Integrated adsorption-photocatalysis of Xylenol Orange using Fe3O4/TiO2 composite: effects of pH, catalyst and PMS dosage, and mineralization with environmental assessment

Abstract

A magnetically recoverable Fe3O4/TiO2 composite was synthesized and applied for the removal of Xylenol Orange, a dye widely used in industrial applications, via a peroxymonosulfate assisted photocatalytic process under UV irradiation. The structural and physicochemical properties of the composite were characterized using XRD, FTIR, and SEM–EDS. Complete color removal (100%) was achieved under the optimum conditions of pH 5.0, PMS concentration of 1.0 mM, catalyst dosage of 1 g l−1, 30 min dark adsorption, and 60 min UV irradiation. An increase in the initial XO concentration (25–100 mg l−1) resulted in a decline in removal efficiency. Kinetic analysis revealed that XO degradation followed a pseudo-first-order Langmuir–Hinshelwood model. The composite maintained its activity up to the second cycle and exhibited dual catalytic behavior, involving both photocatalysis and PMS activation via Fe3O4. Life cycle assessment using the ReCiPe 2016 Midpoint (H) method indicated that energy consumption, mainly from UV irradiation, is the primary contributor to environmental impacts. These findings demonstrate an efficient and environmentally relevant approach for azo dye removal.