Divalent metal ion removal from aqueous solution by acid-treated and garlic-treated Canna indica roots

The biosorption of different metal ions (Cu^2+, Zn^2+, Ni^2+, Pb^2+ and Co^2+) by dried roots of Canna indica biomass was investigated using a batch sorption technique. The equilibrium retention capacities of the metal ions determined from the Langmuir isotherm showed that C. indica had the largest sorption capacity for Pb^2+ ions and the least sorption for Ni^2+. The results also showed that garlic-treatment of C. indica biomass enhanced its sorption capacity for the divalent metal ions, with the enhancement factor varying from 1.22 to 1.44. The biosorption process was found to be exothermic for all metal ions studied (∆H values varying from -4.438 to -12.716 kJ mol^-1), with physisorption being the most likely mechanism of uptake. In conclusion, studies on biosorption of heavy metals by C. indica are important because they may contribute in aiding the innovative removal of metal ions from contaminated industrial effluents.