Preparation Of G-C₃N₄/LSACF And Photocatalytic Performance Under Visible Light Irradiation

At present,environmental pollution,especially water pollution,is still a major problem plaguing human development.Although the traditional methods of pollution control have achieved some results,there are still some shortcomings more or less.Photocatalysis has attracted wide attention for its advantages of high efficiency,low energy consumption and no secondary pollution.The main challenge is to prepare photocatalysts with excellent performance.Graphite carbon nitride（g-C₃N₄）as a new type of semiconductor photocatalytic material,not only has good visible light responsiveness,but also has excellent thermal and chemical stability,which has good application prospects.However,in the practical application,its powder shape is very easy to agglomerate in the solution,and once used,it is difficult to recycle.Therefore,in order to solve the above problems,the luffa sponge activated carbon fibers（LSACF）were prepared by calcining the luffa sponge（one kind of biomass material）at high temperature,and g-C₃N₄ was loaded on it to prepare g-C₃N₄/LSACF composites.XRD,SEM,TEM,EDS,BET,FTIR and UV-Vis were used to characterize the morphology,structure and visible light response of the prepared materials.By using 500 W xenon lamp as catalytic light source,the decontamination properties of the g-C₃N₄/LSACF was investigated by taking RhB and Cr（VI）as the target pollutants in sewage.The disinfection properties of composite materials to E.coli and bacteria in water were also investigated.The main conclusions are as follows:（1）XRD and FTIR analysis showed that g-C₃N₄ was successfully loaded on LSACF without changing its properties;EDS analysis showed that g-C₃N₄ was evenly distributed on the single fiber;SEM and TEM observation showed that the composites had good pore structure;BET showed that the specific surface area of the composites was large,which was conducive to the adsorption of pollutants;UV-Vis analysis showed that the composites had great visible light responsiveness.（2）g-C₃N₄/LSACF had great property of degrading RhB.When the catalyst dosage was low,the degradation effect increased with the increase of the dosage,but the increase was not obvious after 1.6 g.The optimum concentration of catalyst in this experiment was 8.0 g/L.The catalysts had a certain degradation effects on RhB of different concentration and the degradation efficiency at low concentration was obviously higher than that at high concentration.The catalyst is suitable for the degradation of RhB at low concentration.The initial pH of the solution had a great influence on the photocatalytic degradation,and the removal efficiency under acidic conditions was better than neutral and alkaline conditions.The degradation rate of RhB by powdered g-C₃N₄ was about twice that of g-C₃N₄/LSACF.The possible reason was that the bulk morphology of g-C₃N₄/LSACF made its effective catalytic area smaller,but its adsorption effect under dark conditions was better.The degradation efficiency of RhB by g-C₃N₄/LSACF was still above 80%after four cycles of degradation.（3）g-C₃N₄/LSACF had a certain reduction effect on Cr（VI）.When the catalyst dosage was low,the reduction efficiency increased with the increase of the dosage,but the increase was not obvious after 1.8 g.The optimum concentration of catalyst in this experiment was 18 g/L.The catalyst had a certain reduction effect on different concentration of Cr（VI）and the reduction efficiency at low concentration was obviously higher than that at high concentration.The catalyst is suitable for the catalytic reduction of lower concentration of Cr（VI）.The initial pH of the solution had a great influence on the reduction efficiency,which the acidic condition had a reduction effect,while the reduction effect under alkaline condition was poor.The reduction efficiency of g-C₃N₄/LSACF to Cr（VI）was greatly enhanced by the addition of oxalate as sacrificial agent.The optimum concentration of oxalate was 0.04 g/L in this experiment.The reduction efficiency of Cr（VI）by g-C₃N₄/LSACF was still about 80%after four cycles of reduction.（4）g-C₃N₄/LSACF had great disinfection effect.When the dosage of catalyst was low,the disinfection effect increased with the increase of dosage.After 1.8 g,the efficiency decreased slightly.The optimum dosage concentration of catalyst in this experiment was 18 g/L.The catalyst had certain killing effect on E.coli with different initial concentration,and the lower the initial concentration,the greater the disinfection effect was.Cyclic disinfection test showed that the catalyst had good cyclic disinfection performance.g-C₃N₄/LSACF had obvious disinfection effect on E.coli and bacteria in natural rainwater.The results of four sampling disinfection showed that the total number of bacteria and E.coli in water samples after disinfection can meet the limit requirements of"Sanitary Standard for Drinking Water".In conclusion,the composite g-C₃N₄/LSACF prepared by using LSACF as matrix and located with g-C₃N₄ had good effect on pollutant degradation and water disinfection,it also solved the problem that powder g-C₃N₄ is difficult to recycle.It has good application prospects.