Bioremediation of industrial toxic metals with gum kondagogu (Cochlospermum gossypium): A natural carbohydrate biopolymer

The ability of gum kondagogu [Cochlospermum gossypium (L.) DC], a natural carbohydrate biopolymer, was investigated for adsorptive removal of toxic metal ions Cd super(2+), Cu super(2+), Fe super(2+), Pb super(2+), Ni super(2+), Zn super(2+), Hg super(2+) and total Cr present in industrial effluents. Various physico-chemical parameters, such as, pH, temperature, equilibrium contact time, % biosorption and adsorption capacity, were investigated. Metal biosorption (%) and adsorption capacity of the biopolymer was determined by ICP-MS. Gum kondagogu was capable of competitively biosorb 8 toxic metal ions from the samples of industrial effluents tested. The adsorption capacity was observed to be in the following order, Cd super(2+) > Cu super(2+) > Fe super(2+) > Pb super(2+) > Hg super(2+) > total Cr> Ni super(2+) > Zn super(2+). The maximum adsorption capacity of metals by gum kondagogu varied in the range of 31-37 mg g super(-1) for Fe super(2+) and minimum of 5.5-9.3 mg g super(-1) for Hg super(2+) in the effluent samples tested. The equilibrium adsorption data were fitted to Langmuir isotherm models for all the metal ions adsorbed. FT-IR studies were carried out to understand the type of functional groups in gum kondagogu responsible for metal biosorption process. Desorption studies on biosorbed metal ions showed that HC1 was a good eluant for all metals tested. The re-adsorption capacity of the recycled gum kondagogu biopolymer sustained its biosorption property at 90% level, even after 3 cycle of desorption. Gum kondagogu biopolymer has the potential to be used as an effective, non-toxic, economical and an efficient biosorbent clean-up matrix for removal of toxic metals from industrial effluents.