KH570 firmly anchors Ag+/Ag0 on TiO2 nanotubes to enhance organics removal during photocatalytic activation of peroxymonosulfate

Abstract

To enhance the photocatalytic activation of peroxymonosulfate (PMS), the precious metal was used to modify the catalyst. However, the catalyst suffered from metal leaching due to the oxidation of zero-valent metal into the ionic state by PMS. Herein, the silane coupling agent, KH570, was selected to fix metal Ag on the surface of TiO2 nanotubes arrays (TiO2NTAs) firmly and dispersedly. The prepared Ag/KH570/TiO2NTAs were efficient visible-light (VL) photocatalytic PMS activators for the degradation of bisphenol A (BPA). The Ag/KH570/TiO2NTAs/PMS/VL system exhibited a higher degradation rate (kobs = 0.1 min−1) and exceptional stability even after 30 cycles (0.098 min−1) compared to Ag/TiO2NTAs/PMS/VL system (0.074 and 0.015 min−1 for first and fourth use, respectively). KH570 well-dispersed Ag0 on the surface of TiO2NTAs showed significantly enhanced VL absorption, photo-generated current, and electro-transfer ability, which boosted PMS activation. The Ag0 also activated PMS and converted to Ag+, which was quickly reduced to Ag0 again by photo-generated electrons. KH570 well-immobilized Ag0/Ag+ promoted above catalytic cycles with minimal Ag leaching. Activation of PMS by the photo-generated electrons and Ag0 resulted in the generation of •OH and SO4•−, which seized the principal position for BPA removal. The wide pH adaptability and production of more oxidant in water matrixes (Cl−, HCO3−, and humic acid) enabled Ag/KH570/TiO2NTAs/PMS/VL system to exhibit excellent performance in the actual waterbodies (groundwater and tap water). This work would provide useful information in the construction of stable zero-valent metal modified catalysts for the (photo)catalytic activation of PMS/persulfate.