| The COD and chroma of bio-treated effluent of coking wastewater couldn't meet the emission standard of pollutants for coking chemical industry and municipal wastewater treatment plant.Some organic pollutants in the effulent were remained,which couldn't be used by the microorganisms.Most of these pollutants have carcinogenic,teratogenic and mutagenic effects and toxicity,which were likely to bring risks to the ecological security and human health.Therefore,advanced treatment of bio-treated effluent of coking wastewater become imperative.In this paper,activated carbon and magnetic activated carbon was used to catalyze S2O82-to treat bio-treated effluent of coking wastewater from a coking plant in taiyuan city,respectively,Advanced treatment of bio-treated effulent of coking wastewater was conducted by activated carbon catalyzed persulfate.The degradation rate of persulfate was investigated.The adsorption performance in single activated carbon was studied.Some factors of effecting activiated carbon catalyzed persulfate oxidation of bio-treated effulent of coking wastewater were studied which included persulfate dosage,initial pH value,activated carbon dosage.The advanced treatment of bio-treated effulent of coking wastewater by magnetic activated carbon catalyzed persulfate were evluated,investigating to the adsorption performance of single magnetic activated carbon,effect of CuFe2O4/AC mass ratio,initial pH value pH,magnetic activated carbon dose and persulfate dose on removal efficiency,etc.Specific surface area,infrared spectrum and hysteresis line was analyzed to explain the mechanism,The conclusions were as follows:(1)The adsorption of TOC in bio-treated effulent of coking wastewater by single activated carbon achieved equilibrium at 360 min.The adsorption followed the pseudo-second-order kinetics,and isotherms obeyed the Langmuir patterns.The activated carbon adsorption performance reduced after persulfate-oxidating,which was concerned with the increasing of carboxyl,lactone and phenolic hydroxyl acid functional groups and the decreasing of zero point of charge on the surface of activated carbon.The degradation of persulfaer was fitted with first-order kinetics.The optimum conditions are:no pH control,activated carbon dosage of 4 g/L,potassium persulfate dosage of 6 g/L,the time of 360 min.Under these conditions,the effluent TOC,chroma and UV254 were 19.03 mg/L,0.048 m-1 and 0.325 m-1,and the removal efficiency were 86.36%,94.62%and 94.53%,respectively.The proportional distribution of each part of TOC degradation,adsorption removal and remaining in aqueous solution with time was analyzed and the results showed that:the adsorption removal of TOC accounted for 37.92%,degradation removal of TOC accounted for 47.59%,the residual TOC accounted for 14.49%at 360 min.(2)During the advanced treatment of bio-treated effulent of coking wastewater by magnetic activated carbon catalyzed persulfate,when the mass ratio of CuFe2O4 and AC was 1:1.5,the removal efficiency of TOC and chroma were maximum and reached to 86.43%and 98.15%,respectively.The removal efficiency of UV254 decreased with the increasing of CuFe2O4/AC.When the mass ratio of CuFe2O4 and AC was 1:1,the removal efficiency of UV254 was maximum and reached to 82.55%.The best mass ratio of CuFe2O4 and AC was 1:1.5.Single magnetic activated carbon for the removal of TOC in bio-treated effulent of coking wastewater achieved adsorption equilibrium at 360 min,and adsorption kinetic was fitted with the pseudo-second-order model,and Langmuir isotherm was suitable for modeling the adsorption of TOC.The optimum condition are:no pH control,1.5-MACC dosage of 5 g/L,potassium persulfate dosage of 4 g/L,the time of 360 min.In this condition,the effluent TOC,chroma and UV254 were 20.37 mg/L,0.046 m-1 and 0.554 m-1,and the removal efficiency were 85.38%,95.18%and 90.72%,respectively.By analyzing the each part proportion of TOC degradation,adsorption removal and residue in aqueous solution in distribution changing with time,the results showed that:when time was 360 min,the adsorption removal of TOC accounted for 1.37%,degradation removal of TOC accounted for 56.75%,the residual TOC accounted for 11.88%.The specific surface area,acid,alkalinity titration and infrared spectrum of magnetic activated carbon and persulfate-oxidized magnetic activated carbon were nanlyzed,and the results showed that the specific surface area and zero point charge reduced and acid functional groups increased after the oxidation of magnetic activated carbon.And the analyzing of infrared spectrum also confirmed that acid functional groups increased.The saturation magnetization intensity of 1.5-MACC was 10.9 emu/g.(3)The treatment effect of bio-treated effluent of coking wastewater was compared by using two methods of activated carbon and magnetic activated carbon catalyzed persulfate in the optimized condition.The former method was superior to the latter in removal rate of TOC,COD and UV254.The TOC,COD and UV254 for AC/S2O82-were 14.69 mg/L,49.82 mg/L,and 0.281 cm-1,and for MACC/S2O82-were 21.03 mg/L,81.41 mg/L,and 0.571 cm-1.The chroma removal rate had the same effect with two methods.Both were less than 30 times.After advanced treatment,the effulent quality could meet emission standard of pollutants for coking chemical industry,and the effulent quality of AC/S2O82-method achieved requirements of subsequent double membrane process.(4)Through the analysis on the treatment effect and economic performance,the method of activated carbon catalyzing persulfate on advanced treatment of bio-treated effluent of coking wastewater was preferred. |
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