Simultaneous Removal of Copper and Lead Ions from Industrial and Mining Effluents Using Biosorbents Derived from Rhododendron arboreum Plant: Adsorptive Optimization and Mechanism Evaluation

Abstract

The present investigation is focused on developing simple and effective bioadsorbents for the simultaneous removal of Cu²⁺ and Pb²⁺ ions from industrial and mining effluents. Rhododendron arboreum plant biomaterials are identified to have strong adsorptivity for Cu²⁺ and Pb²⁺ ions. Stem powers (RSP), their active carbon (RSAC) and the active carbon doped in Ca-alginate beads, RSAc-Ca.alg, are investigated for the simultaneous removal of Cu²⁺ and Pb²⁺ ions. Various extraction conditions were investigated and optimized for the maximum Cu²⁺ and Pb²⁺ removal. The sorption capacities were 35.0 mg/g for RSP, 38.5 mg/g for RSAC and 45.8 mg/g for RSAC-Ca.alg. Common co-ions were marginally interfered and spent sorbents can be used after regenerating with 0.1 HCl for a multiple number of cycles. Thermodynamic analysis indicated the spontaneity of adsorption process and favourability of adsorption at elevated temperatures. The high positive ΔH values indicate the endothermic nature of sorption and mechanism is ion-exchange and or a sort of complex formation between Cu²⁺/Pb²⁺ ions and functional groups of sorbents. High positive ΔS values indicate intensive disorder at solution/solvent boundary and thereby, favouring enhanced sorption. Sorption is well explained by Langmuir isotherm model and pseudo-second order kinetics. The sorbents were applied to treat effluent samples collected from industries and mining in India and Ethiopia for the removal of Cu²⁺ and Pb²⁺. The results show that both the metal ions can be successfully removed at the optimum extraction conditions arrived in this investigation. The merit of this investigation is that at a convent working pH 6, effective simultaneous removal of toxic Cu²⁺ and Pb²⁺ ions from industries can be achieved with simple biosorbents derived from Rhododendron arboreum plant.