Water Solvent Mixtures Research Articles

Unified pH Measurements of Ethanol, Methanol, and Acetonitrile, and Their Mixtures with Water

Measurement of pH in aqueous-organic mixtures with different compositions is of high importance in science and technology, but it is, at the same time, challenging both from a conceptual and practical standpoint. A big part of the difficulty comes from the fundamental incomparability of conventional pH values between solvents (spH, solvent-specific scales). The recent introduction of the unified pH (pHabs) concept opens up the possibility of measuring pH, expressed as , in a way that is comparable between solvent, and, thereby, removing the conceptual problem. However, practical issues remain. This work presents the experience of the authors with measuring values in mixtures of methanol, ethanol, and acetonitrile, with water, but without the presence of buffers or other additives. The aim was to assigned values to solvent–water mixtures using differential potentiometry and the ‘pHabs-ladder’ method. Measurements were made of the potential difference between glass electrodes immersed in different solutions, separated by an ionic liquid salt bridge. Data were acquired for a series of solutions of varying solvent content. This work includes experiences related to: a selection of commercial electrodes, purity of starting material, and comparability between laboratories. Ranges of values for selected compositions of solvent–water mixtures are presented.

Fabrication of Photoactive Electrospun Cellulose Acetate Nanofibers for Antibacterial Applications

The aim of the study was to investigate the process of electrostatic fabrication of cellulose acetate (CA) nanofibers containing methylene blue (MB) as a photosensitizer. The electrical, physicochemical, and biocidal properties of the prepared material were given. CA nanofibers were prepared by electrospinning method using a solvent mixture of acetone and distilled water (9:1 vv−1) and different concentrations of CA (i.e., 10–21%). Additionally, methylene blue was implemented into the polymer solution with a CA concentration of 17% to obtain fibers with photo-bactericidal properties. Pure electrospun CA fibers were more uniform than fibers with MB (i.e., ribbon shape). Fiber diameters did not exceed 900 nm for the tested polymer solutions and flow rate below 1.0 mL h−1. The polymer properties (i.e., concentration, resistivity) and other parameters of the process (i.e., flow rate, an applied voltage) strongly influenced the size of the fibers. Plasma treatment of nanofibers resulted in reduced biofilm formation on their surface. The results of photo-bactericidal activity (i.e., up to 180 min) confirmed the high efficiency of inactivation of Staphylococcus aureus cells using fibers containing methylene blue (i.e., with and without plasma treatment). The most effective reduction in the number of biofilm cells was equal to 99.99 ± 0.3%.

Zero-Discharge Process for Recycling of Tetrahydrofuran–Water Mixtures

The sustainable design of separation and polymer synthesis processes is of great importance. Therefore, an energy-efficient process for the purification of tetrahydrofuran (THF)–water (H2O) solvent mixtures from an upstream polymer synthesis process in pilot scale was developed with the aim to obtain high purity separation products. The advantages and limitations of a hybrid process in the pilot scale were studied utilizing an Aspen Plus Dynamics® simulation at different pressures to prove the feasibility and energy efficiency. For the rough separation of the two components, distillation was chosen as the first process step. In this way, a separation of a water stream of sufficient quality for further precipitations after polymer synthesis could be achieved. In order to overcome the limitations of the distillation process posed by the azeotropic point of the mixture, a vapor permeation is used, which takes advantage of the heat of evaporation already used in the distillation column. For the purpose of achieving the required low water contents, an adsorption column is installed downstream for final THF purification. This leads to a novel hybrid separation process that is energy efficient and thus allows also the use of the solvents again for upstream polymer synthesis achieving the high purity requirements in a closed-loop process.

In situ growth of NiFe MOF/NF by controlling solvent mixtures as efficient electrocatalyst in oxygen evolution

Two-dimensional metal–organic frame (2D MOF) materials have attracted great attention due to the successful combination of the unique properties of MOF and chemical properties of 2D material. In this paper, NiFe MOF/NF with a two-dimensional layered vertical structure were prepared by bottom-up solvothermal method. We used different solvent mixtures (methanol/water, ethanol/water, acetone/water, N, N-dimethylformamide/water) to control the synthesis of MOF and found that the oligpolar solvent mixture of acetone and water was the best in controlling the formation of these two-dimensional MOFs. The obtained NiFe MOF/NF in acetone/water appeared the best performance as electrocatalyst for the oxygen evolution reaction, in which the NiFe MOF/NF delivered a current density of 50 mA·cm−2 at a low overpotential of 270 mV with a small Tafel slope of 55 mV·dec-1. In addition, NiFe MOF/NF has an excellent stability at a high current density of 100 mA·cm−2.

Effective separation of water-DMSO through solvent resistant membrane distillation (SR-MD)

The treatment of organic waste or wastewater with high organic solvent content has been challenging in industries as it cannot be done effectively using conventional wastewater treatment technologies such as biodegradation and advanced oxidation process. Solvent resistant membrane distillation (SR-MD) was proposed as an energy-efficient alternative to treat these waste streams but its application is hampered by the lack of solvent-resistant membranes, and there is a research gap in studying the feeds with water-solvent mixtures. In this work, ceramic tubular membranes with different pore sizes and structures were molecularly grafted with 1H,1H,2H,2H-perfluorodecyltriethoxysilane to obtain hydrophobic ceramic membranes for SR-MD. The modified membranes exhibited excellent hydrophobicity and solvent resistant properties, and they were tested for SR-MD performance with a wide range of dimethyl sulfoxide (DMSO) feed concentrations, from 3.5 to 85 wt%. The membranes exhibited a high DMSO rejection of >98% and the separation factor of >170, with permeation flux >4.4 kg m−2 h−1 when the DMSO concentration in feed was below 65 wt%. The separation performance was found strongly dependent on the evaporation step and the vapour-liquid equilibrium near the interface. The DMSO rejection was also comparable to pervaporation while the permeation flux was much higher at the feed concentration of 50 wt%. This study establishes the strategy of using SR-MD as a promising membrane process in treating complex industrial wastes with high organic solvent content.

Application of PC-SAFT EOS for Pharmaceuticals: Solubility, Co-Crystal, and Thermodynamic Modeling.

In this study, the applicability of the perturbed chain statistical associating fluid theory (PC-SAFT) was evaluated for pharmaceutical compounds. For this purpose, the parameters of the PC-SAFT equation of state (EOS) were regressed by applying the experimental solubility data of 54 pharmaceuticals in pure solvents. The reported errors for train and test data show the suitability of the PC-SAFT EOS. The applicability of the PC-SAFT EOS was explored by its prediction accuracy for the ternary system of medicine in solvent mixtures. The model errors were 23 and 26% for two ternary systems of salicylic acid and lidocaine HCl in solvent mixtures of ethanol and water, respectively. The co-crystal formation of salicylic acid-sulfamethazine in methanol was investigated by the PC-SAFT EOS. Finally, the reaction and crystallization sections for acetaminophen production from p-aminophenol were simulated by accompanying the PC-SAFT EOS and equilibrium assumption. The purification efficiencies for acetaminophen were obtained to be 93-98% for different temperatures.

Phenolic Composition of Dipteryx alata Vogel Pulp + Peel and Its Antioxidant and Cytotoxic Properties

Dipteryx alata Vogel is a native fruit from Brazil, which has been poorly investigated concerning its phenolic composition and the biological effects of its pulp + peel. Thus, in this study we evaluated the antioxidant activity and total phenolic content of the D. alata pulp + peel extracts obtained with different solvents, as well as determined the phenolic compounds by ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) analysis. In addition, cytotoxic effects of D. alata pulp + peel extract on non-tumor and cancer cell lines were investigated for the first time. The results showed that phenolic compounds can be efficiently extracted from pulp + peel of D. alata by organic solvent-water mixtures as an extraction system. The developed UHPLC-MS/MS method allowed the quantification of eighteen phenolic compounds in D. alata pulp + peel extract for the first time, which luteolin and trans-cinnamic acid were predominant. In addition, D. alata pulp + peel extract exhibited better cytotoxity against SiHa and C33A cervical cancer cell lines, while weak cytotoxicity was noticed against non-tumor HaCaT and L929 cell lines, pointing out its safety and providing preliminary evidence of its anticancer potential. Our findings indicate that D. alata pulp + peel can be explored as a natural source of phenolic compounds with promising antioxidant and cytotoxic properties.

Experimental and Molecular Dynamics Simulation Study on the Primary Nucleation of Penicillamine Racemate and Its Enantiomers in the Mixture Solvent of Water and Ethanol

In this work, the solubilities of (d)- and (d,l)-penicillamine were first experimentally measured in the binary mixtures of ethanol and water. Then, the primary nucleation rate and various nucleati...

Bioinspired carrier-free peptide conjugated BF2-oxasmaragdyrin dye-based nano self-assemblies: a photostable NIR cancer theragnostic agent

Photothermal therapy (PTT) has attracted great interest in cancer treatment, and the quest for potential organic photothermal agents is underway owing to the nonbiodegradable nature and chronic toxicity of existing inorganic nanomaterials. Organic material-based nanoformulations with good photothermal and fluorescence properties in the near-infrared (NIR-I) window are scarce. However, porphyrins are one category of biocompatible systems that are advantageous for photothermal therapy but are currently based in the visible region, causing limited depth of tissue penetration and leading to compromised photothermal and near-infrared fluorescence (NIRF) imaging applications. To overcome these limitations, we report the synthesis of L,L-diphenylalanine conjugated BF2-oxasmaragdyrin (FF-BSC) and the fabrication of monodispersed spherical self-assemblies (FF-BSC NPs) using a USP class 3 solvent-water mixture. The resulting product exhibited excellent photostability (NIR exposure), multicycle photothermal efficacy, and NIR fluorescence. In vitro studies revealed good biocompatibility, efficient cellular internalization, and photothermal efficacy. Preclinical studies of these nano-self-assemblies demonstrated nontoxicity, efficient whole-body NIRF imaging, fractional passive tumor homing, and excellent photothermal tumor ablation potential. The absorbance and fluorescence of FF-BSC NPs in NIR-I make them suitable for theragnostic applications over existing porphyrins/inorganic nanomaterials for future clinical applications.

Solubility measurement and thermodynamic properties of sulfamonomethoxine in pure solvents and sulfamonomethoxine hydrate in acetone + water binary solvent at different temperature

The experimental solubility of sulfamonomethoxine in six different pure solvents (methanol, ethanol, 1-propanol, l-butanol, ethyl acetate and acetone) and sulfamonomethoxine hydrate in acetone + water mixture solvents were measured from 294.55 K to 362.15 K by a laser dynamic method under atmospheric pressure. Experimental results indicated that the solubility data of sulfamonomethoxine increased with temperature increasing in pure solvents and the solubility followed this order: acetone > methanol > ethanol > ethyl acetate > 1-propanol > 1-butanol, but solubility in ethyl acetate was not affected significantly by temperature. In acetone + water mixture solvent, the solubility of sulfamonomethoxine hydrate increased with temperature and the acetone concentration. Thermodynamic equations were applied to correlate solubility data of sulfamonomethoxine and sulfamonomethoxine hydrate including the modified Apelblat equation, λh equation, Wilson equation, NRTL equation, Van’t Hoff-Jouyban Acree equation and modified Apel-Jouyban-Acree equation. Furthermore, thermodynamic properties ΔGd, ΔHd and ΔSd of sulfamonomethoxine and sulfamonomethoxine hydrate in dissolution process were obtained and discussed with the modified Van’t Hoff equation and Gibbs equation.

Solubility of paracetamol in the ternary solvent mixtures of water + ethanol + glycerol at 298.2 and 303.2 K

ABSTRACT The solubility of paracetamol in the ternary mixtures of water + ethanol + glycerol at 298.2 and 303.2 K is determined via the shake-flask method. The reported data extend the solubility database for paracetamol in various solvent mixtures and also is employed to investigate the prediction capability of the cosolvency models for solubility prediction in the sub-binary and the ternary solvent systems. The solubility data are correlated with some cosolvency models and their accuracies are evaluated by the mean relative deviation (MRD) computed for back-calculated solubilities. The results show that the investigated models fit well and can be applied to the ternary solvent system, and the experimental data is relatively more consistent with the calculated values. The prediction ability of the trained Jouyban-Acree model for predicting drug solubility behaviour in the corresponding sub-binary systems is also investigated.

Solubility, Solution Thermodynamics, and Preferential Solvation of Amygdalin in Ethanol + Water Solvent Mixtures.

The equilibrium solubility of amygdalin in [ethanol (1) + water (2)] mixtures at 293.15 K to 328.15 K was reported. The thermodynamic properties (standard enthalpy ΔsolnH°, standard entropy ΔsolnS°, and standard Gibbs energy of solution ΔsolnG°) were computed using the generated solubility data via van’t Hoff and Gibbs equations. The dissolution process of amygdalin is endothermic and the driving mechanism in all mixtures is entropy. Maximal solubility was achieved in 0.4 mole fraction of ethanol at 328.15 K and the minimal one in neat ethanol at 293.15 K. Van’t Hoff, Jouyban–Acree–van’t Hoff, and Buchowski–Ksiazczak models were used to simulate the obtained solubility data. The calculated solubilities deviate reasonably from experimental data. Preferential solvation parameters of amygdalin in mixture solvents were analyzed using the inverse Kirkwood–Buff integrals (IKBI) method. Amygdalin is preferentially solvated by water in ethanol-rich mixtures, whereas in water-rich mixtures, there is no clear evidence that determines which of water or ethanol solvents would be most likely to solvate the molecule.

Optimization of the use of mother liquor in the synthesis of HKUST-1 and their performance for removal of chromium (VI) in aqueous solutions

In this study, copper-benzene tricarboxylic (Cu-BTC), or better known as HKUST-1, was successfully synthesized using the solvothermal method in a solvent mixture of water, ethanol and N,N-Dimethylformamide (DMF). The mother liquor from the first synthesis was reused as a solvent for the subsequent HKUST-1 synthesis for up to four repetitions, cutting back the use of fresh solvent as much as 37 %. The fifth material obtained showed similar thermal stability and specific surface area to that of the first one, even though the surface morphology turned from an octahedral shape in the first material to an irregular shape in the fifth material. The results of the adsorption study on Cr(VI) in aqueous media showed that the first and the fifth materials had adsorption capacities of 91 mg/g and 100 mg/g respectively. Both adsorbents followed a pseudo-second order adsorption kinetics with a Langmuir isothermal adsorption model.

Interface between Water-Solvent Mixtures and a Hydrophobic Surface.

The mechanism behind the stability of organic nanoparticles prepared by liquid antisolvent (LAS) precipitation without a specific stabilizing agent is poorly understood. In this work, we propose that the organic solvent used in the LAS process rapidly forms a molecular stabilizing layer at the interface of the nanoparticles with the aqueous dispersion medium. To confirm this hypothesis, n-octadecyltrichlorosilane (OTS)-functionalized silicon wafers in contact with water-solvent mixtures were used as a flat model system mimicking the solid-liquid interface of the organic nanoparticles. We studied the equilibrium structure of the interface by X-ray reflectometry (XRR) for water-solvent mixtures (methanol, ethanol, 1-propanol, 2-propanol, acetone, and tetrahydrofuran). The formation of an organic solvent-rich layer at the solid-liquid interface was observed. The layer thickness increases with the organic solvent concentration and correlates with the polar and hydrogen bond fraction of Hansen solubility parameters. We developed a self-consistent adsorption model via complementing adsorption isotherms obtained from XRR data with molecular dynamics simulations.

HPTLC fingerprint profile analysis of coffee polyphenols during different roast trials

Coffee beans are a rich source of bioactive phytochemicals such as chlorogenic acids (CGA). During the roasting process, the CGA content changes dramatically. An effective HPTLC method was developed which allows a fast characterization of the eight main CGA present in green and roasted coffee beans and their distribution during roasting trials. The method was optimized with regard to three caffeoylquinic acids (CQA), two feruloylquinic acids (FQA) and three dicaffeoylquinic acids (di-CQA).The best separation for a fingerprint consisting of eight phenolic compounds as markers was achieved on silica gel 60 F254 HPTLC plates with a solvent mixture of diethyl ether, formic acid, acetic acid, water, acetophenone and heptane (30:3:9:50:30:10) (v/v/v/v/v/v). Staining with natural product reagent A enabled visualization and quantitative evaluation. Principal component analysis can help to visualize the evolution of the chlorogenic acids throughout the process also with the aim of controlling the roasting degree.

Conductometric and Refractometric Studies of 1-Propyl-3-methylimidazolium Bromide Ionic Liquid in Water + Ethylene Carbonate Mixtures at T = (298.2, 308.2 and 318.2) K

In this work, we determined thermophysical properties such as electrical conductivity and refractive index for 1-propyl-3-methylimidazolium bromide, [PrMIm]Br in ternary mixtures of [PrMIm]Br + ethylene carbonate + water at T = (298.2, 308.2 and 318.2) K and 0.1MPa. Conductometric measurements were carried out for [PrMIm]Br ionic liquid in ethylene carbonate + water solvent mixture in various composition 10, 20 and 30 mass% of ethylene carbonate (EC) in the ionic strength ranging from 0.0029 to 0.2500 mol.kg-1. These data were treated by Fuoss-Onsager equation, and the values of limiting molar conductivity ( ) and ion association constant (KA) were obtained. These results used to calculate the Walden product ( ) and the corresponding standard thermodynamic functions of ion association process including Gibbs free energy ( ), enthalpy ( ) and entropy ( ) for the investigated system. In addition, refractive indices were measured for the binary and ternary [PrMIm]Br + water + EC mixtures at T = (298.2, 308.2 and 318.2) K. The refractive index deviations (ΔnD) were calculated and the binary and ternary data of ΔnD were correlated using Redlich-Kister and the Cibulka equations, respectively. Also, the measured refractive indices were compared to the calculated values using some mixing rules.

Intensified dewetting of polystyrene thin film under water-solvent mixture: role of solvent composition

Intensified dewetting of ultrathin polystyrene (PS) films induced by immersing in a homogeneous mixture of good solvent and water was previously reported to push the limits of dewetting to the sub-100 nm scale. Here, we systematically analyse the role of dewetting mixture composition, i.e. solvent to water ratio, on the length scales of instability. The effect of the solvent concentration in the dewetting mixture on the instability wavelength ( $$\lambda $$ ) and droplet diameter (d) are determined. The instability wavelength ( $$\lambda $$ ) for 50 nm thick PS film was found to be decreasing from nearly 17 to 7 $$\upmu \hbox {m}$$ as the solvent concentration is decreased from 95 to 35% in the dewetting mixture. This is significantly smaller than the instability wavelength in air, which is nearly $$50~\upmu \hbox {m}$$ for the same PS film. The solubility of PS in the dewetting mixture is also examined and the mechanism of observed variation in the length scale is proposed.

Facile solvothermal synthesis of highly active monoclinic scheelite BiVO4 for photocatalytic degradation of methylene blue under white LED light irradiation

In this study, BiVO4 was successfully synthesized via the solvothermal process using a solvent mixture of ethylene glycol and water under different synthesis conditions of temperature and pH. Physicochemical properties such as crystal phase, morphology, and optical absorption of the as-synthesized BiVO4 samples were characterized by X-ray diffraction (XRD), Raman spectra, field emission scanning electron microscopy (FE-SEM), and ultraviolet–visible diffraction reflection spectroscopy (UV–vis DRS). The XRD analysis showed that different synthesis conditions of temperature and pH significantly affected the growth of monoclinic BiVO4 crystals oriented along (0 4 0) facets. Form SEM results, the synthesis conditions, including pH and temperature, have a great effect on the morphology of monoclinic structured BiVO4. As the pH value increases in the range of 0–9 and temperature increases from 80 °C to 180 °C, the morphology of BiVO4 changed from peanut-, rod-, and leaf-like shapes. The photocatalytic activities of as-synthesized BiVO4 photocatalysts were evaluated by the photodegradation of methylene blue (MB) dye under irradiation of white LED light. We have found that by using appropriate synthesis conditions (the synthesis temperature of 140 °C and the synthesis pH of 7) the BiVO4 exhibited high photocatalytic efficiency for MB degradation (about 82.30% after 180 min of irradiation). This result is due to the development of the BiVO4 crystals oriented along (0 4 0) facets with an increase in the intensity ratio of I(0 4 0)/I(1 2 1). The growth of BiVO4 crystals oriented along (0 4 0) facets may be beneficial to enhance the photocatalytic activity of monoclinic scheelite BiVO4.

Tailoring the morphology, crystalline structure, and electrochemical properties of nanostructured Bi2S3 using various solvent mixtures

Among novel nanostructured materials, transition metal chalcogenides (i.e., sulfides and selenides) emerged as promising candidates due to their unique electrochemical properties. The following study presents a facile synthesis approach of Bi2S3 nanostructures using solvent mixtures of ethanol and water with different volume ratios and ammonium sulfide as a sulfur precursor. The resultant bismuth sulfides were characterized by field-emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and nitrogen sorption at 77 K. The adjustment of the solvent mixture revealed the possibility of customizing the crystalline structure from amorphous to fully crystalline, as well as the morphology of the Bi2S3, which subsequently influenced on their electrochemical properties. Bi2S3 synthesized in a solvent mixture of ethanol-to-water volume ratio 1:2 (Bi2S3-EW12) exhibited almost fully crystalline structure and nanoplatelet-like morphology, which translated to the best electrochemical performance. Bi2S3-EW12 achieved specific capacity of 748 C g−1 in an aqueous 6 mol L−1 KOH electrolyte and maintained the highest capacity value at a large current density of 20 A g−1.

The mechanism of solvent-mediated desolvation transformation of lenvatinib mesylate from dimethyl sulfoxide solvate to form D.

In this work, the mechanism of solvent-mediated desolvation transformation of lenvatinib mesylate (LM) was investigated. Two new solid forms of LM, a dimethyl sulfoxide (DMSO) solvate and an unsolvated form defined as form D, were discovered and characterized using powder X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, polarized light microscopy and Raman spectroscopy. To investigate the thermodynamic mechanism of solvent-mediated desolvation transformation (SMDT) from LM DMSO solvate to form D, solubilities of LM DMSO solvate and form D in binary solvent mixtures of DMSO and water at different water volume fractions and temperatures (293.15-323.15 K) were measured and correlated by non-random two liquids model. The solubility data were used to evaluate the thermodynamic driving force of the SMDT process from DMSO solvate to form D and the effect of the activities of water and DMSO on the transformation process. Raman spectroscopy was used to monitor in situ the solid phase compositions during the SMDT process from LM DMSO solvate to form D while the solution concentration was measured by the gravimetric method. The overall desolvation transformation experiments demonstrated that the SMDT process was controlled by the nucleation and growth of form D. Moreover, effects of operating factors on the SMDT process were studied and the results illustrated that water activity in solution was the paramount parameter in the SMDT process. Finally, a new SMDT mechanism was suggested and discussed.