ASCORBIC ACID TREAD RED MUD IMMOBILIZED IN CaALGINATE BEADS AS AN EFFECTIVE ADSORBENT FOR THE REMOVAL OF COPPER IONS FROM INDUSTRIAL WASTEWATER

摘要

Ascorbic acid treated red mud-immobilized in ‘Calcium alginate’- beads (ARM-Ca-alg) is investigated as an adsorbent for removing toxic Cu2+ ions from water adopting batch modes of extraction methods.Treatment of red mud with a reducing agent like ascorbic acid enhances its adsorption nature towards Cu2+, having easily convertible oxidation states.Extraction parameters are investigated for maximum absorptivity of Cu2+ ions.Adsorption capacity is found to be as high as 126.0 mg/g.Further, ARM-Ca-alg exhibits good adsorption throughout pHs: 3 to 10 and thereby, enabling the adsorbent for its applicability for samples having varying pHs.Cu2+-ions can be removed entirely from Cu2+ solution (50 mg/l) by equilibrating the solution for 2 h with 1.25 g/l of ARM-Ca-alg, at pH: 6, rpm: 350 and temp: 303 K.Spent adsorbents can be re-generated and reutilized for 7 cycles with marginal loss of adsorption capacity.Thermodynamic parameters are evaluated.The observed -ve ΔG values emphasize the endothermic and spontaneity of the process of adsorption.High ?H value (44.404 KJ/mole) for ‘ARM-Ca-alg’ reflects that adsorption is through chemisorption.The primary mechanism of adsorption may be due to ion-exchange and/or reduction of Cu2+ to less soluble Cu+ depending upon the solution's pH.ΔS values (positive) implies disorder at the solid-liquid boundary.It renders the Cu2+ penetrate more into the layers of ‘ARM-Ca-alg,’ resulting in more absorptivity.Of the various adsorption isotherms applied, Langmuir isotherm explains well the sorption process, indicating the monolayer of adsorbate and homogenous distribution of adsorption sites.On analysis of the kinetics of adsorption, the pseudo-2nd-order model describes well.FESEM analysis signifies the adsorption of Cu2+.ARMCa-alg is successfully applied to remove Cu2+ from industrial effluent water samples.