Removal of 4-nitrophenol and indigo carmine dye from wastewaters by magnetic copper ferrite nanoparticles: Kinetic, thermodynamic and mechanistic insights

Magnetic copper ferrite nanoparticles, CuFe2O4-NPs (CFN) were synthesized via a facile sol-gel method for the effective removal of 4-nitrophenol (4-NP) and indigo carmine dye (IC) as typical hazardous organic pollutants from wastewater. The texture, morphology, and composition of the synthesized CuFe2O4 NPs were thoroughly explored by various physicochemical techniques. Various factors affecting the dye adsorption including the effect of adsorbent mass, contact time, pH, initial IC concentration, and temperatures were investigated to determine the optimum conditions for IC dye removal. The impact of diverse species and other coexisting dyes on the adsorption capacity of CFN was investigated. Five adsorption isotherms were investigated using two-parameters (Tekman, Langmuir, and Freundlich) and three-parameters (Sips, and Redlich-Peterson) models. CFN exhibited a maximum adsorption capacity of 57.4 mg/g according to the Sips model, with optimal conditions observed at pH 3, a contact time of 90 minutes, and an adsorbent mass of 0.1 g. Thermodynamic data revealed both the endothermic nature of dye removal and the random arrangement of dye molecules onto CFN adsorbent. The IC dye elimination mechanism was elucidated. Furthermore, the CFN-catalyzed reduction of 4-nitrophenol by NaBH4 followed first-order kinetics at a high rate of 0.4365 min-1, reflecting the high catalytic capacity of the synthesized CFN. The magnetic features, cost-effectiveness, recyclability, and high adsorption and catalytic activities towards IC dye and 4-NP removals made the synthesized CFN a promising catalyst for wastewater remediation.