Wastewater Treatment Performance Of Catalytic Ozonation By Super-fine Powdered Activated Carbon And Its Combination With Ceramic Membrane

Industrial wastewater contains high concentration of pollutants.It will greatly damage water environment if not well-treated.Therefore,advanced treatment should be implemented after common bio-chemical treatment of industrial wastewater,in order to guarantee the effluent can reach the discharge standards or be reused.As an effective advanced treatment process,catalytic ozonation uses catalysts to prompt the ozone decomposition into hydroxyl radicals?·OH?and it has high oxidation ability,less selectivity and is free of secondary pollution.Super-fine powdered activated carbon?SPAC?has potential to enhance the efficacy of catalytic ozonation,as it has higher external surface area and surface oxygen-containing groups.Besides,ceramic membrane can resist the oxidation of ozone and perform well in fine carbon separation.Meanwhile,the fouling of ceramic membrane can be alleviated,due to the oxidation of ozone.In this study,in order to develop a novel and effective catalytic ozonation technology,SPAC was synthesized by ball mill,its efficacy of catalytic ozonation was evaluated and the mechanism of SPAC catalytic ozonation was postulated.Furthermore,a SPAC combined with ceramic membrane catalytic ozonation reactor was established.Its performance in the continuous treatment of bio-chemical treatment effluent of coal gasification wastewater was evaluated.And the alleviation of ceramic membrane fouling by ozone was observed.SPAC with an average radius of 1.33?m was synthesized by ball mill and it outperformed granular activated carbon?GAC?significantly.When dosing 2.0 g/L,the reaction reached equilibrium within 10 min and 90%of total organic carbon?TOC?was removed.By kinetic analysis,the rate constant of TOC removal by SPAC catalytic ozonation was 64-fold than GAC.The efficacy of activated carbon?AC?catalytic ozonation was closely related to its dosage and particle size.Further,total surface area and geometric surface area of AC were recognized as key factors.SPAC had larger meso-and macro-pores,which brought less adsorption resistance and 15-fold increase in adsorption rate than GAC.Meanwhile,96%of catalytic reaction happened on the surface of SPAC and its mechanism was assumed to follow surface reaction mechanism.The conversion efficiency from ozone to hydroxyl radical of SPAC was 330-fold than GAC,which was even close to that of modified carbon nanotubes.A SPAC-ceramic membrane catalytic ozonation reactor was established.According to the results,2.0 g/L SPAC and 1-4 mg/L ozone dosage was chosen as running parameters for the treatment of the effluent of bio-chemical treatment of coal gasification wastewater.Under this condition,the removal rate of chroma and chemical oxygen demand?COD?reached 90%and 75%respectively and?COD/?O₃ reached 1.3.When hydraulic retention time was 30 min and membrane flux was 50 L/?m²·h?,the chroma and COD of the effluent of the reactor was 10 and 50 mg/L.Ozone can enhance the critical flux from 35-40 L/?m²·h?to 50-60 L/?m²·h?.The transmembrane pressure decreased35%-40%and was stable in the operation,which indicated that membrane fouling was controlled.SPAC-ceramic membrane catalytic ozonation reactor provided one of the feasible plans for the advanced treatment of coal gasification wastewater.