Preparation Of Sludge-based Activated Carbon And The Study Of Its Dye Adsorption Property

In this paper, sludge-based activated carbon (SAC) was prepared from paper mill sewage sludge by physical activation with steam. The preparation conditions and mechanism were discussed. Based on characterizition of SAC, the adsorption propertities to methylene blue and reactive brilliant red K-2BP were studied by static and dynamic experiments. In addition, desorption of dyes and regeneration of spent activated carbon was investigated.The optimum prepation conditopns were determined through single factor experiment and orthogonal array experiment. The optimal conditions were at the carbonization temperature of300℃, carbonization time of60min, activation temperature of850℃, and activation time of40min. The iodine number, BET surface area and yield of selected activated carbon were178.45mg/g,130.71m2/g and46.20%, respectively. It was shown that there were some mesopores and macropores besides micropores on the surface of SAC. Most of organic and volatile inorganic matters were decomposed. SAC was electronegative and cationic pollutants were easier to be adsorbed. The contents of metal elements in the lixivium of SAC were lower than the content limit in standard. Consequently, it is considered safe for SAC to be applied in wastewater treatment.In static experients, the adsorption capacities of SAC for two dyes were higher than commercial activated carbon and the maximum adsorption capacity of methylene blue was higher than that of reactive brilliant red K-2BP. The adsorpion of two dyes onto SAC followed the pseudo second-order kinetic model and the intra-particle diffusion was one of the rate-controlling steps, but not the only rate-controlling step. The adsorption process was endothermic and maximum adsorption capacity increased with the increase of temperature. Two dyes could be stably adsorbed by SAC and desorption was not obvious. Besides, thermal treatment was effective for regeneration of SAC.In dynamic experiments, the fixed-bed adsorption system was found to perform better with lower initial dye concentration, smaller particle size, lower flow rate and higher adsorbent mass. At room temperature, the adsorption capacities of SAC for two dyes were both higher than those of commercial activated carbon. It may be caused by mesopores and macropores on SACThe above results indicated that activated carbon with remarkable adsorptive properties could be produced by paper mill sewage sludge and it can be used to remove macromolecular pollutants as an effective, safe and economically feasible substitute for commercial activated carbon. Moreover, it provided approach for realizing the reduction, harmlessness and reutilization of sludge.