Ozonation Of Reverse Osmosis Concentrate From Bio-treated Coking Wastewater With Metal Oxide Supported On ?-Al₂O₃

The Bio-treated Coking Wastewater(BTCW)was characterized by high organic pollutant content,complex composition,and difficulty in biodegradation.After advanced treatment of ultrafiltration and reverse osmosis,Reverse Osmosis Concentrated(ROC)with even higher pollutant concentration was produced.The key to achieve zero liquid discharge is how to treat the ROC derived from Bio-Treated Coking Wastewater.Catalytic ozonation is an effective process to improve the removal efficiency of organic pollutant,and it has the advantages of higher ozone utilization efficiency and no secondary pollution.Herein,we studied on the effectiveness in treating ROC by ozonation alone and ozonation in the presence of metal oxide supported on?-Al₂O₃.Firstly,ROC treated by ozonation alone was investigated.Under the experimental conditions of O₃ dose of 10 mg/min,initial p H of 7.30 and reaction temperature of 25 ^oC,15.7%of COD removal efficiency was obtained.The UV-vis spectrum showed that the absorbance of the whole wavelength segment decreased gradually in the process of ozonation alone.Besides,three dimensional fluorescence spectra showed that the degradation rate of humic acids was fast.Moreover,GC/MS results showed that only 32 of the 77 organics in ROC remained after 30 minutes of ozonation.Secondly,the preparation parameters of MnO₂/?-Al₂O₃ catalyst and its influence on catalytic activity,as well as the efficiency of catalytic ozonation on ROC was investigated.Among all the MnO₂/?-Al₂O₃ catalysts,a highest activity was obtained for the MnO₂/?-Al₂O₃ catalyst prepared under the condition of 1.0 wt%and calcination temperature of 400^oC.XPS shows that Mn exists in the form of+4 valence.Under the experimental conditions of O₃ dose of 10 mg/min,initial p H of 7.30,catalyst dose of 1.0 g/L and reaction temperature of 25 ^oC,the COD removal efficiency was 27.6%for catalytic ozonation.In addition,it still has a high catalytic activity after used for four times.The GC/MS results showed that catalytic ozonation could remove some organic compounds that were difficult to be degraded by ozonation alone.Finally,the preparation parameters of MnO₂-Ce O₂/?-Al₂O₃ catalyst and its influence on catalytic activity,as well as the efficiency of catalytic ozonation on ROC was investigated.Among all the MnO₂-Ce O₂/?-Al₂O₃catalysts,the one prepared under the condition of 1.0 wt%MnO₂+1.0 wt%Ce O₂,calcination temperature of 400 ^oC has the highest activity,and XPS shows that Mn exists in the form of+4 valence,Ce exists in the form of+3 and+4 valence.Under the experimental conditions of O₃ dose of 10 mg/min,initial p H of 7.30,catalyst dose of 1.0 g/L and reaction temperature of 25 ^oC,and the COD removal efficiency is 38.9%.In addition,it still has high a catalytic activity after used for four times.The results of molecular weight distribution showed that the ozonation with MnO₂-Ce O₂/?-Al₂O₃ could increase the degradation efficiency of organic compounds with molecular weight between 5k and 20k Da.