Molar Ratio Mixture Research Articles

Fabrication of highly efficient FeNi-based electrodes using thermal plasma spray for electrocatalytic oxygen evolution reaction

Electrochemical water splitting has emerged as a promising approach for efficient energy production, drawing significant attention in recent research. However, the key challenge lies in identifying cost-effective and highly efficient electrocatalysts based on earth-abundant materials as alternatives to noble metals. Transition metals have garnered considerable interest due to their favorable properties: cost-effectiveness, superior performance, and long-term stability. In this study, we focused on the fabrication of FeNi-based electrocatalysts using atmospheric plasma spray in various mole ratio mixtures of FeNi (1:1, 1:2, 1:3). The phase and elemental composition of the prepared electrocatalysts were analyzed through X-ray diffraction, X-ray photoelectron spectroscopy, and energy-dispersive X-ray spectroscopy. Electrochemical characterization was performed using a three-electrode system. Among the different mole ratio compositions, FeNi (1:3) exhibited remarkable activity towards the Oxygen Evolution Reaction (OER), with an overpotential of 313 mV and a Tafel slope of 64.03 mV/dec at 20 mA cm−2. Furthermore, FeNi demonstrated excellent stability in OER activity even after 1000 cycles. The surface morphology of the coatings before and after electrochemical reactions was examined using Scanning electron microscopy. This study highlights the successful fabrication of FeNi-based electrocatalysts via atmospheric plasma spray, showcasing their potential as binder-free and highly stable electrocatalysts for electrochemical water-splitting applications.

Crystallographic Study of Product Phases of Carbothermic Reduction and Nitridation of Hafnium Dioxide.

Details of the carbothermic reduction/nitridation to synthesize hafnium nitride (HfN) and hafnium carbide (HfC) are scarce in the literature. Therefore, this current study was carried out to evaluate two pathways for synthesizing these two refractory materials: direct nitridation and carbothermic reduction/nitridation. Two mixtures of hafnium dioxide and carbon with C/HfO2 molar ratios of 2.15 and 3.1 were nitridized directly using flowing nitrogen gas at elevated temperatures (1300-1700 °C). The 3.1 C/HfO2 molar ratio mixture was also carbothermically reduced under flowing argon gas to synthesize HfC, which was converted into HfN by introducing a nitridation step under both N2(g) and N2(g)-10% H2(g). X-ray diffraction results showed the formation of HfN at 1300 and 1400 °C and HfC1-yNy at ≥1400 °C under direct nitridation of samples using a C/HfO2 molar ratio of 2.15. These phase analysis data together with lower lattice strain and greater crystallite sizes of HfC1-yNy that formed at higher temperatures suggested that the HfC1-yNy phase is preferred over HfN at those temperatures. Carbothermic reduction of 3.1 C/HfO2 molar ratio samples under an inert atmosphere produced single-phased HfC with no significant levels of dissolved oxygen. Carbothermic reduction nitridation made two phases of different carbon levels (HfC1-yNy and HfC1-y'Ny', where y' < y), while direct nitridation produced a single HfC1-yNy phase under both N2 and N2-10% H2 cover gas environments.

The ceria – Germania solid oxide hydrogen storage hollow porous nanoparticles

The combination of high specific surface area and high porosity content as diffusion routes for adsorption/desorption in monodispersed solid state mixed oxide ceramic nanosized hollow porous particles enabled high hydrogen storage capacity with promising platform for controlled gas molecules delivery. The synthesized thin-walled nanoparticles were characterized for crystallinity, bond structure, morphology, and surface activity/adsorption profiles. The optimum molar ratio mixture of equal parts ceria and germania in hollow porous nanoparticles stored up to 7.8 wt% with specific surface area near 6100 m2/g and about 2 cm3/g volume content of 2.9 Å pores. The maximum discharge capacity of ∼5600 mAh/g after 12 cycles of this mesoporous structure provided a considerable storage performance and reversibility at ambient conditions. The structure dependency of storage was attributed to structural characteristics in CeO4 - GeO6 polyhedras and alterations between oxidation states in ceria.

Catalytic behaviour of transition metal carbides of group 5 in the methanol steam reforming

Transition metal carbides of group 5 (G5TMC=VC, NbC and TaC) with similar crystallite sizes were prepared by a sol-gel route. The catalysts were characterized and studied in the methanol steam reforming (MSR) reaction in the temperature range of 573–723 K at atmospheric pressure and using a stoichiometric CH3OH/H2O = 1/1 mole ratio mixture. Under the MSR reaction conditions used, the route of methanol transformation depends on the G5TMC used as catalyst. The catalytic behaviour of VC differs from that of NbC and TaC, which in turn show a similar behaviour. Over VC, methanol is mainly converted to a mixture of H2+CH4, whereas over NbC and TaC the major product obtained is HCHO, formed from the dehydrogenation of methanol.

Synthesis of ReB2-Al2O3 composite powders and chemical resistance of the products to moisture

Synthesis of composite material from the ReO2 + Al2O3 + Al + B2O3 mixture was carried out. Mixtures were annealed at 1150 °C for 1 h or in two-steps process at 1050 °C and 1150 °C for 4 h, in argon. Different B2O3/ReO2 molar ratios were adopted: 1.0; 1.3; 1.5; 1.8; 2.0; 2.3, 2.5; 2.8; 3.0. The TG/DTA analysis was performed for the synthesis of mixtures of different molar ratios. Produced materials were tested by XRD phase composition studies. In every mixtures, products consisted mainly of ReB2, Al2O3, Re7B3 and aluminum borides. The research was aimed at reducing the share of the Re7B3 phase. Increase of the B2O3/ReO2 molar ratio in the syntheses results in the formation of boromullite phases such as Al5BO9, Al18B4O33, Al4B2O9. XRD and XPS investigations were carried out after prolonged exposure to humidity. Materials produced at a molar ratio B2O3/ReO2 = 1 are characterized by greater resistance to water from moisture compared to other tested mixtures.

Ethaline and related systems: may be not “deep” eutectics but clearly interesting ionic liquids

Abstract Ethaline, the 1:2 molar ratio mixture of ethylene glycol (EG) and choline chloride (ChCl), is generally regarded as a typical type III deep eutectic solvent (DES). However, careful differential scanning calorimetry (DSC) of EG + ChCl mixtures surprisingly revealed that the liquidus lines of the phase diagram apparently follow the predictions for an ideal binary non-electrolyte mixture. Applying broad-band dielectric relaxation spectroscopy to room-temperature solutions of ChCl, and of the related salts choline iodide and chlorocholine chloride, in EG up to saturation, we explored the possible reasons for this conundrum. It appears that in these solutions free ions are rather scarce. Instead, contact ion pairs and larger aggregates predominate.

Impact of Hydrogen Bonds on CO2 Binding in Eutectic Solvents: An Experimental and Computational Study toward Sorbent Design for CO2 Capture

Choline-based amino acid ionic liquids with anions glycinate, β-alaninate, phenylalaninate, and prolinate were synthesized and mixed with ethylene glycol to form lower-viscosity benign eutectic solvents for CO2 capture. The highest capacity measured was 0.7 moles of CO2 per mole of ionic liquid (2 moles CO2 per kg solvent) for a 1 to 2 mole ratio mixture of choline prolinate to ethylene glycol at 1 bar of CO2 and 25 °C. Under 5000 ppm of CO2, half of this capacity was realized. Through a combined study of quantitative 13C NMR spectroscopy, molecular dynamics simulations and density functional theory calculations, we show that hydrogen bonding in the eutectic solvent prevents proton-transfer between prolinate anions upon CO2 absorption, which occurs in the absence of ethylene glycol and deactivates binding sites. Blocking this proton transfer leads to a higher binding capacity compared to neat choline prolinate. This work demonstrates the impact of hydrogen bonding on the CO2 binding mechanism and energetics, as well as physical and thermal properties in eutectic solvents, thus addressing an unmet need and informing future studies on the development of benign sorbents for capturing CO2 from dilute streams.

(Invited) Concentrated Hydrogen Bonded Electrolytes: Definition and Bulk & Interfacial Properties

We broadly refer to deep eutectic solvents (DESs) as concentrated H-bonded electrolytes (CoHBEs) where a composition specific to the “deep eutectic temperature” does not have to be met as long as the electrolyte possesses high salt concentration of the salt or the redox active specie and suppressed volatility are desired in energy storage, electrocatalysis, and electrodeposition processes. Liquid heterogeneity owing to H-bonding, similar to ionic liquids and DESs, CoHBEs present distinct electrode-electrolyte interfacial behavior.As a way to probe the electrode-electrolyte behavior of CoHBEs as a function of composition, we have performed electrochemical impedance spectroscopy and surface enhanced Raman spectroscopy (SERS). The potential dependent differential capacitance of choline chloride and ethylene glycol (1:2, 1:4, 1:6 molar ratio) mixtures do not present camel shaped curves as in the case of more extreme examples of concentrated electrolytes such as ionic liquids. The interfacial behavior is more similar to dilute systems, however, the H-bonding network presents a less mobile diffuse layer. While on glassy carbon, there is no specific ion adsorption, on metal electrodes chloride adsorption is observed. In chloride-free systems that are based choline oxalate mixed with ethylene glycol, capacitance is measured to be almost independent of the applied voltage on glassy carbon and gold. This is attributed to the strong binding energy of the solvation structure, as determined from theory, that hinders voltage-induced reorientations. Consistent to this behavior, the oxalate system also presents a very high viscosity. In addition, the voltage sweep range is limited in the case of oxalate system as it has narrower electrochemical window. On the other hand, choline acetate, which has a very similar chemical structure to the oxalate, undergoes specific ion adsorption particularly on gold electrode at a positive applied potential as confirmed by SERS. This is believed to be due to the reduced binding energy as calculated by density functional theory with -1 charge of the acetate in comparison to -2 charge in oxalate that leads to the desolvation and then the surface adsorption of the acetate. In the case of the choline bis(trifluorosulfonyl)imide and ethylene glycol mixture, a wider electrochemical window accompanied by a dampened u-shaped capacitance was observed with no specific ion adsorption.This study presents tuning of DESs and more broadly CoHBEs in terms of the bulk physical properties, the interfacial behavior near an electrode, and the coupled structuring effects through the variation in anion charge density and the extent of H-bonding.

Controllable Polymerization of N -Substituted β-Alanine N -Thiocarboxyanhydrides for Convenient Synthesis of Functional Poly(β-peptoid)s

Controllable Polymerization of <i>N</i> -Substituted β-Alanine <i>N</i> -Thiocarboxyanhydrides for Convenient Synthesis of Functional Poly(β-peptoid)s

Evaluation of Piperine as Natural Coformer for Eutectics Preparation of Drugs Used in the Treatment of Cardiovascular Diseases.

Piperine (PIP) was evaluated as a natural coformer in the preparation of multicomponent organic materials for enhancing solubility and dissolution rate of the poorly water-soluble drugs: curcumin (CUR), lovastatin (LOV), and irbesartan (IBS). A screening based on liquid assisted grinding technique was performed using 1:1 drug-PIP molar ratio mixtures, followed by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) analyses. Three eutectic mixtures (EMs) composed of CUR-PIP, LOV-PIP, and IBS-PIP were obtained. Therefore, binary phase and Tamman's diagrams were constructed for each system to obtain the exact eutectic composition, which was 0.41:0.59, 0.29:0.71, and 0.31:0.69 for CUR-PIP, LOV-PIP, and IBS-PIP, respectively. Further, bulk materials of each system were prepared to characterize them through DSC, PXRD fully, Fourier transform infrared spectroscopy (FT-IR), and solution-state nuclear magnetic resonance (NMR) spectroscopy. In addition, the contact angle, solubility, and dissolution rate of each system were evaluated. The preserved characteristic in the PXRD patterns and FT-IR spectra of the bulk material of each system confirmed the formation of EM mixture without molecular interaction in solid-state. The formation of EM resulted in improved aqueous solubility and dissolution rate associated with the increased wettability observed by the decrease in contact angle. In addition, solution NMR analyses of CUR-PIP, LOV-PIP, and IBS-PIP suggested no significant intermolecular interactions in solution between the components of the EM. Hence, this study concludes that PIP could be an effective coformer to improve the solubility and dissolution rate of CUR, LOV, and IBS.

Serotonergic drugs modulate the phase behavior of complex lipid bilayers

Serotonin is an endogenous neurotransmitter involved in both physiological and pathophysiological processes. Traditionally, serotonin acts as a ligand for G protein-coupled receptors (GPCRs) leading to subsequent cell signaling. However, serotonin can also bind to lipid membranes with high affinity and modulate the phase behavior in 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC)/N-palmitoyl-D-erythro-sphingosylphosphorylcholine (PSM)/cholesterol model membranes mimicking the outer leaflet of the plasma membrane. Here, we investigated if serotonergic drugs containing the pharmacophore from serotonin would also modulate phase behavior in lipid membranes in a similar fashion. We used 2H NMR spectroscopy to explore the phase behavior of POPC/PSM/cholesterol (4/4/2 molar ratio) mixtures in the presence of the serotonergic drugs aripiprazole, BRL-54443, BW-723C86, and CP-135807 at a lipid to drug molar ratio of 10:1. POPC and PSM were perdeuterated in the palmitoyl chain, respectively, and prepared in individual samples. Numerical lineshape simulations of the 2H NMR spectra were used to calculate the order parameter profiles and projected lengths of the saturated acyl chains. All serotonergic drugs induce two components in 2H NMR spectra, indicating that they increased the hydrophobic mismatch between the thickness of the coexisting lipid phases leading to larger domain sizes, relatively similarly to serotonin. AFM force indentation and Raman spectral studies, which interrogate membrane mechanical properties, also indicate changes in membrane order in the presence of these drugs. These findings highlight how serotonergic drugs alter membrane phase behavior and could modulate both target and other membrane proteins, possibly explaining the side effects observed for serotonergic and other clinically relevant drugs.

An Antimicrobial Peptide-Mimetic Methacrylate Random Copolymer Induces Domain Formation in a Model Bacterial Membrane.

To address the emerging issue of drug-resistant bacteria, membrane-active synthetic polymers have been designed and developed to mimic host-defense antimicrobial peptides (AMPs) as antibiotic alternatives. In this study, we investigated the domain formation induced by synthetic polymer mimics of AMPs using model membranes to elucidate the biophysical principles that govern their membrane-active mechanisms. To that end, lipid vesicles mimicking Escherichia coli(E. coli) membrane were prepared using an 8:2 (molar ratio) mixture of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol), sodium salt (POPG). Our studies using differential scanning calorimetry (DSC) and fluorescence microscopy indicated that cationic amphiphilic methacrylate random copolymers induced the phase separation to form POPE- or POPG-rich domains. A rhodamine-labeled polymer also showed the binding to separated domains in the membrane. Based on these results, we propose the mechanism that the copolymers induce domain formation by clustering of anionic POPG lipids similar to natural AMPs. In addition, the time-course of polymer binding to the GUV membrane was sigmoidal, suggesting the positive feedback loop in the membrane binding. We also hypothesize that this cooperative binding of the polymer is driven by the domain formation. This study demonstrates the potential of the amphiphilic copolymers to modulate the lipid organization of cell membranes, which may provide a new strategy to design membrane-active antimicrobial agents.

Effect of NaCN:ZnSO4 Mixture Molar Ratio and Particle-Size Distribution on Pb-Zn and Fe Selective Separation by Froth Flotation

Effect of NaCN:ZnSO4 Mixture Molar Ratio and Particle-Size Distribution on Pb-Zn and Fe Selective Separation by Froth Flotation

Viologen Derivatives in Deep Eutectic Solvents for Energy Storage

Redox flow batteries (RFBs) serve as one of the most promising battery technologies to meet the grid-scale energy storage requirements, owing to their scalable nature and acceptable redox chemistry. To achieve economical and sustainable energy storage, there has been a rapid transition from redox-active inorganic materials to the earth-abundant and tunable redox-active organic compounds for RFBs. Among explored redox-active organic materials, viologen derivatives show promise for battery applications due to their two successive redox reactions and low cost. Taking advantage of both redox reactions, however, may not be possible in aqueous electrolytes due to the insolubility of the charge-neutral viologen in aqueous solutions.1 Deep eutectic solvents (DESs) can offer an inexpensive electrolyte for energy storage which could potentially solve the solubility issues associated with these materials.2 Owing to their low vapor pressure, DESs can be also utilized at elevated temperatures for lower viscosity and enhanced conductivity.3 In an attempt to identify a high-concentrated and reversible redox-active DES, the electrochemical properties and solubility of methyl, ethyl, and benzyl viologens in choline chloride (ChCl) and ethylene glycol (EG) (1:4 molar ratio) mixture were investigated. To better qualify these redox-active molecules as an anolyte material for RFBs, the redox reactions were studied to assess the redox reversibility, the potential separation between the consecutive electron transfer reactions, and the redox kinetics. The electron-transfer rate constants were estimated using linear sweep voltammetry (LSV) at a glassy carbon rotating-disk electrode in a three-electrodes configuration cell. Diffusion coefficients were also calculated from the steady-state diffusion-limited current using the rotating-disk electrode as well as a microelectrode. Elucidating the kinetic parameters, diffusion coefficients, and transport properties of the viologen derivatives in DESs will bring insight into designing a concentrated redox-active DES for energy storage. B. Hu and T. L. Liu, J. Energy Chem., 27, 1326 (2018).B. Chen, S. Mitchell, N. Sinclair, J. Wainright, E. Pentzer, and B. Gurkan, Mol. Syst. Des. Eng., 5, 1147 (2020).N. S. Sinclair, D. Poe, R. F. Savinell, E. J. Maginn, and J. S. Wainright, J. Electrochem. Soc., 168, 020527 (2021).

Hydrogen bonding and surface tension properties of aqueous solutions of tetrahydrofuran

Significant changes observed in the tetrahydrofuran—water mixtures of different molar ratios have been determined the extent of intermolecular association via quantitative Raman experiment. The hydrogen bonding changes with the addition of tetrahydrofuran. The changes of surface tension are analyzed with hydrogen bonding in the mixtures. The result shows that the strengthening of hydrogen bonding between tetrahydrofuran and water contributes to weak the surface tension in the solutions. The correlation between surface tension and mole fractions of tetrahydrofuran is non-linear. This study provides an experimental basis for enriching the hydrogen bonding theory of multivariate aqueous solution systems.

Evaluation of canonical choline chloride based deep eutectic solvents as dye-sensitized solar cell electrolytes.

Deep eutectic solvents (DESs) are beginning to attract interest as electrolyte alternatives to conventional organic solvents and ionic liquids within dye-sensitized solar cells (DSSCs). The precise roles played by DES components and whether they simply represent a benign medium for mobilizing charge carriers or present beneficial functionality that impacts device performance remain unclear. To begin to address this deficiency in understanding, we performed a comprehensive characterization of the three "canonical" choline chloride-based DESs (i.e., reline, ethaline, and glyceline) as DSSC electrolytes hosting the iodide-triiodide (I-/I3 -) redox couple. The measurement of electrolyte viscosities, determination of triiodide diffusion coefficients, and photovoltaic performances assessed for water contents up to 40 wt. % allow the emergence of several important insights. A comparison to the observed photovoltaic performance arising from the individual components aids in further clarifying the impact of DES chemistry and solution viscosity on photovoltaic and charge carrier diffusion characteristics. Finally, we introduce the DES guaniline-consisting of a 1:1 molar ratio mixture of choline chloride with guanidinium thiocyanate-demonstrating it to be a superior DSSC electrolyte over those formulated from the three most widely studied canonical DESs at all water contents investigated.

Influence of Blending of Nonionic Emulsifiers Having Various Hydrophilic Head Sizes on Lipid Oxidation: Investigation of Antioxidant Polarity Interfacial Characteristics Relationship.

The purpose of this study was to deliver insights into the effect of interfacial composition and antioxidant polarity on the lipid oxidation of emulsions. Emulsions were created using blends of nonionic ethoxylated fatty acid alcohol surfactants with different hydrophilic head sizes, and lipophilic (TBHQ) and amphiphilic (lauryl gallate) antioxidants were incorporated into the emulsions. At the same surfactant concentration, emulsion stabilized with surfactant with a smaller hydrophilic head was more susceptible to lipid oxidation than that stabilized with surfactant with a larger hydrophilic head. When surfactants with a similar hydrophilic head size were used, lipid oxidation in emulsion containing more surfactant was slightly faster than that containing less surfactant. When emulsions were created with a 1:1 molar ratio mixture of surfactants with small and large hydrophilic heads, surfactant concentration (1.00 and 2.932 mM) had little effect on lipid peroxide generation rate. However, the concentration of thiobarbituric acid-reactive substances (TBARSs) in the emulsion prepared at 1.00 mM increased faster than that prepared at 2.93 mM. Alteration of interfacial composition and surfactant concentration did not affect antioxidant ability, regardless of antioxidant polarity, to inhibit lipid peroxide generation. However, the ability of lauryl gallate and TBHQ to prevent TBARS generation was elevated by mixing surfactants with small and large hydrophilic heads and by decreasing surfactant concentration. In most emulsions, lauryl gallate showed a more effective antioxidant ability than TBHQ.

Electrochemical Decomposition of Ethylene Glycol-Choline Chloride Deep Eutectic Solvent

Deep eutectic solvents (DES) are a form of ionic liquid that can offer a larger electrochemical window than water while remaining relatively conductive as compared to other non-aqueous options. DES are made from the eutectic combination of a variety of hydrogen bond donors and acceptors. At a molar ratio of donor and acceptor specific to each DES, the melting point of the mixture is significantly depressed resulting in a room temperature liquid with a high boiling point. As a result, they are considerably less volatile and therefore a safer alternative to traditional organic solvents such as acetonitrile. The low vapor pressure associated with a deep eutectic composition allows for operation at elevated temperatures for faster kinetics, increased conductivity and lower viscosity. DES can also contain a greater concentration of supporting charge carries than many organic solvents (up to 8 M) and many redox active organic compounds are also highly soluble in DES. These factors make DES a promising electrolyte for redox flow batteries, with the potential for higher energy densities than can be achieved in aqueous electrolytes.One of the most commonly studied DES is a 1:2 molar ratio mixture of choline chloride and ethylene glycol respectively. This mixture, commonly called ‘ethaline’ is one of the most conductive, lowest viscosity DES. While these are desirable characteristics, the stable electrochemical window is only ≈2 V which is only somewhat larger than the usable window of an alkaline aqueous electrolyte. The objective of this effort is to investigate the electrochemical decomposition of ethaline at the anodic and cathodic limits.Relatively little literature exists on the decomposition of ethaline. It has been claimed that at the anode, several different chlorinated organics are created by various mechanisms and that hydrogen is evolved at the cathode from water contained in the electrolyte.1 While the oxidation of ethylene glycol (EG) is well studied2 , 3, the oxidation of ethaline and the reduction of EG and ethaline both are somewhat unknown. A series of electrolysis experiments using a divided cell were carried out using dry ethaline prepared in a glove box with a water vapor content below 5 ppm. The water content in the electrolyte was determined by Karl Fischer titration to be less than 300 ppm. The products of these experiments were analyzed using mass spectroscopy (of both the anodic and cathodic electrolytes and of the headspace above each) and FTIR. These results show that the positive decomposition involves the oxidation of ethylene glycol to glycolaldehyde, and subsequent formation of the glycolaldehyde dimer in solution. At the negative limit, hydrogen is evolved in direct proportion to the current passed. However, it can be conclusively shown that the reduction current can exceed the maximum possible current due to the reduction of water, implying that the reduction of the DES components is necessary. GC-MS analysis of the negative electrolyte showed the presence of higher molecular weight fragments consistent with the reaction scheme shown in Fig 1 below. In this scheme, the reduction of ethylene glycol results in the generation of H2 gas as observed, and the formation of ethylene oxide. The ethylene oxide produced then can react chemically with ethylene glycol to yield dimers and trimers of polyethylene glycol whose molecular masses are consistent with the peaks observed in the GC-MS analysis.The identification of these breakdown pathways will provide insight into safety concerns related to overcharge of ethaline electrolytes and will allow for the development of alternative formulations that can extend the potential limits to allow for the incorporation of higher voltage redox couples in redox flow batteries based on DES electrolytes.

Graphene oxide-MnO2-goethite microsphere impregnated alginate: A novel hybrid nanosorbent for As (III) and As (V) removal from groundwater

This study presents a simple method for facile synthesis of core-shell microspheres of Graphene oxide-MnO2-Goethite (GO-MnO2-Goe). Synthesised GO was used as the core material for treatment with the pre-decided molar ratio mixture of Fe and Mn to form a MnO2-Goe shell over the GO surface optimising various parameters. Subsequently the GO-MnO2-Goe nanoparticles were impregnated into alginate polymer to form GO-MnO2-Goethite impregnated alginate hydrogel beads (GO-MnO2-Goe-Ca-Alg) using displacement reaction. The product was characterized by XRD, FTIR, BET, SEM-EDS and zeta potential measurement. The GO-MnO2-Goe-Ca-Alg hybrid nanosorbent was used to efficiently remove both arsenic (III) and arsenic (V) from groundwater (80–96 % for 0.1−100 μg mL−1 concentration range) at pH 4–6. Uptake processes for both As (III) and As (V) followed Langmuir isotherm model with maximum sorption capacity evaluated as 27.53 and 34.17 mg g-1 respectively for As (III) and As (V). The reaction kinetics, thermodynamic parameters, interparticle diffusion model were studied. Mechanism of uptake was suggested based on fraction diagram of As (III) and As (V) species along with zeta potential of GO-MnO2-Goe at various pH. The in-situ transformation of As (III) to As (V) before its sorption was investigated and explained with the help of XPS analysis.

Cooperative dynamics and speciation in deep eutectic solvent + DMSO mixtures

Dielectric relaxation (DR) spectra within the frequency range of 0.05 ≤ ν/GHz ≤ 89 were measured at T = 308.15 K to reveal structure and dynamics of mixtures of deep eutectic solvents (DESs) with dimethylsulfoxide (DMSO). Studied DESs were reline, glyceline and ethaline, ie. 1:2 molar ratio mixtures of choline chloride (ChCl) and the hydrogen bond donors (HBDs) urea, glycerol and ethylene glycol. The obtained DR spectra were best fit by a superposition of relaxations associated with the reorientation of dipolar DES components and individual DMSO molecules. In contrast to previously studied mixtures of glyceline and reline with water, the analysis of the obtained relaxation amplitudes revealed that the present DES/DMSO systems cannot be simply regarded as mixtures of individual Ch+, Cl−, HBD and DMSO units over the entire mixture range. Instead, a significant amount of ChCl contact ion pairs (CIPs) is formed at moderate DES concentrations. Due to their high dipole moment these CIPs cause pronounced maxima at ChCl:HBD:DMSO ratios of ~1 : 2 : 9 in the static permittivity of the mixtures. Pronounced solute-solvent interactions slow down the rotational motion of solvating DMSO molecules. At infinite dilution the derived total effective solvation numbers, Zt, extrapolate to ~8 − 9 DMSO per ethaline, ~16 per glyceline and ~7 − 8 per reline unit but numbers decrease rapidly with rising DES mole fraction. For the latter two DESs Zt could be split into ChCl and HBD contributions. Finally, careful analysis of the relaxation times provided evidence for pronounced micro-heterogeneity of the studied mixtures.