Permanganate Research Articles

Enhanced removal of phenolic contaminants with permanganate oxidation mediated by SiO2@TEMPO: Performance, transformation pathway, and selectivity

The core bottleneck in water decontamination lies in trigging the selective removal of trace contaminants in the presence of complex water matrices, overcoming the inevitable consumption of oxidants and energy input by the water matrix. Here, the selective removal of phenolic contaminants with permanganate (PM) oxidation mediated by 2,2,6,6-tetramethylpiperidinooxy (TEMPO)-functionalized silica (SiO2@TEMPO) was firstly reported. SiO2@TEMPO was synthesized by covalently bonding 4-oxo-2,2,6,6-tetramethylpiperidinooxy onto SiO2 through a 3-aminopropyltriethoxysilane bridge. The loading capacity of Wt% for nitrogen element in SiO2@TEMPO are 1.01–1.27 %. The degradation rate of tetracycline (around 1.50 min−1) with SiO2@TEMPO/PM are around 15 folds higher than that with PM, attributed to the formation of the reactive N-oxoammonium cation via single-electron transfer during PM oxidation. SiO2@TEMPO exhibited excellent stability and recyclability after five consecutive cycles of tetracycline degradation. Three transformation pathways (hydroxylation, demethylation, and dehydration) for tetracycline degradation by SiO2@TEMPO/PM were proposed based on the identification of 36 transformation products using HPLC/Q-Orbitrap HRMS. Thereinto, the attack of the N-oxoammonium cation in SiO2@TEMPO on the phenolic hydroxyl group to form corresponding hydroxylation and quinylation products accounted for the dominant degradation pathway. SiO2@TEMPO/PM also demonstrated remarkable adaptability across a wide pH range of 5.0–9.0, indicating its potential for practical applications. The significant resistance to the inhibitory effects of co-existing water matrix components (humic acid, cations and anions), along with the marked differences in degradation efficiency between phenolic and non-phenolic contaminants, demonstrate the selectivity of SiO2@TEMPO/PM towards phenolic contaminants. These results offer new insights into the selective removal of phenolic contaminants and pave the way for the development of efficient and sustainable strategies for water remediation.

Sustainable synthesis and environmental application of chitosan-Ocimum basilicum leaves-ZnO composite membrane for permanganate ion removal in wastewater treatment.

This study introduces a novel and environmentally friendly method for developing a cross-linked chitosan-Ocimum basilicum leaves-ZnO (ChOBLZnO) composite membrane, specifically designed for the adsorption of permanganate ions (MnO4-) from wastewater. Various characterization techniques, including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) surface area analysis, were employed to confirm the membrane's synthesis quality, structural integrity, and surface properties crucial for adsorption. The BET analysis revealed a surface area of 228.64 m2/g, indicating a highly porous structure. The membrane exhibited a high adsorption capacity of 142.8mg/g and an outstanding removal efficiency of 98.5%. The adsorption kinetics were best described by the pseudo-second-order model, with a correlation coefficient (R2) of 0.998, while the Freundlich isotherm model provided the most accurate fit for the adsorption behavior, with an R2 of 0.995. Thermodynamic studies indicated that the adsorption process is spontaneous and endothermic, with negative Gibbs free energy and positive enthalpy and entropy values. Reusability tests showed that the ChOBLZnO composite membrane maintained a high removal efficiency across five cycles, with minimal performance loss. These results demonstrate the ChOBLZnO composite membrane's potential as an efficient and sustainable solution for wastewater treatment, offering both high efficiency and durability.

Enhanced degradation of bisphenol A through electroreduction of potassium permanganate activated by periodate

This study is first to elucidate the efficacy of electrochemical activation of periodate (PI) by permanganate (PM) in enhancing the degradation of bisphenol A (BPA) over a wide pH spectrum. Utilizing a current density of 4 mA/cm2, 200 μM PI, and 20 μM PM, the proposed system achieved a 99.8 % degradation of 40 μM BPA within 30 min and a 65.5 % total organic carbon (TOC) removal in 120 min. The combined system yielded a synergistic coefficient of 15.23 for BPA degradation, and energy efficiency of 0.14 KWh•m−3. The exceptional performance is attributed to the reduction of PM to low-valent manganese species at the cathode, which facilitates the activation of PI. Additionally, the system preserved high BPA degradation efficiency across a pH range of 3–11. Radical quenching and electron paramagnetic resonance spectroscopy experiments confirmed the pivotal role of singlet oxygen in the degradation process. Furthermore, the system exhibited relative insensitivity to actual water matrix constituents, including inorganic ions and humic acid. In conclusion, the proposed system constitutes an eco-friendly treatment process for BPA removal characterized by low energy consumption.

Optimization of an Aqueous Zn-Mn Redox Flow Battery System

Zinc-based negative electrodes are chosen for their cost-effectiveness, low equilibrium potential, and high electrochemical reversibility, making them widely utilized in redox flow batteries. To achieve a high cell voltage, zinc electrodes are usually paired with positive half-cells featuring high equilibrium potentials, such as Zn-air and Zn-Br systems [1]. The work investigates the feasibility of an alkaline redox flow battery with high energy density and operating voltage involving Zn/ Zn(OH)₄2- and MnO₄⁻/MnO₄²⁻ redox couples. The study focuses on the less-explored permanganate half-cell, which offers a high equilibrium potential (+0.55 V vs SHE) and excellent solubility in alkaline conditions (~3.6 M). These properties make it a promising candidate for positive electrolytes with high energy density [2]. In the study, the electrolytes of the two cells were optimized separately to increase conductivity and avoid side reactions. Cyclic voltammetry experiments at different scan rates confirm the excellent reversibility of electrochemical reactions in both the zinc and permanganate-based electrolytes, characterized by high faradic efficiency. Subsequently, a prototype flow battery is assembled and subjected to galvanostatic charge/discharge tests to assess stability and performance. The cell is evaluated at varying catholyte concentrations and different current densities to determine rate performance. The galvanostatic tests demonstrate remarkable cycling stability and notable cell potential compared to other aqueous systems. The battery exhibits high energetic efficiency (EE > 75%) and Coulombic efficiency (CE) and voltage efficiency (VE) both around 85%. Capacity tests at full charge reveal stable electrochemical reactions throughout the charging and discharging processes. Additionally, ex-situ UV-vis spectroscopy is employed to investigate the mechanism of the manganate/permanganate redox reaction and evaluate the permeability of permanganate ions through membranes during cycling. Overall, the study provides significant insights into the development of high-voltage aqueous batteries. The alkaline Zn-MnO₄⁻ flow battery described in this work emerges as a promising candidate for energy storage applications, offering enhanced stability, high energy efficiency, and energy density.

Unveiling the critical roles of nascent MnO2 in accelerating permanganate carbocatalysis

To probe the underlying mechanisms of carbocatalysis in enhanced permanganate (PM) oxidation and identify the exact roles of nascent MnO2, graphene aerogels (GA) were fabricated to activate PM for naproxen (NPX) degradation. All the three GA samples could accelerate NPX oxidation by PM, the rate constants and reaction stoichiometric efficiency (RSE) followed the order of GA900 > GA600 > GA300. Mechanistic studies revealed that Mn(VI), Mn(V) and Mn(III) were not the major reactive species involved in NPX oxidation, but highlighted the essential contribution of electron transfer pathway (ETP) mediated directly by GA and indirectly by nascent MnO2. For GA300 with strong electron-donating capability, it mainly served as the electron donor for PM decomposition, and indirectly oxidized NPX via nascent MnO2 mediated ETP, thereby exhibiting inferior RSE as well as mediocre recycling performance. GA600 and GA900 could serve as the electron shuttle to directly mediate the ETP for NPX degradation, the nascent MnO2 accumulated on GA framework during the reaction would also mediate the ETP from NPX to PM, thus displaying an obvious accelerating recycling performance. This work provides novel insights into the structure-dominated PM carbocatalysis, which contributes better to development of promising carbocatalysts and utilization of nascent MnO2.

Visible light activation of permanganate by nitrogen vacancy-modified g-C3N4: Insight into the role of photo-generated electrons and holes

The photo-activation of permanganate (PM) for pollutant degradation in water has garnered significant interest due to its potential, yet it is impeded by efficiency constraints. In this study, the nitrogen-vacancy (NV) engineered graphitic carbon nitride (CN) catalysts with high light absorption, well photocarrier separation, and robust photoreduction capability were employed to activate PM under visible light irradiation (Vis) for sulfadiazine degradation. A high first-order rate constant of 0.185 min−1 was observed with the Vis/PM/NV-modified CN system, which was 25.2 and 7.1 times greater than those from Vis/PM and Vis/PM/CN system respectively. More interestingly, it was found that PM predominantly engaged with photo-generated holes as Lewis acid sites, elevating its oxidation potential and concurrently stimulating the production of photo-generated electrons. Meanwhile, dissolved oxygen (DO) was reduced by photo-generated electrons to form superoxide ions, singlet oxygen, and hydroxyl radicals. These produced reactive species through the synergistic activation of PM and DO, finally participated in the degradation of pollutants. Furthermore, the versatility and reusability of NV-CN catalysts were assessed under different reaction conditions, demonstrating promising prospects for practical applications. The results will contribute to a comprehensive understanding of the mechanism of photoactivation of PM for pollutant degradation.

Influence of surface properties of transition metal oxides for permanganate activation: Key role of Lewis acid sites

Permanganate (PM) activation to remove contaminants in aqueous solution has gained increasing interest, and effective approaches to enhance its oxidation ability are becoming one of the hot spots. Transition metal oxides (TMOs) stand out as the most potential catalysts, but have received little attention in this area until now. Their mechanism towards PM activation also remains controversial. In this study, a series of TMOs with diverse surface properties were synthesized, and their effectiveness was compared. It was observed that α-MnO2, NiO and Co3O4 exhibited significantly higher rates of degrading sulfadiazine, levofloxacin and phenol through PM activation than CeO2, α-Fe2O3 and CuO. A performance evolution depended on the surface Lewis acid (LA) strength was established, while a less consistent correlation was observed between the degradation rate and other surface properties. Based on electrochemical analysis and density functional theory calculations, the spontaneous adsorption of MnO4- anions on LA sites in TMOs with an increase in oxidation potential of PM was further confirmed. This research would deepen the understanding of PM activation mechanism, and offer new guidance in the design of more efficient catalysts.

Selective Detection of Chromate and Permanganate Ions Using Gallic Acid Capped CaF2:Tb3+ Nanocrystals.

In this study, we have developed ligand-sensitized Ln3+-doped nanocrystals (NCs) for the selective sensing of Cr2O7 2- and MnO4 - ions in nanomolar concentrations. This is accomplished with the gallic acid capped-CaF2:Tb3+ NCs. These NCs display bright green emission through an efficient energy transfer from surface functionalized gallic acid molecules to Tb3+ ions upon UV light excitation. The luminescence from Tb3+ ions are selectively quenched by the addition of Cr2O7 2- and MnO4 - anions. The reduction in the luminescence intensity is found to be quite selective, as the addition of other strong oxidizing species (I-, F-, Br-, Cl-, PO3 2-, SO4 2-, VO3 -, WO4 2-, IO3 -, ClO4 -,) had minimal impact on the luminescence intensity of Tb3+ ions. The calculated limit of detection from the experimental results (for the 3σ/slope criterion) is 77 nM and 55 nM for K2Cr2O7 and KMnO4, respectively. The findings show that tuning the resonance energy transfer (RET) between analytes and Tb3+ inside the NCs serves as a tool for the detection of dichromate and permanganate ions selectively.

Multifunctional nitrogen-sulfur codoped carbon quantum dots: Determining reduced glutathione, broad-spectrum antibacterial activity, and cell imaging

In this study, nitrogen-sulfur codoped carbon quantum dots (N-S/CQDs) with various functions and properties were synthesized through a one-step method utilizing citric acid and cysteine as reaction substrates. The fluorescence of N-S/CQDs can be specifically quenched by permanganate ion (MnO4−), and the quenched fluorescence can be recovered by the presence of reduced glutathione (GSH). A fluorescence sensing system based on N-S/CQDs@MnO4− was developed and successfully applied for the determination of GSH in pharmaceutical preparations. Additionally, N-S/CQDs demonstrated broad-spectrum antibacterial activity, with minimum inhibitory concentrations of 32 μg/ml against Staphylococcus aureus (gram-positive bacterium) and 64 μg/ml against Escherichia coli (gram-negative bacterium). N-S/CQDs also proved effective for cell imaging, exhibiting excellent biocompatibility. These findings underscore the multifunctional characteristics and promising application potential of N-S/CQDs. Furthermore, this study provides a solid foundation for the development of multifunctional carbon quantum dots and the expansion of their applications in various fields.

An Unprecedented Tridentate-Bridging Coordination Mode of Permanganate Ions: The Synthesis of an Anionic Coordination Polymer-[CoIII(NH3)6]n[(K(κ1-Cl)2(μ2,2',2″-(κ3-O,O',O″-MnO4)2)n∞]-Containing Potassium Central Ion and Chlorido and Permanganato Ligands.

A unique compound (compound 1) with structural features including an unprecedented tridentate-bridging coordination mode of permanganate ions and an eight-coordinated (rhombohedral) κ1-chlorido and tridentate permanganato ligand in a potassium complex containing coordination polymer (CoIII(NH3)6]n[(K(κ1-Cl)2(μ2,2',2″-(κ3-O,O',O″-MnO4)2)n∞) with isolated regular octahedral hexamminecobalt(III) cation was synthesized with a yield of >90%. The structure was found to be stabilized by mono and bifurcated N-H∙∙∙Cl and N-H∙∙∙O (bridging and non-bridging) hydrogen bonds. Detailed spectroscopic (IR, far-IR, and Raman) studies and correlation analysis were performed to assign all vibrational modes. The existence of a resonance Raman effect of compound 1 was also observed. The thermal decomposition products at 500 °C were found to be tetragonal nano-CoMn2O4 spinel with 19-25 nm crystallite size and KCl. The decomposition intermediates formed in toluene at 110 °C showed the presence of a potassium- and chloride-containing intermediates combined into KCl during aqueous leaching, together with the formation of cobalt(II) nitrate hexahydrate. This means that the CoIII-CoII redox reaction and the complete decomposition of the permanganate ions occurred in the first decomposition step, with a partial oxidation of ammonia into nitrate ions.

A 1H-imidazo[4,5-f][1,10]phenanthroline based ligand and its binuclear Cu(I) complexes: Syntheses, structures and luminescence sensing for Cr2O72− and MnO4−

Dichromate (Cr2O72−) and permanganate (MnO4−) ions have been important targets for sensing and detection in the field of luminescent complexes and their corresponding ligands due to their significant impact on the ecological environment and human health. However, many Cu(I) complexes with good room-temperature phosphorescence are rarely used as luminescent sensors for ions in water due to the insolubility and the disproportionation of the Cu(I) ion. Herein, 2,6-di-1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl-4-tertbutylphenol (diptpH3) and its two luminescent binuclear Cu(I) complexes, [Cu(diptpH3)(POP)]ClO4 (1) and [Cu(diptpH3)(xantphos)]ClO4 (2), were designed and synthesized (POP = bis[(2-diphenylphosphino)phenyl] ether, and xantphos = 9,9-dimethyl-4,5-bis(diphenylphosphino)-9H-xanthene). All compounds in DMSO/H2O (1: 9, v: v) show high stability to water, which was confirmed by the results of electrospray ionization mass spectrometry (ESI-MS). Cr2O72− and MnO4− ions showed high luminescence quenching coefficients (Cr2O72−: 3.042 × 104 − 2.946 × 105 M−1; MnO4−: 1.476 × 104 − 2.254 × 105 M−1) for all the three compounds. DiptpH3, complexes 1 and 2 exhibited good luminescent sensing properties toward Cr2O72− and MnO4− ions with short response times, good selectivity and low detection limits (Cr2O72−: 1.845 × 10−7 − 2.359 × 10−6 mol⋅L−1; MnO4−: 1.850 × 10−7 − 6.221 × 10−6 mol⋅L−1) in DMSO/H2O. The plausible sensing mechanisms were fully discussed.

Investigation of the Activity and Stability of Manganese-Based Electrocatalysts for the Electrochemical Oxidation of Water and Small Organic Molecules in Acidic Electrolyte

Water electrolysis is a crucial process for hydrogen production, providing a clean and sustainable method for H2 production. Iridium-based catalysts are particularly effective in promoting the oxygen evolution reaction (OER) that takes place at the anode of electrolyzers. The unique properties of iridium make it well-suited for this purpose, but its high cost becomes a bottleneck in making water electrolysis economically viable on a large scale. Manganese-based electrocatalysts have emerged as promising candidates for the OER, mainly due to their earth abundance, low toxicity, and activity. It has been shown that manganese oxide can operate stably in acid, in a restricted potential window, where the formation of permanganate ions is avoided. Thus, for practical application, the stability must be improved, so a larger potential window can be employed. To address this challenge, some approaches have emerged from combining a catalytically active, but instable oxide, with the one that is stable, but inactive for the OER. In the presentation, we will show the results of activity, stability, and faradaic efficiency (FE) for O2 formation for water electro-oxidation on manganese oxide, and on manganese oxide combined with antimony, tin, titanium, niobium, and silicon oxide. The faradaic efficiencies, determined via EC-MS (Electrochemistry coupled to mass spectrometry) measurements revealed that manganese antimonate and pure manganese oxide have the highest values for O2 formation, with the former presenting higher stability at high overpotentials. We will discuss the obtained trends in stability and FEs for the other synthesized oxides. Additionally, for these two most efficient electrocatalysts, EC-MS measurements were conducted for the electrochemical oxidation of some small organic molecules, such as formic acid, methanol, ethanol, and ethylene glycol (electrochemical reforming for H2 production). The results showed that the selectivity for the electro-oxidation of water and/or of the organic molecule (monitoring the formation of CO2) strongly depends on the catalyst composition and on the number of carbon atoms of the molecule. We will further discuss, in the presentation, the factors that govern the selectivity and stability for each case. The obtained results of this study may be helpful for developing more efficient, selective and, mainly, more stable earth-abundant electrocatalysts for electrolyzers.

Enhanced Nickel Recovery from Mixed Hydroxide Precipitate Through Selective Leaching with KMnO4 Oxidant

Mixed Hydroxide Precipitate (MHP), a metal precipitate with the dominant nickel and cobalt content in hydroxide compounds, can be leached as a lithium battery precursor. In this study, KMnO4 was used as an oxidant agent to increase the solubility of Ni and Co. The variation of the sulfuric acid concentration (0.5 - 1.5 M) as a leachate reagent, the concentration of KMnO4 (2.5 - 7.5 g/L), and the selective leaching temperature (60 - 80°C) were investigated. Solvent extraction using CYANEX 272 and D2EHPA was performed to separate the Ni, Co, and Mn. Atomic Absorption Spectrometry (AAS), Inductively coupled plasma mass (ICP-OES), and X-ray Fluorescence (XRF) were used to analyze the chemical compositions. At the same time, crystallographic analysis was observed with X-Ray Diffraction. It was observed that potassium permanganate increased the dissolution of Ni and Co to 91.3% and 85.4% but decreased the dissolution of Mn (37.53%) under the following conditions: 1.75 M sulfuric acid, 7.5 g/L potassium permanganate, and 60°C temperature. High purity of nickel crystal (99.64%) was observed with spontaneous nucleation due to the supersaturated nickel solution after solvent extraction with CYANEX 272. Thus, using permanganate ion as selective leaching of Ni and Co from Mn is promising.

Selective detection of MnO4- in non-standard explosives by nitrogen-doped carbon quantum dots-copper complexes (NCQDs@Cu)

Nitrogen-doped carbon quantum dots (NCQDs) with bright yellow fluorescence (quantum yield of 27.3 %) were synthesized via a solvothermal method using 2,3-diaminopyridine as the carbon and nitrogen source and ethanol as the solvent. Subsequently, the NCQDs were reacted with Cu2+ in an aqueous solution, forming nitrogen-doped carbon quantum dots-copper complexes (NCQDs@Cu) with great potential for selective determination of MnO4- ions. The aqueous solution of NCQDs@Cu exhibiting a very weak fluorescence (quantum yield of 2.2 %) demonstrated a significant enhancement (quantum yield of 10.0 %) upon interaction with MnO4-(Turn-on). Furthermore, this enhancement remained unaffected by the interfering conventional or unconventional explosives, inorganic ions, and oxidants. Moreover, a good linear relationship existed between the fluorescence intensity of the NCQDs@Cu and the concentration of the permanganate ions in a range of 0 to 5 μmol/L with a detection limit of 32.4 nmol/L. Additionally, the study investigated the underlying principles of the detection mechanism using advanced technologies such as X-ray photoelectron spectroscopy(XPS), The Fourier-transform infrared (FTIR), ultraviolet visible spectrometer (UV–Vis), fluorescence spectrometer and other methods. Finally, the NCQDs@Cu were successfully applied for detecting MnO4- in simulated and actual unconventional explosives, demonstrating a good correlation with standard methods. Therefore, the developed NCQDs@Cu can be used for rapid on-site inspection in explosive incident scenarios. This new method of using carbon dots-metal complexes as fluorescent probes will also provide new ideas for researchers.

Orchestrating Nuclear Dynamics in a Permanganate Doped Crystal with Chirped Pump-Probe Spectroscopy.

Pump-probe spectroscopy is a powerful tool to investigate light-induced dynamical processes in molecules and solids. Targeting vibrational excitations occurring on the time scales of nuclear motions is challenging, as pulse durations shorter than a vibrational period are needed to initiate the dynamics, and complex experimental schemes are required to isolate weak signatures arising from wavepacket motion in different electronic states. Here, we demonstrate how introducing a temporal delay between the spectral components of femtosecond beams, namely a chirp resulting in the increase of their duration, can counterintuitively boost the desired signals by 2 orders of magnitude. Measuring the time-domain vibrational response of permanganate ions embedded in a KClO4 matrix, we identify an intricate dependence of the vibrational response on pulse chirps and probed wavelength that can be exploited to unveil weak signatures of the doping ions─otherwise dominated by the nonresonant matrix─or to obtain vibrational excitations pertaining only to the excited state, suppressing ground-state contributions.

A complete and sustained organic/inorganic reaction mechanism of Baeyer’s test

The Baeyer’s test for unsaturation has been used in Qualitative Organic Analysis for a long time. However, if an alkaline reagent is used, compounds having an active hydrogen (carbon acids) also give a positive test with potassium permanganate, detracting the test for unsaturation. The first steps of the reaction sequence have been described but the next stages are missing. These are very important because they involve the formation mode of the observed end product, brown manganese dioxide. In this communication, a complete and sustained reaction mechanism is provided for both reaction mediums, neutral and alkaline. It is in accordance with observed experimental facts. The missing steps are a redox reaction between hypomanganate and permanganate ions, and a second cyclic intermediate now formed with manganate ion. The instability of this intermediate leads directly to manganese dioxide and alkalinization of the neutral medium, as observed experimentally.

Crossover Flux and Ionic Resistance Metrics in Polysulfide-Permanganate Redox Flow Battery Membranes

A survey of 23 commercially available cation exchange membranes was performed for the downselection of membranes for use in a polysulfide-permanganate redox flow battery (pS-Mn RFB). The survey measured the flux of permanganate ions across a 0.1 mol L−1 concentration gradient as well as the membrane resistance in a 0.5 mol L−1 sodium chloride solution. The membranes exhibited the characteristic flux/resistance trade-off observed in most classes of membranes. To connect the individual membrane testing to how the membranes will perform in a device, cell performance data in a pS-Mn RFB was collected for three membranes from the survey. The coulombic, voltaic, and energy efficiency at low cycle counts aligned with the predictions from the membrane flux and resistance survey results. The study also identified three membranes—Fumapem F-930-RFS, Fumapem FS-715-RFS, and Aquivion E98-09S—that outperformed most other membranes regarding their position on the flux-resistance trade-off curve, indicating them to be good candidates for further testing.

Understanding the mechanism of permanganate ion rejection in TpPa-1/Ti3C2T2 composite membranes via molecular dynamic simulation

The purification and separation of small molecules can be improved by fabricating different composite membranes, in this work, the TpPa-1/Ti3C2T2 composite membranes with different structural parameters and terminating functional groups were designed for better permanganate (PP) ions separation with non-equilibrium molecular dynamics simulations. The rejection mechanism was explored from molecular level. It is found that water flux is mainly influenced by the offset and interlayer spacing of Ti3C2T2, while the rejection rate of PP ion is affected more by the slit width of MXene. The combination of TpPa-1 and Ti3C2(OH)2 membrane provides a comfortable zone in for PP ion rejection from the viewpoint of thermodynamic. While the other two composite membranes constructed with terminating functional groups (-F, –O) in Ti3C2T2 show different rejection mechanism from that in TpPa-1/Ti3C2(OH)2 composite membrane. The rejection of PP ions mainly caused by the dynamic hindrance caused by water wall formed in the entrance of Ti3C2T2 (T = –F, –O) slits.

Chromium/nickel-free conversion coating as cold post-treatment to anodized AA2024-T3 for corrosion resistance increase

The AA2024-T3 alloy exhibits significant properties for industrial applications, including low weight and high mechanical strength. However, its susceptibility to corrosion, attributed to precipitation hardening, requires effective surface treatments. Anodized aluminum alloys offer a robust protective structure; nevertheless, their porous layer must enable the anchoring of an additional coating or be adequately sealed. Boiling water sealing, though a non-toxic process, demands substantial energy consumption, while toxicity concerns limit the use of sealing with dichromate and Ni salts. Consequently, there is a pressing need to explore novel sealing methods capable of operating at lower temperatures for brief durations without Cr(VI) or Ni. This study proposes an alternative post-treatment for AA2024-T3 anodic layers generated in tartaric sulfuric acid (TSA). The method involves immersing the samples for 5 min in solutions containing H2ZrF6 alone, Na2MoO4 with KMnO4, and a combination of all three. The resulting layers underwent analysis using scanning electron microscopy (SEM), energy dispersion X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), open circuit potential (OCP) measurements during coating deposition, electrochemical impedance spectroscopy (EIS), and a visual examination post-immersion in a NaCl solution. The findings indicate that the Zr and Zr-Mo-Mn conversion coatings partially sealed the porous structure of the anodic oxide film, thereby enhancing its corrosion resistance in chloride medium. The incorporation of molybdate and permanganate ions intensified the precipitation of Zr oxide-fluorides within and on the porous layer, leading to improved corrosion resistance of the anodized alloy compared to Zr-only coating.

Effective Treatment Methodology for Environmental Safeguard Catalytic Degradation of Fluconazole by Permanganate Ions in Different Acidic Environments: Kinetics, Mechanistics, RSM, and DFT Modeling.

In this paper, the degradation of fluconazole drug (Flz) was explored kinetically utilizing permanganate ion [MnO4-] as an oxidant in different acidic environments, namely sulfuric and perchloric acids at various temperatures. Stoichiometry of the reactions between Flz and [MnO4-] in both acidic environments was attained to be 1.2 ± 0.07 mol. The kinetics of the degradation reactions in both cases were the same, being unit order regarding [MnO4-], fewer than unit orders in [Flz], and fractional second orders in acid concentrations. The rate of oxidative degradation of fluconazole in H2SO4 was higher than that in HClO4 at the same investigational circumstances. The addition of small amounts of Mg2+ and Zn2+ enhanced the degradation rates. The activation quantities were evaluated and debated. The gained oxidation products were characterized using spot tests. A mechanistic approach for the fluconazole degradation was suggested. Finally, the rate law expressions were derived which were agreed with the acquired outcomes. The rates of degradation for various [Flz] were mathematically modeled using the response surface methodology (RSM). The RSM model's conclusions and the experimental findings are in agreement. The oxidative degradation mechanism of Flz using density functional theory (DFT) was performed. The fluconazole drug degrades in acidic settings, protecting both the environment and human health, according to a method that is easy to use, powerful, inexpensive, practical, affordable, and safe.