1/1 800/800/800 457.9/587.6/571.0 表 2 氧化剂与活化剂、络合剂比例设定数值
Table 2. Setting values of oxidants, activators and complexant
因素
Factors水平1
Level 1水平2
Level 2水平3
Level 3水平4
Level 4n(H2O2):n(FeSO4) 1:0.05 1:0.1 1:0.2 1:0.4 n(Na2S2O8):n(FeSO4) 1:0.025 1:0.05 1:0.1 1:0.2 n(FeSO4):n(柠檬酸) 1:6 1:3 2:3 4:3 -
[1] 欧盛江. 环境空气中的苯系物检测及其治理研究 [J]. 科技资讯, 2009, 7(25): 241-242. doi: 10.3969/j.issn.1672-3791.2009.25.198 OU S J. Study on detection and treatment of benzene series in ambient air [J]. Science & Technology Information, 2009, 7(25): 241-242(in Chinese). doi: 10.3969/j.issn.1672-3791.2009.25.198
[2] 刘芬芬, 孙小华, 丁力, 等. 搬迁企业原址场地土壤挥发性有机物污染特征: 以北京某搬迁化工厂为例 [J]. 城市地质, 2021, 16(1): 18-24. doi: 10.3969/j.issn.1007-1903.2021.01.003 LIU F F, SUN X H, DING L, et al. Characteristics of soil volatile organic compound pollution in the original site of relocated enterprises—A case study of a relocated chemical plant in Beijing [J]. Urban Geology, 2021, 16(1): 18-24(in Chinese). doi: 10.3969/j.issn.1007-1903.2021.01.003
[3] 张宏凯, 左锐, 王金生, 等. 加油站泄漏污染物的迁移分布规律 [J]. 中国环境科学, 2018, 38(4): 1532-1539. doi: 10.3969/j.issn.1000-6923.2018.04.041 ZHANG H K, ZUO R, WANG J S, et al. The underground migration and distribution of petroleum contamination at a gas station [J]. China Environmental Science, 2018, 38(4): 1532-1539(in Chinese). doi: 10.3969/j.issn.1000-6923.2018.04.041
[4] 王艳俊. 焦化工业区土壤中苯/甲苯污染状况及吸附行为研究[D]. 太原: 山西大学, 2009. WANG Y J. The study of benzene/toluene pollution and adsorption in coked-area[D]. Taiyuan: Shanxi University, 2009(in Chinese).
[5] 李克, 丁文娟, 王芳, 等. 石油开采行业土壤污染防治对策与建议 [J]. 化工环保, 2019, 39(6): 603-607. doi: 10.3969/j.issn.1006-1878.2019.06.001 LI K, DING W J, WANG F, et al. Countermeasures and suggestions for soil contamination prevention and control of oil exploration industry [J]. Environmental Protection of Chemical Industry, 2019, 39(6): 603-607(in Chinese). doi: 10.3969/j.issn.1006-1878.2019.06.001
[6] 董炎青, 陈英, 陈勇, 等. 土壤甲苯泄漏扩散及影响因素的三维数值模拟 [J]. 油气田地面工程, 2018, 37(7): 14-18. doi: 10.3969/j.issn.1006-6896.2018.07.005 DONG Y Q, CHEN Y, CHEN Y, et al. Three-dimensional numerical simulation of toluene leakage and influencing factors in soil [J]. Oil-Gas Field Surface Engineering, 2018, 37(7): 14-18(in Chinese). doi: 10.3969/j.issn.1006-6896.2018.07.005
[7] 何黎, 白娟, 殷俊, 等. 苯系物污染治理的研究进展 [J]. 应用化工, 2017, 46(10): 2039-2042,2047. doi: 10.3969/j.issn.1671-3206.2017.10.043 HE L, BAI J, YIN J, et al. Research progress of pollution control of benzene series [J]. Applied Chemical Industry, 2017, 46(10): 2039-2042,2047(in Chinese). doi: 10.3969/j.issn.1671-3206.2017.10.043
[8] 周欣, 张代荣, 李萍. 多环芳烃污染土壤化学氧化修复技术应用研究 [J]. 环境与发展, 2020, 32(2): 89-90. ZHOU X, ZHANG D R, LI P. Application of chemical oxidative remediation technology to PAHs contaminated soil [J]. Environment and Development, 2020, 32(2): 89-90(in Chinese).
[9] CRIMI M L, TAYLOR J. Experimental evaluation of catalyzed hydrogen peroxide and sodium persulfate for destruction of BTEX contaminants [J]. Soil and Sediment Contamination:an International Journal, 2007, 16(1): 29-45. doi: 10.1080/15320380601077792 [10] 杨玲, 赵勇胜, 孙威, 等. Fenton试剂快速氧化处理地下水中BTEX可行性研究 [J]. 水文地质工程地质, 2010, 37(6): 107-111. doi: 10.3969/j.issn.1000-3665.2010.06.021 YANG L, ZHAO Y S, SUN W, et al. Feasibility of rapid treatment of BTEX in groundwater by Fenton's reagent [J]. Hydrogeology & Engineering Geology, 2010, 37(6): 107-111(in Chinese). doi: 10.3969/j.issn.1000-3665.2010.06.021
[11] LEMAIRE J, CROZE V, MAIER J, et al. Is it possible to remediate a BTEX contaminated chalky aquifer by in situ chemical oxidation? [J]. Chemosphere, 2011, 84(9): 1181-1187. doi: 10.1016/j.chemosphere.2011.06.052 [12] ANDRADE L N, ARAUJO S F, MATOS A T, et al. Performance of different oxidants in the presence of oxisol: Remediation of groundwater contaminated by gasoline/ethanol blend [J]. Chemical Engineering Journal, 2017, 308: 428-437. doi: 10.1016/j.cej.2016.09.069 [13] YANG Z H, VERPOORT F, DONG C D, et al. Remediation of petroleum-hydrocarbon contaminated groundwater using optimized in situ chemical oxidation system: Batch and column studies [J]. Process Safety and Environmental Protection, 2020, 138: 18-26. doi: 10.1016/j.psep.2020.02.032 [14] 江晓铭, 蒋亚萍, 陈余道, 等. 过硫酸盐在岩溶管道地下水中的稳定性及其对苯系物的去除效果 [J]. 环境工程学报, 2021, 15(4): 1395-1402. JIANG X M, JIANG Y P, CHEN Y D, et al. Stability of persulfate in Karst conduit groundwater and its removal effect of aromatics [J]. Chinese Journal of Environmental Engineering, 2021, 15(4): 1395-1402(in Chinese).
[15] 盛益之, 张旭, 翟晓波, 等. 化学氧化技术异位处理地下水非水相有机污染物中试研究 [J]. 现代地质, 2019, 33(2): 422-430. SHENG Y Z, ZHANG X, ZHAI X B, et al. Ex-situ chemical oxidation treatment for non-aqueous liquid contaminated groundwater: A pilot study [J]. Geoscience, 2019, 33(2): 422-430(in Chinese).
[16] 赵丹, 阎秀兰, 廖晓勇, 等. 不同化学氧化剂对焦化污染场地苯系物的修复效果 [J]. 环境科学, 2011, 32(3): 849-856. ZHAO D, YAN X L, LIAO X Y, et al. Chemical oxidants for remediation of BTEX-contaminated soils at coking sites [J]. Environmental Science, 2011, 32(3): 849-856(in Chinese).
[17] 杨永奇. 活化过硫酸盐降解BTEXs和PAHs研究[D]. 北京: 中国石油大学(北京), 2018. YANG Y Q. Study on degradation of BTEXs and PAHs by activated persulfate[D]. Beijing: China University of Petroleum (Beijing), 2018(in Chinese).
[18] 孙威, 赵勇胜, 杨玲, 等. 过硫酸盐活化技术处理地下水中的BTEX及其动力学 [J]. 安徽农业大学学报, 2012, 39(3): 446-450. SUN W, ZHAO Y S, YANG L, et al. Treatment of BTEX in groundwater by persulfate oxidation reaction and its kinetics [J]. Journal of Anhui Agricultural University, 2012, 39(3): 446-450(in Chinese).
[19] SUN P, SHEN G Q, TAN Q R, et al. Degradation of BTEXS with stable and pH-insensitive iron-manganese modified biochar from post pyrolysis [J]. Chemosphere, 2021, 263: 128092. doi: 10.1016/j.chemosphere.2020.128092 [20] SRA K S, THOMSON N R, BARKER J F. Persulfate treatment of dissolved gasoline compounds [J]. Journal of Hazardous, Toxic, and Radioactive Waste, 2013, 17(1): 9-15. doi: 10.1061/(ASCE)HZ.2153-5515.0000143 [21] LIANG C J, HUANG C F, CHEN Y J. Potential for activated persulfate degradation of BTEX contamination [J]. Water Research, 2008, 42(15): 4091-4100. doi: 10.1016/j.watres.2008.06.022 [22] RINALDI A, SILVA M R. Degradation of BTX in contaminated soil by using hydrogen peroxide (H2O2) and potassium permanganate (KMnO4) [J]. Water, Air, & Soil Pollution, 2011, 217(1/2/3/4): 245-254. [23] 杨玲, 赵勇胜, 马百文, 等. Fenton和类Fenton氧化处理地下水中BTEX及其动力学 [J]. 环境工程学报, 2011, 5(5): 992-996. YANG L, ZHAO Y S, MA B W, et al. Treatment of BTEX in groundwater by Fenton's and Fenton-like oxidation reaction and the kinetics [J]. Chinese Journal of Environmental Engineering, 2011, 5(5): 992-996(in Chinese).
[24] WATTS R J, HALLER D R, JONES A P, et al. A foundation for the risk-based treatment of gasoline-contaminated soils using modified Fenton’s reactions [J]. Journal of Hazardous Materials, 2000, 76(1): 73-89. doi: 10.1016/S0304-3894(00)00173-4 [25] KANG N, HUA I. Enhanced chemical oxidation of aromatic hydrocarbons in soil systems [J]. Chemosphere, 2005, 61(7): 909-922. doi: 10.1016/j.chemosphere.2005.03.039