Preparation Of Sewage Sludge/Pine Sawdust Activated Carbon Adsorbent And Its Application In Adsorption Of Cr(?)

In recent years, activated sludge production increased year by year in the process of wastewater treatment. The utilization of sludge was paid more and more attention. This study was to utilize sludge and sawdust for the preparation of the activated carbon by chemical activation. The activated carbon was used to treat the Cr(VI) from aqueous solutions with great environment benefits and economic value.Activated carbon was prepared from pine sawdust and sewage sludge from Wuhan wastewater treatment plant using a chemical activating agent(ZnCl2) and pyrolysis in a quartz tube. The influence of the mixing ratio of sewage sludge(ss) and pine sawdust(ps), the mixing ratio of ps/ss and ZnCl2, carbonization temperature, carbonization time were studied based on single factor experiments and orthogonal experiments. According to the iodine adsorption value, the optimal preparation conditions for the activated carbon were found to be admixture at 2:1 ratio of pine sawdust and sewage sludge, admixture at 1:0.7 ratio of ps/ss and ZnCl2, carbonization temperature 550 ?, carbonization time 60 min. In this case, the iodine adsorption value of the activated carbon was 641mg/g. After the range analysis and variance analysis, four factors influencing the experimental results are listed as follows: mixing ratio of sewage sludge and pine sawdust> carbonization temperature> carbonization time> mixing ratio of ps/ss and ZnCl2.The activated carbon was characterized using thermal analysis, BET-N2 adsorption, FTIR, SEM photography. Carbonization process of ps/ss mainly includes evaporation stage of water, organic matters and activation stage. It is considered that ZnCl2 penetrated to the interior of sludge/sawdust and thereafter accelerated the swell and dissolution of mucus. Analysis of FTIR for the Z-AC-750 showed that it contained some functional groups such as hydroxyl, carbonyl oxygen in the surface. The average mesoporous diameter, the mesoporous volume, the average micropore, the micropore volume and the BET area of the Z-AC-750 were 6.587 nm, 0.735 cm3/g, 1.2963 nm, 0.1967 cm3/g, 446m2/g, respectively. Analysis of SEM for the Z-AC-750 was carried out for the study of the rich pore structure.The activated carbon prepared was used to the treatment of Cr(VI). The adsorption experiments were conducted to investigate the removal rate of Cr(VI) at different conditions such as p H value, adsorption time, adsorption dose and initial metal concentrations. The experiments showed that the best activated carbon had a good capacity for removing Cr(VI) from aqueous solutions. The kinetic data of the adsorption was fitted with the pseudo-second order model, indicating that the adsorption was affected by diffusion and adsorption reactions. The adsorption isotherms were fitter with Langmuir model than Freundlich model and Tempkin model. The calculated adsorption capacities of Cr(VI) were 107.5mg/g.