Mechanistic insights on immobilization and decontamination of hexavalent chromium onto nano MgS/FeS doped cellulose nanofibres

Abstract Sustainable bio nano composite comprising of nanoMgS/FeS doped cellulose nanofibres (FeMgSCNF) was prepared, characterized by various techniques and assessed for the decontamination of Cr(VI). Cellulose nanofibres (CNF) acts as a template and stabilizer and prevents agglomeration of FeS/MgS nano particles. MgS present in the nano-composite provides a barrier to suppress aerial oxidation of Fe(II) and provided additional source of sulfide ions. An adsorption capacity in the order of 142.8 mg/g of the bionano composite was exhibited towards hexavalent chromium. Both FeSCNF and FeMgSCNF followed pseudo first order and pseudo second order kinetics with regression coefficients >0.96. X-ray photoelectron spectroscopy (XPS) studies indicated that decontamination of Cr(VI) follows the route of electrostatic attraction, ion-exchange followed by reduction of Cr(VI) to Cr(III) and immobilization of Cr(III) as chromic oxide and Fe-Cr mixed oxide. Toxicity characteristics leaching tests revealed the efficacy of immobilization. Finally the developed sorbents were successfully applied to the removal of chromium from tannery waste effluents.