Efficient activation of persulfate with bismuth tungstate in dark for degradation of organic pollutants

Bismuth tungstate (Bi2WO6, BWO) is usually utilized as a photocatalyst for the degradation of various organic pollutants. However, its catalytic potential without light irradiation in persulfate (PS) based advanced oxidation processes (AOPs) has been overlooked, despite its significant redox capacity. Herein, the flower-like orthorhombic BWO was synthesized using a simple hydrothermal method, followed by an evaluation of its catalytic activity in dark through the removal of aqueous organic dye rhodamine B and antibiotic levofloxacin in PS based AOPs. The results indicate that the BWO/PS system exhibits remarkable efficacy in removing both pollutants compared to the counterparts, demonstrating the effective activation of PS with BWO. Additionally, N-de-ethylation and conjugated ring destruction processes during rhodamine B removal were confirmed by liquid chromatography-mass spectrometry, further substantiating the occurrence of degradation reactions. Furthermore, the electrochemical and radical identification experiments were conducted to elucidate the mechanism underlying PS activation with BWO for pollutant degradation. The results suggest that the electron transfer between BWO and PS induces PS activation, leading to the generation of singlet oxygen and superoxide radical. Therein, singlet oxygen acts as the dominate active species while superoxide radical plays a supportive role in pollutant degradation. Moreover, cyclic experiments reveal the moderate phase and structural stability of BWO in terms of activating PS and the BWO/PS system still can remove rhodamine B exceeding 80% in actual waters. The work provides a new candidate for PS activation and highlights the applicability of conventional bismuth compounds in PS based AOPs system for wastewater treatment without additional energy input.