Effective heterogeneous Fenton-like degradation of antibiotics by ferroferric oxide nanoparticle coated reduced iron powder with accelerated Fe(ii)/Fe(iii) redox cycling

Heterogeneous Fenton-like processes based on Fe-based catalysts are effective technology to degrade emerging organic pollutants in water and wastewater such as tetracycline (TC). However, the kinetically limited redox cycling between Fe2+ and Fe3+ is still a persistent challenge for their widespread application. To address this issue, we designed a novel Fe-based catalyst by coating reduced iron powder (RIP) with ferroferric oxide nanoparticles (FONP@RIP) using a simple chemical co-precipitation method. The reduced iron could rapidly reduce Fe(iii) to Fe(ii) and accelerate the cycle of Fe(ii)/Fe(iii) in the heterogeneous Fenton-like system. Benefiting from the accelerated cycle of Fe(ii)/Fe(iii), TC could be efficiently degraded in the FONP@RIP/H2O2 system over a wide pH range of 3-6, with a removal efficiency of 94.5% within 60 min (TC0 = 150 ppm). The predominant reactive oxygen species were identified as OH and HO2. Based on the identified intermediates, the possible pathway of TC degradation was deduced and the toxicity of pollutants could also be significantly reduced during the degradation process. Moreover, FONP@RIP exhibited stable catalytic performance during multiple cyclic tests with only a marginal loss of catalytic components. This study presents a new catalyst design strategy for heterogeneous Fenton-like processes, which provides a promising way for the degradation of residual antibiotics in water and wastewater.