Removal of Cr (VI) from simulated electroplating wastewater by magnetite nanoparticles

Chromium is considered as one of the important environmental pollutants. There is high concentration of chromium in the wastewater of electroplating industries. Magnetic iron nanoparticles are used to control and eliminate heavy metals from industrial effluents through the mechanisms of adsorption, ion exchange and electro-static forces. The aim of this study was to evaluate the efficiency of magnetic nanoparticles for removal of hexavalent chromium (VI) from simulated electroplating wastewater and the parameters that influence the removal. The magnetite nanoparticles were prepared by sol-gel method through the addition of bivalent and trivalent iron chloride in the water environment under alkaline conditions. Then the factors influencing this process, including nanoparticle concentration, initial concentration of chromium, pH, mixing rate and retention time were studied. The taguchi method was used to determine sample size and data analysis. Sampling was performed based on sampling protocol. Removal efficiency was increased with significant increasing the mixing speed (P<0.001). There was a significant reduction in the removal efficiency by increasing the pH and chromium concentration (P<0.001). The findings of this study showed that in pH 2, 10 mg/L initial chromium concentrationy a dose of 1 g/L synthesized magnetite nanoparticles, 5 minutes retention time and 250 rpm mixing rate, about 82 % of chromium (VI) was removed. In addition, characteristics of nanoparticles including: particles structure, composition, size and zeta potential were determined using analytical devices such as: XRD, XRF, Zeta potential and particle seizer. Magnetite nanoparticles have high competency for removal of chromium (VI) from simulated electroplating wastewater, and removal efficiency is reversely related to pH.