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随着我国工业化的快速发展,工业废水的排放量在显著增长[1]。尤其是煤化工、石化、制药等废水处理不当,将会对环境造成严重的危害。在煤化工、石化和制药废水中,酚类化合物是一类常见的有机污染物,其中的间甲酚因其具有较大的毒性和强烈的腐蚀性,对生物体具有直接或潜在的危害,其直接进入人体会引起蛋白质的团聚和变性,同时抑制环氧化酶的活性和血小板的凝结,进而影响中枢神经系统[2],间甲酚已被多国环保机构列入优先控制污染物的名单中。因此,对含有间甲酚废水的处理、转化和降解的研究已引起广泛的关注[3-6]。常用的间甲酚废水处理方法有生化法[7]、吸附法[8]和高级氧化法(催化臭氧氧化[9]、电催化氧化[10]、催化过氧化氢氧化[11])。由于传统方法对间甲酚的去除效果并不理想,高级氧化方法(advanced oxidation processes)被认为是处理间甲酚废水最常用的方法。
众所周知,臭氧对有机污染物具有较强的降解和矿化能力[12]。催化臭氧氧化技术的核心为催化剂,目前,在催化臭氧氧化中常用的非均相催化剂有活性炭类、活性金属铁、金属氧化物、分子筛和天然矿物等[13-14]。在这些非均相催化剂的作用下,臭氧可以更有效地和有机物发生反应,以实现污染物的降解和矿化。然而上述非均相催化剂在应用于催化臭氧氧化反应时,仍存在一定问题,如催化剂稳定性不够、活性组分易流失、催化效率不高等[15]。
钙钛矿类混合金属氧化物具有明确的晶体结构,通用单元分子式为ABO3,式中的A表示稀有或碱土金属,B表示过渡金属,因其结构的复杂性和多样性,可作为催化剂应用于各类催化反应中,如光催化、燃料电池、三效催化剂、VOCs的治理和催化湿式过氧化物的氧化等[16]。这种催化剂在高温和腐蚀性介质中是稳定的,同时B位元素位于晶体结构的中心,可以防止活性组分的流失,这对于钙钛矿催化剂的活性和结构稳定性至关重要。笔者前期的研究发现,钙钛矿材料也可被用于催化臭氧氧化技术中,许多学者也已经证明了钙钛矿在催化臭氧氧化反应中有着较好的活性[15, 17-20]。RIVAS等[21]将LaTi0.15Cu0.85O3用于催化臭氧氧化丙酮酸的实验中,在重复使用3次后,其活性甚至有所提高。因此,有必要进一步研究钙钛矿型催化剂在降解污染物中的应用情况。锆酸钙(CaZrO3)复合材料是一种重要的钙钛矿材料,常应用于发光材料[22-23]、湿度传感器[24]、陶瓷电容器[25]和超高温下的保护材料[26]等。与其他钙钛矿氧化物不同,有关其在催化臭氧氧化反应中的研究较少。因此,有必要对CaZrO3复合材料在废水处理中的应用及催化机制进行详细研究,以便更深入地了解其催化性能。
本研究采用共沉淀法制备了一系列Ca-Zr复合材料,在不同焙烧温度下,对复合材料进行了焙烧。鉴于制备方法对钙钛矿的结构性质和相纯度的决定性影响,考察了合成条件(主要是焙烧温度)对降解间甲酚催化性能的影响,且将使用XRD、SEM、TEM等表征手段对不同焙烧温度下制备的Ca-Zr复合材料催化剂的结构、形貌和组分进行了分析,对其在催化臭氧氧化中的催化活性、机理和稳定性进行阐释。
高分散纳米钙锆复合材料催化臭氧氧化降解间甲酚废水
Degradation of m-cresol wastewater by catalytic ozonation with highly dispersed nano-calcium-zirconium composites
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摘要: 采用共沉淀法制备了一系列Ca-Zr复合材料,探究了不同的焙烧温度对材料结构和化学性质的影响。使用X射线衍射、扫描电子显微镜及高分辨透射电镜等分析手段表征了所制备样品的物相变化和颗粒形貌特征,以间甲酚为底物,采用臭氧催化氧化方法对所得催化剂的催化性能进行了分析。结果表明:当焙烧温度升高到1 000 ℃以上时,样品晶型以斜方晶系CaZrO3为主,随着焙烧温度的升高,颗粒更加均匀分散。在催化臭氧氧化降解间甲酚实验中,当焙烧温度为800 ℃时, TOC去除率最高可达到79%。800 ℃焙烧所得的样品由纳米颗粒组成,晶格间距为0.29 nm,说明样品的高暴露晶面为CaZrO3的(121)晶面;XPS结果证实了样品的高活性可能是由晶格氧和表面羟基基团起重要作用而导致的。这种高效的纳米钙锆复合材料为催化臭氧氧化处理废水奠定了良好的基础。Abstract: A series of Ca-Zr composites were prepared by co-precipitation method. The effects of calcination temperatures on the structure and chemical properties of the materials were explored. X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy were used to characterize the phase changes and particle morphology of the prepared samples. The performance of this catalyst was analyzed with catalytic ozonation of m-cresol. The results showed that when the calcination temperature was above 1 000 ℃, the crystal form of the catalyst sample was mainly orthorhombic CaZrO3, and the particles were more uniformly dispersed with the increase of calcination temperature. In the experiments of m-cresol degradation by catalytic ozone oxidation, at the calcination temperature of 800 ℃, TOC removal rate could reach up to 79%. The sample calcined at 800 ℃ was composed of nanoparticles with a lattice spacing of 0.29 nm, indicating that the highly exposed crystal plane of the sample was the (121) plane of CaZrO3.The XPS results confirmed that the lattice oxygen and surface hydroxyl groups may play important role in the high activity of the sample. This high-efficiency nano Ca-Zr composite material lays a good foundation for catalytic ozone oxidation treatment of wastewater.
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Key words:
- Ca-Zr composites /
- calcination temperature /
- catalytic ozonation /
- TOC removal rate
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[1] GAO P, TIAN X, NIE Y, et al. Promoted peroxymonosulfate activation into singlet oxygen over perovskite for ofloxacin degradation by controlling the oxygen defect concentration[J]. Chemical Engineering Journal, 2019, 359: 828-839. doi: 10.1016/j.cej.2018.11.184 [2] CHEN D, LIU F, ZONG L, et al. Integrated adsorptive technique for efficient recovery of m-cresol and m-toluidine from actual acidic and salty wastewater[J]. Journal of Hazardous Materials, 2016, 312: 192-199. doi: 10.1016/j.jhazmat.2016.03.056 [3] JIANG Y, CAI X, WU D, et al. Biodegradation of phenol and m-cresol by mutated Candida tropicalis[J]. Journal of Environmental Sciences, 2010, 22(4): 621-626. doi: 10.1016/S1001-0742(09)60154-6 [4] LIU P, HE S, WEI H, et al. Characterization of α-Fe2O3/γ-Al2O3 catalysts for catalytic wet peroxide oxidation of m-cresol[J]. Industrial & Engineering Chemistry Research, 2015, 54(1): 130-136. [5] WANG Y, WEI H, ZHAO Y, et al. The optimization, kinetics and mechanism of m-cresol degradation via catalytic wet peroxide oxidation with sludge-derived carbon catalyst[J]. Journal of Hazardous Materials, 2017, 326: 36-46. doi: 10.1016/j.jhazmat.2016.12.014 [6] YANG Y, ZHANG H, YAN Y. The preparation of Fe2O3-ZSM-5 catalysts by metal-organic chemical vapour deposition method for catalytic wet peroxide oxidation of m-cresol[J]. Royal Society Open Science, 2018, 5(3): 1-15. [7] 于晨阳, 毛缜. 蜡状芽孢杆菌菌株SMC的间甲酚降解特性及动力学[J]. 化工进展, 2015, 34(5): 1453-1458. [8] KENNEDY L J, VIJAYA J J, SEKARAN G, et al. Equilibrium, kinetic and thermodynamic studies on the adsorption of m-cresol onto micro- and mesoporous carbon[J]. Journal of Hazardous Materials, 2007, 149(1): 134-143. doi: 10.1016/j.jhazmat.2007.03.061 [9] LV A, HU C, NIE Y, et al. Catalytic ozonation of toxic pollutants over magnetic cobalt-doped Fe3O4 suspensions[J]. Applied Catalysis B: Environmental, 2012, 117-118: 246-252. doi: 10.1016/j.apcatb.2012.01.020 [10] 刘伟军, 段平洲, 胡翔, 等. 活性炭纤维三维电极电催化降解水中间甲酚: 效能及影响因素研究[J]. 中国环境科学, 2019, 39(1): 164-169. doi: 10.3969/j.issn.1000-6923.2019.01.018 [11] YANG Y, ZHANG H, YAN Y. Preparation of novel iron-loaded microfibers entrapped carbon-nanotube composites for catalytic wet peroxide oxidation of m-cresol in a fixed bed reactor[J]. Separation and Purification Technology, 2019, 212: 405-415. doi: 10.1016/j.seppur.2018.11.050 [12] ZHUANG H F, HAN H J, HOU B L, et al. Heterogeneous catalytic ozonation of biologically pretreated Lurgi coal gasification wastewater using sewage sludge based activated carbon supported manganese and ferric oxides as catalysts[J]. Bioresource Technology, 2014, 166: 178-186. doi: 10.1016/j.biortech.2014.05.056 [13] ZHANG F, HAN H, HOU B, et al. Ozonation of aqueous phenol catalyzed by biochar produced from sludge obtained in the treatment of coking wastewater[J]. Journal of Environmental Management, 2018, 224: 376-386. doi: 10.1016/j.jenvman.2018.07.038 [14] NAWROCKI J, KASPRZYK-HORDERN B. The efficiency and mechanisms of catalytic ozonation[J]. Applied Catalysis B: Environmental, 2010, 99(1/2): 27-42. [15] AFZAL S, QUAN X, ZHANG J. High surface area mesoporous nanocast LaMO3 (M=Mn, Fe) perovskites for efficient catalytic ozonation and an insight into probable catalytic mechanism[J]. Applied Catalysis B: Environmental, 2017, 206: 692-703. doi: 10.1016/j.apcatb.2017.01.072 [16] GRABOWSKA E. Selected perovskite oxides: Characterization, preparation and photocatalytic properties: A review[J]. Applied Catalysis B: Environmental, 2016, 186: 97-126. doi: 10.1016/j.apcatb.2015.12.035 [17] CARBAJO M, BELTRÁN F J, GIMENO O, et al. Ozonation of phenolic wastewaters in the presence of a perovskite type catalyst[J]. Applied Catalysis B: Environmental, 2007, 74(3/4): 203-210. [18] ORGE C A, ÓRFÃO J J M, PEREIRA M, et al. Lanthanum-based perovskites as catalysts for the ozonation of selected organic compounds[J]. Applied Catalysis B: Environmental, 2013, 140-141: 426-432. doi: 10.1016/j.apcatb.2013.04.045 [19] GONG S, XIE Z, LI W, et al. Highly active and humidity resistive perovskite LaFeO3 based catalysts for efficient ozone decomposition[J]. Applied Catalysis B: Environmental, 2019, 241: 578-587. doi: 10.1016/j.apcatb.2018.09.041 [20] ZHANG Y, XIA Y, LI Q, et al. Synchronously degradation benzotriazole and elimination bromate by perovskite oxides catalytic ozonation: Performance and reaction mechanism[J]. Separation and Purification Technology, 2018, 197: 261-270. doi: 10.1016/j.seppur.2018.01.019 [21] RIVAS F J, CARBAJO M, BELTRÁN F J, et al. Perovskite catalytic ozonation of pyruvic acid in water: Operating conditions influence and kinetics[J]. Applied Catalysis B: Environmental, 2006, 62(1): 93-103. [22] EVANGELINE B, AZEEM P A, PRASADA RAO R, et al. Structural and luminescent features of cerium doped CaZrO3 blue nanophosphors[J]. Journal of Alloys and Compounds, 2017, 705: 618-623. doi: 10.1016/j.jallcom.2016.11.115 [23] JI Y M, JIANG D Y, WU Z H, et al. Combustion synthesis and photoluminescence of Ce3+-activated MHfO3 (M=Ba, Sr, or Ca)[J]. Materials Research Bulletin, 2005, 40(9): 1521-1526. doi: 10.1016/j.materresbull.2005.04.026 [24] ANDRÉ R S, ZANETTI S M, VARELA J A, et al. Synthesis by a chemical method and characterization of CaZrO3 powders: Potential application as humidity sensors[J]. Ceramics International, 2014, 40(10): 16627-16634. doi: 10.1016/j.ceramint.2014.08.023 [25] POLLET M, MARINEL S, DESGARDIN G. CaZrO3, a Ni-co-sinterable dielectric material for base metal-multilayer ceramic capacitor applications[J]. Journal of the European Ceramic Society, 2004, 24(1): 119-127. doi: 10.1016/S0955-2219(03)00122-5 [26] RAI D P, SANDEEP, SHANKAR A, et al. Electronic and optical properties of cubic SrHfO3 at different pressures: A first principles study[J]. Materials Chemistry and Physics, 2017, 186: 620-626. doi: 10.1016/j.matchemphys.2016.11.045 [27] KALINKIN A M, NEVEDOMSKII V N, KALINKINA E V, et al. Milling assisted synthesis of calcium zirconate CaZrO3[J]. Solid State Sciences, 2014, 34: 91-96. doi: 10.1016/j.solidstatesciences.2014.06.002 [28] JAHN C, SCHAFFÖNER S, CHRISTIAN O, et al. Investigation of calcium zirconate formation by sintering zirconium dioxide with calcium hydroxide[J]. Ceramics International, 2018, 44(10): 11274-11281. doi: 10.1016/j.ceramint.2018.03.172 [29] BRIK M G, MA C G, KRASNENKO V. First-principles calculations of the structural and electronic properties of the cubic CaZrO3 (001) surfaces[J]. Surface Science, 2013, 608: 146-153. doi: 10.1016/j.susc.2012.10.004 [30] CHEN J, WU S, ZHANG F, et al. Calcination temperature dependence of synthesis process and hydrogen sensing properties of In-doped CaZrO3[J]. Materials Chemistry and Physics, 2016, 172: 87-97. doi: 10.1016/j.matchemphys.2015.12.064 [31] ZHAO H, DONG Y M, JIANG P P, et al. An α-MnO2 nanotube used as a novel catalyst in ozonation: Performance and the mechanism[J]. New Journal of Chemistry, 2014, 38(4): 1743-1750. doi: 10.1039/C3NJ01523H [32] 刘莹, 何宏平, 吴德礼, 等. 非均相催化臭氧氧化反应机制[J]. 化学进展, 2016, 28(7): 1112-1120.