Catalytic ozonation of chloramphenicol with manganese-copper oxides/maghemite in solution: Empirical kinetics model, degradation pathway, catalytic mechanism, and antibacterial activity

Abstract Rampant water pollution events and rising water demand caused by exponential population growth and depleting freshwater resources speak of an impending water crisis. The inability of conventional wastewater treatment systems to remove Contaminants of Emerging Concern (CEC) such as Bisphenol-A (BPA) beckons for new and efficient technologies to remove them from wastewater and water sources. Advanced oxidation processes such as ozonation are primarily known for their capability to oxidize and degrade organic entities in water but optimum mineralization levels were hard to achieve. In this study, we synthesized an activated carbon impregnated nanocomposite-bimetallic catalyst (AC/CeO2/ZnO) and used it along with ozonation to remove BPA from water. The catalyst was characterized using BET, XRD, FESEM, Raman spectra, and DLS studies. Catalytic ozonation achieved TOC removal 25% higher than non-catalytic ozonation process. The degradation pathway of BPA was proposed using LC-MS/LC-Q-TOF studies that found six main aromatic degradation byproducts. Catalytic ozonation and non-catalytic ozonation followed similar degradation pathways. The formation of persistent aliphatic acidic byproducts in the treated sample made TOC removal above 61% difficult.

Download Full-text

Facet Engineered α-MnO2 for Efficient Catalytic Ozonation of Odor CH3SH: Oxygen Vacancy-Induced Active Centers and Catalytic Mechanism

Environmental Science & Technology ◽

10.1021/acs.est.0c05235 ◽

2020 ◽

Vol 54 (19) ◽

pp. 12771-12783

Author(s):

Chun He ◽

Yunchen Wang ◽

Zhiyao Li ◽

Yajing Huang ◽

Yuhong Liao ◽

...

Keyword(s):

Oxygen Vacancy ◽

Catalytic Mechanism ◽

Catalytic Ozonation ◽

Active Centers

Download Full-text

Catalytic ozonation of thymol in reverse osmosis concentrate with core/shell Fe 3 O 4 @SiO 2 @Yb 2 O 3 catalyst: Parameter optimization and degradation pathway

Chinese Journal of Chemical Engineering ◽

10.1016/j.cjche.2016.10.017 ◽

2017 ◽

Vol 25 (5) ◽

pp. 665-670 ◽

Cited By ~ 1

Author(s):

Liang Wang ◽

Anqi Liu ◽

Zhaohui Zhang ◽

Bin Zhao ◽

Yingming Xia ◽

...

Keyword(s):

Reverse Osmosis ◽

Parameter Optimization ◽

Degradation Pathway ◽

Catalytic Ozonation ◽

Core Shell

Download Full-text

Catalytic activity of aluminum silicate for ozonation of chloronitrobenzenes in aqueous solution

Water Science & Technology Water Supply ◽

10.2166/ws.2013.121 ◽

2013 ◽

Vol 13 (6) ◽

pp. 1437-1443

Author(s):

Y. Liu ◽

J. M. Shen ◽

Z. L. Chen ◽

L. Yuan ◽

Y. Liu

Keyword(s):

Catalytic Mechanism ◽

Chemical Oxidation ◽

Butyl Alcohol ◽

Catalytic Ozonation ◽

Degradation Efficiency ◽

Polluted Water ◽

Aluminum Silicate ◽

Obvious Effect ◽

Water Matrix ◽

Attractive Option

Chemical oxidation using ozone with appropriate catalysts offers an attractive option for removing inhibitory and toxic pollutants in micro-polluted water. This work investigated the catalytic ozonation of three chloronitrobenzenes (CNBs, i.e. p-CNB, o-CNB, and m-CNB) in the presence of a novel and efficient synthesized aluminum silicate catalyst. Experiments were carried out with focus on the degradation efficiency of CNBs at different reaction pH values, water matrices and repeated uses, as well as the possible catalytic mechanism. Regardless of the water matrix, the results showed that the catalytic ozonation had considerably higher degradation efficiency of CNBs than the single ozonation process at the same ozone dose. The change of pH had an obvious effect on the removal efficiency of CNBs, which suggested that the aluminum silicate catalyst was more appropriate for application in the neutral pH condition. Ozonation processes in the presence of the aluminum silicate were significantly influenced by tert-butyl alcohol, which confirmed that the aluminum silicate catalytic ozonation followed a hydroxyl radical-type mechanism.

Download Full-text

Structural, Mechanistic, and Functional Insights into an Arthrobacter nicotinovorans Molybdenum Hydroxylase Involved in Nicotine Degradation

Molecules ◽

10.3390/molecules26144387 ◽

2021 ◽

Vol 26 (14) ◽

pp. 4387

Author(s):

Lei Wang ◽

Xia Mu ◽

Wenjin Li ◽

Qin Xu ◽

Ping Xu ◽

...

Keyword(s):

Structural Model ◽

Catalytic Mechanism ◽

Catalytic Efficiency ◽

Degradation Pathway ◽

Site Directed Mutagenesis ◽

Functional Study ◽

Iron Sulfur Clusters ◽

Nicotine Degradation ◽

Arthrobacter Nicotinovorans ◽

Important Enzyme

Arthrobacter nicotinovorans decomposes nicotine through the pyridine pathway. 6-hydroxypseudooxynicotine 2-oxidoreductase (also named ketone dehydrogenase, Kdh) is an important enzyme in nicotine degradation pathway of A. nicotinovorans, and is responsible for the second hydroxylation of nicotine. Kdh belongs to the molybdenum hydroxylase family, and catalyzes the oxidation of 6-hydroxy-pseudooxynicotine (6-HPON) to 2,6-dihydroxy-pseudooxynicotine (2,6-DHPON). We determined the crystal structure of the Kdh holoenzyme from A. nicotinovorans, with its three subunits KdhL, KdhM, and KdhS, and their associated cofactors molybdopterin cytosine dinucleotide (MCD), two iron-sulfur clusters (Fe2S2), and flavin adenine dinucleotide (FAD), respectively. In addition, we obtained a structural model of the substrate 6-HPON-bound Kdh through molecular docking, and performed molecular dynamics (MD) and quantum mechanics/molecular mechanics (QM/MM) calculations to unveil the catalytic mechanism of Kdh. The residues Glu345, Try551, and Glu748 of KdhL were found to participate in substrate binding, and Phe269 and Arg383 of KdhL were found to contribute to stabilize the MCD conformation. Furthermore, site-directed mutagenesis and enzymatic activity assays were performed to support our structural and computational results, which also revealed a trend of increasing catalytic efficiency with the increase in the buffer pH. Lastly, our electrochemical results demonstrated electron transfer among the various cofactors of Kdh. Therefore, our work provides a comprehensive structural, mechanistic, and functional study on the molybdenum hydroxylase Kdh in the nicotine degradation pathway of A. nicotinovorans.

Download Full-text

Amoxicillin in Water: Insights into Relative Reactivity, Byproduct Formation, and Toxicological Interactions during Chlorination

Applied Sciences ◽

10.3390/app11031076 ◽

2021 ◽

Vol 11 (3) ◽

pp. 1076

Author(s):

Antonietta Siciliano ◽

Marco Guida ◽

Giovanni Libralato ◽

Lorenzo Saviano ◽

Giovanni Luongo ◽

...

Keyword(s):

Antibacterial Activity ◽

Wastewater Treatment ◽

Wastewater Treatment Plants ◽

Parent Compound ◽

Treatment Plant ◽

Parent Drug ◽

Degradation Pathway ◽

Hplc Method ◽

Consistent Finding ◽

Byproduct Formation

In recent years, many studies have highlighted the consistent finding of amoxicillin in waters destined for wastewater treatment plants, in addition to superficial waters of rivers and lakes in both Europe and North America. In this paper, the amoxicillin degradation pathway was investigated by simulating the chlorination process normally used in a wastewater treatment plant to reduce similar emerging pollutants at three different pH values. The structures of 16 isolated degradation byproducts (DPs), one of which was isolated for the first time, were separated on a C-18 column via a gradient HPLC method. Combining mass spectrometry and nuclear magnetic resonance, we then compared commercial standards and justified a proposed formation mechanism beginning from the parent drug. Microbial growth inhibition bioassays with Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus were performed to determine the potential loss of antibacterial activity in isolated degradation byproducts. An increase of antibacterial activity in the DPs was observed compared to the parent compound.

Download Full-text

Structural Insights into Regulation of Quinate Degradation in Bacteria

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314085945 ◽

2014 ◽

Vol 70 (a1) ◽

pp. C1405-C1405

Author(s):

Stephanie Prezioso ◽

Dinesh Christendat

Keyword(s):

Catalytic Mechanism ◽

Shikimate Pathway ◽

Aromatic Amino Acids ◽

Degradation Pathway ◽

Structural Basis ◽

Shikimate Dehydrogenase ◽

Fourth Step ◽

Key Residues ◽

Structural Insights ◽

Lysr Family

The shikimate pathway is an essential metabolic pathway in bacteria, as well as plants and fungi, which ultimately leads to the synthesis of three aromatic amino acids among other important aromatic compounds. The fourth step in the pathway is the reduction of dehydroshikimate to shikimate, catalyzed by shikimate dehydrogenase (SDH/AroE). In addition to AroE, at least four functionally distinct SDH homologs exist in bacteria. The structure and catalytic residues of the SDH enzyme family are highly conserved, however the key residues for substrate binding vary among the different homologs. Together, these data suggest that the catalytic mechanism is maintained among homologs, yet each may bind a different substrate. The YdiB homolog catalyzes the first step in the quinate degradation pathway, which is a branch of the shikimate pathway. In various species, the operons containing the ydiB gene are predicted to be controlled by one of two different transcriptional regulators belonging to either the TetR or LysR family. In both cases, these regulators are predicted to be activated or repressed by intermediates of the quinate degradation pathway. We will be using structural biology to determine how these regulators recognize pathway intermediates, and to understand the structural basis of how two distinct regulators can control transcription of the equivalent operon in different species.

Download Full-text