Investigation of depolluting and antimicrobial properties of magnetic AgIO3/Fe3O4@SiO2 photocatalytic marine concrete

Abstract

Visible light photocatalytic concrete represents an emerging technology with substantial potential for mitigating environmental challenges in marine ecosystems. This photocatalytic concrete demonstrates multifunctional capabilities including self-cleaning, decontamination, and antibacterial properties essential for sustainable marine environments. In this study, magnetic AgIO₃/Fe₃O₄@SiO₂ was first synthesized and in situ sprayed onto low porosity underwater non-dispersible concrete fabricated by a conduit method. The 56 day compressive strength, cubic and prismatic compressive strength, and impermeability grade of the low porosity underwater non-dispersible concrete are 40.60 MPa, 37.28 MPa, 24.89 MPa and P12-grade, indicating its suitability for marine infrastructure applications. Moreover, the AgIO₃/Fe₃O₄@SiO₂ modified concrete demonstrated photocatalytic performance with 85.1% tetracycline hydrochloride (TC) degradation within 60 minutes, effective inactivation of Escherichia coli (E. coli) cultures in seawater within 2 hours, and 75% formaldehyde decomposition within 4 hours under visible light exposure. These excellent properties can be attributed to the high specific surface area of 517.25 m² g⁻¹, narrow band gap of 1.41 eV, Z-scheme charge transfer mechanism and efficient reactive oxygen species (ROS) generation of AgIO₃/Fe₃O₄@SiO₂. Moreover, analysis revealed that seawater chloride ions (Cl⁻) undergo conversion to hypochlorite ions (ClO⁻) through superoxide radical (·O₂⁻)-mediated pathways, synergistically facilitating TC degradation. This work provides a sustainable approach for the industrial preparation of multifunctional photocatalytic underwater concrete, with prospective applications in offshore structures for biofilm inhibition and interfacial organic pollutant degradation at air–water boundaries.