Phytochemical-mediated design of magnetic MgFe2S4/CoBiO2I heterojunction for enhanced photocatalytic degradation of ciprofloxacin

Abstract

This study addresses the environmental threat of ciprofloxacin (CIP) by presenting a nanocomposite synthesized via a plant-extract-mediated route, which eliminates the need for harsh chemical reducing agents. This approach minimizes the use of hazardous chemicals while maintaining high photocatalytic efficiency. Characterizations (XRD, FTIR, FESEM, TEM, EDX, Mapping, DRS, PL and VSM) confirmed a crystalline heterostructure with enhanced optical absorption, efficient charge separation, and strong magnetic behavior. Simulated sunlight-driven photocatalytic activity was investigated with varying pH, catalyst loading, and CIP concentration. After optimization (pH 9, 1 g/L catalyst, 200 min), the composite achieved 100% CIP degradation, showing a 35% higher degradation efficiency and improved mineralization (79.03% COD and 54.23% TOC) compared to MgFe 2 S 4 (41.91% COD and 31.81% TOC). Kinetic studies followed pseudo-first-order kinetics, with k = 0.0349 1/min at the optimized CIP concentration (20 mg/L), while lower concentrations (5 mg/L) showed k = 0.0654 1/min, reflecting the concentration dependence of the rate constant. Radical scavenging experiments identified •OH and h + as the dominant reactive species, with electrons (e − ) and superoxide radicals (•O 2 − ) playing minor roles. The MgFe 2 S 4 /CoBiO 2 I heterojunction simultaneously increased photon usage, improved light-harvesting, advanced conductivity and prolonged photo-induced carrier lifetime, as verified by quenching experiments, UV-Vis DRS analysis, PL and Mott–Schottky techniques. The composite retained 87.25% of its initial degradation efficiency after ten consecutive cycles, thereby confirming its excellent structural and photocatalytic stability. Although methanol extraction and high-temperature calcination were used, this route remains significantly more sustainable than conventional chemical or hydrothermal syntheses These results highlight MgFe 2 S 4 /CoBiO 2 I as a stable, efficient, and recyclable visible-light photocatalyst, demonstrating a plant-based, sustainable approach in water treatment.