Ternary Bi2O3/(BiO)2CO3/g-C3N4 multi-heterojunction nanoflakes for highly efficient photocatalytic degradation of dyes and xanthates under visible light

Abstract

To enhance the separation efficiency of photogenerated carriers, the formation of photocatalysts with strong interfacial contact heterojunctions is considered an effective approach for the removal of diverse environmental contaminants. In this study, a ternary heterojunction photocatalyst, Bi2O3/(BiO)2CO3/g-C3N4, demonstrated a multifunctional high photocatalytic performance in the degradation of various dyes, including methyl orange (MO), methylene blue (MB), rhodamine B (RB) and xanthates such as potassium ethyl xanthate (PEX), potassium amyl xanthate (PAX) and sodium isopropyl xanthate (SIPX), under visible light irradiation. The Bi₂O₃/(BiO)₂CO₃/g-C₃N₄ photocatalyst was synthesized by heating a mixture of urea and arc discharge synthesized Bi₂O₃-based nanoparticles at 550 °C. This photocatalyst exhibited higher photocatalytic activity compared to Bi2O3/(BiO)2CO3 and g-C3N4. The photocatalysts were characterized and studied by FTIR, XRD, FESEM-EDS elemental mapping, HR-TEM, UV–visible, BET and PL. The formation of an interface between Bi2O3/(BiO)2CO3 and g-C3N4 significantly improved photocatalytic performance by facilitating the effective separation of photogenerated electron-hole pairs. Stability tests of Bi2O3/(BiO)2CO3/g-C3N4 during the degradation of MO demonstrated the photocatalyst's excellent stability and reusability, indicating its potential for practical applications in mineral processing wastewater treatment. Reactive species trapping experiments revealed that holes (h⁺) played the most significant role in photodegradation, followed by hydroxyl radicals (•OH), while superoxide radicals (•O₂⁻) had a lesser impact. Study of two possible photocatalytic mechanisms suggested that the transfer of photogenerated carriers in Bi2O3/(BiO)2CO3/g-C3N4 is more likely to follow a double Z-scheme photocatalytic system. The enhanced photocatalytic performance of Bi2O3/(BiO)2CO3/g-C3N4 can be attributed to considerable specific surface area, stronger visible light absorption and most importantly, well-matched band potentials between Bi₂O₃, (BiO)₂CO₃, and g-C₃N₄. The promising photocatalytic performance of Bi2O3/(BiO)2CO3/g-C3N4, introduces a notable photocatalyst for photodegradation of dyes and xanthates in mineral processing wastewater.