Chemically activated carbon residue from biomass gasification as a sorbent for iron(II), copper(II) and nickel(II) ions

The main goal of this research was to investigate the possibility of the utilization of carbon residue from biomass gasification process with and without chemical activation as a low cost sorbent for iron(II), copper(II) and nickel(II) ions from an aqueous solution. Commercial activated carbon was used as a reference sample. Batch experiments were done to evaluate the influence of pH, initial metal concentration and contact time. The optimum pH required for maximum adsorption was found to be 4, 5 and 8, for iron, copper and nickel, respectively. According to the results, the removal of metals by carbon residue with and without chemical activation was higher than commercial activated carbon. The highest maximum experimental sorption capacities (qm,exp) for iron, copper and nickel by activated carbon residue were 21, 23 and 18 mg g−1, respectively. The experimental equilibrium sorption data were tested for the Langmuir, Freundlich and Dubinin–Radushkevich (D–R) equations. Depending on the system the Langmuir or Freundlich isotherms have been found to provide the best correlation. The kinetics of iron, copper and nickel sorption by different adsorbent materials followed the pseudo-second-order model. Other tested kinetic models were the pseudo-first-order and the Elovich models. Weber Morris's intraparticle diffusion model showed that there are two or three different stages for the removal of metals.