Transformation of sewage sludge into activated carbon by molten salt synthesis for adsorption of CO2 and dyes

Wastewater treatment generates increasing amounts of unwanted sewage sludges, calling for advanced recycling methods. Here, we transformed sewage sludge into activated carbon by molten salt synthesis with ZnCl2. We analyzed the structure and specific surface area of sludge-derived activated carbon by Fourier transform infrared spectroscopy and Brunauer–Emmett–Teller analysis. Results show that the mass ratio of ZnCl2 to sludge had a significant effect on the textural properties and adsorption performance of sludge-derived activated carbon. The maximum specific surface area was 549.72 m2/g, and the carbon utilization potential was 178.56 mg(C atom)/g(sludge), for a mass ratio of ZnCl2 to sludge of the total carbon mass in sludge-derived activated carbon adsorbed CO2 and methylene blue can be achieved to 186.68 and 203.18 mg(C atom)/g(sludge), respectively.