Biochar-based iron-doped alginate microspheres combined with Fenton-like reaction for removing oxytetracycline hydrochloride: Performance, mechanism, and degradation pathway

• Published in: Journal of water process engineering 2025-01, Vol.69, Article 106723
• Main Authors: Zou, Weiao, Zhang, Meng, Zhang, Xinbo, Zhang, Dan, Li, Chaocan, Zhong, Lingling, Guo, Wenshan, Ngo, Huu Hao
• Format: Article
• Language: English
• Subjects: Biochar beads; Fenton-like reaction; Free radicals; Heterogeneous catalysis; Oxytetracycline hydrochloride
• ISSN: 2214-7144; 2214-7144
• DOI: 10.1016/j.jwpe.2024.106723

This study prepared two novel millimetre-sized ferric crosslinked alginate materials-biochar beads (FCB beads) and hydrogel beads (FCH beads) using coffee grounds, a common household waste. These beads served as heterogeneous catalysts for H2O2 in removing oxytetracycline hydrochloride (OTC) from aqueous solutions. Under optimal conditions, FCB beads/H2O2 and FCH beads/H2O2 achieved OTC (30 mg/L) removal efficiencies exceeding 91 % within 60 min, with total organic carbon removals of 36.22 % and 41.94 %, respectively. This demonstrated both high OTC removal efficiency and adequate mineralization. Additionally, after five consecutive catalytic cycles, OTC removal rates remained above 70 %, indicating good cyclic stability for both bead types. Both Fenton-like systems exhibited strong resistance to interference, maintaining OTC removal rates of over 77 % across various water qualities, including tap, lake, and river water. The removal mechanism suggested that OTC degradation was driven by radical species (•OH and O2•–) and non-radical species (1O2), with •OH being the dominant active species. The degradation pathway primarily involved hydroxylation, demethylation, and ring-opening reactions. Toxicity assessments of the intermediates revealed a significant reduction in toxicity, demonstrating the potential of these systems for the safe degradation of OTC. In summary, FCB and FCH beads addressed challenges associated with the recovery and high loss rates of powdered catalysts, broadening the application of biochar in environmental fields. These findings offer a sustainable and effective solution for antibiotic removal. [Display omitted] •Two novel millimetre-sized Fenton-like catalysts were prepared using coffee grounds.•Both beads showed broad pH applicability and strong interference resistance.•Hydroxylation, demethylation and ring-opening were the main OTC degradation pathways.•The reduced toxicity of OTC intermediates benefited the ecological environment.•The beaded materials offered a practical solution for catalyst recovery.