Studies in the synthesis and chromium adsorption behaviour of microcrystalline cellulose immobilized zero valent iron nanoparticles (MCC-nZVI)

Abstract

In this study iron nanoparticles (nZVI) are used for the chromium removal from water. nZVI are synthesized in ionic liquid [BMIM]Cl and water, binary solution by borohydride reduction method. For stability of the nZVI, it is immobilized in microcrystalline cellulose (MCC). Varying concentration of iron was used for both the MCC-nZVI synthesized in ionic liquid and water. 6%, 12% and 24% w/w loading of Fe were studied in MCC-nZVI (5-7) synthesized in ionic liquid-water binary mixture, whereas MCC-nZVI (8) and MCC-nZVI (9) were synthesized in water. The synthesized MCC-nZVI materials were characterized by SEM, TEM and FTIR analysis. The MCC-nZVI material was fully dispersed in water with a particle size distribution of 30-100 nm estimated from TEM. The MCC-nZVI contained spherical nZVI; with few of them immobilized in MCC and attached to the surface. FTIR analysis of MCC and MCC-nZVI (5-7) upon comparison showed the strong binding of nZVI to the hydroxyl moieties of MCC. The MCC-nZVI materials were studied for the adsorption of Cr(VI). Batch experiments were performed for chromium adsorption with optimization for contact time, pH, concentration, adsorbent dose etc. on the extent of adsorption by MCC-nZVI. Langmuir and Freundlich adsorption isotherm were best applied to analyze the adsorption data of chromium. MCC-nZVI(6) shows optimum adsorption efficiency. The adsorption efficiency of MCC-nZVI was dependent on their surface area. Maximum adsorption of chromium was found to be 57 mg of Cr(VI)/g of MCC-nZVI (6) at pH 3 and 24 h equilibrium time. The adsorption kinetics could be described by pseudo second order kinetic model