Study On The Purification Of Organic Sewage By Coupling Process Of Photocatalysis And Membrane Separation

The photocatalytic technology is a kind of advanced oxidation treatment technology,which has great potential in the treatment of refractory organic pollutants.TiO₂ has attracted wide attention from domestic and foreign scholars with its advantages of high photocatalytic activity,good chemical stability,non-toxic and harmless,etc.However,the separation and recovery of nano-TiO₂ limits the application of nano-TiO₂ photocatalytic technology.The combination of photocatalysis and membrane separation can play a synergistic effect,which can not only recover the photocatalyst effectively,but also realize continuous operation.However,in the suspended photocatalytic membrane reactor,the photocatalyst continuously deposited onto the membrane surface,which causing the continuous attenuation of the membrane flux and affecting the efficiency of photocatalytic reaction.On the other hand,it still takes a lot of time and processing cost to completely recover the photocatalyst from the reaction fluid.In view of the above problem,this paper chooses tetrabutyl titanate as titanium source and anhydrous ethanol as organic solvent,TiO₂ sol prepared by sol-gel method,which load on glass fibre by dipping pulling method,thus prepared the loaded TiO₂ with good photocatalytic activity.Then,X-ray diffractometer?XRD?was used to characterize the phase composition of the catalyst.Finally,three kinds of organic wastewater were treated,the photocatalytic activity and the processing capacity of the loaded photocatalytic membrane reactor were investigated.The results are as follows:?1?In the study of photocatalytic degradation of phenol,phenol degradation rate can reach 97.05%when phenol initial concentration of 10 mg/L,pH at 3,UV LED output power of 2.968 W,the aeration intensity of 1.8L/min,and the degradation process fits pseudo-first-order kinetics.Compared with other photocatalytic experiments with mercury lamps as the light source,the power consumption of UV LED is very small.?2?In the photolysis and adsorption experiment of reactive brilliant red X-3B solution with UV LED and glass fiber photocatalytic fillers respectively.The experimental results show that the main wavelength of 365 nm UV LED have no photolysis decoloring effect on the reactive brilliant red X-3B solution,but glass fiber photocatalytic fillers have certain adsorption effect on the reactive brilliant red X-3B solutions.?3?Study on decolorization of reactive brilliant red X-3B solutions by photocatalytic membrane reactor,the results show that the initial solution pH,initial concentration of solution and source consumed power have a bigger influence on the decolorization effect.In addition,the decolorization rate of the membrane effluent is always higher than photocatalytic reactor.With the extension of time,the decolorization rate of the membrane effluent will decline,which proved that PVDF hollow fiber membrane can adsorb but not intercept active brilliant red X-3B molecules.?4?In the treatment of bath wastewater by using three kinds of technology,it is found that the removal rate of COD was photocatalytic-ultrafiltration>single ultrafiltration>single light catalysis,COD removal rate of membrane effluent is more stable,and can only remove the larger molecular weight of pollutants,while photocatalysis can continuously degrade the contaminants in the waste water until they are fully collateralize.Therefore,coupling process of photocatalytic oxidation and membrane separation for pollutants removal is relatively complete.?5?In the long-running treatment experiment of bath wastewater by the coupling reactor of photocatalysis and membrane separation,the result shows that the reaction is stable after a period of time,and COD removal rate of photocatalytic reactor is almost no longer changed,while COD removal rate of the membrane effluent has slight growth,which mainly depends onthe adsorption of pollutants by the filter cake layer;The turbidity of membrane effluent has been relatively stable,which is always below 0.6NTU,while the turbidity of photocatalytic reactor fluctuated greatly,but the overall activity decreased.This may be due to the adsorption of glass fiber photocatalytic fillers.?6?The study on membrane fouling shows that photocatalytic-ultrafiltration membrane fouling degree is lower than that of single ultrafiltration,indicating that photocatalysis can reduce membrane fouling to a certain extent.In addition,operation pressure has great influence on membrane fouling.Aeration scrubbing,intermittent stopping and backwashing can reduce membrane fouling,but can only remove reversible membrane fouling,and chemical cleaning method must be adopted for irreversible membrane fouling.