Visible-light-active porous Fe–carbon composite derived from recycled PET for photocatalytic Cr(VI) reduction

This study demonstrates an organic solvent-free, single-step synthesis of a magnetic porous metal–carbon composite (PMCC), derived from the calcination of a metal–organic composite of recycled terephthalic acid (TPA) and iron(II), offering a sustainable and efficient visible-light active photocatalyst for Cr(VI) removal. The photocatalyst achieved its highest efficiency, with a specific surface area of 187 m² g⁻¹, at an Fe/TPA mass ratio of 0.8. X-Ray Diffraction analysis confirmed the presence of Fe₃O₄ and FeO in its structure, while Differential Reflectance Spectroscopy determined a band gap of 2.10 eV. Furthermore, Vibrating-Sample Magnetometer analysis indicated a saturation magnetization value of 12.56 emu g⁻¹. Under optimized conditions (pH: 2, formic acid: 2 ml, reaction time: 40 min, and sample volume: 100 ml), an impressive Cr(VI) removal efficiency of 99.9 ± 0.5% was achieved for an initial concentration of 100 mg L⁻¹. Regeneration experiments demonstrated sustained performance over 10 cycles without any decrease in efficiency. High activity in the visible light region, low-cost raw materials, and exceptional regenerative capabilities highlight the potential of the prepared photocatalyst as an environmentally friendly, durable, and cost-effective solution for Cr(VI) removal.