No abstract

Harmful non-indigenous microorganism invasion caused by ballast water discharge poses severe threats to marine environments. In this study, a conceptual in situ photo-Fenton system without additional oxidants was first established for ballast water sterilization. Pyromellitic acid diimine (PDI)-modified g-C3N4 was utilized as a photocatalyst to produce H2O2, which was in situ activated by Fe­(II) to produce •OH for deep oxidation. Marine bacterium Vibrio alginolyticus (7 log) in ballast seawater was totally inactivated within 35 min of visible light irradiation. Simultaneous bacterial inactivation and H2O2 production was monitored to confirm the in situ coupling mechanism, and •OH instead of H2O2 was determined to be the dominant reactive species. The influence of seawater parameters, such as salinity, pH, and dissolved oxygen, on the inactivation efficiency was revealed. In addition, the bacterial inactivation mechanisms in terms of cell membrane rupture, intracellular enzyme activity, and total protein change were clarified. The organic matter release profile during bacterial lysis was probed by fluorescence excitation–emission matrix technology, which revealed minimal acute toxicity and impacts on the marine environment. This work not only advances an external oxidant-free system for on-board ballast water sterilization using sustainable solar energy but also creates an avenue for exploring bacterial inactivation mechanisms in seawater.

Visible light-driven defluorination of PFOA was achieved via a photo-reductive pathway by using Pt–Bi2O4 as a photocatalyst and KI as an electron donor.

No abstract

Silver is among the most essential antimicrobial agents. Increasing the efficacy of silver-based antimicrobial materials will reduce operating costs. Herein, we show that mechanical abrading causes atomization of Ag nanoparticles (AgNPs) into atomically dispersed Ag (AgSAs) on the surfaces of an oxide-mineral support, which eventually boosts the antibacterial efficacy considerably. This approach is straightforward, scalable, and applicable to a wide range of oxide-mineral supports; additionally, it does not require any chemical additives and operates under ambient conditions. The obtained AgSAs-loaded γ-Al2O3 inactivated Escherichia coli (E. coli) five times as fast as the original AgNPs-loaded γ-Al2O3. It can be utilized over 10 runs with minimal efficiency loss. The structural characterizations indicate that AgSAs exhibit a nominal charge of 0 and are anchored at the doubly bridging OH on the γ-Al2O3 surfaces. Mechanism studies demonstrate that AgSAs, like AgNPs, damage bacterial cell wall integrity, but they release Ag+ and superoxide substantially faster. This work not only provides a simple method for manufacturing AgSAs-based materials but also shows that AgSAs have better antibacterial properties than the AgNPs counterpart.