Coupled capture and photocatalysis of g-C3N4 based magnetic composites: Mechanism and disinfection activity against Staphylococcus aureus

The disinfection ability of g-C3N4 by photocatalysis is restricted, owing to its small surface area and rapid combination of holes (h+) and electrons (e−). Moreover, recycling of g-C3N4-based photocatalysts from aqueous solution is difficult, which increases the cost of application. In the present study, g-C3N4 was combined with magnetic biochar (MBC) by high temperature calcination to fabricate g-C3N4/MBC composites. The as-prepared g-C3N4/MBC composites acquired larger specific surface area, narrow bandgap, and broad-range of visible absorption capability. The g-C3N4/MBC composites showed good killing efficiency towards Staphylococcus aureus (S. aureus) under visible light irradiation. Efficient photocatalysis was achieved by the effective separation of e−/h+ within the g-C3N4/MBC composites. Moreover, the capture effect of MBC for S. aureus reduced the distance and increased the contact area between the g-C3N4/MBC composite and S. aureus. The g-C3N4/MBC-10 % showed notable stability and reusability over a broad pH range of 4–8 and in presence of different inorganic ions (Cl− and SO42−) and humic acid. After 5 cycles, the g-C3N4/MBC-10 % could still eliminate about 95 % of S. aureus cells. The g-C3N4/MBC-10 % was also highly effective in reducing the bacterial population in water samples taken from a nearby lake, thus showing considerable promise for use in water sterilization. In addition, g-C3N4/MBC composites were highly effective in eliminating the biofilm and inhibiting the growth of the new biofilm of S. aureus. The main active species in photocatalytic disinfection were determined, to be •OH, h+, and •O2−. This study would help to understand the capture and photocatalysis of g-C3N4 based composites for environmental applications. [Display omitted] •The g-C3N4/MBC composites efficiently killed S. aureus under visible-light irradiation.•The g-C3N4/MBC composites showed highly effective anti-biofilm ability under visible light.•The capture of MBC to S. aureus was coupled with photocatalytic activity of g-C3N4.•Efficient separation of electrons and holes in g-C3N4/MBC composites achieved.