Enhancing Carbon Utilization and Adsorption Performance of Sludge Derived Activated Carbon through Molten Salt Synthesis Method

Sewage sludge is carbonaceous organic material and an inevitable by-product of biological wastewater treatment process. The traditional sludge disposal routes may cause serious pollution risks, e. g. large amounts of carbon emissions. Molten salt synthesis (MSS) method could complete the carbonization and activation two processes within a single-step, and the complexity of chemical activation process could be significantly reduced. In this work, sludge derived activated carbon (SDAC) was prepared by MSS method with ZnCl2 . The mass ratio of ZnCl2 to sludge had a significant effect on both the physicochemical properties and surface chemistry of SDAC. As the mass ratio of ZnCl2 to sludge was 1, the maximum specific surface area of SDAC was 549.72 m2/g. The maximum adsorbing capacity of methylene blue (MB) and CO2 were 0.0786 and 0.0575 mg/mg(SDAC), respectively. The highest yield and carbon utilization potential of SDAC were 517.87 mg(SDAC)/g(sludge) and 178.56 mg(carbon)/g(sludge), respectively. According to carbon mass balance, the total carbon mass in SDAC adsorbed MB and CO2 can be achieved to 203.00 and 186.68 mg(carbon)/g(sludge), respectively. It was suggested that MSS method can be used to reduce carbon emissions and improve carbon adsorption during SDAC preparation.