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Degradation of antibiotic amoxicillin using 1 x 1 molecular sieve-structured manganese oxide
Wen-Hui Kuan1, Ching-Yao Hu2, Bin-Sheng Liu3
1Department of Safety, Health and Environmental Engineering, Ming Chi University of Technology, New Taipei City, Republic of China. whkuan@mail.mcut.edu.tw
Abstract:
The kinetics and mechanism ofamoxicillin (AMO) degradation using a 1 x 1 molecular sieve-structured manganese oxide (MnO2) was studied. The presence of the buffer solution (i.e., NaHCO3, NaH2PO4 and KH2PO4) diminished AMO binding to MnO2, thus reducing AMO degradation in the pretest; therefore, all other experiments in this study were conducted without the addition of a buffer. Third-order rate constants, second-order on AMO and first-order on MnO2 increased with elevating pH level (2.81-7.23) from 0.54 to 9.17 M(-2) s(-1), and it decreased to 4.27 M(-2) s(-1) at pH 8.53 beyond the pk(a2) of AMO (7.3). The dissolution of the MnO2 suspension with and without AMO exhibited a similar trend; that is, Mn2+ concentration increased with decreasing pH. However, the dissolution of MnO2 with AMO was greater than that without AMO, except for the reaction occurring at pH 8.53, partially indicating that MnO2 acts as an oxidant in AMO degradation. The preliminary chromatogram data display different products with varying pH reaction s, implying that AMO elimination using this 1 x 1 molecular sieve-structured MnO2 is by adsorption as well as oxidative degradation. A complementary experiment indicates that the amount of oxidatively degraded AMO increases substantially from 65.5% at 4 h to 95% at 48 h, whereas the AMO adsorbed onto MnO2 decreases slightly from 4.5% at4 h to 2.4% at 48 h. The oxidative degradation accounted for more AMO removal than adsorption over the whole reaction course, indicating that the oxidative reaction of AMO on MnO2 dominated the AMO removal.
Insights
Manganese oxide (MnO2) effectively degrades amoxicillin (AMO) through oxidative processes, with degradation rates increasing at higher pH levels. Oxidative degradation is the primary removal mechanism, surpassing adsorption over time.
Area of Science:
- Environmental Chemistry
- Materials Science
- Chemical Engineering
Background:
- Amoxicillin (AMO) is a widely used antibiotic, and its removal from the environment is crucial.
- Manganese oxide (MnO2) with a 1x1 molecular sieve structure shows potential for pollutant degradation.
- Understanding the degradation kinetics and mechanisms is essential for effective remediation strategies.
Purpose of the Study:
- To investigate the kinetics and mechanism of amoxicillin (AMO) degradation using 1x1 molecular sieve-structured manganese oxide (MnO2).
- To determine the influence of pH on the degradation rate and mechanism.
- To elucidate the roles of adsorption and oxidative degradation in AMO removal by MnO2.
Main Methods:
- Kinetic studies of AMO degradation by MnO2 at various pH levels (2.81-8.53).
- Analysis of Mn2+ concentration in MnO2 suspension with and without AMO.
- Chromatographic analysis to identify degradation products and complementary experiments to quantify adsorption and oxidative degradation.
Main Results:
- Third-order rate constants increased with pH from 2.81 to 7.23, peaking at 9.17 M(-2) s(-1), and decreased at pH 8.53.
- MnO2 dissolution increased with decreasing pH, and was greater with AMO present (except at pH 8.53), indicating MnO2 acts as an oxidant.
- Oxidative degradation (95% at 48h) was the dominant removal mechanism for AMO compared to adsorption (2.4% at 48h).
Conclusions:
- 1x1 molecular sieve-structured MnO2 effectively degrades amoxicillin primarily through oxidative pathways.
- pH significantly influences the degradation kinetics, with optimal performance observed in the acidic to neutral range.
- The study highlights MnO2 as a promising material for the oxidative removal of amoxicillin from aqueous environments.
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