Study On Hybrid Zeolite For Photocatalytic Degradation Of Organic Pollutants

In recent years,water pollution caused by organic dyes is a major problem facing water pollution treatment,which seriously affects the ecological balance of nature.From the perspective of sustainable development,photocatalysis technology is a low-cost,safe and efficient environmentally friendly water pollution treatment technology,which is considered as one of the best ways to solve the energy crisis and environmental pollution problems.Research on photocatalysis mainly focuses on semiconductor materials such as TiO₂ and Zn O,but most of them only respond to ultraviolet light,and the quantum efficiency is low.Zeolites have a large specific surface area,adjustable skeleton composition,adjustable active center,which can transmit most visible and ultraviolet light.Research on modified molecular sieve,modified molecular sieve and nano-photocatalyst composite catalyst is an effective way to solve the problem of nano-photocatalyst agglomeration and improve the photocatalytic activity of the catalyst.Therefore,in this paper,TiO₂,TiO₂/A zeolite composite photocatalyst,Zn hybrid A zeolite and TiO₂/Zn hybrid A zeolite composite photocatalyst were prepared by sol-gel method and hydrothermal method.The catalysts were characterized by XRD,SEM,FT-IR and other methods.Using Rh B as the target degradant,the effect of loading amount?doping amount?,p H,reaction time and light sources on photocatalytic performance of the catalyst was studied,respectively.The main research conclusions are as follows:1. Study on the photocatalytic performance of TiO₂/A zeoliteThe composite photocatalysts of TiO₂ and TiO₂/A zeolite were synthesized by sol-gel method.The TiO₂/A zeolite with 30%loading had a minimum particle size of 17.5nm,and O,Si,Al,Na,Ti elements were evenly distributed in the TiO₂/A zeolite.TiO₂/A zeolite had good photocatalytic activity.When the TiO₂ content was 30%,the photocatalytic activity was the best.The photocatalytic stability of TiO₂/A zeolite was good.When p H=7,the degradation rates of Rh B in three repeated experiments were 98.2%,95.2%and 91.8%,and the degradation rate increased with the increase of p H.When p H=11,the degradation rates of Rh B in three repeated experiments were 99.1%,95.8%and 92.6%.The photocatalytic degradation process complies with the Langmuir-Hinshelwood first-order kinetic equation.The photocatalytic reaction rate of TiO₂/A zeolite with a loading capacity of 30%was the largest,which was 0.03182min^-1.The photocatalytic degradation rate increased with increasing p H.When the p H was 11,the maximum photocatalytic reaction rate of the sample was 0.52776min^-1,which was consistent with the photocatalytic experiment results.2. Study on the photocatalytic performance of Zn hybrid A zeoliteZn hybrid A zeolite was synthesized by hydrothermal method.The average particle size of the sample was about 500nm,and the surface had rich hydroxyl functional groups,which was beneficial to the photocatalytic reaction.The Zn hybrid A zeolite had good photocatalytic performance and chemical stability,and the sample with a Zn doping ratio of1 had the highest degradation efficiency.Under UV conditions,the degradation rates of Rh B at p H 4,7,and 11 were 85.8%,92.9%,and 95.4%,respectively.Under visible light conditions,the degradation rate of Rh B was 50.8%,which was 16.4%higher than that of Zn O.The degradation rates of Rh B in three replicates were 50.8%,48.12%,and 46.18%,respectively.The photocatalytic process complied with the Langmuir-Hinshelwood first-order kinetic equation.When the Zn doping ratio was 1,the photocatalytic reaction rate of the catalyst was the largest,which was 0.02043min^-1.When the p H was 4,7,and 11,the degradation rates were 0.01672min^-1,0.02195min^-1,and 0.02484min^-1,respectively.And the results were consistent with the results of the photocatalysis experiment.The modification of A zeolite realized the red shift of the absorption spectrum of molecular sieve,formed electron trap and hole trap,changes the electron/hole recombination rate,and increased the number of active sites of molecular sieve.Therefore,the photocatalytic activity of the ultraviolet light and visible light of the catalyst was improved.3. Study on the photocatalytic performance of TiO₂/Zn hybrid A zeoliteTiO₂/Zn hybrid A zeolite composite photocatalyst was synthesized by sol-gel method.The average particle size of the sample was about 500nm,and the average particle size of TiO₂was about 18nm.The photocatalytic process complies with the Langmuir-Hinshelwood first-order kinetic equation.The photocatalytic activity of the catalyst had been greatly improved.The degradation rate of Rh B was 92.61%after 60 minutes under ultraviolet light and 98.44%after 120 minutes,which were 1.26%and 0.2%higher than TiO₂/A zeolite,respectively.And the degradation rate was improved by 8.21%and 5.54%compared with Zn hybrid A zeolite.The degradation rate of Rh B was 52.62%after 60 minutes under visible light,and 58.57%after 120 minutes,which were 8.09%and 7.77%higher than Zn hybrid A zeolite.The results showed that there was a synergistic effect between Zn hybrid A zeolite and TiO₂,which improved the photocatalytic activity of the catalyst.