Biosorption of Nickel and Copper from a Mixed Metals Solution Using Chitosan Derived from Crabs

Aims: To ascertain the adsorptive potentials of chitosan derived from crab shell for the removal of copper and nickel from mixed metals solution in order to evaluate the competition of different metallic ions for the chelation sites of chitosan.
Study Design: Multifactorial design.
Place and Duration of Study: Chemistry department, The Federal University of Technology, Akure, Ondo State, Nigeria between April 2011 and December 2012.
Methodology: Chitosan was derived from crab shells through deacetylation process using 50% NaOH. The obtained chitosan was characterized by FTIR and used for removal of nickel and copper from aqueous mixture. Adsorption parameters such as pH, contact time, metal concentration, adsorbent dosage and temperature were investigated.
Results: It was observed that optimum pH for the adsorption of both nickel and copper was 5 while maximum adsorption for both metals was achieved within 120 minutes. Evaluation of the effect of temperature on adsorption showed that metal removal decreased with increase in temperature since the adsorption process was exothermic (negative ΔHº). Isotherm studies showed that the adsorption process obeyed Freundlich model with high R2 values.
Conclusion: Crab shell derived chitosan effectively removed copper and nickel ions from a mixed metals solution. The removal processes followed second order kinetic model and the sorption capacity was high for both metals.