Visible light activation of persulfate by magnetic hydrochar for bacterial inactivation: Efficiency, recyclability and mechanisms

• Published in: Water research (Oxford) Vol. 176; p. 115746
• Main Authors: Wang, Wanjun, Wang, Hanna, Li, Guiying, Wong, Po Keung, An, Taicheng
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.06.2020
• Subjects: Bacterial inactivation; Catalysis; Disinfection; Escherichia coli; Light; Magnetic hydrochar; Persulfate activation; Photocatalysis; Staphylococcus aureus; Visible light; Water Purification; Visible light; Persulfate activation; Bacterial inactivation; Magnetic hydrochar; Photocatalysis
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2020.115746

The development of “green” water disinfection technology utilizing solar energy is highly desired but remains challenging. In this study, sulfate radical (•SO4−)-mediated bacterial inactivation was first attempted by using Fe3O4-based magnetic hydrochar (MHC) as a recyclable catalyst for persulfate (PS) activation under visible light (VL) irradiation. Complete treatment of 8.0 log E. coli cells was reached within 40 min in VL/PS/MHC system, compared with that of only 2.0 log-reduction was obtained in the PS/MHC system under the same conditions. The system was applicable in wide range of pH (3.0–9.0), and increasing dissolved O2 could further promote the efficiency. A three-route mechanism was proposed, in which the PS activation by ≡Fe(II) of Fe3O4 and photo-generated electron captured by PS were the major processes. The bacterial cell lesion process was found to be triggered directly via •SO4−, which caused the damage of outer membrane, followed by up-regulation of intracellular ROSs and destroy of chromosomal DNA, finally leading to irreversible cell death. Moreover, the VL/PS/MHC system is also effective to inactivate versatile pathogenic bacteria including P. aeruginosa and S. aureus. As a proof-of-concept, our study provides meaningful information to advance the areas of “green” water disinfection technology which can be realized by recyclable photocatalytic systems using solar energy. [Display omitted] •Magnetic hydrochar was used for bacterial inactivation with persulfate under VL.•Persulfate was activated synergistically by Fe(II) and photo-induced electrons.•The hydrochar can be recycled by external magnetic field with photo-stability.•Bacterial cell lesion was triggered by .•SO4−, leading to generate intracellular ROSs.•Killing of versatile pathogenic bacteria can be realized by the recyclable systems.