| After treatment of urban sewage,the content of pollutants has been significantly reduced,but when reclaimed water is used as the ecological landscape water and irrigation water,it will still harm the soil,shallow groundwater and people's body,which will affect the whole regional ecological circulation system.Among them,heavy metals and environmental hormone pollution risk is the most prominent problem.Activated carbon adsorption is one of the most important treatment methods in water treatment.It has good removal effect on heavy metals and organic pollutants,and has the advantages of simple process and low cost.This subject takes the typical heavy metal lead,copper,chromium and three kinds of environmental hormones in the two grade effluent of the sewage plant,as the target pollutants,including two butyl phthalate,atrazine and sulfamethoxazole.6 common activated carbons were selected as the research objects.The physicochemical properties of activated carbons were characterize d by BET,Boehm titration,FT-IR and SEM.The adsorption effect of 6 kinds of activated carbon on the target pollutants was compared by studying the adsorption isotherm and removal rate,and the surface properties and economic practicability of the 6 kinds of activated carbons were compared and analyzed.Among them,Xinhua high efficiency coal activated carbon has less impurity content,lower price,the highest content of acidic functional groups on the surface,and the highest removal rate of target pollutants.Therefore,we chose Xinhua high-efficiency coal activated carbon as the research object of modification.4 modified methods,named mixed acid modification,reduction modification,Potassium Permanganate modification and SDS modification,were used to modify the Xinhua high efficiency coal activated carbon.The BET specific surface area,the content of acidic oxygen functional groups,the total pore volume,the surface area and the removal rate of the target pollutants were increased in varying degrees after modification.AC-S has the highest removal rate of 3 heavy metals including Pb,Cu and Cr,and the removal rates are 95.3%,94.8% and 92.7% respectively.AC-K had the best adsorption effect on DBP,atrazine and SMZ,and the removal rates are 94.5%,93.8% and 95.5% respectively.And the quasi two stage dynamic model can better describe the adsorption process of AC-S and AC-K on the target pollutants.The adsorption rate constant of activated carbon is increased after modification.Taking the removal rate of lead,copper and chromium in water as an evaluation index by AC-S,the modification conditions were optimized by orthogonal test.The optimum preparation conditions of AC-S are as follows: the initial concentration of SDS solution is 0.07mol/L,the pH value is 5,the modification temperature is 20 ?,and the modification time is 4h.With the AC-K removal rate of DBP,Atrazine and SMZ as assessment criteria,the optimum preparation conditions of AC-K are as follows: the initial concentration of Potassium Permanganate solution is 0.07mol/L,the value of pH is 7,the modified temperature is 40?,and the modification time is 4h.The modified activated carbon AC-K was combined with AC-S,and the static adsorption experiment was carried out to investigate the removal rate of 6 target pollutants,such as lead,copper,chromium,DBP,Atrazine,SMZ,and so on.The optimum ratio of composite modified activated carbon is 30%AC-K+70%AC-S.The optimum reaction conditions of the composite modified activated carbon were as follows: the dosage of activated carbon was 0.5g/L,the value of pH was 8,and the adsorption time was 8h.Through the small-scale test,the optimum parameters for the advanced treatment process of composite modified activated carbon were determined.The initial pollutant concentration does not affect the removal rate of the target pollutants,increasing the contact time of the granular carbon and the dosage of the powdered activated carbon,and the removal rate of the target pollutants is obviously increased.However,the excessive amount of powdered activated carbon will lead to the penetration of the filter layer and the increase of turbidity.According to the actual water quality and water quantity,the operation cost of conventional advanced treatment process and enhanced advanced treatment process is compared.,it is found that the composite modified activated carbon is not only feasible,but also economical.To sum up,the compound modified activated carbon has good treatment efficiency for heavy metals and environmental hormones,and can obviously improve the water quality of the effluent.The actual operation process is mature and stable.It has some reference value for practical engineering. |
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