聚乙烯塑料/铬渣共热解还原Cr(Ⅵ)的实验研究
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摘要
在分析聚乙烯热解特性的基础上,研究热解时间、热解温度及聚乙烯与铬渣质量比对Cr(VI)还原的影响,并运用XANES和EXAFS光谱研究铬元素的形态变化,并对反应机制进行分析.结果表明,(1)聚乙烯在热解过程中可以有效将Cr(VI)还原,还原率随着温度的升高而升高,当热解温度达到550℃,还原率为99.93%;随着PE投加量增大,Cr(VI)还原率逐渐上升,当质量比超过0.05时趋于稳定;Cr(VI)还原伴随塑料热解反应进行,6min后趋于稳定;最优反应条件为热解温度550℃、热解时间6min、PE/铬渣质量比0.05.(2)使用XAS铬形态分析过程中以Cr2O3作为Cr(Ⅲ)的参考物较CrCl_3更为合理,铬渣中Cr(VI)还原产物为无定型Cr_2O_3;(3)由于PE主要由C、H两种元素组成,不含O元素,相比生物质还原剂,可以更高效还原Cr(VI);(4)Cr(VI)与挥发份充分接触反应条件下,Cr(VI)可持续还原.
The influences of reaction parameters, including pyrolysis temperature, reaction time and the mass ratio of PE/COPR, on Cr(VI) reduction were evaluated. The change of chromium speciation during the treatment was studied by XANES and EXAFS spectroscopy. The results indicated that,(1) Through the co-pyrolysis treatment, the Cr(VI) reduction can be effectively reduced. When the temperature reaches 550℃, the reduction rate could reached to 99.93%. The Cr(VI) reduction rate gradually increased with the rising dose of PE and then became stable when the mass ratio was over 0.05. Cr(VI) reduction rate rapidly increased during the initial reaction time while almost unchanged after 6min. The optimum reaction condition was evaluated as below: pyrolysis temperature: 550℃, pyrolysis time: 6min, and PE/COPR: 0.05.(2) Cr_2O_3 as the reference material of Cr(III) is more accurate and reasonable than CrCl_3 during the Cr(VI) detection by XANES, and the Cr(VI) in the COPR was reduced as amorphous Cr+2O_3.(3) Compared to the biomass, PE as the reducing agent can be more efficient in Cr(VI) reduction, ascribed to the higher content of C, H and no O.(4) Cr(VI) can be continuously reduced under continuous contact with the volatile compounds generated from the pyrolysis of PE.
The influences of reaction parameters, including pyrolysis temperature, reaction time and the mass ratio of PE/COPR, on Cr(VI) reduction were evaluated. The change of chromium speciation during the treatment was studied by XANES and EXAFS spectroscopy. The results indicated that,(1) Through the co-pyrolysis treatment, the Cr(VI) reduction can be effectively reduced. When the temperature reaches 550℃, the reduction rate could reached to 99.93%. The Cr(VI) reduction rate gradually increased with the rising dose of PE and then became stable when the mass ratio was over 0.05. Cr(VI) reduction rate rapidly increased during the initial reaction time while almost unchanged after 6min. The optimum reaction condition was evaluated as below: pyrolysis temperature: 550℃, pyrolysis time: 6min, and PE/COPR: 0.05.(2) Cr_2O_3 as the reference material of Cr(III) is more accurate and reasonable than CrCl_3 during the Cr(VI) detection by XANES, and the Cr(VI) in the COPR was reduced as amorphous Cr+2O_3.(3) Compared to the biomass, PE as the reducing agent can be more efficient in Cr(VI) reduction, ascribed to the higher content of C, H and no O.(4) Cr(VI) can be continuously reduced under continuous contact with the volatile compounds generated from the pyrolysis of PE.
引文
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[16]Srakeaw V,Yodjai S,Wetwatana U.Catalytic Pyrolysis of LDPE Plastic Wastes over Mortar Cement Catalyst[J].Advanced Materials Research,2014,931-932:47-51.
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[22]Dermatas D,Chrysochoou M,Moon D H.Ettringite-induced heave in chromite ore processing residue(COPR)upon ferrous sulfate treatment[J].Environmental Science&Technology,2006,40(18):5786-5792.
[23]Rajapaksha A U,Vithanage M.Cr(VI)Formation related to Cr(III)-muscovite and birnessite interactions in ultramafic environments[J].Environmental Science&Technology,2013,47(17):9722-9729.
[24]Zhang M,Pan G,Zhao D.XAFS study of starch-stabilized magnetite nanoparticles and surface speciation of arsenate[J].Environmental Pollution,2011,159(12):3509-3514.
[25]Park D,Yun Y S,Park J M.XAS and XPS Studies on Chromiumbinding Groups of Biomaterial during Cr(VI)Biosorption[J].Journal of Colloid&Interface Science,2008,317(1):54-61.
[26]Wazne M,Jagupilla S C,Moon D H.Assessment of calcium polysulfide for the remediation of hexavalent chromium in chromite ore processing residue(COPR)[J].Journal of Hazardous Materials,2007,143(3):620-628.
[27]Li P,Xu H B,Zheng S L.A Green Process to Prepare Chromic Oxide Green Pigment[J].Environmental Science&Technology,2008,42(19):7231-7235.
[2]Rogers C M,Burke I T.Immobilization of chromate in hyperalkaline waste streams by green rusts and zero-valent iron[J].Environmental Technology,2013,35(1-4):508-513.
[3]张钊,黄瑾辉,曾光明,等.3MRA风险模型在铬渣整治项目制定过程中的应用[J].中国环境科学,2010,30(1):139-144.
[4]Jagupilla S C,Moon D H,Wazne M.Effects of particle size and acid addition on the remediation of chromite ore processing residue using ferrous sulfate[J].Journal of Hazardous Materials,2009,168(1):121-128.
[5]Moon D H,Wazne M,Dermatas D.Long-term treatment issues with chromite ore processing residue(COPR):Cr6+,reduction and heave[J].Journal of Hazardous Materials,2007,143(3):629-635.
[6]Chrysochoou M,Fakra S C,Marcus M A.Microstructural Analyses of Cr(VI)Speciation in Chromite Ore Processing Residue(COPR)[J].Environmental Science&Technology,2009,43(14):5461-5466.
[7]酆婧轩,李芸邑,师帅,等.硫代硫酸钠、磷酸钠联合处理铬渣中的六价铬[J].中国环境科学,2015,35(11):3333-3339.
[8]张大磊,李依韩,孔海南.铬渣秸秆共热解产物铬稳定性研究[J].环境污染与防治,2013,35(7):17-21+26.
[9]Du J,Lu J,Wu Q.Reduction and immobilization of chromate in chromite ore processing residue with nanoscale zero-valent iron[J].Journal of Hazardous Materials,2012,215-216(4):152-8.
[10]张大磊,何圣兵,蔡荣宝,等.铬渣的热解无害化处理[J].环境污染与防治,2009,(10):1-5.
[11]Zhang D,He S,Dai L.Impact of pyrolysis process on the chromium behavior of COPR[J].Journal of Hazardous Materials,2009,172(2/3):1597-1601.
[12]陈忠林,李金春,王斌远,等.零价铁和碱激发矿渣稳定/固定化处理铬渣研究[J].环境科学,2015,(8):3026-3031.
[13]Moon D H,Wazne M,Koutsospyros A.Evaluation of the treatment of chromite ore processing residue by ferrous sulfate and asphalt[J].Journal of Hazardous Materials,2009,166(1):27-32.
[14]薛浩,孟凡生,王业耀,等.酸化-电动强化修复铬渣场地污染土壤[J].环境科学研究,2015,(8):1317-1323.
[15]Stefanidis S D,Kalogiannis K G,Iliopoulou E F.A study of lignocellulosic biomass pyrolysis via the pyrolysis of cellulose,hemicellulose and lignin[J].Journal of Analytical&Applied Pyrolysis,2013,105(5):143-150.
[16]Srakeaw V,Yodjai S,Wetwatana U.Catalytic Pyrolysis of LDPE Plastic Wastes over Mortar Cement Catalyst[J].Advanced Materials Research,2014,931-932:47-51.
[17]Zhu H,Chen W,Jiang X.Study on HCl removal for medical waste pyrolysis and combustion using a TG-FTIR analyzer[J].Frontiers of Environmental Science&Engineering,2015,9(2):230-239.
[18]Namioka T,Saito A,Inoue Y.Hydrogen-rich gas production from waste plastics by pyrolysis and low-temperature steam reforming over a ruthenium catalyst[J].Applied Energy,2011,88(6):2019-2026.
[19]Lin H.T.,Hydrocarbon fuels produced by catalytic pyrolysis of hospital plastic wastes in a fluidizing cracking process.Fuel Processing Technology,2010,91(11):1355-1363.
[20]Ressler T.Win XAS:a Program for X-ray Absorption Spectroscopy Data Analysis under MS-Windows[J].Journal of Synchrotron Radiation,2007,5(Pt 2):118-122.
[21]Malherbe J,Isaure M P,Séby F.Evaluation of Hexavalent Chromium Extraction Method EPA Method 3060A for Soils Using XANES Spectroscopy[J].Environmental Science&Technology,2011,45(24):10492-10500.
[22]Dermatas D,Chrysochoou M,Moon D H.Ettringite-induced heave in chromite ore processing residue(COPR)upon ferrous sulfate treatment[J].Environmental Science&Technology,2006,40(18):5786-5792.
[23]Rajapaksha A U,Vithanage M.Cr(VI)Formation related to Cr(III)-muscovite and birnessite interactions in ultramafic environments[J].Environmental Science&Technology,2013,47(17):9722-9729.
[24]Zhang M,Pan G,Zhao D.XAFS study of starch-stabilized magnetite nanoparticles and surface speciation of arsenate[J].Environmental Pollution,2011,159(12):3509-3514.
[25]Park D,Yun Y S,Park J M.XAS and XPS Studies on Chromiumbinding Groups of Biomaterial during Cr(VI)Biosorption[J].Journal of Colloid&Interface Science,2008,317(1):54-61.
[26]Wazne M,Jagupilla S C,Moon D H.Assessment of calcium polysulfide for the remediation of hexavalent chromium in chromite ore processing residue(COPR)[J].Journal of Hazardous Materials,2007,143(3):620-628.
[27]Li P,Xu H B,Zheng S L.A Green Process to Prepare Chromic Oxide Green Pigment[J].Environmental Science&Technology,2008,42(19):7231-7235.