Development of an electro-Fenton catalyst from iron slag waste for degrading ceftriaxone in hospital wastewater: Reusability and leaching tests

Pharmaceutical residues such as ceftriaxone are frequently detected in hospital effluents, posing environmental and public health risks, particularly through the spread of antibiotic resistance. Conventional treatment methods are largely ineffective against persistent β-lactam antibiotics. This study investigates the use of iron slag as a low-cost heterogeneous catalyst for the Electro-Fenton (EF) process, focusing on degradation efficiency, reusability, and metal leaching during the treatment of ceftriaxone in actual hospital wastewater. The slag was analyzed using SEM, XRD, XRF, TGA, and pH PZC techniques. XRD showed 93.6 % crystallinity, and XRF revealed 45 wt% Fe. TGA confirmed thermal stability up to 800 °C. These findings highlight the slag's heat resistance and the presence of catalytically active iron phases (FeO, Fe 3 O 4 ). Batch EF experiments were conducted using stainless-steel and iridium-coated titanium dioxide (Ir/TiO 2 ) electrodes under optimized conditions (pH 5, 75 min, 1.9 g/L catalyst). In synthetic wastewater, iron slag reached up to 90 % ceftriaxone degradation, surpassing FeSO 4 (80.1 %). In real hospital wastewater, the slag catalyst achieved 71.7 % removal, compared to 84.8 % with FeSO 4 under optimal conditions. Reusability tests showed that iron slag retained 73.2 % of its activity after five cycles, with minimal iron leaching (2.66 %), demonstrating good stability and low environmental impact. Overall, the results indicate that waste-derived iron slag provides competitive performance, durability, and safety, making it an affordable and sustainable catalyst for EF treatment of pharmaceutical wastewater. • Waste iron slag was valorized as a heterogeneous catalyst in the electro-Fenton process. • Electro-Fenton degradation of ceftriaxone using iron slag was achieved 90 % within 75 min in synthetic wastewater. • The catalyst retained >85 % efficiency after five reuse cycles with 2.66 % iron leaching. • Treatment of real hospital wastewater achieved 82 % ceftriaxone degradation, showing stability. • Iron slag provides a sustainable and low-cost alternative to conventional FeSO 4 catalysts.