Preparation Of C/TiO₂ Photocatalytic Self-cleaning Membrane And Its Visible Light Catalytic Performance

The reuse of industrial wastewater represented by dye wastewater is an important measure to improve the utilization rate of water resources.In recent years,photocatalytic methods represented by TiO₂ have attracted much attention due to their ability to fully degrade dyes while being environmentally friendly.However,the low photocatalytic activity of TiO₂ under visible light limits its application.In addition,most photocatalysts are mostly used in powder form in order to increase their specific surface area,which makes the recovery and recycling of catalysts face great difficulties.At the same time,there is also the risk of secondary pollution caused by the entry of the photocatalyst powder into the product liquid.To this end,it is necessary to improve and modify the TiO₂ photocatalyst to enhance its photocatalytic activity under visible light conditions;at the same time,the photocatalyst should be loaded to improve the recovery and recycling ability of the photocatalyst while solving the problem of secondary pollution.Based on this,firstly in this thesis,the patterned porous TiO₂ was synthesized by the self-assembly dual-template method,and then pyrrole was selected as the carbon source,and the C/TiO₂ photocatalyst with the patterned porous structure,which selected pyrrole as the carbon source,was prepared by the UV self-polymerization-burning method.The incorporation of C can enhance the photocatalytic ability of C/TiO₂ and extend the photoresponse range of the catalyst to the visible wavelength range.With the increase of pyrrole dosage,the photocatalytic activity of C/TiO₂ increased first and then decreased,and the photocatalytic activity of C/TiO₂-0.4 with 0.4 mol/L pyrrole dosage was the best.It can achieve 91.8%degradation rate of 10mg/L Rhodamine B（Rh B）within 90 min under visible light.Under visible light,the degradation process of Rh B by C/TiO₂ is a first-order kinetic reaction.The active particle capture experiment and electron spin resonance（ESR）test proved that the process was dominated by the photogenerated hole reaction route,and OH·and O₂^-·were the main oxidants in the dye degradation process.Based on this,a cross-reaction route mechanism for photocatalytic reaction is proposed.In order to solve the recycling problem of photocatalyst powder,C/TiO₂ photocatalyst was mixed into PVDF membrane solution,and C/TiO₂ photocatalytic membrane was prepared by phase inversion method.This photocatalytic membrane can achieve a degradation rate of 80.18%for 5 mg/L Rh B in a single simulated sunlight degradation test,and can maintain a degradation rate of more than 60%for Rh B in 4 cycles of degradation.The degradation process belongs to the first-order kinetic reaction.In addition,the C/TiO₂ photocatalytic membrane also has the characteristics of photo-self-cleaning,which can be restored to the initial state within 5 h under simulated sunlight irradiation.And the self-cleaning time of this process can be shorten to 1 h by adding 3 ml of H₂O₂,which greatly improves the cyclic degradation efficiency.In order to enhance the adsorption capacity of the C/TiO₂ photocatalytic membrane and give full play to the role of the photocatalyst in the membrane,poly（4-styrenesulfonic acid-co-maleic acid）sodium salt（PSSMA）was used to coat the membrane by coating method.The charge modification resulted in a negatively charged C/TiO₂ photocatalytic membrane（PCT membrane）,which improved the adsorption capacity of the positively charged dye Rh B.The PCT membrane can achieve nearly 100%dye removal for 10 mg/L Rh B within 30 min.The degradation process conformed to first-order kinetics.Under the assistance of H₂O₂,the PCT membrane can complete the degradation of the dyes in the membrane within 3 h and restore the membrane to the original state.At the same time,the PCT membrane after photo-self-cleaning can still maintain a adsorption removal rate of 78.82%and a photocatalytic degradation rate of91.62%for a new round of Rh B degradation.Materials Studio was used to simulate the molecular electrostatic potential,it is proved that the electrostatic adsorption can occur between PSSMA and RhB.