不同制备方法对铝基催化剂臭氧催化氧化的效果研究

Effects of Different Preparation Methods on Catalytic Ozonation of Alumina-Based Catalysts

为改善混合法制备催化剂催化效率低以及浸渍法制备过程中能耗大、耗时长、成本高的问题,以混合法为基础,研究不同活性组分负载方案,并在最佳的负载方案下探究了过量浸渍法、等体积浸渍法和混合法制备的催化剂催化臭氧氧化处理石化二级出水的效果,并分析了这3种方法制备催化剂的晶型结构、比表面积、孔径和孔体积.结果表明:①混合法负载单活性组分的催化剂在催化臭氧氧化处理石化二级出水时,Mn/Al_(2)O_(3)催化剂表现出较高的催化活性,但出水不能满足《石油化学工业污染物排放标准》(GB 31571—2015)标准中规定的排放限值;负载双活性组分的催化剂中,Mn-Cu/Al_(2)O_(3)催化剂对石化二级出水催化臭氧氧化的去除效果较好,TOC、COD和UV_(254)去除率分别达34.54%、49.53%和56.81%,荧光类物质中类腐殖质的去除率也达到72.34%,出水满足GB 31571—2015标准限值.②X-射线粉末衍射仪(XRD)和比表面积分析仪(BET)的结果表明,混合法、过量浸渍法和等体积浸渍法3种方法制备的同组分催化剂均具有γ-Al_(2)O_(3)的晶型结构,吸附等温线均属于Ⅳ型等温线,吸附量最大的为过量浸渍法,达到326.37 cm3/g.③在催化臭氧氧化石化二级出水试验中,催化活性较高的是浸渍法,混合法稍次之,但处理后出水均可满足GB 31571—2015标准限值;3种方法制备的催化剂金属离子溶出量范围均为8.74~10.15μg/L,远低于《城镇污水处理厂污染物排放标准》(GB 18918—2002)标准中规定的排放限值.研究显示,混合法制备催化剂在深度处理石化废水时,出水可达标排放,而混合法制备催化剂工艺简单,成本低于浸渍法.因此,混合法在满足实际需求时,有望代替浸渍法制备臭氧催化剂.

The current preparation methods of ozonation catalysts have the problems of low catalytic efficiency of catalysts prepared by the blending method,and high energy and time consumption and high cost for preparation by impregnation method.We studied different loading schemes of active components based on the blending method,and then prepared catalysts under the optimal loading scheme by the blending method and the impregnation method including the pore volume impregnation(PVI)and wet impregnation(WI),respectively.The obtained catalysts were used in the catalytic ozonation treatment of petrochemical secondary effluent(PCSE),and the effects of different preparation methods were analyzed by characterizing the crystal structure,specific surface area,pore size and pore volume of the catalysts and comparing their catalytic performance.The main findings of the experimental results are as follows:(1)For the catalysts prepared by the blending method:although the Mn/Al_(2)O_(3)catalyst showed the highest catalytic activity among all the catalysts loaded with a single active component in catalytic ozonation of PCSE,the water quality of the effluent still exceeded the discharge limits specified in the Petrochemical Industry Pollutant Emission Standard(GB 31571-2015).The Mn-Cu/Al_(2)O_(3)catalyst presented a better removal effect than other catalysts loaded with dual active components in PCSE treatment.The removal rates of TOC,COD and UV_(254)reached 34.54%,49.53%and 56.81%,respectively,while the removal rate of humic-like substances in fluorescent substances was 72.34%,and the effluent quality met the GB 31571-2015 discharge limits.(2)The results of the X-ray powder diffraction(XRD)and specific surface area analysis(BET)showed that catalysts of the same composition prepared by three different methods all had the crystal structure ofγ-Al_(2)O_(3),and their adsorption isotherms were TypeⅣ.The highest adsorption of 326.37 cm3/g was obtained with the catalysts prepared by the WI method.(3)In the catalytic ozonation treatment of PCSE,the catalysts prepared by two impregnation methods had higher catalytic activity than that prepared by the blending method,but the water quality of all treated effluent could meet the GB 31571-2015 discharge limits.The metal ion solubility of the catalysts prepared by the three methods was all in the range of 8.74-10.15μg/L,which was much lower than the discharge limits in the Emission Standard of Pollutants for Urban Sewage Treatment Plants(GB 18918-2002).This study found that the quality of PCSE effluent treated by the catalyst prepared by the blending method can meet the discharge standard,while the preparation process of the blending method is simple and the cost is lower than that of the impregnation method.Therefore,the blending method is expected to replace the impregnation method to prepare ozonation catalysts when the practical requirements are met.