Study On Long-Term Adsorption Characteristics Of Polychlorinated Biphenyls With Different Carbonaceous Adsorbents And Their Practical Application

Sediment is a large storage of persistent organic pollutants,although POPs in 1974 had been banned on production,but the pollutants of POPs in the sediment will still be released into the water environment,threatening human health,so the treatment of sediment pollution has been become a hot topic.In this paper,five kinds of carbonaceous adsorbents(coconut shell activated carbon,charcoal activated carbon,raw carbon(unactivated charcoal),Donghai power plant ash,coal-based activated carbon),polychlorinated biphenyls(PCBs)for the adsorbate,the use of bionic passive sampling.The adsorptive kinetics and isothermal curves of carbonaceous adsorbents were extracted and determined.The adsorption principle of carbonaceous adsorbents was explored,and the coal-based activated carbon,coconut shell activated carbon,fruit shells and carbon were used as repairing agents.The study on the treatment and restoration of the actual pollution sediments(a river section of the Puhe tributary)provides a theoretical basis for the application of carbonaceous adsorbents.The conclusions of the study are as follows:(1)Coal-based activated carbon,wood activated carbon has a high specific surface area,and to the hole and micro-hole-based,coconut shell activated carbon,carbon,Donghai power plant ash surface area is small,Donghai power plant ash to large,almost no microporous structure.In this study,five carbonaceous adsorbents were used to contain the benzene ring and the hydroxyl group,and the functional groups contained are similar.Three-dimensional fluorescence spectroscopy showed that the main constituents of the natural organic matter(NOM)used in the study were fulvic acid,and the average molecular weight was around 5000 in combination with exclusion chromatography.(2)Adsorption kinetics studies show that quasi-second-order kinetics can well fit the adsorption kinetics of PCBs(correlation coefficient R2>0.99)for five kinds of carbonaceous adsorbents,indicating that the adsorption process is a multiple and complex process(such as:Donghai power plant ash,coconut shell activated carbon,raw carbon).Apparent adsorption rate is fast,to achieve the balance of the shorter time required,Indicating that the main surface adsorption to the effect of NOM on the adsorption properties of carbonaceous adsorbents was studied.The results showed that the adsorption of carbonaceous adsorbents on the adsorption of carbonaceous adsorbents was significant.(eg,raw carbon,coconut shell activated carbon and carbon in Donghai power plant),and the difference between the fast and slow adsorption rates increases,while the NOM is more adsorbed(such as:coal-based activated carbon,charcoal)has the opposite effect.(3)The adsorption isotherm curve shows that the Freundlich adsorption model can simulate the experimental data(R2>0.6).The adsorption time is 1 month and 12 months,and the adsorption of coal-based activated carbon and charcoal activated carbon with better pore structure the amount is larger than that of other carbon adsorbents,but the adsorption is not significant for 1 month,and the gap is larger at 12 months because the adsorption does not reach equilibrium for 1 month,adsorption kinetics(K<d)does not reflect the actual adsorption capacity of the adsorbent.When adsorbed for 12 months,the adsorption reaches equilibrium,and the Kd value can reflect the actual adsorption capacity of the adsorbent.In the short-term adsorption,NOM reduced the adsorption capacity of five kinds of carbonaceous adsorbents to PCBs,especially for coconut shell activated carbon,carbon and Donghai power plants.When the adsorption time was 12 months,The effects of NOM to carbonaceous adsorbents are small,the reason for their short-term adsorption,NOM attached to the surface of carbonaceous adsorbents(especially in mesopores and macroporous-based adsorbents),competition and clogging impede its PCBs adsorption,with the passage of time,PCBs molecules can pass through the NOM,and then into the carbonaceous adsorbent of the internal channels,NOM greatly reduced the impact.(4)Field experiments show that the coal-based activated carbon has the best effect on the treatment of PCBs,and the order of treatment effect is:coal-based activated carbon>shell activated carbon>coconut shell activated carbon>raw carbon.This result is in good agreement with the laboratory research results.