铈钛氧化物介孔毫米球的制备及其催化臭氧氧化特性与机理

Preparation of mesoporous Ce-Ti oxide millispheres for efficient catalytic ozonation: Performance and mechanism

开发兼具高催化活性和优良流体力学与传质性能的催化剂对发展高效水处理臭氧氧化技术具有重要意义.本研究开发了以廉价无机金属盐为原料的前驱体溶胶预混-海藻酸水凝胶球模板法,实现了Ce-Ti双金属氧化物介孔毫米球催化剂的经济制备.通过N_2吸附-脱附、XRD、XPS、SEM-EDS、TEM-SAED、拉曼光谱、NH_3-TPD等手段对制备的催化剂进行系统表征,考察Ce/Ti摩尔比和煅烧温度对催化剂结构和催化活性的影响,探究其催化臭氧氧化的特性与机理.结果表明无定形材料催化活性高于晶型材料,催化活性与表面酸性位点密度呈正相关,阐明了羟基自由基为该材料催化臭氧氧化的主要活性物种.优选的Ce_(0.5)Ti_(0.5)O_2介孔毫米球具有高比表面积(199 m^2g^(–1))、适宜的介孔结构(平均孔径3.59 nm),富含Ce–O–Ti键活性位点,催化臭氧氧化活性高,可在90 min内将100 mg L^(–1)草酸几乎完全矿化(99%),连续5轮重复实验后催化活性无明显降低,呈现出优异的催化稳定性.另外, Ce_(0.5)Ti_(0.5)O_2介孔毫米球催化臭氧氧化降解双氯芬酸等四种污染物的矿化率相比无催化剂臭氧氧化提高18.7%～54.0%,展现出优良的应用前景.

To achieve highly efficient ozonation during water treatment,it is crucial to develop catalysts combining high activity and excellent hydrodynamic as well as mass transfer properties.In this study,a series of catalysts of Ce-Ti bimetal oxide mesoporous millispheres were prepared through a green and economical route of precursor sol premixing-alginate hydrogel bead template method employing the low cost inorganic salts as the raw materials.The resulting catalysts were comprehensively characterized by N2 adsorptiondesorption,XRD,XPS,SEM-EDS,TEM-SAED,Raman spectroscopy,and NH3-TPD.The effects of Ce/Ti ratio and calcination temperature on the structure and activity of the catalyst were investigated,and the performance and mechanism of the corresponding catalytic ozonation were explored.The results showed that the activities of amorphous catalysts were higher than those of the crystalline ones,and the catalytic activity was positively correlated with the density of surface acidic sites.It was revealed that hydroxyl radicals were the predominant reactive species during the catalytic oxidation by the prepared catalyst.The optimized Ce05Ti05O2 mesoporous millisphere of high specific surface area (199m^2g^-1)and suitable mesoporous structure (average pore diameter of 3.59 nm),was rich in Ce-O-Ti active sites and exhibited high catalytic activity.Almost complete (99%) mineralization of 100 mg L^- 1 oxalic acid could be achieved during the catalytic ozonation in 90 min.Moreover,negligible loss of catalytic activity was observed in five consecutive experiments.In addition,as compared with catalyst free,the Ce05Ti05O2 millisphere catalyst could in crease the TOC removal by 18.7%-54.0% during ozonation of four toxic organic pollutants such as diclofenac,thus exhibiting promising potential in authentic water treatment.