Adsorption of Hexavalent Chromium by magnetite particles synthesized at various temperatures: effect of magnetic properties of the particles on individual adsorption mechanisms

Chromium (VI) [Cr(VI)] is abundantly used for several industrial applications especially in stainless steel production and as an anti-corrosive agent in ceramics, textile industries and tanneries. Despite its versatile uses, Cr (VI) is a major environmental threat and is a known carcinogen. Therefore, proper precaution must be implemented while working with Cr (VI) or while disposing it after use. Due to improper handling and lack of proper care, Cr(VI) is still found in industrial wastewaters or landfill sites. The Cr(VI) in landfills can leach into the ground during rainfall and can risk the contamination of the groundwater causing a health catastrophe when consumed. This study focuses on effective Cr(VI) remediation by the process of adsorption. Magnetite particles synthesized by co-precipitation method at various temperatures (room temperature of 25^οC, 60^οC and 90^οC) are used as an absorbent for achieving maximum removal efficiency of Cr(VI) from water. An initial concentration of 10mg/l at pH 7.2 and time of contact 10 minutes is taken as the starting parameters for Cr(VI) for the batch adsorption studies. The surface morphology, chemical composition and the magnetic properties of the magnetite particles are determined from FESEM (Field Emission Scanning Electron Microscope), EDS (Energy-Dispersive  Spectroscopy) and VSM (Vibrating Sample magnetometer) characterization methods, respectively. The synthesis of the magnetite particles at various temperatures can affect both its physical (mainly pore size, shape, texture etc.) and magnetic properties and therefore can pose significant changes on the adsorption efficiency. The effect of the magnetite particle dose, pH of Cr(VI), time of contact between the magnetite particles and Cr(VI) and the effect of the change in the concentration of Cr(VI) are predicted in this study. A special focus is given on determining the variation in the magnetic properties of the magnetite particles due to different temperatures of synthesis. In case of any such noteworthy change in the magnetic properties, the alteration in the individual adsorption capacities of the iron-oxide particles are highlighted in this study. Langmuir and Freundlich isotherm models are used to predict the adsorption mechanisms.

Keywords: Adsorption; Magnetite particles; Characterization; Magnetic properties; Langmuir and Freundlich isotherms.