Study on the organics adsorption capacities of powdered activated carbon and activated coke in reclaimed water

In this study, the adsorption capacities of powdered activated carbon (PAC) and activated coke (AC) for organic components with different characteristics from the secondary effluents of urban waste water plant were examined, and their adsorption mechanisms were discussed. The results showed that Freundlich isothermal model and pseudo-second-order model could describe the processes of PAC and AC to effluent organic matter (EfOM) from urban wastewater plant effectively. Soluble microbial metabolites and humus were the major components of organics in the secondary effluents, and most of them were with small molecular weight which is less than 3 kDa (the proportion is 28.3%). PAC effectively adsorbed the organics with small molecular weight (less than 3 kDa) and the removal rate of dissolved organic carbon (DOC) was 67.2%, whereas AC effectively adsorbed the organics with molecular weight of 3 kDa–10 kDa and the DOC removal rate was 45.5%. Compared with AC, PAC has characteristics of smaller particle size, larger specific surface area, rougher surface and lower Zeta potential, which leads to more effective adsorption sites and better results. AC can effectively adsorb the organics with variable molecular weight in water and can be used as replacement of PAC in the advanced purification of reclaimed water.