Efficient degradation of minocycline by natural bornite-activated hydrogen peroxide and persulfate: kinetics and mechanisms

Mimicking the reactivity of drug metabolites: Biomolecule conjugation of an electrochemically-generated, reactive oxidation product of the antibiotic minocycline

Minocycline is an antibiotic of the tetracycline family which is widely used to treat a range of medical conditions. Although it has been in use for more than 50 years, little information is available on its metabolism in the human body. In this study, we simulate the biotransformation of minocycline by means of electrochemistry coupled to mass spectrometry. This analytical technique has already been used successfully in several cases to imitate enzyme-catalyzed reactions. Using this approach, we could show the generation of multiple electrochemical oxidation products which were characterized by tandem mass spectrometry. A N-dealkylated product was found to correspond to a literature-known in vivo metabolite. Two further oxidation products were detected, one of which exhibiting a reactive quinone moiety formed through electrochemical oxidation. The reactivity of this transformation product was assessed by conjugation reactions with glutathione, human hemoglobin and human serum albumin as model biomolecules. For all three peptides, conjugation reactions took place within minutes, corresponding to the number of free cysteine residues in the respective molecule, which are particularly susceptible to electrophiles like quinones. For glutathione, serum albumin and α-hemoglobin, a single conjugation of the reactive transformation product took place, whereas a twofold conjugation was detected for β-hemoglobin. This project showcases the capability of the purely instrumental approach to simulate the metabolism of xenobiotics without an interfering matrix to screen for reactive transformation products and to assess the reactivity of these products with regard to biomolecules.

Enhanced degradation of reactive black 5 via persulfate activation by natural bornite: influencing parameters, mechanism and degradation pathway

Reactive black 5 (RBk5) is a refractory azo dye that constitutes a serious threat to the environment and humans. Herein, natural bornite (Nbo) was utilized to activate persulfate (PDS) for the RBk5 removal. The particle size of the Nbo catalyst was optimized and the RBk5 degradation rate constant that responded positively to the particle size of the Nbo catalyst was exhibited. Then, the operational factors affecting RBk5 removal were comprehensively investigated. With the addition of 1.5 g L-1 Nbo and 1.5 mM PDS, 99.05% of the RBk5 (20 mg L-1) was removed in 150 min compared with 0.46% removal with PDS only, which was caused by the additional reactive oxygen species (ROS) produced by the synergistic action of Fe-Cu bimetallic metal and reductive sulfur species. The Nbo catalyst presented high stability and reusability toward RBk5 removal. Identification of reactive oxygen species revealed that SO 4 ⋅ - , ·OH, O 2 ⋅ - and 1O2 collectively participated in RBk5 removal. Additionally, a possible degradation pathway for RBk5 was proposed, including cleavage of the azo, C-S and S-O bonds, hydroxylation, hydrolyzation, direct oxidation and other pathways. This work developed a highly effective and low-cost natural mineral-based bimetallic sulfide material for PDS activation for the degradation of contaminants and environmental remediation.

Research on carbon black and cerium co-doped Ti4O7-CB-Ce electrocatalytic oxidation of tetracycline-based antibiotics

Elemental doping is a promising way for enhancing the electrocatalytic activity of metal oxides. Herein, we fabricate Ti/ Ti4O7-CB-Ce anode materials by the modification means of carbon black and cerium co-doped Ti4O7, and this shift effectively improves the interfacial charge transfer rate of Ti4O7 and •OH yield in the electrocatalytic process. Remarkably, the Ti4O7-CB-Ce anode exhibits excellent efficiency of minocycline (MNC) wastewater treatment (100% removal within 20 min), and the removal rate reduces from 100 to 98.5% after five cycles, which is comparable to BDD electrode. •OH and 1O2 are identified as the active species in the reaction. Meanwhile, it is discovered that Ti/ Ti4O7-CB-Ce anodes can effectively improve the biochemical properties of the non-biodegradable pharmaceutical wastewater (B/C values from 0.25 to 0.44) and significantly reduce the toxicity of the wastewater (luminescent bacteria inhibition rate from 100 to 26.6%). This work paves an effective strategy for designing superior metal oxides electrocatalysts.

Harnessing the power of natural minerals: A comprehensive review of their application as heterogeneous catalysts in advanced oxidation processes for organic pollutant degradation

The release of untreated wastewater into water bodies has become a significant environmental concern, resulting in the accumulation of refractory organic pollutants that pose risks to human health and ecosystems. Wastewater treatment methods, including biological, physical, and chemical techniques, have limitations in achieving complete removal of the refractory pollutants. Chemical methods, particularly advanced oxidation processes (AOPs), have gained special attention for their strong oxidation capacity and minimal secondary pollution. Among the various catalysts used in AOPs, natural minerals offer distinct advantages, such as low cost, abundant resources, and environmental friendliness. Currently, the utilization of natural minerals as catalysts in AOPs lacks thorough investigation and review. This work addresses the need for a comprehensive review of natural minerals as catalysts in AOPs. The structural characteristics and catalytic performance of different natural minerals are discussed, emphasizing their specific roles in AOPs. Furthermore, the review analyzes the influence of process factors, including catalyst dosage, oxidant addition, pH value, and temperature, on the catalytic performance of natural minerals. Strategies for enhancing the catalytic efficiency of AOPs mediated by natural minerals are explored, mainly including physical fields, reductant addition, and cocatalyst utilization. The review also examines the practical application prospects and main challenges associated with the use of natural minerals as heterogeneous catalysts in AOPs. This work contributes to the development of sustainable and efficient approaches for organic pollutant degradation in wastewater.

Application of FeS-activated persulfate oxidation system for the degradation of tetracycline in aqueous solution

Tetracycline (TC), an antibiotic used to treat bacterial infectious diseases, is easily transferred to environmental matrixes and then sparks environmental concerns. In this study, TC was selected as a target pollutant to investigate the degradation performance of persulfate (PS) based advanced oxidation processes (AOPs) using FeS as the activator (FeS/PS). The results showed that with optimal PS and FeS concentrations of 1 mM and a pseudo-second-order rate constant (k₂) of 3.45 L mmol^-1 min^-1, 91.39% of TC, was effectively removed within 60 min. From the perspective of degradation rate, apart from CO₃^2-, TC decompositions by FeS/PS were hardly disturbed by the coexistence of different concentrations of Cl^-, NO₃^-, SO₄^2-, and humin acid. The degradation of TC under the O₂ bubbling, N₂ bubbling, and light-proof conditions also had limited effects on these AOPs. In addition, FeS exhibited excellent stability and recyclability when used as a PS activator for TC removal. The PS activated by old FeS and used FeS showed nearly identical performances on TC removal compared with the fresh FeS. It is suggested that homogeneous and heterogeneous reactions are jointly responsible for TC oxidation by FeS/PS. With the contributions of the generated, highly reactive SO₄^-•, and, in particular, •OH, TC enabled the mineralization of inorganic products eventually. Therefore, FeS/PS is highly recommended as an alternative AOPs in the future for TC-contaminated wastewater purification.