Preparation Of Expanded Graphite-activated Carbon Composites And Its Adsorption Capacity Of Phenol

The phenolic waste water is one of the representative wastewater which is difficult to treat in industry.And activated carbons(AC) have presented excellent sorption performance in the phenolic wastewater treatment.However,high pressure drop,low mass transfer rate and fragile mechanical property of power and granular carbon have been the main hindrance to AC in actual application.It is practical and meaningful to explore a new kind of porous material with suitable strength and sorption performance.At present study,a new carbon monolith which is composed of expanded graphite and activated carbon(EG-ACs) was prepared by different active agent(CO₂,KOH and H₃PO₄),using the sequence processes of impregnation,solidification,carbonization and activation. The pore textures were analysed by the adsorption measurement of N₂ at 77K.It revealed that both the active agent and the preparation conditions had strong influence on the micropore structure.The material activated by H₃PO₄ had the best pore structure,and the highest surface area could reach 1978m²/g,while the surface areas of materials activated by CO₂ and KOH are 1098m²/g and 937m²/g respectively.The structure of the material was characterized by XRD,SEM and mercury porosimetry.It indicated that the composite was composed of graphite and amorphous carbon.The surface of the worm-like particles was covered with pyrolytic carbons,while the large open spaces among entangled worm-like particles were filled with eggshell-like carbons.And only little interior pores of the particles were modified by pyrolytic carbons.The micropores mainly distributed in the pyrolytic carbon while the mesopores and macropores mainly in the graphite base.The static adsorption and FT-IR was used to describe the adsorption capacity of phenol.It demonstrated that the materials activated by CO₂ and KOH had the adsorption capacity of 299.6mg/g and 272mg/g respectively,but the material activated by H₃PO₄ only had the adsorption capacity of 168mg/g,though it had the highest surface area.The results of the FT-IR showed that there were a lot of acid groups on the surface of material activated by H₃PO₄ which had an adverse influence on the adsorption capacity.After the high temperature modification,the acid groups decomposed and the adsorption capacity reach up to 310mg/g.Fixed-bed adsorption studies with granular activated carbon and EG-ACs as a sorbent for the removal of phenol from aqueous were conducted.It was observed that the EG-ACs had a better permeability and use efficiency,the breakthrough volume of the EG-ACs was 178.4mg/g,while the granular activated carbon was 66.7mg/g; furthermore,the effluent concentration could meet the national standard of discharge,which can satisfy the needs of industrial wastewater treatment.