Synthesis of Silica Supported Iron Oxide (Fe3O4) Nanoparticles for Hexavalent Chromium Removal from Aqueous Solutions

Abstract

Heavy metals in the environment are hazardous to human health and require better methods for detection and removal. Industrial effluent often contains significant amount of toxic hexavalent chromium (Cr(VI)). In this study, iron oxide (Fe3O4) nanoparticles were synthesized by chemical precipitation method using ferric chloride hexahydrate(FeCl3.6H2O) and ferrous sulphate heptahydrate(FeSO4.7H2O) as a precursors and sodium hydroxide (NaOH) and ammonium hydroxide(NH4OH) as Precptating agent. To prevent excess aggregation of iron oxide nanoparticles silicon dioxide (SiO2) was used as a supporting material. The obtained nanoparticles (unsupported and supported) were characterized by XRD and FT-IR spectroscopy analysis. The average crystallite size of the products were calculated for both unsuported and supported MNPs and were found to be 13.5 and 12.8nm respectively. The effect of different parameters such as pH, Cr(VI)concentration, adsorbent dose and contact time for efficiency of of Cr(VI) adsorption has been analyzed. The results showed that maximum Cr adsorption of 96.5% at pH levels of about 3. Optimum dosage of sorbent, chromium concentration and contact time were 0.7g, 20mg/l and 120min, respectively. Adsorption isotherms and kinetics were analyzed. The experimental data was analyzed by both the Langmuir and Freundlich models of adsorption. The adsorption isotherm data was fitted well to Langmuir isotherm. Results showed that the kinetic model of pseudo-first order provided a good description of the experimental data.