Optimization of the green and low-cost ammoniation-activation method to produce biomass-based activated carbon for Ni(II) removal from aqueous solutions

Abstract Activated carbon (AC) is an adsorbent that is used extensively in environmental treatment, and improving its performance and reducing costs remain sustainable goals. To reduce production costs and attain a green production process, a novel ammoniation-activation method (AAM) for the preparation of AC to enhance its physicochemical and adsorptive performance was provided. The experimental parameters were optimized by orthogonal experiments and the carbon product was characterized. These results show that the S BET (1142.0 m 2 /g), V tot (0.618 cm 3 /g) and content of carbon functional groups (2.953 mmol/g) from the AAM method (hereafter termed AAC) were higher than those obtained by conventional methods (AC, 863.6 m 2 /g, 0.506 cm 3 /g and 2.071 mmol/g, respectively). Accordingly, the AAC (38.91 mg/g) demonstrated a 30% higher adsorptive capacity for Ni(II) than the AC (27.55 mg/g). Furthermore, the behavior of Ni(II) sorption on the AAC was investigated by batch experiments using various Ni(II) concentrations, time durations, pH levels and ionic strengths. The associated sorption isotherms and kinetics well fitted to the Langmuir model and pseudo-second-order model, respectively. Possible sorption mechanisms were further explored by XPS. The chemical affinity of Ni(II) toward oxygen- and nitrogen-containing groups plays a key role in the sorption process.