ZnFe2O4 loaded on municipal waste-char: outstanding adsorption and photocatalytic removal of contaminants.

Low-cost carbonaceous materials have been synthesized and explored for the removal of harmful colored pollutants from an aqueous medium. However, most of them are not economically viable under continuous-flow conditions and because of their slow kinetics. In this study, we report an economically viable, magnetically reparable adsorbent material synthesized by incorporating spinel zinc ferrite within a waste-char matrix obtained from municipal solid waste (MSW). X-ray diffraction (XRD), fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and elemental mapping analyses confirm the successful incorporation of cube-shaped ZnFe₂O₄ into the multichannel system of the waste-char matrix. The as-prepared waste-char-ZnFe₂O₄ possesses a large surface area with multiple functional groups that aid in fast catalysis and in the removal of contaminants. Waste-char-ZnFe₂O₄ follows pseudo-first-order kinetics with photocatalytic degradation efficiencies of ∼72% and 92% and first-order rate constant (K₁) values equal to 0.023 and 0.0039 min⁻¹ for tetracycline and rhodamine B, respectively. The adsorption of model contaminants onto waste-char-ZnFe₂O₄ is best described by the Langmuir isotherm model with an R² value of 0.99 and a pseudo-second-order kinetic model with an adsorption capacity of 25 mg g⁻¹. The as-synthesized composite gives excellent results for real water samples with negligible interference due to other salt ions present in water. Moreover, the superparamagnetic nature of ZnFe₂O₄ facilitates the separation and reusability of the nanocomposite material. The material offers the advantage of converting MSW into a functional and more robust magnetic nanotrap for contaminants. [ABSTRACT FROM AUTHOR]