Peroxydisulfate Activation by Lignosulfonate-Derived Iron–Carbon Catalyst for Tetracycline Hydrochloride Removal: Contributions of 1O2 and Iron Cycle

A lignosulfonate-derived iron–carbon composite catalyst was fabricated via hydrothermal pyrolysis and employed to activate peroxydisulfate (PDS) for tetracycline hydrochloride (TCH) degradation. The optimized LFC possessed a porous carbon matrix uniformly decorated with Fe0/Fe3O4/Fe2O3 crystals, providing abundant active sites for catalytic reactions. The LFC/PDS system achieved nearly 100% TCH removal within 30 min at neutral pH and exhibited high efficiency over a broad pH range, strong anti-interference ability, and good universality for various organic pollutants. Mechanistic investigation confirmed that TCH degradation was dominated by a singlet oxygen (1O2)-mediated non-radical pathway, with minor contribution from radical species. The synergistic effect of iron cycle and surface functional groups promoted the generation of reactive oxygen species and 1O2. This research provides a low-cost, eco-friendly and efficient strategy for antibiotic wastewater treatment.