Acidic Media Research Articles

Phase-Engineered Dichalcogenides/Fluorine-Free V4C3Tx (T=OH, O) Heterostructures for pH-Universal Hydrogen Evolution Reaction.

This research addresses the pH-dependency limitation in electrocatalytic hydrogen evolution reactions (HER) by creating heterostructures through the chemical bonding between 2D-dichalcogenides and V4C3Tx (T=OH, O) planes. The one-step solvothermal synthesis employed in this study constructs a synergistically interacted 1T phase of, e.g., MoS2 and V4C3Tx MXene, demonstrating an omnidirectional improvement on catalytic stability, active site exposure, surface area enlargement, electrical conductivity, and hence enhancement of water dissociation activities. Despite the notable progress in creating hydrogen production catalysts with ground breaking performances, a significant gap remains in the availability of catalysts capable of functioning effectively under high current densities. The catalyst 1T MoS2@V4C3Tx shows remarkable activities under the current density of 1000mAcm-2, which require overpotentials of 16, 24, and 37mV in 0.5m H2SO4, 1 m KOH, and 0.1 m PBS electrolytes, respectively at 10 mA cm-2, and exhibits excellent HER performance with small overpotentials of 103.16 and 138mV to achieve current densities of 500 and 1000mAcm-2, respectively, with outstanding stability for 1000 cylic voltammetriccycle HER test without degradation in acidic media. Enhanced HER performance has also been observed in other 2D-dichalcogenides/V4C3Tx heterostructures, providing prospects for phase-engineered dichalcogenides/fluorine-free V4C3Tx composites for pH-universal HER.

One-dimensional photonic crystals based on porous anodic alumina: Optical and morphology changes under thermal and chemical treatments

One-dimensional photonic crystals (1D PCs) based on porous anodic aluminium oxide (AAO) are promising for light manipulation and sensing. As-prepared AAO, being amorphous material, suffers degradation in acidic and alkaline media. It is commonly known that the chemical stability of AAO increases drastically after thermal treatment. Here, the effect of annealing up to 1200 °C on the morphology and the optical properties of AAO PCs is studied. The two-step crystallization of as-prepared AAO at 860 and 1190 °C leads to a two-step blue shift of the central wavelength of photonic band gap (PBG) and the decrease in PBG depth, whereas the Q-factor of the PBG enhances. The observed changes in optical transmittance spectra of PCs are mainly attributed to the increase in pore diameter, the formation of crystalline particles of alumina polymorphs, and the removal of impurities. Annealed AAO PCs demonstrate much higher stability of optical parameters during exposure in acidic media compared to the as-prepared ones. Thermal treatment at 600 °C results in 30% decrease in the rate of the PBG shift during chemical etching. Furthermore, AAO crystallization into a mixture of low-temperature alumina polymorphs at 860 °C leads in a negligible change in transmittance spectra even after chemical etching in 1 M HCl for 75 h. The excellent stability achieved for the annealed AAO PCs in aggressive media proves the perspectives of their application as the optical sensors with long-term stability.

Magnetic Field Enhanced Cobalt Iridium Alloy Catalyst for Acidic Oxygen Evolution Reaction.

Magnetic field mediated magnetic catalysts provide a powerful pathway for accelerating their sluggish kinetics toward the oxygen evolution reaction (OER) but remain great challenges in acidic media. The key obstacle comes from the production of an ordered magnetic domain catalyst in the harsh acidic OER. In this work, we form an induced local magnetic moment in the metallic Ir catalyst via the significant 3d-5d hybridization by introducing cobalt dopants. Interestingly, CoIr nanoclusters (NCs) exhibit an excellent magnetic field enhanced acidic OER activity, with the lowest overpotential of 220 mV at 10 mA cm-2 and s long-term stability of 120 h under a constant magnetic field (vs 260 mV/20 h without a magnetic field). The turnover frequency reaches 7.4 s-1 at 1.5 V (vs RHE), which is 3.0 times higher than that without magnetization. Density functional theory results show that CoIr NCs have a pronounced spin polarization intensity, which is preferable for OER enhancement.

Itaconic acid inhibits nontuberculous mycobacterial growth in pH dependent manner while 4-octyl-itaconic acid enhances THP-1 clearance of nontuberculous mycobacteria in vitro.

Increasingly prevalent, nontuberculous mycobacteria (NTM) infections affect approximately 20% of people with cystic fibrosis (CF). Previous studies of CF sputum identified lower levels of the host metabolite itaconate in those infected with NTM. Itaconate can inhibit the growth of M. tuberculosis (MTB) in vitro via the inhibition of the glyoxylate cycle enzyme (ICL), but its impact on NTM is unclear. To test itaconic acid's (IA) effect on NTM growth, laboratory and CF clinical strains of Mycobacterium abscessus and Mycobacterium avium were cultured in 7H9 minimal media supplemented with 1-10 mM of IA and short-chain fatty acids (SCFA). M. avium and M. abscessus grew when supplemented with SCFAs, whereas the addition of IA (≥ 10 mM) completely inhibited NTM growth. NTM supplemented with acetate or propionate and 5 mM IA displayed slower growth than NTM cultured with SCFA and ≤ 1 mM of IA. However, IA's inhibition of NTM was pH dependent; as similar and higher quantities (100 mM) of pH adjusted IA (pH 7) did not inhibit growth in vitro, while in an acidic minimal media (pH 6.1), 1 to 5 mM of non-pH adjusted IA inhibited growth. None of the examined isolates displayed the ability to utilize IA as a carbon source, and IA added to M. abscessus isocitrate lyase (ICL) decreased enzymatic activity. Lastly, the addition of cell-permeable 4-octyl itaconate (4-OI) to THP-1 cells enhanced NTM clearance, demonstrating a potential role for IA/itaconate in host defense against NTM infections.

A synthesis of dibenzo[b,h][1,5]naphthyridin-7(12H)-ones: the Pictet–Spengler reaction vs a rearrangement of 4-phenyl[1,3]oxazolo[4,5-c]quinolines

Two approaches were proposed to the synthesis of dibenzo[b,h][1,5]naphthyridin-7(12H)-ones. The one-step method based on the Pictet–Spengler reaction of 3-amino-2-phenylquinolin-4(1H)-one with aromatic aldehydes requires heating in a strong acidic media, which leads to significant limitations on the possible products. The second approach is based on the conversion of 3-amino-2-phenylquinolin-4(1H)-one to 4-phenyl[1,3]oxazolo[4,5-c]quinolines followed by rearrangement under the action of AlCl3. A significant advantage of the two-step synthesis is the possibility of obtaining a wider range of dibenzo[b,h][1,5]naphthyridin-7(12H)-ones, including those not available using the Pictet–Spengler reaction.

Study of the Adsorption and Separation Behavior of Scandium and Zirconium by Trialkyl Phosphine Oxide-Modified Resins in Sulfuric and Hydrochloric Acid Media

Zirconium is recognized as one of the main impurities of the rare earth element scandium during purification. It presents significant challenges due to its similar chemical properties, making separating it difficult. This study used trialkyl phosphine oxide (TRPO) as a functional ligand, and the effects of carrier type and acidity on adsorption performance were first investigated. Among these, the novel extraction resin SiO2-P as a carrier for TRPO demonstrated more prominent separation performance in 0.2 M H2SO4 and 5 M HCl solutions. The kinetic and isotherm data were consistent with the pseudo-secondary kinetics and Langmuir model, respectively, and the adsorption process could be regarded as homogeneous monolayer adsorption subject to the dual effects of chemisorption and internal diffusion. In addition, thermodynamic analysis showed that the adsorption process of zirconium under the experimental conditions was a spontaneous endothermic process. Combined with the results of SEM-EDS, FT-IR, and XPS analyses, scandium and zirconium were successfully adsorbed by the resin and uniformly distributed on its surface, and the greater affinity of the P=O groups on the resin for zirconium was the critical factor contributing to the separation of scandium and zirconium. Finally, scandium and zirconium in sulfuric acid and hydrochloric acid media were extracted and separated by column experiments, and the purity of scandium could reach 99.8% and 99.99%, respectively.

Recent Advances in Carbon-Based Single-Atom Catalysts for Electrochemical Oxygen Reduction to Hydrogen Peroxide in Acidic Media

Electrochemical oxygen reduction reaction (ORR) via the 2e− pathway in an acidic media shows great techno-economic potential for the production of hydrogen peroxide. Currently, carbon-based single-atom catalysts (C-SACs) have attracted extensive attention due to their tunable electronic structures, low cost, and sufficient stability in acidic media. This review summarizes recent advances in metal centers and their coordination environment in C-SACs for 2e−-ORR. Firstly, the reaction mechanism of 2e−-ORR on the active sites of C-SACs is systematically presented. Secondly, the structural regulation strategies for the active sites of 2e−-ORR are further summarized, including the metal active center, its species and configurations of nitrogen coordination or heteroatom coordination, and their near functional groups or substitute groups, which would provide available and proper ideas for developing superior acidic 2e−-ORR electrocatalysts of C-SACs. Finally, we propose the current challenges and future opportunities regarding the acidic 2e−-ORR pathway on C-SACs, which will eventually accelerate the development of the distributed H2O2 electrosynthesis process.

Nanosilica from canary seed husk for corrosion protection of structural steel

AbstractAn alternative technique is presented for the corrosion protection of the A36 structural steel (A36SS) in acid medium (H2SO4) using silica obtained from canary seed husk (CSH). The silica was obtained in a solid amorphous state with a particle size of 10–22 nm. The anticorrosive properties of nanosilica (NS) were studied using potentiodynamic polarization (PDP), linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS). Before carrying out the corrosion tests, the A36SS was subjected to a treatment with NaOH solution without and with the presence of NS. The A36SS treated with NS presented the lowest current density values and the noblest corrosion potential values, indicating that the corrosion rate decreased. The surface morphological study of the tested systems using SEM/EDS showed that the NS‐treated A36SS had a more efficient physical barrier against corrosive species.

Synthesis, Spectral Characteristics, Sensing Properties and Microbiological Activity of New Water-Soluble 4-Sulfo-1,8-naphthalimides

A new water-soluble polyamidoamine (PAMAM) dendrimer modified with 4-sulfo-1,8-naphthalimide (DSNI) and its monomeric structural analogue (MSDI) were synthesized. Their photophysical properties were investigated in organic solvents of different polarities and aqueous solutions. The effect of pH on fluorescence intensity was determined. It was found that the dendrimer emits blue fluorescence in an acidic medium, which is quenched in an alkaline environment. This phenomenon is due to the possibility of suppression of nonradiative photoinduced electron transfer in acidic media. The influence of different metal ions (Cu2+, Pb2+, Sn2+, Sr2+, Mg2+, Ba2+, Co2+, Hg2+, Zn2+, Ni2+, Fe3+, Al3+) and anions (CN−, S2−, S2O52−, HPO42−, H2PO4−, F−, CH3COO−, NO2−, CO32−, SO42−) on the intensity of the emitted fluorescence was studied. Quenching was only found in the presence of Cu2+. This makes the dendrimer suitable for determining copper ions in water solutions in the presence of other metal ions and anions. Additionally, DSNI was used as a ligand to obtain a stable copper complex, the structure of which was investigated by electron paramagnetic resonance (EPR), infrared spectrum, and elemental analysis. Two copper ions were found to form a complex with one dendrimer. The in vitro microbiological activity of the new compounds against bacteria Pseudomonas aeruginosa and two viruses HRSV-2 and HAdV-5 was investigated. With a view to obtaining antibacterial and anti-viral textiles, cotton fabrics were treated with the three compounds, and then their activity against the same microbial strains was investigated. It was found that the microbiological activity was preserved after the application of the new compounds to the cotton fabrics.

Bicontinuous RuO2 nanoreactors for acidic water oxidation

Improving activity and stability of Ruthenium (Ru)-based catalysts in acidic environments is eager to replace more expensive Iridium (Ir)-based materials as practical anode catalyst for proton-exchange membrane water electrolyzers (PEMWEs). Here, a bicontinuous nanoreactor composed of multiscale defective RuO2 nanomonomers (MD-RuO2-BN) is conceived and confirmed by three-dimensional tomograph reconstruction technology. The unique bicontinuous nanoreactor structure provides abundant active sites and rapid mass transfer capability through a cavity confinement effect. Besides, existing vacancies and grain boundaries endow MD-RuO2-BN with generous low-coordination Ru atoms and weakened Ru-O interaction, inhibiting the oxidation of lattice oxygen and dissolution of high-valence Ru. Consequently, in acidic media, the electron- and micro-structure synchronously optimized MD-RuO2-BN achieves hyper water oxidation activity (196 mV @ 10 mA cm−2) and an ultralow degradation rate of 1.2 mV h−1. A homemade PEMWE using MD-RuO2-BN as anode also conveys high water splitting performance (1.64 V @ 1 A cm−2). Theoretical calculations and in-situ Raman spectra further unveil the electronic structure of MD-RuO2-BN and the mechanism of water oxidation processes, rationalizing the enhanced performance by the synergistic effect of multiscale defects and protected active Ru sites.

Synthesis and drug release kinetics of ciprofloxacin from polyacrylamide/dextran/carbon quantum dots (PAM/Dex/CQD) hydrogels

Sustainable release of drug by utilizing β-cyclodextrin (β-CD) based inclusion complex (IC) is the prime objective of the present work. Herein, polyacrylamide/dextran containing carbon quantum dots (PAM/Dex/CQD) nanocomposite hydrogels are prepared by in situ polymerization of acrylamide. The incorporation of CQD triggers the change in orientation of the PAM/Dex polymeric chains to result the formation of stacked surface morphology of the hydrogel. The average particle size of CQD is found to be 4.13 nm from HRTEM analysis. As-synthesized nanocomposite hydrogel exhibits an optimum swelling ratio of 863 % in aqueous medium. The cytotoxicity study is conducted on HeLa cells by taking up to 2 μM concentration of the prepared nanocomposite hydrogel demonstrate 78 % cell viability. In present study, ciprofloxacin (Cipro) is taken as model drug that achieves release of 64.15 % in 32 h from β-Cipro@PAM/Dex/CQD hydrogels in acidic medium. From theoretical study, release rate constants, R2, Akaike information criterion (AIC) and model selection criterion (MSC) are computed to determine the best fitted kinetics model. Peppas-Sahlin model is the best fitted kinetics model for β-Cipro@PAM/Dex/CQD and concluded that the release of Cipro follows Fickian drug diffusion mechanism in acidic medium.

Insights from Syzygium aromaticum Essential Oil: Encapsulation, Characterization, and Antioxidant Activity

Alginate encapsulates loaded with clove essential oil (CEO) were prepared by ionic gelation, with subsequent freeze-drying. The objective of the present work was to develop a product with the ability to protect CEO against its easy volatility and oxidation. The following techniques were used to characterize the formulations: eugenol release, degree of swelling, GC/MS, TGA/DSC, and SEM. The alginate solution (1.0%) containing different concentrations of CEO (LF1: 1.0%; LF2: 0.5%; LF3: 0.1%) was dropped into a 3.0% CaCl2 solution. After lyophilization, the encapsulated samples were wrinkled and rigid, with high encapsulation power (LF3: 76.9% ± 0.5). Three chemical components were identified: eugenol (the major one), caryophyllene, and humulene. The antioxidant power (LF1: DPPH IC50 18.1 µg mL−1) was consistent with the phenol content (LF1: 172.2 mg GAE g−1). The encapsulated ones were thermally stable, as shown by analysis of FTIR peaks, eugenol molecular structure was kept unaltered. The degree of swelling was 19.2% (PBS). The release of eugenol (92.5%) in the PBS solution was faster than in the acidic medium. It was concluded that the low-cost technology used allows the maintenance of the content and characteristics of CEO in the three concentrations tested, offering a basis for further research with essential oil encapsulates.

Improved interfacial adhesion of carbon fiber‐reinforced polydicyclopentadiene layered composite material by modification of norbornene derivatives

AbstractSurface chemical grafting modifications of carbon fibers (CFs) using 5‐(triethoxysilyl)norbornene (TOS), norbornene carboxylic acid tert‐butyl ester (NB‐TBE), and 5‐norbornene‐2,3‐dicarboxylic anhydride (NA) improved interfacial interactions between CFs and poly(dicyclopentadiene) (PDCPD) resin. The ring‐opening metathesis polymerization (ROMP) of DCPD, catalyzed by Grubbs catalyst II, enabled the fabrication of PDCPD/CF layered composite materials with resin and fibers tightly adhered. The optimal composite exhibited remarkable mechanical properties, with a tensile strength of 654.6 MPa and flexural strength of 510.7 MPa. Excellent thermal stability with a maximum weight loss rate in temperatures above 450°C and good chemical resistance with a weight change of about 1% in both acidic and alkaline media highlight the promising potential of these materials for use in harsh environments. The simple yet efficient approach of TOS, NB‐TBE, and NA‐enhanced layered CF shows great promise as advanced composite materials for industrial applications.Highlights Norbornene derivatives such as TOS, NB‐TBE, and NA are suitable modifiers for CF. ROMP of DCPD and norbornene group onto CFs, fabrication of PDCPD/CF composite materials. The composite exhibited remarkable interfacial adhesion and mechanical properties.

Synthesis, characterization, and optical studies of lead-free perovskite, Cs3M2Br9 (M = Bi, Sb) nanocrystals

In recent years, there has been a surge in research interest surrounding all inorganic lead perovskite nanocrystals (NCs) owing to their exceptional performance in various optoelectronic devices. Nevertheless, the presence of lead and concerns regarding its toxicity and stability have cast a shadow over their potential wide-ranging applications. In this study, we present the synthesis of two lead-free all-inorganic perovskite materials, Cs3M2Br9 (where M = Bi or Sb), in bulk form, using an aqueous halide acid medium. Additionally, we describe a top-down approach for the fabrication of two lead-free all-inorganic perovskite, Cs3M2Br9 (M = Bi or Sb) NCs. The Cs3Sb2Br9 NCs display a sheet-like morphology, while Cs3Bi2Br9 NCs exhibit a cubic structure. The PL spectra of Cs3Sb2Br9 and Cs3Bi2Br9 NCs exhibit distinct emission peaks at 476 nm and 472 nm, respectively, with relatively narrow full width at half maximum (FWHM) of 44 nm and 38 nm, respectively. Cs3Sb2Br9 and Cs3Bi2Br9 NCs demonstrate excellent thermal stability up to 320 °C and 470 °C, respectively. Notably, the high photoluminescence quantum yield (PLQY) of these NCs, Cs3Sb2Br9 NCs (31 %) and Cs3Bi2Br9 NCs (36 %) are highly beneficial for optoelectronic applications is observed.

Study of mesomorphism behavior and protonation-induced emission of symmetrical benzalazines

Rod-shaped and polycatenar symmetric benzalazines with protonation-induced emission were synthesized, characterized, and studied for their thermal and optical behavior. Benzalazines lacking hydroxy groups at the ortho position did not show luminescence in the solid state or solution. In the presence of HCl (either in solution or vapor form) these compounds became good emitters. The protonation of azine nitrogen that may hinder the NN bond rotation by intermolecular interactions toward aggregates provided an explanation for the emission characteristics observed. The protonation-induced emission was thermally reversible. A benzalazine derived from 4-alkoxysalicylaldehyde with AIE property was prepared. For this compound with ortho-OH groups, the optical properties were not affected by the presence of acidic media. It exhibited a stable SmC phase characterized by POM, DSC, and XRD. The luminescence capability of the molecular arrangement within the smectic phase was investigated. The intense yellow-green emission in the crystals decreased significantly at the phase transition due to the non-radiative decay that occurs with increasing temperature, and loss of intermolecular H-bonding which prevents molecular rotations in the crystal.

Synthesis and characterization of selenium-polyvinyl alcohol nanoparticles as eco-friendly corrosion inhibitor for carbon steel in 1.0 M H2SO4

Selenium nanoparticles capped with polyvinyl alcohol (Se-PVA NPs) have been synthesized by chemical reduction using ascorbic acid as a reducing agent. The synthesized nanoparticles were characterized using XRD, DLS, zeta potential, FT-IR, and TEM analysis and found to be stable. The solution of Se-PVA NPs was used as a carbon steel corrosion inhibitor in 1.0 M H2SO4. The effect of the presence of Se-PVA NPs in the corrosion medium was studied by potentiodynamic polarization and gravimetric analyses In the presence of Se-PVA NPs with a concentration of 600 ppm at 303 K, corrosion inhibition efficiency values of 92.86 % and 92.3 % were recorded by potentiodynamic polarization and gravimetric analysis methods, respectively. Over the Se-PVA NPs concentration range 100–600 ppm, it was found that increasing the concentration increases the inhibition efficiency, while the temperature has an adverse effect, inhibition efficiency values of 80.0 % was recorded at 323 K for the 600 ppm Se-PVA NPs solution. The potentiodynamic polarization measurements suggested that Se-PVA NPs work as a mixed-type inhibitor. The corrosion inhibition process was confirmed by testing the used specimens’ metal surface using SEM and AFM techniques, which showed that the acidic medium’s negative impact (distortion and roughness) on the carbon steel surface was reduced significantly in the presence of Se-PVA NPs. The inhibitor’s adsorption on the metal surface was studied. It obeys the Langmuir isotherm with a mixed-type adsorption process. The related kinetic and thermodynamic parameters were investigated.

Torrefaction and hydrothermal carbonization of waste from the paper industry: Effects of atmosphere choice and pretreatment with natural acidic reagent on fuel properties

The hydrothermal carbonization (HTC) and torrefaction of paper sludges and biological sludges from the paper industry were investigated and the effect of pretreatment of the samples with alcoholic vinegar was evaluated. The HTC was performed at two different reaction times, while the torrefaction took place at two different temperatures and two atmospheres. The gas analysis showed that the optimal torrefaction time for the N2 atmosphere can be determined by observing the CO2 content in the gas phase, which is not possible for the CO2 atmosphere. The TGA analysis showed that the choice of atmosphere influences further combustion, with samples torrefied at lower temperatures being more sensitive to it. The carbon (C) content in the thermally treated samples increases from 39.85 to 48.06 wt% for biological sludge and from 40.02 to 60.21 wt% for paper sludge. The H/C and O/C ratios decrease and approach the values of conventional fuels. The fuel ratio is higher for the torrefied samples. The higher heating value (HHV) increased from 17.4 to 21.4 MJ/kg for biological sludge and from 16.2 to 22.4 MJ/kg for paper sludge. Higher temperature and longer treatment time led to products with a higher HHV and a higher energy density. The highest energy yields were achieved during torrefaction at 250 °C, regardless of the atmosphere, with temperature and type of material having the greatest influence. Acidification of the samples or acidic media in the HTC affects the properties of the products by increasing the C content and HHV and affecting combustion.

In-situ biosynthesized plant exudate gums‑silver nanocomposites as corrosion inhibitors for mild steel in hydrochloric acid medium

Natural gums due to availability, multifunctionality, and nontoxicity are multifaceted in application. In corrosion inhibition applications, their performance, in unmodified form is unsatisfactory because of high hydration rate, solubility issues, algal and microbial contamination, as well as thermal instability. This work attempts to enhance the inhibitive performance of Berlinia grandiflora (BEG) and cashew (CEG) exudate gums through various modification approaches. The potential of biogenic BEG and CEG gums−silver (Ag) nanocomposites (NCPs) for corrosion inhibition of mild steel in 1 M HCl is studied. The nanocomposites were characterized using the FTIR, UV–vis, and TEM techniques. The corrosion studies through the gravimetric and electrochemical (PDP, EIS, LPR, and EFM) analyses reveal moderate inhibition performance by the nanocomposites. Furthermore, the PDP results reveal that both inhibitors are mixed-type with maximum corrosion inhibition efficiencies (IEs) of 61.2 % and 54.2 % for BEG-Ag NCP and CEG-Ag NCP, respectively at an optimum concentration of 1.0 %. Modification of these inhibitors with iodide ion (KI) significantly increased the IE values to 90.1 % and 88.5 % for BEG-Ag NCP and CEG-Ag NCP at the same concentration. Surface observation of the uninhibited and inhibited steel samples using SEM/EDAX, 3D Surface profilometer, and AFM affirm that the modified nanocomposites are highly effective.

A novel cloud point back-extraction of uranium(VI) from organic radioactive solution to slightly acidic aqueous medium

ABSTRACT Stripping back uranium(VI) from an organic radioactive solution to an aqueous medium was rendered simple and quantitative by an unprecedented cloud point back-extraction (CPEback) method. The concentration difference of nitrate ions in and out of the micelle was employed to change the uranium distribution coefficient in favor of the bulk aqueous phase. In addition, the monophasic nature of cloud point extraction and the complexing ability of oxalic acid with uranyl ion in the bulk aqueous phase resulted in the quantitative recovery of uranium in a single step. The CPEback parameters were optimized through a cross-optimization process and the recovered uranium was quantified by the biamperometric titration method. The proposed analytical procedure resulted in high back-extraction efficiency and recovery of (99.6 ± 0.2)% and 99.2%, respectively. The process turned large volumes of organic radioactive solution into small volumes of a less hazardous organic medium having high viscosity and negligible vapor pressure. Analysis of two real samples of ~17 and 165 mL organic radioactive solutions resulted in 99% and 98.2% uranium recoveries, respectively. The leftover organic phase containing the extractant and nonionic surfactant can now be easily stored or reused.

Selectivity of Mn rich Ru Mn O phases in parallel oxygen and chlorine evolution

Single phase Mn rich RuxMn1-x O2 conforming to a highly disordered γ MnO2 with pyrolusite-like blocks dominating in the structure were prepared in the low Ru content range (0.15 ≥ x ≥ 0.30). All synthesized materials were electrochemically active in oxygen and chlorine evolution in acidic media with variable chloride content. The total anodic activity increased with increasing Ru content in the structure as well as with increasing concentration of chlorides in the solution. The selectivity towards oxygen evolution reaction was predominant for all chloride concentrations (from 0.02 to 0.3 M), and its value was not dependent on the total Ru content in the material structure. The reaction mechanism with respect to chlorine evolution reaction was discussed on the basis of the determined order of reactions, which apparently increases with increasing Ru content.