Value-added utilization of paper sludge: Preparing activated carbon for efficient adsorption of Cr(VI) and further hydrogenation of furfural

After normal alkali treatment process, the industrial Cr(VI) containing wastewater still contains a ppm level of Cr(VI) ions which should be further purified before discharging. In this study, the Cr(VI)-containing wastewater has been efficiently treated by the porous paper sludge-based activated carbon (psAC) with an excellent specific surface area and rich oxygen functional groups. The batch experimental results showed that under acidic conditions, pH has little effect on the Cr(VI) removal. The kinetic and isotherms studies showed that the Elovich and Freundlich model could describe the adsorption process well and the maximum adsorption capacity of psAC was 54.04 mg/g. The thermodynamic studies indicated that the reaction process was endothermic and spontaneous. Adsorption enthalpy was 17.37 kJ/mol, showing that the chemisorption process was a hydrogen bonding-controlled that has been also verified by some analytical techniques. Lastly, this study also provided an idea for reutilization of waster Cr(VI)-contained psAC in furfural hydrogenation.