Nickel and copper removal from aqueous solution by an immature coal (leonardite):: effect of pH, contact time and water hardness

The removal of Ni(II) and Cu(II) from aqueous solutions by a low cost sorbent (leonardite) was studied. The metal uptake was pH-dependent and the maximum sorption for two metals was obtained at around pH 5-6. Batch kinetic studies showed that equilibrium time was reached after 2 h of contact time. Equilibrium isotherms were obtained for the adsorption data of the two metals in single and binary systems. Equilibrium data were fitted to Langmuir and Freundlich models and the maximum adsorption capacities were found to be 0.33 mmol of copper and 0.26 mmol of nickel per gram of leonardite. In binary solutions containing the two metals an important reduction of nickel uptake was observed while the sorption of copper was less affected. The presence of Ca2+ affected the removal of both copper and nickel ions, although the adsorption of nickel was reduced more than that of copper. (c) 2005 Society of Chemical Industry