Synthesis, characterization, and mechanistic insights into enhanced photocatalytic tetracycline degradation by zinc-doped ferrite nanoparticles

Abstract

This study presents the first systematic investigation of zinc-doped barium copper aluminum ferrite (Zn<inf>X</inf>Ba<inf>0.8-x</inf>Cu<inf>0.2</inf>Al<inf>0.7</inf>Fe<inf>1.3</inf>O<inf>4</inf>, (X = 0, 0.2, 0.4, 0.6)) nanocomposites, demonstrating unprecedented multi-element synergistic effects. The nanocomposites were synthesized via sol-gel auto-combustion and characterized using X-ray diffraction (XRD), Fourier-transform infrared (FTIR, SEM-EDX, BET, scanning electron microscopy-energy dispersive X-ray (SEM–EDX), Brunauer–Emmett–Teller (BET), and other techniques. The novel findings revealed that increasing the Zn content systematically decreased the crystallite size (from 35.746 to 24.197 nm) and reduced the lattice parameters (from 8.4625 to 8.3915 Å), indicating successful Zn incorporation into the spinel structure. BET analysis showed an increase in the surface area (18.86 to 43.75 m²/g) and pore volume (0.039 to 0.088 cm³/g) with increasing Zn concentration in the catalyst. Remarkably, the optimized Zn₀.₆Ba₀.₂Cu₀.₂Al₀.₇Fe₁.₃O₄ catalyst achieved 97.67% tetracycline degradation efficiency within 140 min, a significant improvement over undoped ferrites (66.70%), with superior quantum efficiency (1.25 × 10⁻⁶ molecules/photon) and space-time yield (1.25 × 10⁻⁷ molecules/photon). The broad-spectrum efficacy of the catalyst was demonstrated by the effective degradation of diverse pollutants: ciprofloxacin (87.34%), atrazine (84.54%), methylene blue (63.56%), and methyl orange (52.54%). Breakthrough performance was achieved when combined with peroxymonosulfate (PMS), enabling complete tetracycline removal within 40 min, compared to persulfate (120 min) and hydrogen peroxide (80 min). Mechanistic studies identified superoxide and hydroxyl radicals as the primary reactive species, and exceptional stability (78.23% activity retention after eight cycles) was demonstrated. These findings address the critical global water scarcity challenges affecting 2.3 billion people, offering a sustainable solution for pharmaceutical wastewater treatment through innovative multi-element catalyst designs. (Figure presented.)