Hydrothermally Synthesized Co3O4, α-Fe2O3, and CoFe2O4 Nanostructures: Efficient Nano-adsorbents for the Removal of Orange G Textile Dye from Aqueous Media

Abstract

We herein report the preparation of Co3O4, α-Fe2O3, and CoFe2O4 nanostructures through a hydrothermal method followed by a subsequent heat treatment. The as-prepared nanostructures exhibited good adsorption properties for the removal of Orange G (OG) textile dye. Various parameters influencing the adsorption process have been investigated such as contact time, initial dye concentration, ionic strength, adsorbent dose, and temperature. The maximum adsorption capacity values were found to be 33.3, 53.2, and 62.0 mg/g, for Co3O4, CoFe2O4, and α-Fe2O3 nano-adsorbents, respectively. The adsorption data fit the pseudo-second-order kinetic and Langmuir isotherm models well. Based on the calculated thermodynamic constants: ΔH° (3.660, 14.82, and 0.4710 kJ/mol), ΔG° (from −0.8090 to −1.109, from −0.6444 to −1.682, and from −3.665 to −3.943 kJ/mol), and Ea (9.277, 5.060, and 12.10 kJ/mol), the adsorption of OG dye on the aforementioned nano-adsorbents, respectively, was found to be endothermic, spontaneous, and physisorption process. In addition, because of the relatively high adsorption capacity and chemical stability, the as-synthesized α-Fe2O3 adsorbent is suggested as a promising candidate for the removal of OG textile dye from aqueous solutions.