A new carbonaceous adsorbent for heavy metal removal from aqueous solution prepared from paper sludge by sulfur-impregnation and pyrolysis

Abstract

Abstract A new carbonaceous adsorbent for heavy metals removal was prepared from paper sludge using sulfur impregnation. The sulfur-impregnated carbonaceous adsorbent with heavy metals removal ability can be obtained from sulfur-immersed sludge by pyrolysis. The product pyrolyzed at 400 °C has a maximum removal ability for nickel and lead ions, which has high specific surface area with sulfur-based functional to remove heavy metal ions. The product obtained at 400 °C indicates more effective removal for heavy metals ion than commercial charcoal, especially Ni2+ (66.7%) and Pb2+ (71.7%). With increasing pH of the solution, the adsorptions of Ni2+ and Pb2+ were increased and maximum removals of Ni2+ and Pb2+ were 99.6% above pH 7 and 100% above pH 6, respectively, The equilibrium data for nickel ion was found to fit the Langmuir isotherm better than Freundlich isotherm, with the calculated maximum adsorption capacity of 0.63 mmol/g, whereas the adsorption kinetics followed the pseudo-second-order kinetic model. The thermodynamic values, ΔG0, ΔH0 and ΔS0, indicated that adsorption was an endothermic and spontaneous process. The adsorbent can remove nickel ion from high saline water selectively. The desorption of nickel using H2SO4 solution is the most effective, but the cycle stability of the adsorbent is low.