Comparative sorption of copper and nickel from aqueous solutions by natural neem (Azadirachta indica) sawdust and acid treated sawdust

This study investigates the potential use of neem (Azadirachta indica) sawdust treated with hydrochloric acid for the removal of copper (II) and nickel (II) ions from wastewater. The effects of different system variables, viz, adsorbent dosage, initial metal ion concentration, pH and contact time were studied. The results showed that as the amount of the adsorbent was increased, the percentage of metal ion removal increased accordingly. Optimum pH value for metal adsorption is determined as 5.0 for Cu (II) and 4.0 for Ni (II) ions. Maximum metal is sequestered in 150 min for Cu (II) and 180 min for Ni (II) after the beginning of every experiment. Similar experiments were carried out with acid treated sawdust to compare the results. The adsorption of metal ions followed a first order rate equation. Both Freundlich and Langmuir adsorption models are suitable for describing the sorption of Cu (II) and Ni (II) on the two forms of sawdust. Furthermore, the natural organic matter (neem sawdust) is characterized by FTIR spectra and surface area analysis. At optimal conditions the maximum adsorption capacity is found to be 48.3 and 286 mg/g for Cu (II) and 31.5 and 74.1 mg/g for Ni (II) in natural and acid treated forms, respectively.