Peroxidation and photo-peroxidation of pantoprazole in aqueous solution using silver molybdate as catalyst

In this study, silver molybdate was used as a catalyst in different oxidation processes to degrade pantoprazole (PAN) from aqueous suspension. The catalyst was synthesized using a controlled precipitation method and characterized by XRD, FTIR spectroscopy, BET analysis, Zeta potential, FEG-SEM/EDS, DRS and EPR. The alpha- and beta-phases of Ag2MoO4 were identified as crystalline structure of the butterfly-shaped particles. The metastable alpha-phase could be completely converted into beta-Ag2MoO4 by thermal treatment at 300 degrees C. The band gap energy of beta-Ag2MoO4 (E-g = 3.25 eV) is slightly higher than for as-prepared catalyst (alpha-Ag2MoO4 + beta-Ag2MoO4) (E-g = 3.09 eV), suggesting that as-prepared catalyst should be active under visible light. PAN is sensible to UV light irradiation, and the addition of H2O2 as electron acceptor enhanced the mineralization rate. In the catalytic UV-based reactions, high PAN oxidation efficiencies were obtained (>85%) but with low mineralization (32-64%). Catalytic peroxidation and photocatalytic peroxidation under visible light showed the highest PAN oxidation efficiency, leading to its almost complete mineralization (>95%), even under dark conditions (98% in 120 min). Several degradation byproducts were identified and three mechanistic routes of PAN decomposition were proposed. The identified byproducts are less toxic than the parent compound. EPR coupled with the spin trapping method identified (OH)-O-center dot radicals as the main ROS species in both photocatalytic and catalytic peroxidation reactions. Ag2MoO4 showed to be a promising catalyst to promote the decomposition of hydrogen peroxide into ROS. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

In this study, silver molybdate catalyst was synthesized and characterized, showing efficient degradation of pantoprazole. Pantoprazole is sensitive to UV light, and the addition of H2O2 enhances mineralization rate. Various reaction methods can achieve high oxidation efficiency and complete mineralization of pantoprazole.