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

This study presents the results of synthesis and characterization of nanoparticles of cobalt ferrite (CoFeO) and nickel ferrite (NiFeO) 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 CoFeO and NiFeO, 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 m/g and 62 m/g for CoFeO and NiFeO, respectively. Vibrating sample magnetometer (VSM) showed super-paramagnetic behavior for all samples with magnetic saturation (M) at 7.269 and 6.61 emu/g for CoFeO and NiFeO, 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 CoFeO as 98, 97, and 93%, and by NiFeO 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 (R). 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 CoFeO and NiFeO is a spontaneous, favorable, and exothermic physical adsorption process.