Photocatalytic removal of sulfamethoxazole using yeast biomass-derived NixP/biocarbon composites in the presence of dye sensitizer

Abstract

Photocatalysis represents an environmental-benign approach for organic pollutant treatment. Herein, a photocatalytic system composed of NixP/biocarbon composite as reactive center and erythrosine B (ErB) as sensitizer was constructed for the removal of sulfamethoxazole (SMX) antibiotic under visible light irradiation. NixP/biocarbon composites were fabricated via a facile impregnation-pyrolysis approach using baker’s yeast as both phosphorus and carbon precursor. It was found that NixP with pure Ni12P5, almost pure Ni2P or mixed crystal phases could be obtained by simply adjusting Ni:P molar ratio in precursor and pyrolysis temperature. Interestingly, the variation of NixP crystal phases remarkably affected photocatalytic removal efficiency of SMX. The obtained NixP(1:4)− 900 sample with mixed phases of Ni12P5 and Ni2P displayed excellent photodegradation performance with 98.71% removal efficiency for SMX (C0 = 20 mg L−1) in ErB-sensitized photocatalytic system. Moreover, the reusability of NixP/biocarbon composite was confirmed by four consecutive runs. The slight loss of activity in recycle study could be fully recovered after thermal regeneration. Further investigation indicated that photo-generated electrons from excited ErB molecules could be transferred to NixP/biocarbon, triggering a series of reactions to form various reactive oxygen species (eg., •O2−, H2O2, •OH) for SMX degradation. The better photocatalytic activity of NixP mixed crystal phases should be ascribed to its faster electron transfer ability. Overall, this study provides useful guidance in terms of the development of transition metal phosphide and efficient photocatalytic system.