Synthesis and characterization of nanoparticles of cobalt and nickel ferrites for elimination of hazardous organic dyes from industrial wastewater

Abstract

This study presents the results of synthesis and characterization of nanoparticles of cobalt ferrite (CoFe₂O₄) and nickel ferrite (NiFe₂O₄) using co-precipitation method followed by application for removal of hazardous organic textile dyes of thiazole yellow G (TYG) and alizarin yellow R (AYR). XRD analysis confirmed formation of cubic spinel structure with average crystallite sizes at 16.07 nm and 13.84 nm for CoFe₂O₄ and NiFe₂O₄, respectively. Field emission scanning electron microscopy (FESEM) analysis showed agglomeration of spherical shape morphology with uniformly distributed Co, Ni, Fe, and O elements. The surface area calculated from Brunauer-Emmett-Teller (BET) analysis was 64 m²/g and 62 m²/g for CoFe₂O₄ and NiFe₂O₄, respectively. Vibrating sample magnetometer (VSM) showed super-paramagnetic behavior for all samples with magnetic saturation (M_s) at 7.269 and 6.61 emu/g for CoFe₂O₄ and NiFe₂O₄, respectively. The adsorption influencing parameters such as pH of solution, quantity of adsorbent, and contact time on dye removal efficiency were thoroughly investigated. Overall, acidic condition of samples with pH at 4 favored the maximum removal efficiency by CoFe₂O₄ as 98, 97, and 93%, and by NiFe₂O₄ as 96, 93, and 92%, respectively, for TYG, AYR, and mixture sample. The Langmuir adsorption isotherm model describes the equilibrium of all samples with the best fit of coefficient of determination (R²). The adsorption results fitted well with a pseudo-second-order kinetic model for all samples. The regeneration-reuse ability of adsorbents and cost estimation analysis of the dye removal process suggested that the economic suitability of nano-adsorbents for remediation of textile effluents was favored. The estimated thermodynamic parameters inferred that the removal of organic dyes onto the surface of CoFe₂O₄ and NiFe₂O₄ is a spontaneous, favorable, and exothermic physical adsorption process.

Keywords: Adsorption isotherms-kinetics-thermodynamics; Co-precipitation method; Hazardous organic textile dyes; Magnetic nano-adsorbent; Regeneration-reuse capacity.