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

Abstract

The ability of gum kondagogu [<i>Cochlospermum gossypium </i>(L.) DC.], a natural carbohydrate biopolymer, was investigated for adsorptive removal of toxic metal ions Cd²⁺, Cu²⁺, Fe²⁺, Pb²⁺, Ni²⁺, Zn²⁺, Hg²⁺ and total Cr present in industrial effluents. Various physico-chemical parameters, such as, <i style="">p</i>H, 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, Cd²⁺ > Cu²⁺ > Fe²⁺ > Pb²⁺ > Hg²⁺ > total Cr> Ni²⁺ > Zn²⁺. The maximum adsorption capacity of metals by gum kondagogu varied in the range of 31-37 mg g^-1 for Fe²⁺ and minimum of 5.5-9.3 mg g^-1 for Hg²⁺ 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 HCl 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.