Chemical Oxidation Research Articles

Anticorrosive and Antibacterial Evaluation of ZnO Nanoscale Sheets Electrosynthesized onto Ti6Al4V and Nitinol Alloys Previously Modified by Chemical Oxidation in H2O2

Anticorrosive and Antibacterial Evaluation of ZnO Nanoscale Sheets Electrosynthesized onto Ti6Al4V and Nitinol Alloys Previously Modified by Chemical Oxidation in H2O2

The Feasibility of Using Electrostatic Interactions for Immobilizing Ru-bda Catalysts in Covalent Organic Framework: A Proof-of-Concept.

Heterogenization of molecular catalysts effectively resolves the separation issues of homogeneous catalysts and expands their application scenarios. In recent years, more and more studies have been using non-covalent interactions to achieve the heterogenization of molecular catalysts. Herein, electrostatic attraction was used to immobilize molecular catalysts, Ru-bda small molecular catalysts in COF materials, where the charged Ru-bda catalysts were immobilized in the oppositely charged COF with a high [Ru] loading content of ~0.2 mmol [Ru] g-1 COF. The leakage experiment verified that the immobilization of Ru-bda catalysts in COF by electrostatic interactions is stable in 0.1 M HClO4 and less than 5 % of molecular Ru-bda catalysts were leached into the solution in 2 hours. The chemical water oxidation experiment was conducted as a model catalysis reaction to verify the feasibility of using electrostatic interactions for immobilizing Ru-bda catalysts in COFs. The prepared Ru(bda)@COFs demonstrate a high catalytic activity of 268 μmol L-1 s-1 O2 for chemical water oxidation, illustrating the electrostatic attractions between COF and small molecules that can be used to immobilize homogeneous catalysts in heterogeneous materials. However, the robustness of COF material itself under catalytic conditions should be considered in practical applications.

3D Bimetallic Platinum‐Nickel Electrodes for Electro‐Oxidation of Glycerol at Ambient Conditions

AbstractPartial electro‐oxidation using renewable electricity offers a sustainable route for valorizing glycerol, a major by‐product of biofuel production. This study introduces a bimetallic electrode with nanostructured platinum dendrites on nickel foam (Pt/NiF), achieving a peak geometric current density of 235 mA cm−2 and a Pt‐mass normalized current density of 3.71 for glycerol electro‐oxidation at 0.92 V versus a reversible hydrogen electrode (RHE) in 3 m KOH electrolyte containing 1 m glycerol, outperforming most previously reported Pt‐containing catalysts. The Pt/NiF electrode demonstrates over 92% cumulative selectivity toward C3 products, with 64% selectivity for lactic acid at 0.65 V versus RHE over 5 h of testing. This research also highlights the role of chemical oxidation pathways (isomerization and rearrangements) in converting glycerol to lactic acid. After 5 h at 0.65 V versus RHE, the Pt/NiF electrode maintains 35% of its initial current density, plateauing at 12.2 mA cm−2 (0.15 ), with performance loss likely due to surface poisoning by carbon‐based reaction intermediates/byproducts or passivating platinum (hydr)oxide species. These findings pave the way for developing low‐platinum group metal catalysts with high glycerol oxidation affinity and highlight the importance of considering chemical transformations during catalyst evaluation and reactor design.

Oxoammonium-Catalyzed Ether Oxidation via Hydride Abstraction: Methodology Development and Mechanistic Investigation Using Paramagnetic Relaxation Enhancement NMR.

Hydride abstraction represents a promising yet underexplored approach in the functionalization of C-H bonds. In this work, we report the oxidation of α-C-H bonds of ethers via oxoammonium catalysis using 3-chloroperbenzoic acid (mCPBA) as the terminal chemical oxidant or by means of electrochemistry. Mechanistic studies revealed intricate equilibria and interconversion events between various catalytic intermediates in the presence of mCPBA, which alone however was incompetent to drive catalytic turnover. The addition of a small amount of strong acid HNTf2 or weakly coordinating salt NaSbF6 turned on catalytic turnover and promoted ether oxidation with excellent efficiency. NMR experiments leveraging paramagnetic relaxation enhancement effect allowed for quantification of open-shell catalytic intermediates in real time during the reaction course, which aided the identification of catalyst resting states and elucidation of reaction mechanisms.

Mechanical properties of poly(ethylene succinate) thin films incorporated with chemical synthesis copper oxide nanoparticles

This study investigates the synthesis and characterization of poly(ethylene succinate) (PES) thin films and their composites with copper oxide (CuO) nanoparticles. CuO nanoparticles were synthesized using a chemical synthesis method, achieving an average size of 20 nm. PES/CuO composites were prepared by incorporating CuO at various concentrations of 0, 1, 3, and 5 wt%. The thin films were produced through solution polymerization followed by casting. Mechanical testing revealed that the tensile strength of pure PES was 25 MPa, while incorporating 1 wt% CuO increased the tensile strength to 30 MPa. At 3 wt%, the tensile strength reached 35 MPa, and at 5 wt%, it peaked at 40 MPa, demonstrating a significant enhancement in mechanical properties. The elongation at break also improved, increasing from 200% for pure PES to 250% for the 5 wt% CuO composite. Characterization of the materials was performed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) to analyze structural and morphological properties. The results confirm that the PES/CuO composites exhibit enhanced mechanical properties, indicating their potential for diverse applications in sustainable materials and biomedical fields.

Formylation facilitates the reduction of oxidized initiator methionines

Within a cell, protein-bound methionines can be chemically or enzymatically oxidized, and subsequently reduced by methionine sulfoxide reductases (Msrs). Methionine oxidation can result in structural damage or be the basis of functional regulation of enzymes. In addition to participating in redox reactions, methionines play an important role as the initiator residue of translated proteins where they are commonly modified at their α-amine group by formylation or acetylation. Here, we investigated how formylation and acetylation of initiator methionines impact their propensity for oxidation and reduction. We show that in vitro, N-terminal methionine residues are particularly prone to chemical oxidation and that their modification by formylation or acetylation greatly enhances their subsequent enzymatic reduction by MsrA and MsrB. Concordantly, in vivo ablation of methionyl-tRNA formyltransferase (MTF) in Escherichia coli increases the prevalence of oxidized methionines within synthesized proteins. We show that oxidation of formylated initiator methionines is detrimental in part because it obstructs their ensuing deformylation by peptide deformylase (PDF) and hydrolysis by methionyl aminopeptidase (MAP). Thus, by facilitating their reduction, formylation mitigates the misprocessing of oxidized initiator methionines.

Kinetic analysis on low‐temperature oxidation of wood pellets by isothermal microcalorimetry

AbstractLow‐temperature chemical oxidation is the major driver of self‐heating during storage of wood pellets and its kinetics is essential to describe the heat evolution. In the present work, isothermal microcalorimetry was used to characterize heat generation behavior of three types of wood pellets (pine, fir, and redwood pellets) at 30–70°C. The obtained data were employed to derive the kinetics of low‐temperature oxidation by the peak power, iso‐conversional method, and non‐steady analysis. The consistency and applicability of the kinetics derived by the three methods were evaluated. Kinetic parameters determined by the peak power method were observed to match those from the iso‐conversional method at lower conversions of the oxidation for heat generation. The kinetics derived by the iso‐conversional method indicated the oxidation reactivity generally decreasing and activation energy increasing with the conversion because of O2 consumption and reaction mechanism changing. With the impact of O2 consumption considered separately, the kinetics from the non‐steady analysis is capable of describing the evolution of heat power with the conversion and also consistent with that from the peak power method in describing intrinsic reactivity of pellet materials. The kinetics from the peak power and iso‐conversional methods lump the impact of O2 concentration with the reaction reactivity, suggesting their applications requiring additional models for connecting with O2 consumption.

Selective Oxidation of Alcohols to Carbonyls Under Decatungstate-Mediated Photoelectrochemical Conditions.

The oxidation of alcohols to the corresponding carbonyl derivatives has been realized under photoelectrochemical conditions in the presence of tetrabutylammonium decatungstate (TBADT) as the homogeneous photocatalyst. The protocol can be applied to both primary and secondary, benzylic and aliphatic alcohols. The desired products are obtained selectively, skipping the need for purposely added chemical oxidants. An in-depth study of photoelectrochemical conditions revealed that the protocol works best under amperostatic conditions in an undivided electrochemical cell irradiated with a 390 nm LED lamp. The comparison with analogous electrochemical and chemical oxidant-promoted photocatalytic transformations demonstrates the superior efficiency and selectivity of the hereby reported photoelectrochemical conditions.

A hybrid oxidation approach for converting high-strength urine ammonia into ammonium nitrate

Nutrient resources contained in human urine have great potential to alleviate global agricultural fertilizer demand. Microbial nitrification is a recognized strategy for stabilizing urine ammonia into ammonium nitrate, a common fertilizer worldwide, but faces a core bottleneck of process instability due to microbial inhibition. This study reports a new approach by developing a hybrid oxidation process involving three stages—microbial ammonia oxidation, chemical nitrite oxidation and microbial nitrite oxidation. Candidatus Nitrosoglobus, a γ-proteobacterial ammonia oxidizer highly tolerant to free nitrous acid, was introduced in the first stage to oxidize half of the total ammonia in the influent (8 g NH4+-N/L) to nitrite. The nitrite was then chemically oxidized by using hydrogen peroxide via a rapid chemical reaction to form nitrate. The third stage, microbial nitrite oxidation, was employed to ensure the complete removal of residual nitrite following chemical oxidation. The overall concept demonstrated in this work showcased the robust performance of the hybrid system. Moreover, the system also had a dual advantage in achieving antimicrobial ability in the first and second stages, making treated urine a safe fertilizer.

Does short-span chemical oxidation induce more weathering than prolonged thermal aging on polypropylene microplastics? Its consequence during the interaction with cadmium

Weathering and degradation of plastics in the environment are evident in almost all conditions. However, the difference is the changes in the polymer properties, which varies with the aging mechanism, polymer type, and other prevailing environmental conditions. Aging is an essential factor that further determines the fate and transportation of smaller plastics. Apart from UV radiation for microplastics (MPs) aging, other mechanisms also play a crucial role in changing the physicochemical properties of polymers in natural environments. Other aging mechanisms, such as chemical and thermal oxidation, were used in this study. Also, thermally stable and chemical resistant polypropylene MP is used in this study to understand the oxidation mechanisms and to know the breakpoint where it becomes susceptible to the reactions. From the results, the aged MPs showed roughness, pore formation, and cracks on the surface; more specifically, PP MPs were more weathered during thermal oxidation, revealed in both physicochemical characterizations of MPs. However, the chemical oxidation reached almost half the aging of the thermal process within a short period. The additives in the PP MPs make it resistant to the treatment, where it takes time to break during the thermal treatment, which was contradictory with Fenton aging. Further, the adsorption study was conducted to determine its interaction with Cd2+ and which aged MPs adsorb more. It can be concluded that PP MPs are more vulnerable towards chemical aging within a short duration, but it takes time to stimulate weathering under increased temperature.

Competition & UV254 projection in odorants vs natural organic matter adsorption onto activated carbon surfaces: Is the chemistry right?

Powdered activated carbon (PAC) adsorption remains an indispensable method for addressing odor problems in drinking water. While natural organic matter (NOM) is ubiquitous and competes strongly in deteriorating odorant adsorption capacity, it can also serve as a promising indicator for predicting odorant adsorption through online measurement. However, the impact of PAC surface chemistry on NOM competition and feasibility of prediction across various adsorbents are not well understood. Here, we examined the role of PAC properties (pore structure and surface chemistry) in the competitive adsorption between odorants and NOM components, aligned with the applicability assessment of using NOM optical properties for odorant adsorption projection across various PAC samples. Chemical oxidation and thermal treatment achieved considerable changes in surface functional group composition, alongside minimal changes in pore structure, of two typical PAC products with microporous/mesoporous pore characteristics. The effect of NOM interference on the reduction of odorant adsorption exhibited a similar level regardless of the PACs with different pore structure (average pore size of 1.7 nm vs. 4.2 nm). Surface modification increased the equilibrium adsorption capacity (qe50) of odorants by 15.1% to 146.4% (thermal treatment) or decreased by -81.3% to -34.1% (chemical oxidation), respectively, but minimal changes in odorant-NOM selectivity. For various odorants, hydrophobicity (log D) influenced the adsorption capacity while the structural flexibility (reflected by the rotatable bonds) affected the vulnerability of odorant adsorption to NOM competition. It was found for the first time that four-parameter Richards model (RMSE = 2.6%) is superior to the linear model (RMSE = 12.5%) or logarithmic model (RMSE = 77.6%) to describe the S-shape UV254 projection curves associated with odorant adsorption on PAC. Moreover, the feasibility was confirmed to use UV254 projection curves of pristine PAC fitted with the Richard model to predict the odorant adsorption on surface-modified PAC in two different surface waters (RMSE 9.2% and 7.4%, respectively). This study provides insight into the role of PAC surface chemistry and pore characteristics in odorant adsorption in NOM-containing waters and enhances the feasibility of the NOM surrogate model for odorant monitor and control during PAC adsorption.

Unusual Paralytic Shellfish Poisoning Toxins in Cayuga Lake, New York

Cyanobacteria blooms were detected in 2017 and 2018 in Cayuga Lake, New York, with paralytic shellfish poisoning toxins (PSPTs) the primary toxin detected. Analysis of these samples by HPLC with chemical oxidation, receptor binding assay, ELISA, and LC-MS/MS confirmed the presence of PSPTs but each method gave highly unusual results based on the theory establishing each method. The structures of the toxins could not be identified and may be ‘unusual’ or unelucidated PSPTs.

Characterization and evaluation of the recovery process of saturated reverse osmosis membranes by chemical oxidation

Characterization and evaluation of the recovery process of saturated reverse osmosis membranes by chemical oxidation

Fabrication and electrochemical investigations of nanostructured PtSn-NiTiO3 heterostructured electrocatalysts for direct methanol oxidation

The methanol oxidation reaction of a PtSn nanoparticle decorated NiTiO3 nanostructured material system is reported in this paper. NiTiO3 and PtSn nanoparticles were formed in rhombohedral and cubic phases, respectively. The crystallite size of the PtSn nanoparticles was calculated to be 2.8 nm from the XRD peak parameters and TEM studies. The surface plasmon resonance peak observed at 308 nm indicates the decoration of PtSn-NiTiO3 nanostructures with Pt nanoparticles on the surface. The chemical oxidation states investigated by XPS showed a metallic state of Pt and Sn with a small amount of surface oxidization. From the electrochemical analysis, the Pt0.5Sn0.5-NiTiO3 nanostructures showed superior electrocatalytic performance with higher electrochemical surface area (252 m2/g), high current density (196 mA/cm2), lower Tafel value (161.31 mV/dec) and small charge transfer resistance. This work demonstrated that the Pt0.5Sn0.5 −NiTiO3 nanostructure would be a suitable electrocatalyst for oxidation for methanol in DMFC.

Synthesis and surface engineering of carbon-modified cobalt ferrite for advanced supercapacitor electrode materials

The precise design and surface modification of electrode materials are crucial challenges for advancing the supercapacitor technology. In this study, we report a straightforward two-step process for the synthesis of a cobalt ferrite (CoFe2O4)/carbon hetero nanostructure. The CoFe2O4 nanoparticles were first synthesized using a simple chemical oxidation method, followed by carbon modification using glucose. The modified samples were calcined at 400 and 600 °C for 4 h in N2 atmosphere to optimize the structural and electrochemical properties.. The increase in the grain size of carbon modified cobalt ferrite magnetic nanoparticles (MNPs) was observed from 22 to 28 nm with post annealing temperature. The presence of carbon was confirmed by the FTIR spectroscopy, FESEM and TEM analyses. The carbon decoration on the cobalt ferrite partially showed a core–shell like morphology. The saturation magnetization of bare cobalt ferrite was observed to be 76 emu/g and the same was decreased by the surface modification with carbon. A high specific capacitance of 323 F/g was observed for the carbon-modified cobalt ferrite MNPs annealed at 600 °C. The electrochemical impedance spectroscopy (EIS) analysis demonstrated that the charge-transfer resistance (Rct) decreased significantly in the carbon-modified CoFe2O4 MNPs, particularly for the sample annealed at 600 °C, with an Rct value of 17 Ω. The carbon layer effectively enhanced conductivity and reduced the electrode/electrolyte interface, led to the improved electrochemical performance, as reflected in the enhanced specific capacitance. An improved capacitance retention of 84 % was achieved in the case of carbon-modified cobalt ferrite MNPs based electrode even after 4000 cycles. The study suggested that the prepared carbon-modified cobalt ferrite MNPs stand in the limelight as a better candidate electrode material for the electrochemical applications.

Catalytic membrane with dual-layer structure for ultrafast degradation of emerging contaminants in surface water treatment

The catalytic membrane-based oxidation-filtration process integrates physical separation and chemical oxidation, offering a highly efficient water purification strategy. However, the oxidation-filtration process is limited in practical applications due to the short residence time of milliseconds within the catalytic layer and the interference of coexisting organic pollutants in real water. Herein, a dual-layer membrane containing a top selective layer and a bottom catalytic layer was fabricated using an in situ co-casting method with a double-blade knife. Experimental results demonstrated that the selective layer rejected macromolecular organic pollutants, thereby alleviating their interference with bisphenol A (BPA) degradation. Concurrently, the catalytic layer activated peracetic acid oxidant and achieved a high BPA degradation exceeding 90 % in milliseconds with reactive oxygen species (especially •OH). The finite-element analysis confirmed a high-concentration reaction field occupying the pore cavity of the catalytic layer, enhancing collision probability between reactive oxygen species and BPA, i.e., the nano-confinement effect. Additionally, the dual-layer membrane achieved a long-term stable performance for emerging contaminant degradation in surface water treatment. This work underscores a novel catalytic membrane structure design for high-performance oxidation-filtration processes and elucidates its mechanisms underlying ultrafast degradation.

Selective Photocatalytic C-H Oxidation of 5-Methylcytosine in DNA.

Selective C-H activation on complex biological macromolecules is a key goal in the field of organic chemistry. It requires thermodynamically challenging chemical transformations to be delivered under mild, aqueous conditions. 5-Methylcytosine (5mC) is a fundamentally important epigenetic modification in DNA that has major implications for biology and has emerged as a vital biomarker. Selective functionalisation of 5mC would enable new chemical approaches to tag, detect and map DNA methylation to enhance the study and exploitation of this epigenetic feature. We demonstrate the first example of direct and selective chemical oxidation of 5mC to 5-formylcytosine (5fC) in DNA, employing a photocatalytic system. This transformation was used to selectively tag 5mC. We also provide proof-of-concept for deploying this chemistry for single-base resolution sequencing of 5mC and genetic bases adenine (A), cytosine (C), guanine (G), thymine (T) in DNA on a next-generation sequencing system. This work exemplifies how photocatalysis has the potential to transform the analysis of DNA.

Heavier Diferrocenylpnictogenium Ions.

The synthesis, characterization and reactivity of the diferrocenylphosphenium ion [Fc2P]+ was extended to the heavier diferrocenylpnictogenium ions, [Fc2E]+ (E = As, Sb, Bi). The lighter diferrocenylnitrenium ion, [Fc2N]+, was detected by mass spectrometry, but could not be isolated. The molecular structures of [Fc2E]+ (E = P, As, Sb, Bi) reveal intramolecular coordination of the iron atoms, which counterbalance the electron deficiency of the pnictogens without affecting the strong Lewis acidities, which were determined according to the method of Gutmann and Beckett. The (electro-)chemical oxidation and reduction afforded the dications [Fc2E]2+ (E = P (unstable), As) and the neutral dipnictogens Fc2EEFc2 (E = P, As).

Synergistic Effects of Polydopamine/Medical Stone Bio-Adsorbents for Enhanced Interfacial Adsorption and Dynamic Filtration of Bacteria.

Polymer-based wastewater disinfection, which is typically performed using chemical oxidation or irradiation, can result in various toxic byproducts and corrosion under harsh environments. This study introduces a robust bio-adsorbent prepared from naturally abundant polydopamine-modified medical stone (MS@PDA) for the high-efficiency removal of bacteria from water. The PDA nanocoating can be easily applied through an in situ self-polymerization process, resulting in a considerably high bacterial adsorption capacity of 6.6 k pcs mm-2 for Staphylococcus aureus. A cyclic flow-through dynamic filtration and a disinfection system was implemented using an MS@PDA porous filter with an average pore size of 21.8 ± 1.4 µm and porosity of ~83%, achieving a 5.2-6.0-fold enhancement in the cumulative removal efficiency for MS@PDA2. The underlying mechanisms were elucidated through the synergistic effects of interfacial bio-adsorption and size-dependent interception. Notably, the bacteria captured on the surface could be killed using the enhanced photothermal effects of the PDA nanocoating and the inherent antimicrobial properties of the mineral stone. Thus, this study not only provides a new type of advanced bio-adsorbent but also provides new perspectives on an efficient and cost-effective approach for sustainable wastewater treatment.

Solar Selectivity of Silver Nanoparticles Modified Copper Oxide Nanocomposite Thin Films Prepared by Facile Chemical Oxidation Method

AbstractSilver nanoparticles modified copper oxide nanocomposite thin films (Ag‐CuO NC TFs) and pristine CuO TF were successfully synthesized on copper substrates using a chemical oxidation route. X‐ray diffractometry (XRD) characterization of Ag‐CuO NC TFs revealed the formation of monoclinic crystal structured CuO. Scanning electron microscopy (SEM) images showed a star‐like grain morphology of the Ag‐CuO NC TFs. Energy dispersive X‐ray spectroscopy (EDX) analysis ascertained the presence of anticipated elements without impurities. Fourier transform infrared spectroscopy (FTIR) investigation confirmed the presence of Ag NPs on CuO in the Ag‐CuO NC TFs. Raman spectroscopy examination indicated the presence of a spinel structure with vibrational and tetrahedral sites. UV‐Vis‐NIR reflectance analysis demonstrated that Ag‐CuO NC TFs with 2.0 wt.% Ag NPs exhibited solar absorptance of 72.39 %, thermal emittance of 4.3 %, and a highest solar selectivity of 16.83 among the prepared thin films. These results suggest that the Ag‐CuO NC TFs could be promising candidates for use as solar selective absorbers in solar thermal energy conversion devices.