Tungsten Trioxide (WO3)-assisted Photocatalytic Degradation of Amoxicillin by Simulated Solar Irradiation

Abstract

This study investigates the photocatalytic degradation of amoxicillin (AMO) by simulated solar irradiation using WO 3 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%).

Sunlight-driven photocatalysis of dissolved organic matter: Tracking by excitation emission matrix-parallel factor analysis and optimization using response surface methodology

“…These experimental runs included a complete factorial design with (2 n ) experiments, 4-star points, and 5 central points. Third, after we obtained the results, the experimental data were fitted to the second-order (quadratic) polynomial models, which had a common expression as follows [21,29,41]:…”

“…The dissolution of ZnO into Zn 2+ and would slow the mass transport rate and consequently reduce the active surface area of ZnO. Second, acidic conditions (i.e., less OH -) were less favorable for the generation of • OH by the hole oxidation of OH -, lowering the efficiency of the attack of hydroxyl radicals on DOM and the photocatalytic oxidation rate [21,27].…”

“…The mechanism of heterogeneous photocatalysis is based on the in-situ generation of highly reactive oxygen species (ROS) (e.g., ⦁ OH, ) which degrade organic pollutants into CO 2 , H 2 O and other inorganic substance by irradiat-ing semiconductor catalysts (e.g., TiO 2 , ZnO, WO 3 , Fe 2 O 3 , CdO, CdS, SnO 2 , etc.) with a light source (e.g., ultraviolet (UV), visible, or solar light) [20][21][22][23]. Typically, the electron-hole pairs ( ) are generated by the light absorption of semiconductor photocatalyst [21][22][23].…”

“…with a light source (e.g., ultraviolet (UV), visible, or solar light) [20][21][22][23]. Typically, the electron-hole pairs ( ) are generated by the light absorption of semiconductor photocatalyst [21][22][23]. Subsequently, the VB hole ( ) reacts with H 2 O and OHto generating hydroxyl radicals ( ⦁ OH), while the CB electrons ( ) reacts with O 2 to generating superoxide radicals ( ) [23][24][25][26].…”

“…However, the amount of UV radiation in sunlight is limited (only 5-7%), greatly restricting practical application of the UV photocatalytic oxidation technology. Sunlight, a renewable, abundant, non-polluting, and cheap energy source [21,26], can be used as a low-cost and sustainable replacement for UV light in the photocatalysis. Additionally, sunlight irradiation has been noted to change the characteristics on DOM [30,31].…”