Preparation Of Acidic Bio-based TiO₂ And Its Photocatalytic Performance For Rapid Reduction Of Cr?VI? In Water Under Visible Light And Original PH

As a heavy metal contaminant that is persistently harmful to the environment,Cr?VI?is widely present in wastewater with the rapid development of the world industry.However,conventional treatment technologies for chromium-containing wastewater still have problems such as high cost and low efficiency.Photocatalysis as an emerging wastewater treatment technology is an effective strategy for removing Cr?VI?from wastewater based on its low cost,high efficiency and environmental protection photocatalytic reduction.Based on the advantages of low cost and environmentally friendly,as a semiconductor photocatalyst that has been semi–in–dustrially produced and applied,nano–TiO₂ is widely used in the field of environmental photocatalysis.However,due to its wide band gap,TiO₂ can only be excited by ultraviolet light,and its photogenerated electron-hole recombination rate is high,resulting in low utilization of photogenerated electrons and holes.In addition,although TiO₂ can reduce Cr?VI?under the original pH condition of Cr?VI?solution,most of the reported TiO₂–based photocatalysts reduce Cr?VI?by adding inorganic acid or organic acid.Whether adding inorganic or organic acids will introduce new pollutants into the system or cause secondary pollution.Based on the above problems of low solar light utilization,high photoelectron–hole recombination rate and secondary pollution caused by external acid,this paper constructs acidic core–shell structure non–metal co–doped TiO₂ and acid carbon dot–modified TiO₂ heterojunction and its use for the reduction of Cr?VI?.1.In this chapter,the core–shell bio–based TiO₂ was prepared by using carbon microspheres as the core and tetrabutyl titanate as the titanium source.The effects of the addition amount of titanium source,the amount of ammonia added,the stirring time,the stirring temperature and the calcination temperature on the bio–based TiO₂ with core–shell structure were studied.The results show that when the amount of tetrabutyl titanate is 1 mL,the amount of ammonia added is 0.75 mL,the stirring time is 24 h,the stirring temperature is 35°C and the calcination temperature is 350°C,a large number of core–shell structure TiO₂ with uniform sizes and diameters larger than 1?m can be prepared.As a catalyst for the hydrolysis condensation of tetrabutyl titanate,ammonia controls the hydrolysis condensation rate of tetrabutyl titanate,which is the key parameter for constructing the core–shell structure.In addition,the bio–based TiO₂ with core–shell structure has a visible light response due to co–doping of C and N elements,wherein the C element is mainly derived from an anhydrous ethanol solvent,a carbon core,and an unhydrolyzed hydrocarbon group in the titanium source,and the N element is mainly derived from ammonia and nitrogen–containing groups in the carbon core.2.In this chapter,based on bio–based TiO₂ with core–shell structure and visible light response,acidic bio-based TiO₂ with core–shell structure and visible light response prepared by further sulfonation technology,that is,the sulfonic acid group is connected to the carbon core.The morphology and structure characterization,composition and structure characterization,photo–electric property characterization and surface charge characterization of the prepared acidic bio–based TiO₂ with core–shell structure and visible light response were also investigated.The successful loading of sulfonic acid groups was also confirmed.Finally,the material was used to reduce the Cr?VI?in the aqueous solution under the original pH and visible light conditions.The reduction rate of Cr?VI?was greatly improved,and the reduction mechanism of Cr?VI?was proposed.In order to further improve the photoreduction rate of Cr?VI?,the material was used in a composite system of Cr?VI?and organic pollution.The results show that the material has a synergistic effect in the reduction of Cr?VI?and the degradation of organic pollutants,and the reduction rate and oxidative degradation rate increase simultaneously.