Preparation And Catalytic Performance Of Titanium Dioxide-based Ozonation Catalyst

Although China has abundant water resources,the per capita amount is relatively low,and the amount of discharged wastewater is increasing.The efficient degradation of organic pollutants,such as Organic pollutants in sewage（COD）has become a research focus.Currently,catalytic ozonation is an effective and low-cost technology for removing COD from wastewater.Nanomaterials exhibit excellent performance in catalytic ozonation of COD.However,the catalysts currently used in practical wastewater treatment processes have issues such as being unsuitable for complex water quality environments,difficult to recover and ion leaching.In this paper,the preparation methods of TiO₂-doped ozone oxidation catalyst and TiO₂-coated metal oxide ozone oxidation catalyst were explored.The influence of factors such as calcination temperature and the amount of butyl titanate added on the performance of powder catalysts was studied.The catalysts were characterized by XRD,TEM,SEM,BET,FT-IR,and XPS.Using aniline as a pollutant,the effect of catalyst dosage,ozone flux,and p H value on the catalyst’s performance was investigated,and the mechanism of catalytic ozonation was also studied.This article also investigated the effect of molding time,molding speed,curing time,and curing temperature on the hardness and porosity of catalysts prepared using TiO₂-coated Ni O as the active component andρ-Al₂O₃as the carrier.The effect of different catalyst dosages,ozone fluxes,and p H value on the actual application of wastewater treatment using different catalysts was explored.The main conclusions were as follows:1.Preparation and catalytic performance of doped TiO₂ozonation catalystDoped TiO₂precursors were prepared using a hydrothermal method,followed by calcination at 550°C to obtain Fe/TiO₂and Ni/TiO₂catalysts.XRD analysis showed that Fe-doped TiO₂formed pure rutile phase,while Ni-doped TiO₂formed pure hematite phase.SEM observations showed that doped TiO₂had a plate-like structure,with a thickness of about 15 nm and a side length of about 55 nm for Fe/TiO₂as well as a thickness of about 13 nm and a side length of about 50 nm for Ni/TiO₂.Under the conditions of catalyst dosage of 0.2 g/L,solution p H value of10,and ozone dosage of 0.2 L/min,the COD removal rates of Fe/TiO₂and Ni/TiO₂catalysts for aniline wastewater reached 95.96%and 93.70%,respectively after 80min of catalytic ozonation reaction.The COD removal rate was stable at about88%after 5 times repeat experiments,demonstrating the good stability of the catalysts.The metal elements doped into the catalysts replaced some Ti⁴⁺,effectively interacted with ozone,and promoted the generation of·OH,thereby the catalytic ozonation ability of the catalysts was improved.When preparing anion-doped TiO₂catalysts,excess HF was added to obtain TiOF₂.XRD analysis showed that TiOF₂had high crystallinity without other peaks.SEM observations showed that the TiOF₂particle size was 180～200 nm,and the specific surface area was 105.38 m²/g.Under the conditions of catalyst dosage of 0.2 g/L,initial COD concentration of 250 mg/L,ozone concentration of 0.1 L/min,and p H value of 10,the degradation rate reached 98.83%after 80 min of reaction.The flower-shaped TiOF₂was formed by the splicing of nanosheets with a larger specific surface area.F^-generated oxygen vacancies and Ti³⁺in the catalyst.2.Preparation and catalytic performance of TiO₂coated metal oxide ozonation catalystFe₂O₃@TiO₂,Cu O@TiO₂,and Ni O@TiO₂catalysts were prepared by using iron nitrate,nickel nitrate,copper nitrate and butyl titanate as precursors.XRD analysis showed that the catalysts were composed of TiO₂and Fe₂O₃,Cu O and Ni O.SEM morphology observations showed that the prepared catalysts had a coating structure.Using aniline as the target pollutant,under the conditions of catalyst dosage of 0.2 g/L,ozone flux of 0.2 L/min,and p H value of 10,Ni O@TiO₂had the highest reaction efficiency,with a maximum efficiency of 98.77%.Quenching experiments showed that·OH was the main free radical involved in the reaction.The improvement of catalytic performance was closely related to TiO₂as a permeable outer shell which protected the core and provided a reaction site,as well as the diffusion of active molecules in the internal environment.3.Application research of titanium-based ozonation catalystA Ti-based ozonation catalyst was prepared using Ni O@TiO₂as the active component andρ-Al₂O₃as the catalyst carrier by roll-forming.The optimal molding conditions were a molding time of 2 h,deionized water as the binder,continuous hydration curing time of 8 days,and a Ni O@TiO₂addition of 5 wt%.The prepared catalyst had a particle size of 6～8 mm,a high strength of 220 N,a wear rate of 0.84%,a porosity of 63.64%,and the surface with a loose porous structure,with a specific surface area of 313.88 m²/g.In pilot experiments,under the conditions of a catalyst dosage of 500 g/L and ozone flux of 0.2 L/min,the highest COD removal rate was achieved after 20 min of reaction,reaching 98.27%.The leaching amounts of Ni and Ti ions were 0.002098 mg/L and 0.0007523 mg/L after steeping 25 days,and the wear was less than 1.1%.For 18 consecutive days,the COD removal rate remained above 85.71%,demonstrating the good stability of the catalyst.The experimentally prepared industrial Ti-based ozonation catalysts have good durabilityThis Ti-based catalyst can solve the problems of inconvenience,difficult recovery,and excessive ion leaching of catalysts in complex water quality applications,providing more ideas for catalytic ozonation and expanding the selection range of ozonation catalysts.