Sorption of nickel ions from aqueous solutions using activated carbon derived from walnut shell waste

Studies on a batch sorption process using activated carbon derived from walnut shell were investigated to remove Ni(II) ions from aqueous solutions. The influence of operational conditions such as contact time (0-150 min), solution initial pH (2-8), Ni(II) initial concentration (10-80 mg/L), sorbent mass (0.05-1.0 g/100 mL) and temperature (293-313 K) on the sorption was studied. Sorption data of Ni(II) ions onto walnut shell carbon (WSC) obeys the Langmuir isotherm model. Maximum sorption capacity of sorbent was 15.34 mg/g at 303 K. The kinetic data was fitted to pseudo-first-order model and pseudo-second-order model for different initial concentration to evaluate the model parameters. Pseudo-second-order model is better to represent the sorption process. Values of Delta G(0) ranging from -1.58 to -3.47 kJ/mol suggest that the sorption process is spontaneous and mainly governed by specific surface interaction mechanism. The values of Delta H-0 and Delta S-0 were 26.35 kJ/mol and 0.095 kJ/mol K, respectively. Results of this study will be useful for future scale up for using this waste material as a low-cost sorbent for the removal of Ni(II) ions from wastewater.