Synergetic effect of photocatalytic oxidation plus catalytic oxidation on the performance of coconut shell fiber biochar decorated α-MnO2 under visible light towards BPA degradation

Photocatalytic technology is regarded as a promising approach for fast degradation of refractory organic pollutant in water. However, the performance of the photocatalyst can be restricted by the variation of water matrix conditions. Herein, coconut shell fiber was pyrolyzed to biochar (CSB800) and incorporated with α-MnO2 to degrade bisphenol A (BPA) in water under visible light irradiation. The prepared α-MnO2/CSB800 composites demonstrated high efficacy in degrading BPA. Specifically, 0.01 mM of BPA could be completely degraded by 0.1 g/L of MnO2/CSB800 within 45 min. It was found that the incident light could effectively trigger the separation of electron and hole in α-MnO2. The electron and hole were afterwards converted to hydroxyl radical (●OH), superoxide radical (●O2−) and non-radical singlet oxygen (1O2), which subsequently initiated the photocatalytic degradation of BPA. Additionally, α-MnO2/CSB800 could simultaneously participate the oxidative degradation pathway of BPA with its high oxidation-reduction potential. The introduction of CSB800 led to higher BPA degradation efficiency since CSB800 could accelerate the charge carrier transferring rate during BPA degradation process via either pathway. The co-existence of both photocatalytic and oxidative degradation synergy enables α-MnO2/CSB800/visible light system with high catalytic performance stability towards various water matrices. This study proposes an effective strategy to prepare easy-available photocatalysts with high and stable performance towards for addressing organic pollution issues in water.