Z-scheme FeOOH/g-C3N4 nanosheets promoted PDS activation for efficient tetracycline degradation under visible light

Recently, photocatalysis combined peroxydisulfate (PDS) activation as a novel advanced oxidation processes (AOPs) was applied to remove pharmaceuticals and personal care products (PPCPs) in waterbody. Under visible light irradiation, photocatalysts, such as graphitic carbon nitride (g-C3N4, CN), could generated holes and electrons for both organic oxidation and PDS activation. However, it exhibits the drawbacks of low organics removal rate, high electron-hole recombination rate and low activation efficiency of PDS. In this study, amorphous iron oxyhydroxide (FeOOH) was intercalated into the surface of the g-C3N4 nanosheets (CNNS) to form a Z-scheme heterojunction to solve these problems. Electrochemical impedance spectroscopy (EIS) and photoluminescence spectrum (PL) tests proved the enhancement of the charge separation and migration capability of FeOOH/CNNS. The density functional theory (DFT) supported the constructive role of the Z-type heterojunction between FeOOH and CNNS in promoting photocarrier transfer and facilitating more effective PDS activation reactions. The removal rate of tetracycline (TC) achieved 98.8 % within 80 min by FeOOH/CNNS coupled PDS under visible light (FeOOH/CNNS-PDS/Vis) system. Finally, electron spin resonance (ESR) approved the pivotal role of (OH)-O-center dot, SO4 center dot-, and O-center dot(2)- during the process.