Construction of novel dual Z-scheme g-C3N4/ZnFe2O4/Ag2CO3 heterojunction with enhanced visible-light-driven performance for tetracycline degradation and bacterial inactivation

Dual Z-scheme heterojunction with highly separation efficiency of photoinduced carriers and outstanding redox capability has received considerable attention and hold great promise for environmental remediation. Herein, magnetic dual Z-scheme g-C3N4/ZnFe2O4/Ag2CO3 heterojunction was successfully constructed, and applied as a dual-function photocatalyst for tetracycline (TC) degradation and bacterial inactivation. The optimized g-C3N4/ ZnFe2O4/Ag2CO3 heterojunction exhibited excellent photocatalytic capacity for TC degradation with a rate constant of 0.0154 min-1, which is 2.73, 3.08, and 2.92 times higher compared to that of the g-C3N4, ZnFe2O4, and g-C3N4/ZnFe2O4, respectively. Impressively, the g-C3N4/ZnFe2O4/Ag2CO3-1.25 heterojunction displayed satisfying activity within a wider range of pH (3.0-9.0), TC concentration (5-25 mg L-1), and with the addition of various anions including Cl-, HCO3- , SO42-, and NO3- . Meanwhile, 6.5-log of Escherichia coli cells could also be inactivated by g-C3N4/ZnFe2O4/Ag2CO3-1.25 heterojunction under visible light. Mechanism exploration based on trapping experiment, electron paramagnetic resonance (EPR) analysis, and liquid chromatography-mass spectrometer (LC-MS) indicated that the improved photocatalytic performance resulted from the synergetic effect of semiconductors and constructed dual Z-scheme heterojunction, which significantly promotes charge separation rate and endows strong redox capacity. As expected, the toxicity of TC degradation intermediates was reduced according to the Toxicity estimation analysis based on a quantitative structure activity relationships (QSAR) method. Further, the g-C3N4/ZnFe2O4/Ag2CO3 heterojunction also demonstrated magnetic separation property and satisfactory photocatalytic stability even after 4 cycles. This work offers a new perspective on constructing novel magnetic dual Z-scheme heterojunction with dual-function photocatalytic properties and is of significance for water remediation.

Automated summary

In this study, a magnetic dual Z-scheme g-C3N4/ZnFe2O4/Ag2CO3 heterojunction was successfully constructed and exhibited excellent photocatalytic activity for tetracycline degradation and bacterial inactivation. The optimized structure showed high photocatalytic capacity and satisfactory activity under a wider range of conditions. The improved performance was attributed to the enhanced charge separation rate and strong redox capability of the dual Z-scheme heterojunction. The heterojunction also demonstrated magnetic separation property and satisfactory photocatalytic stability.