Application of chitosan-coated magnetite (Fe3O4) nanoparticles for remediation of chromium-polluted wastewater

Hexavalent chromium Cr(VI) is one of the most toxic heavy metals and a major water pollutant. Studies have shown chromium to be carcinogenic and mutagenic at very low/ concentrations; these can be attributed to its strong oxidizing property. Therefore, the removal of chromium from wastewater is essential for the protection of public health. Conventional methods for chromium removal such as electrochemical and chemical precipitation, reduction, membrane filtration, reverse osmosis and ion exchange are known to have relatively high operating costs. Hence, there is a need for a cost-effective and non-toxic alternative. Nanotechnology is proven to be a promising technique for heavy metal remediation and there have been reported studies of effective removal of heavy metals including Cr(VI) from aqueous solutions by magnetite (Fe3O4) nanoparticles. However, Fe3O4 nanoparticles have the disadvantage of agglomerating in solution which reduces their effectiveness. Therefore, Fe3O4 nanoparticles needs to be modified with surface coatings to maintain its dispersity. Fe3O4 nanoparticles coated with chitosan was employed in this research work and its performance in removing chromium from wastewater was evaluated. Batch adsorption experiments carried out revealed chromium removal to be dependent on pH and nanoparticle dosage. The Freundlich isotherm fitted well with adsorption data at pH 4 and 6 while Langmuir isotherm fitted well with adsorption data at pH 8 and 10. The chitosan-coated Fe3O4 nanoparticles showed a better adsorption capacity (16.34 mg/g) than the adsorption capacity of unsupported Fe3O4 nanoparticles reported in literature (8.90 mg/g). These results demonstrated the suitability of the chitosan as coating material for Fe3O4 nanoparticles for chromium removal