Preparation Of Core-Shell And Hollow Structure TiO₂/Biochar Composite Photocatalyst And Study On Dye Removal Performance In Water

Environmental pollution and fossil energy crisis are common concerns around the world.Creating a harmonious ecological environment and developing clean and sustainable energy production technology are great challenges faced by scientists around the world.Semiconductor photocatalytic technology driven by solar energy provides an effective and green way to efficiently solve environmental and energy problems.TiO₂ semiconductor photocatalyst is widely used as a cheap,efficient,pollution-free and stable photocatalyst.However,at present,due to some conditions and technical limitations,TiO₂ photocatalytic technology cannot be well used to serve industrial production.Its technical difficulties are mainly manifested in:（1）titanium dioxide has a large band gap and cannot effectively absorb sunlight;（2）The separation efficiency of photogenerated electrons-holes is low,which makes the photon utilization rate lower;（3）The specific surface area of TiO₂photocatalyst is small,the active site is small,and the effective reaction efficiency between reactants and photocatalyst is insufficient.In order to solve the above problems,this paper uses wheat straw as the carbon source to prepare biochar materials,and prepares core shell and hollow TiO₂ by template method,which is used to composite biochar materials and study their photocatalytic removal performance of dyes.The main contents and results are as follows:（1）Using wheat straw as raw material,biomass charcoal was prepared by pyrolysis.Taking Si O₂ as the template and loading it on the biochar prepared above,a core-shell structure TiO₂/biochar composite photocatalyst was obtained,and the influence of different biomass char doping amounts on the performance of dye removal in water was explored,and the types of free radicals affecting the dye removal efficiency were clarified.The results show that the core-shell TiO₂ composite photocatalyst prepared by biochar loading increases the specific surface area of TiO₂,expands the photoresponse range of TiO₂,reduces the band gap width of TiO₂,and improves the photocatalytic activity.In the photocatalytic performance test experiment of the composite with the optimal biomass load,it was found that the composite showed a good removal effect on rhodamine B（RhB）with a concentration of 20 ppm and a p H of 5,and the removal rate was increased by 40.7%compared with pure TiO₂.Combined with radical capture experiments,it was found that·O₂^-reactive radicals are the main active substances for degrading RhB dyes.（2）In order to further explore and enhance the activity of the above photocatalysts,this experiment proposes to use lye to remove the Si O₂ template,obtain hollow structure TiO₂,and load it on biochar to obtain hollow structure TiO₂/biomass char composite photocatalytic material.The effects of different biomass char doping amounts on dye removal performance in water were studied,and the types of free radicals affecting dye removal efficiency were identified.The results show that when the biochar loading is 700 mg,the composite photocatalyst has a larger specific surface area,the largest absorption wavelength,and correspondingly a smaller band gap width.The results of electrochemical impedance analysis show that the composite has excellent photogenerated carrier separation efficiency.In the photodegradation experiment,the material has a high sensitivity to RhB with a concentration of 20 ppm and a p H of 5,and can reach a removal rate of 96.6%in 120 min,which is 10.4%higher than that of the core-shell TiO₂/biochar composite photocatalyst,which greatly exerts the synergy between adsorption and photocatalysis.It was concluded by the capture experiment that·O₂^-radicals are the main active substances that cause the degradation of RhB dyes.