Enhanced synergetic effect of Cr(VI) ion removal and anionic dye degradation with superparamagnetic cobalt ferrite meso–macroporous nanospheres

Abstract

Abstract The overall effectiveness of a photocatalytic water treatment method strongly depends on various physicochemical factors. Superparamagnetic photocatalysts have incomparable advantage of easy separation using external magnetic fields. So, the synthesis of efficient superparamagnetic photocatalysts and the development of a deep understanding of the factors influencing their catalytic performances are important. Co x Zn1−x Fe2O4 (x = 0, 0.5, 1) ferrite nanospheres were synthesized by the solvothermal route. The reduction of Cr(VI) and degradation of methyl orange (MO) impurities were carried out in single- and binary-component system under visible light irradiation. The adsorption experiments were done by the catalyst in the water solution containing the impurities. The magnetic and optical properties were studied by VSM and UV–Vis analysis. The nature of porosity was investigated using the BET method. 3D nanospheres of diameter about 5–10 nm were fabricated. The binary-contaminant system exhibited synergetic photocatalytic effect (80% improvement in activity rate) against the nanoparticles. The corresponding mechanism is discussed. CoFe2O4 exhibited better adsorption, photocatalytic and magnetic separation efficiency due to its higher surface area (50% higher), narrower band gap (25% lesser), smaller crystallite size, a strong magnetic strength (51.35 emu/g) and meso–macro hierarchical porous structure. The adsorption of Cr(VI) and MO can be approximated to the Langmuir and Freundlich model, respectively.