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Nanoparticles of zinc ferrite (ZnFe 2 O 4 ) and copper ferrite (CuFe 2 O 4 ) were synthesized, and characterized, and these materials were applied for removal of organic dyes of alizarin yellow R (AYR), thiazole yellow G (TYG), Congo red (CR), and methyl orange (MO) from industrial wastewater through adsorption technique. Synthesis of ZnFe 2 O 4 and CuFe 2 O 4 was achieved through chemical co-precipitation method. These nanomaterials were characterized for physicochemical properties using XRD, FTIR, BET, VSM, DLS, Zeta-potential, and FESEM-EDX analytical instruments. BET surface areas of ZnFe 2 O 4 and CuFe 2 O 4 were 85.88 m 2 /g and 41.81 m 2 /g, respectively. Adsorption-influencing parameters including effect of solution pH, adsorbent quantity, initial concentration of dye pollutant, and contact time were examined. Acidic medium of the solution favored higher percentage of removal of dyes in wastewater. Out of different isotherms, Langmuir equilibrium isotherm showed the best fit with experimental data, indicating monolayer adsorption in the treatment process. The maximum monolayer adsorption capacities were found as 54.58, 37.01, 29.81, and 26.83 mg/g with ZnFe 2 O 4 , and 46.38, 30.06, 21.94, and 20.83 mg/g with CuFe 2 O 4 for AYR, TYG, CR, and MO dyes, respectively. From kinetics analysis of the results, it was inferred that pseudo-second-order kinetics were fitting well with better values of coefficient of determination (R 2 ). The removal of four organic dyes from wastewater through adsorption technique using nanoparticles of ZnFe 2 O 4 and CuFe 2 O 4 was observed to be spontaneous and exothermic. From this experimental investigation, it has been inferred that magnetically separable ZnFe 2 O 4 and CuFe 2 O 4 could be a viable option in removal of organic dyes from industrial wastewater., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

This study presents the results of synthesis and characterization of nanoparticles of cobalt ferrite (CoFe 2 O 4 ) and nickel ferrite (NiFe 2 O 4 ) 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 CoFe 2 O 4 and NiFe 2 O 4 , 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 2 /g and 62 m 2 /g for CoFe 2 O 4 and NiFe 2 O 4 , 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 CoFe 2 O 4 and NiFe 2 O 4 , 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 CoFe 2 O 4 as 98, 97, and 93%, and by NiFe 2 O 4 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 2 ). 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 CoFe 2 O 4 and NiFe 2 O 4 is a spontaneous, favorable, and exothermic physical adsorption process., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)