Acidic Media Research Articles

Protein-derived carbon dots as green corrosion inhibitors for carbon steel in sulfuric acid solution

At present, the development of eco-friendly corrosion inhibitors (CIs) is considered an important and attractive method for controlling the corrosion of metals in acidic media. In this study, protein-derived carbon dots (P-CDs) were prepared via hydrothermal reaction using protein as the raw material, and the corrosion inhibition performances of P-CDs for carbon steel (CS) were investigated systematically. The electrochemical test results showed that the corrosion inhibition efficiency of 500 mg/L P-CDs on CS reached 95.1 % in 0.5 M H2SO4, and the corrosion inhibition efficiency was enhanced to 98.1 % after 8 h of immersion time. The composition and characterization of P-CDs was analysed using Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet Spectroscopy (UV), X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) characterization showed that the surface of CS with P-CDs was smoother than that without P-CDs, and that P-CDs was able to adsorb on the surface of CS to form a protective layer, thereby inhibiting corrosion. Adsorption studies indicate that P-CDs form a protective layer on the surface of CS through both physisorption and chemisorption. Overall, these findings demonstrate that P-CDs exhibit superior protective effects against the corrosion of CS in 0.5 M H2SO4.

Efficiency of novel polyionic liquid toward the chemical separation of petroleum crude oil emulsions

AbstractIn the present study, a new polyionic liquid, PEST‐BU, were synthesized and characterized using proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, pendant drop technique, and thermal gravimetric analysis. The efficiency of PEST‐BU and its parent (PE‐ST) for separating petroleum crude oil emulsion was explored using several affecting parameters, including water ratio, separation time, pH, temperature, and demulsifier concentration. The results indicated that PEST‐BU exhibited higher separation efficiency (SE) than PE‐ST. In addition, the results revealed that the increased water ratio, separation time, temperature, and demulsifier concentration promoted the SE of PE‐ST and PEST‐BU. The data also showed that the optimal pH value to achieve maximum SE is 7; however, the SE of PE‐ST and PEST‐BU in acidic and basic mediums declined, possibly due to the increasing polarity of water droplets in these mediums, which increased electrostatic repulsion between them, increasing oil emulsion stability.

Cu, Fe, N‐doped Carbon Nanotubes Prepared through Silica Coating for Selective Oxygen Reduction to Water in Acidic Media

We report Cu, Fe, N‐doped carbon nanotubes, (Cu,Fe)–N–CNT, as electrocatalysts for the oxygen reduction reaction (ORR) in acidic media. (Cu,Fe)–N–CNT was prepared using a silica coating method in pyrolysis to minimize the formation of carbon‐coated metal oxide or carbide nanoparticles, which are known to be inactive for the H2O2 reduction. (Cu,Fe)–N–CNT shows a turnover frequency of 0.66 e– site–1 s–1 at +0.8 V vs. RHE and H2O2 yields of <1% for the ORR with a utilization factor of active sites of 82%. Kinetic analysis reveals that 4e– transfer rates for (Cu,Fe)–N–CNT are higher than those of a monometallic counterpart of Fe–N–CNT. In situ X‐ray absorption spectroscopy enables us to determine redox potentials: Eº’(FeIII/FeII) = 0.65 V vs. RHE and Eº’(CuII/CuI) = 0.45 V for (Cu,Fe)–N–CNT, and Eº’(FeIII/FeII) = 0.65 V for Fe–N–CNT. These results indicate that bimetallic doping into carbon nanotubes gives the effect on kinetic parameters but not on thermodynamic ones. In other words, there is no direct electronic interactions between the Cu and Fe active sites for (Cu,Fe)‐N‐CNT because such interactions should modulate their redox potentials.

Enrooted‐type metal‐support interaction boosting oxygen evolution reaction in acidic media

Supported metal catalysts with appropriate metal‐support interactions (MSIs) hold a great promise for heterogeneous catalysis. However, ensuring tight immobilization of metal clusters/nanoparticles on the support while maximizing the exposure of surface active sites remains a huge challenge. Herein, we report an Ir/WO3 catalyst with a new enrooted‐type MSI in which Ir clusters are, unprecedentedly, atomically enrooted into the WO3 lattice. The enrooted Ir atoms decrease the electron density of the constructed interface compared to the adhered (root‐free) type, thereby achieving appropriate adsorption toward oxygen intermediates, ultimately leading to high activity and stability for oxygen evolution in acidic media. Importantly, this work provides a new enrooted‐type supported metal catalyst, which endows suitable MSI and maximizes the exposure of surface active sites in contrast to the conventional adhered, embedded, and encapsulated types.

Enrooted-type metal-support interaction boosting oxygen evolution reaction in acidic media.

Supported metal catalysts with appropriate metal-support interactions (MSIs) hold a great promise for heterogeneous catalysis. However, ensuring tight immobilization of metal clusters/nanoparticles on the support while maximizing the exposure of surface active sites remains a huge challenge. Herein, we report an Ir/WO3 catalyst with a new enrooted-type MSI in which Ir clusters are, unprecedentedly, atomically enrooted into the WO3 lattice. The enrooted Ir atoms decrease the electron density of the constructed interface compared to the adhered (root-free) type, thereby achieving appropriate adsorption toward oxygen intermediates, ultimately leading to high activity and stability for oxygen evolution in acidic media. Importantly, this work provides a new enrooted-type supported metal catalyst, which endows suitable MSI and maximizes the exposure of surface active sites in contrast to the conventional adhered, embedded, and encapsulated types.

Self-Supported WO3@RuO2 Nanowires for Electrocatalytic Acidic Water Oxidation.

Developing catalysts with high catalytic activity and stability in acidic media is crucial for advancing hydrogen production in proton exchange membrane water electrolyzers (PEMWEs). To this end, a self-supported WO3@RuO2 nanowire structure was grown in situ on a titanium mesh using hydrothermal and ion-exchange methods. Despite a Ru loading of only 0.098 wt %, it achieves an overpotential of 246 mV for the oxygen evolution reaction (OER) at a current density of 10 mA·cm-2 in acidic 0.5 M H2SO4 while maintaining excellent stability over 50 h, much better than that of the commercial RuO2. After the establishment of the WO3@RuO2 heterostructure, a reduced overpotential of the rate-determining step from M-O* to M-OOH* is confirmed by the DFT calculation. Meanwhile, its enhanced OER kinetics are also greatly improved by this self-supported system in the absence of the organic binder, leading to a reduced interface resistance between active sites and electrolytes. This work presents a promising approach to minimize the use of noble metals for large-scale PEMWE applications.

Corrosion inhibition of martensitic stainless steel by sodium benzoate in acidic medium: Solanum tuberosum extract as surfactant

Research on corrosion inhibitor efficacy has been seen as essential to enhancing the robustness of martensitic stainless steel (MSS), which finds use in a variety of industrial settings. Thus, the aim of this study is to examine the inhibitory efficacy of sodium benzoate with solanum tuberosum (potato) extract as surfactant in a 0.5 M HCl solution for MSS. The techniques of electrochemical measurements and weight loss were adopted for the MSS samples cut into corrosion coupons and submerged in 0.5 M HCl solution at room temperature. A scanning electron microscopy equipped with an electron dispersive x-ray spectroscopy (SEM-EDS) was utilized for the morphology analyses of the samples. From the obtained results, the maximum inhibition efficiency of 32.58 % was recorded at 1.0 M inhibitor concentration, indicating that sodium benzoate is an effective corrosion inhibitor. It was noticed that the rise in the inhibitor concentration up to 1.0 M results in the reduction on corrosion rates being recorded, hence, the inhibition performance. However, 1.5 M and 2.0 M inhibitor concentration had higher corrosion rates compared to others. This study demonstrated that the inhibitor produces a film which adhere strongly to the MSS surface based on the Langmuir adsorption isotherm. Consequently, the combination of sodium benzoate with solanum tuberosum extract would be beneficial to significantly prolong MSS in industrial applications like oil drilling rigs, heat exchangers and marine installations.

Innovative application of plasma-activated water in the inactivation of Escherichia coli: Temperature-dependent chemical processes leading to the synergistic microbicidal effect

Plasma-based technologies, including plasma-activated water (PAW), offer the capability to deactivate microorganisms on fruits and vegetables, preserving their sensory and nutritional quality. Although many studies have reported a synergistic microbicidal effect between PAW and mild heating, the underlying chemical processes driving these effects remain unexplored. Our study aims to evaluate the microbicidal capacity of two PAW types, one containing NO2− (PAW-N) and the other H2O2 (PAW-H), as well as their mixture (PAW-M), at different temperatures, and to elucidate the underlying temperature-dependent chemical processes. Using E. coli DH5α as the target microorganism, we measured colony-forming units under varying exposure times for each PAW type and their mixture at 8 and 28 °C. Additionally, we determined the time-dependent concentrations of NO2−, H2O2, and NO3− in the mixture, and calculated the reaction rate constant for peroxynitrous acid generation. The kinetic study revealed a fivefold increase in the reaction constant between H2O2 and NO2− in PAW-M at 28 °C compared to 8 °C, leading to a significant rise in hydroxyl radical production. The microbicidal efficacy of PAW-M exceeded that of individual PAWs or temperatures. Moreover, this effect was significantly enhanced by mild heating, resulting in log reductions of 0.24, 0.34, 2.3 (at 8 °C) and 0.74, 2.3, 3.6 (at 28 °C) for PAW-H, PAW-N, and PAW-M, respectively, after a 10-min exposure. In conclusion, the synergistic effect between PAW and mild heating may be attributed to the accelerated reaction rate of peroxynitrous acid formation in an acidic medium, leading to heightened hydroxyl radical generation.

Acid-Sensitive Outwardly Rectifying Cl- Current in OV2944 Mouse Ovarian Cancer Cells.

Extracellular acidic conditions impair cellular activities; however, some cancer cells drive cellular signaling to adapt to the acidic environment. It remains unclear how ovarian cancer cells sense changes in extracellular pH. This study was aimed at characterizing acid-inducible currents in an ovarian cancer cell line and evaluating the involvement of these currents in cell viability. The biophysical and pharmacological properties of membrane currents in OV2944, a mouse ovarian cancer cell line, were studied using the whole-cell configuration of the patch-clamp technique. Viability of this cell type in acidic medium was evaluated using the MTT assay. OV2944 had significant acid-sensitive outwardly rectifying (ASOR) Cl- currents at a pH50 of 5.3. The ASOR current was blocked by pregnenolone sulfate (PS), a steroid ion channel modulator that blocks the ASOR channel as one of its targets. The viability of the cells was reduced after exposure to an acidic medium (pH 5.3)but was slightly restored upon PS administration. These results offer first evidence for the presence of ASOR Cl- channel in ovarian cancer cells and indicate its involvement in cell viability under acidic environment.

Green Synthesis and Antibacterial Activity of a 3-Nitroaniline-3-Nitrobenzaldehyde Schiff Base

3-nitroaniline and 3-nitrobenzaldehyde were refluxed in ethanol for 2 hours in an acidic medium to afford pale-yellow crystals of a Schiff base at 58% yield. The melting point and retention factor (Rf) of the product were checked, giving a value of 151 – 152°C and 0.54 respectively. The IR spectrum showed the following bands (cm-1); 1637 (imino, C=N), 1577 (Aromatic C=C stretch), 3074 and 3096 (Aromatic C – H stretch), 1346 and 1525 (Aromatic NO2 stretch) and 896 (Aromatic NO2 scissors). In addition, the 1HNMR spectrum showed a singlet at 8.44 ppm which represented the 1 H of the imino group, and a 8H multiplet between 7.18 – 8.41 ppm representing the aromatic protons. Furthermore, an antibacterial screening was done using the Schiff base on four (4) bacteria strains; Pseudomonas aeruginosa, Staphylococcus aureus, Serratia marcescens, and Escherichia coli. The result from the screening portrayed that the highest zone of inhibition (ZOI) recorded for all bacteria was at a concentration of 200 mg/ml of the test compound, while the lowest was at a concentration of 50 mg/ml. This gave a ZOI of 12 mm, 10 mm, 13 mm, and 11mm for P. aureginosa, S. aureus, S. marcescens, and E. coli respectively. The results generally showed an increase in ZOI with increased concentration of the product. The best result observed was that obtained for S. marcescens which showed ZOIs of 7 mm, 10 mm, 12 mm, and 13 mm for concentrations of 50, 100, 150, and 200 mg/ml respectively.

Copper corrosion inhibition in acidic aqueous media through tolyltriazole application: performance analysis

Tolyltriazole (TTA) is recognized as an effective copper corrosion inhibitor in cooling systems due to its low toxicity and versatile properties. With the increasing focus on sustainable development, the employment of compounds of this nature has become increasingly widespread, driving the search for environmentally responsible alternatives. In this context, the aim of this work was to evaluate the efficiency of a corrosion inhibitor formulated with TTA on copper specimens in HCl 0.1 mol L−1 medium. The samples were exposed to the corrosive electrolyte with inhibitor concentrations ranging from 0 to 20 ppm. Electrochemical methods, including open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy were employed for corrosion monitoring. Overall, the results revealed that TTA behaves as a predominantly anodic inhibitor. Additionally, polarization curves demonstrated that within the Tafel region, the inhibitor adsorbs to the copper surface, following the Langmuir isotherm model. Regarding inhibitory effectiveness, the observed values ranged between 81.3 and 96.1%, while morphological analyses indicated the presence of nitrogen on the surface of the copper specimens after electrochemical tests, confirming the formation of a protective TTA film. In conclusion, this study highlights TTA's efficacy as a corrosion inhibitor, demonstrating its significant potential in safeguarding copper against acidic environments.

Reaction Environment Regulation for Electrocatalytic CO2 Reduction in Acids.

The electrocatalytic CO2 reduction reaction (CO2RR) is a sustainable route for converting CO2 into value-added fuels and feedstocks, advancing a carbon-neutral economy. The electrolyte critically influences CO2 utilization, reaction rate and product selectivity. While typically conducted in neutral/alkaline aqueous electrolytes, the CO2RR faces challenges due to (bi)carbonate formation and its crossover to the anolyte, reducing efficiency and stability. Acidic media offer promise by suppressing these processes, but the low Faradaic efficiency, especially for multicarbon (C2+) products, and poor electrocatalyst stability persist. The effective regulation of the reaction environment at the cathode is essential to favor the CO2RR over the competitive hydrogen evolution reaction (HER) and improve long-term stability. This review examines progress in the acidic CO2RR, focusing on reaction environment regulation strategies such as electrocatalyst design, electrode modification and electrolyte engineering to promote the CO2RR. Insights into the reaction mechanisms via in situ/operando techniques and theoretical calculations are discussed, along with critical challenges and future directions in acidic CO2RR technology, offering guidance for developing practical systems for the carbon-neutral community.

Synthesis, Characterization and Dissolution behavior of Nitrides of U-Zr and U-Pu-Zr metallic alloy fuels for Aqueous reprocessing

The aqueous based PUREX process is an alternate choice to pyro-reprocessing of metallic alloy fuels (U-Zr/U-Pu-Zr). Direct dissolution of metallic alloy fuels in a nitric acid medium is not feasible due to vigorous reaction exhibited by the alloys when exposed to this medium. Conversion of metallic alloys into their oxides is a challenging method due to poor dissolution of oxides in nitric acid. Excellent dissolution of nitrides compared to oxides of metallic alloy fuels lead to exploit the nitride route for aqueous reprocessing. Hence, a novel method was adopted to prepare the nitrides of unirradiated U-Zr and U-Pu-Zr alloys via hydridation using UH3, as source-cum-getter instead of hydrogen cylinder. In this context, nitrides of unirradiated U-Zr/U-Pu-Zr metallic alloys were prepared by nitridation via hydridation. Initially, nitrides of U and Zr metals were synthesized and the formation of ZrN and U2N3 and UN phases were confirmed by powder X-ray diffraction measurements. Subsequently, nitrides of unirradiated U-Zr and U-Pu-Zr alloys were synthesized and characterized by X-ray diffraction, scanning electron microscopy and particle analyzer. The dissolution behavior of nitrides of Zr, U, U-Zr and U-Pu-Zr alloys were examined in nitric acid (12 M) medium under reflux conditions at 383 K for 8 h. The present study highlights the potential of the nitride route for efficient dissolution of actinides (U and Pu) and it is very important to develop flow sheets for the aqueous reprocessing of metallic alloys fuels.

Use of a Clay from Southern Ivory Coast (Bingerville) for the Adsorption of Methyl Orange in Aqueous Media

Increasing levels of textile dyes being discharged into the environment as industrial waste represent a serious threat to human health, life, resources and ecological systems. It is therefore necessary to treat wastewater from textile industries before discharging it into the environment. The aim of this project is to eliminate methyl orange (MO) from textile industry wastewater using clay from Bingerville (Ivory Coast). The clay used was characterized by Scanning Electron Microscopy, Brunauer-Emmett-Teller and pH of Zero Charge. MO concentration was monitored using a UV-visible spectrophometer. Characterization of the clay by SEM and BET showed that our clay is microporous. The study showed that the surface of our clay has a pH of zero. Adsorption of methyl orange on our clay reaches adsorption equilibrium in 60 minutes. The adsorption model corresponds to the pseudo-order 2 kinetic model. Two adsorption isotherm models (Langmuir and Freundlich) are applicable to the adsorption of our dye on clay. This implies that the dye adsorption process on our clay is governed by a bimolecular process involving a collision between an active site on the clay and a dye molecule. Bingerville clay can be used to effectively treat dye-contaminated wastewater, since the maximum adsorbed quantity is equal to 58.139 mg g<sup>-1</sup>. The best adsorption rate was obtained in acid medium (pH = 2.26) with an adsorption rate of 91.84%.

Efficient oxidation of hydrazine over electrochemically activated glassy carbon electrode surface: Kinetics and sensing performance

Hazardous chemical hydrazine (HZ) can enter the body through the skin and harm the kidneys and liver. Consequently, it is imperative to accurately determine HZ concentrations in samples. One significant challenge in the direct and sensitive detection of analytes is the higher oxidation overpotential and inferior voltammetric response over the conventional bare electrode surface, attributed to the passivation of the electrode surface. To address this issue, we electrochemically activated (oxidized) a pristine glassy carbon electrode (GCE) in a mild acidic medium. The activated GCE demonstrated improved HZ oxidation efficiency. The activated GCE exhibited a distinct redox pair in 0.1 M H2SO4 because of the growth of C=O groups onto the electrode surface during electrochemical oxidation. We characterized the GCE surface before and after the functionalization using electrochemical processes, Scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). This activated electrode surface was utilized for electrochemical HZ oxidation in an alkaline medium, revealing enhanced electrochemical performance compared to the pristine GCE regarding HZ oxidation following conventional Butler-Volmer kinetics. Thorough electrochemical analyses and characterizations of the sensor were performed utilizing techniques such as Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), Open Circuit Potential (OCP), Chronoamperometry (i-t curve), and Differential Pulse Voltammetry (DPV). The correlation between the current response and HZ concentration displayed an extensive linear dynamic range (LDR) spanning from 6 to 1000 μM, boasting a limit of detection (LOD) at 0.48 μM. The sensor's sensitivity was determined to be 3.1 μA μM−1 cm−2. The proposed activated GCE effectively reduces HZ oxidation overpotentials, thereby enhancing its potential application as an anode in direct hydrazine fuel cells.

Development of Eco-Friendly Scattering and Fluorimetric Methods for the Determination of Clemastine Through Its Interaction with Eosin Y: Assessment of Whiteness, Blueness, and Greenness Tools.

For the first time, clemastine was estimated in this work utilizing two validated resonance Rayleigh scattering (RRS) and fluorimetric methods. The methods relied on forming an association complex in an acidic medium between eosin Y reagent and clemastine. In the spectrofluorimetric approach, the investigated drug was quantified by quenching the fluorescence-emission intensity of eosin Y at 543.5nm. The RRS method relied on enhancing the RRS spectrum at 331.8nm, which is produced when eosin Y interacts with clemastine. Suitable conditions were established for the reaction to achieve maximum sensitivity. The linear values obtained from the spectrofluorimetric approach and the RRS method fall into the ranges of 0.2-1.5µg mL- 1 and 0.25-2.0µg mL- 1, respectively. It was established that the detection limits for these methods were 0.045µg mL- 1 and 0.059µg mL- 1, respectively. The developed methodologies yielded acceptable recoveries when used to estimate the quantity of clemastine in its pharmaceutical tablet dosage form. Regarding the use of greener solvents that were chosen, the suggested and reported methods were compared with the help of the Green Solvents Selecting (GSST) tool for assessing hazardous solvents to achieve sustainability. Furthermore, analytical Eco scale and comprehensive assessments of whiteness, blueness, and greenness were carried out utilizing Modified NEMI, ComplexGAPI, and AGREE evaluation tools. Additionally, recently developed tools such as BAGI and RGB 12 were applied to assess the blueness and the whiteness of the suggested methods.

Modification of amino functionalized silica nanoparticles with L-proline and furanacrylic acid as novel composites for the efficient removal of methyl orange

The present study deals with the preparation of new composites in which L-proline (LP) and furnacrylic acid (FA) have been grafted on surface of amino functionalized silica nanoparticles (AFS). At first, AFS were prepared by sol-gel approach using tetraethoxysilane (TEOS) as silica source and aminopropyltriethoxysilane (APTES) as silica modifiers. Taking the advantage of amino group on AFS surface, LP and FA were easily grafted on silica surface to obtain LP grafted silica (AFS-LP) and FA grafted silica (AFS-FA) nanocomposites by post modification approach. As prepared composites were characterized by FTIR, SEM, XRD and TGA. The evidence of LP and FA on AFS was elucidated from the FTIR bands found at 1650–1698 cm−1 related to carbonyl group CO) of amide. Additionally, peaks observed at 2965 cm−1 (C-H stretching) of propyl groups and at 1050 cm−1 (Si-O-Si) indicated that the backbone of the material is preserved as silica. The micro images of SEM depicted that the AFS are spherical in shape and have more degree of monodispersivity whereas the SEM images of composites (AFS-LP and AFS-FA) have larger particle size and less degree of monodispersivity. Likewise, XRD peaks at 2θ (∼12°) revealed the mesoporosity of silica as well as hybrid silica and further depression in this peak in case of AFS-LP and AFS-FA depicted the existence of organic moieties on silica. TGA analysis depicted three decomposition steps (high weight loss) in case of AFS-LP and AFS-FA in contrast to two decomposition steps observed in case of AFS. The higher weight loss observed in the case of hybrid composites depicted the grafting of organic molecules on AFS. The prepared composites AFS-LP and AFS-FA were deployed to investigate their adsorption capacity to remove methyl orange (MO) from aqueous media. Experiments revealed that the composites have high adsorption capacity in acidic media (pH=2) with % removal of 85.05 % for AFS-LP and 81.70 % for AFS-FA. The experimental data was evaluated for adsorption isotherms and value of correlation factor (R2) was close to unity in case of Freundlich representing that the adsorption follows Freundlich isotherm. The data was also evaluated for kinetic models and higher values of R2 as well as closeness of experimental and calculated values of Qe predicted that adsorption of MO followed pseudo-second order kinetic model.

In Situ Performance Monitoring of Electrochemical Oxygen and Hydrogen Peroxide Sensors in an Additively Manufactured Modular Microreactor.

Miniaturized and microstructured reactors in process engineering are essential for a more decentralized, flexible, sustainable, and resilient chemical production. Modern, additive manufacturing methods for metals enable complex reactor-geometries, increased functionality, and faster design iterations, a clear advantage over classical subtractive machining and polymer-based approaches. Integrated microsensors allow online, in situ process monitoring to optimize processes like the direct synthesis of hydrogen peroxide. We developed a modular tube-in-tube membrane reactor fabricated from stainless steel via 3D printing by laser powder bed fusion of metals (PBF-LB/M). The reactor concept enables the spatially separated dosage and resaturation of two gaseous reactants across a membrane into a liquid process medium. Uniquely, we integrated platinum-based electrochemical sensors for the online detection of analytes to reveal the dynamics inside the reactor. An advanced chronoamperometric protocol combined the simultaneous concentration measurement of hydrogen peroxide and oxygen with monitoring of the sensor performance and self-calibration in long-term use. We demonstrated the highly linear and sensitive monitoring of hydrogen peroxide and dissolved oxygen entering the liquid phase through the membrane. Our measurements delivered important real-time insights into the dynamics of the concentrations in the reactor, highlighting the power of electrochemical sensors applied in process engineering. We demonstrated the stable continuous measurement over 1 week and estimated the sensor lifetime for months in the acidic process medium. Our approach combines electrochemical sensors for process monitoring with advanced, additively manufactured stainless steel membrane microreactors, supporting the power of sensor-equipped microreactors as contributors to the paradigm change in process engineering and toward a greener chemistry.

A novel bidentate diamide ligand DODQ for the separation of uranium and rare earth ions in nitric acid medium

High efficiency extractants play a necessary role in the selective removal of uranium from rare earth minerals. In this paper, a novel cyclic bidentate diamine extractant, 1, 4-dioctyl-1, 4-dihydroquinoxaline-2, 3-dione (DODQ), was synthesized, and the complexation and extraction of UO22+ in nitric acid medium were systematically studied. The results indicate that DODQ exhibits a unique combination of properties in removing UO22+, with an extraction capacity 132 times higher than that of DODPhOA (acyclic structure). Extraction isotherm experiments and slope analyses illustrate the formation of a 1:1 DODQ/UO22+ regime during the extraction process. Electrospray mass spectrometry, fluorescence spectroscopy, and X-ray crystal diffraction analyses further corroborated its stoichiometric properties. In addition, DODQ can remove UO22+ from rare earth solutions containing UO22+ with high selectivity. This study provides an alternative method to separate uranium from the leaching solution of rare earth ore and has a new understanding of the coordination and complexing behavior of UO22+ with bidentate oxygen-containing ligands.

Dibutylamide hydrophobic deep eutectic solvent used for selective extraction of Au(III) from hydrochloric acid medium

The effective and environmentally friendly recovery of gold from secondary resources has recently received increased attention. Hydrophobic deep eutectic solvent (HDES) composed of N,N-di-butylacetamide and 1-decanoic acid was used to construct the liquid-liquid extraction system to extract Au(III) from HCl medium. At first, DSC, TGA, FT-IR, and 1H NMR were used to describe the evidence of internal hydrogen bond interaction. The above evidence was verified in the molecular dynamics study of HDES. Then, a series of optimization experiments were carried out to investigate the extraction behaviors of HDES. Based on the results of optimization experiments, response surface method was used to explore the best experimental conditions and the results showed that HDES extracted 99% Au(III) under 0.56 mol/L HCl, 2.19 mol/L NaCl, and 5.83 mmol/L Au(III), and the maximum loading reached 77.0 mg/g. Further studies on the kinetics and thermodynamics of the extraction were used to propose an ion association mechanism. In addition, using 0.1 mol/L thiourea as the stripping agent, HDES displayed outstanding Au(III) selectivity and maintained the extraction efficiency in tests which involved 5-cycles. Overall, this study provides a green and efficient Au(III) recovery strategy for secondary resources.