Removal of chromium (VI) by adsorption on Manganese ferrite Nanoparticles: kinetic and thermodynamic study

The present study aimed to remove hexavalent chromium from aqueous solution by manganese ferrite nanoparticle. In this study, MnFe2O4 was prepared based on co-precipitation method. The adsorbent properties were determined using scanning electron microscopy (SEM), X-ray diffraction (XRD). In this research, the effects of pH (2, 5, 7, 9 and 11), contact time of 2 to 360 minutes and concentrations of 1 to 200 mg/l and temperature (283 to 328 K) for the removal of hexavalent chromium were investigated. The agitation parameter was kept constant for all experiments at 170 rpm. The results of nanoparticle synthesis showed that the nanoscale dimensions were less than 200 nm, and the shape of the spherical particles followed the cubic spinel structure. Moreover, the pH of zero point of the nanoparticle was 6.8. Kinetic studies showed that the removal of chromium followed the second-order kinetic model. Intrinsic particle diffusion model showed that single-particle intrusiveness was not present and absorption consists of two steps: first, pushing the absorbent layer onto the adsorbent surface and then penetrating the molecule inside the pores. It was found that the removal of chromium is followed the Langmuir model, and the maximum absorption capacity of the hexavallent-chrome is 34.84 mg/g. The resulting value of n=2.92 (Freundlich isotherm) indicates the chemical absorption of chromium on the adsorbent of hexavalent chromium. The highest adsorption rate occurred at 328 ° K. The amount of ΔG was negative and ΔH reacted positively. This is because that chromium-reacted manganese ferrite is chemically thermostable and spontaneous.