Abstract
This study investigates the photocatalytic degradation of amoxicillin (AMO) by simulated solar irradiation using WO3 as a catalyst. A three-factor-three-level Box-Behnken design (BBD) consisting of 30 experimental runs is employed with three independent variables: initial AMO concentration, catalyst dosage, and pH. The experimental results are analyzed in terms of AMO degradation and mineralization, the latter of which is measured using dissolved organic carbon (DOC). The results show that the photocatalytic degradation of AMO follows pseudo-first-order kinetics. AMO degradation efficiency and the pseudo-first-order rate constants decrease with increasing initial AMO concentration and pH and increase with increasing catalyst dosage. Though AMO degradation is almost fully complete under the experimental conditions, DOC removal is much lower; the highest DOC removal rate is 35.82% after 180 min. Using these experimental results, second-order polynomial response surface models for AMO and DOC removal are constructed. In the AMO removal model, the first-order terms are the most significant contributors to the prediction, followed by the quadratic and interaction terms. Initial AMO concentration and pH have a significant negative impact on the photocatalytic degradation of AMO, while catalyst dosage has a significant positive impact. In contrast, in the DOC removal model, the quadratic terms make the most significant contribution to the prediction and the first-order terms the least. The optimal conditions for the photocatalytic degradation of AMO are found to be an initial AMO concentration of 1.0 μM, a catalyst dosage of 0.104 g/L, and a pH of 4, under which almost complete removal of AMO is achieved (99.99%).
Highlights
With the increased use of AMO worldwide, AMO levels in water and wastewater are expected to rise, so the effective removal of AMO using wastewater treatment processes has become more important
Though a few studies have focused on the degradation of AMO via solar photocatalysis using TiO226,27,33, no research on visible/solar photocatalysis assisted by tungsten trioxide (WO3) has been reported to date
It was found that WO3 photocatalysis was much more efficient than direct photolysis in terms of AMO degradation as the pseudo-first-order rate constants for WO3 photocatalysis increased at least 22-fold compared to that for direct photolysis (Table 5)
Summary
With the increased use of AMO worldwide, AMO levels in water and wastewater are expected to rise, so the effective removal of AMO using wastewater treatment processes has become more important. AOPs rely on the in-situ production of highly reactive hydroxyl radicals (OH) with the help of one or more primary oxidants (e.g., ozone, hydrogen peroxide, and oxygen), energy sources (e.g. ultraviolet, solar and visible light), and/or catalysts (e.g. tungsten trioxide, and titanium dioxide)[17,18,19]. Though a few studies have focused on the degradation of AMO via solar photocatalysis using TiO226,27,33, no research on visible/solar photocatalysis assisted by tungsten trioxide (WO3) has been reported to date. WO3 is physiochemically stable and is mechanically robust in aqueous solutions, while the production of high-purity WO3 is relatively facile and cost-effective, making it a suitable choice for the photocatalytic degradation of organic pollutants under solar irradiation[34,35,36,37,38,39,40,41].
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