Copper phosphide promoted BiVO4 photocatalysts for the degradation of sulfamethoxazole in aqueous media

Abstract

A series of copper phosphide promoted bismuth vanadate (Cu3P/BiVO4) photocatalysts of various Cu3P loadings (0 - 1 wt. % Cu3P), were prepared according to a solution-phase method and their photocatalytic activity was tested for sulfamethoxazole (SMX) degradation under simulated solar irradiation. Their physicochemical and optical properties were identified with the use of X-Ray diffraction (XRD), UV-vis diffuse reflectance spectra (DRS), Brunauer–Emmett–Teller (BET) method, scanning electron microscopy (SEM/EDS) and high-resolution transmission electron microscopy (HR-TEM). Results showed that the addition of Cu3P on BiVO4 improves its photocatalytic activity, which is optimized for the sample containing 0.25 wt. % Cu3P. This observation is probably attributed to the efficient separation of photogenerated charge carriers at the p-n junction formed at the Cu3P-BiVO4 interface. SMX degradation rate was found to increase by increasing catalyst concentration up to 750 mg/L or decreasing SMX concentration in the range of 250-2000 μg/L. The reaction was enhanced under basic conditions while slowed down in acidic environment due to some extent to adsorption phenomena. Additional experiments were performed under visible light alone, showing 0.25Cu3P/BVO high photocatalytic efficiency. Experiments were also performed in bottled water (BW) and wastewater (WW), revealing similar efficiency in BW but significantly lower in WW. The addition of humic acid (HA), significantly lowered the SMX degradation rate. SMX removal was slightly decreased in the presence of chloride ions., but increased in the case of bicarbonates. According to trapping experiments, photogenerated holes were found as the main oxidation species in the present system. Finally, reuse experiments showed 0.25Cu3P/BVO high stability.