Low Distribution Coefficients Research Articles

Anhydrous volatile fatty acid extraction through omniphobic membranes by hydrophobic deep eutectic solvents: Mechanistic understanding and future perspective

Volatile fatty acids (VFAs) derived from arrested anaerobic digestion (AD) can be recovered as a valuable commodity for value-added synthesis. However, separating VFAs from digestate with complex constituents and a high-water content is an energy-prohibitive process. This study developed an innovative technology to overcome this barrier by integrating deep eutectic solvents (DESs) with an omniphobic membrane into a membrane contactor for efficient extraction of anhydrous VFAs with low energy consumption. A kinetic model was developed to elucidate the mechanistic differences between this novel omniphobic membrane-enabled DES extraction and the previous hydrophobic membrane-enabled NaOH extraction. Experimental results and mechanistic modeling suggested that VFA extraction by the DES is a reversible adsorption process facilitating subsequent VFA separation via anhydrous distillation. High vapor pressure of shorter-chain VFAs and low Nernst distribution coefficients of longer-chain VFAs contributed to DES-driven extraction, which could enable continuous and in-situ recovery and conversion of VFAs from AD streams.

Purification of copper foils driven by single crystallization

High-purity copper (Cu) with excellent thermal and electrical conductivity, is crucial in modern technological applications, including heat exchangers, integrated circuits, and superconducting magnets. The current purification process is mainly based on the zone/electrolytic refining or anion exchange, however, which excessively relies on specific integrated equipment with ultra-high vacuum or chemical solution environment, and is also bothered by external contaminants and energy consumption. Here we report a simple approach to purify the Cu foils from 99.9% (3N) to 99.99% (4N) by a temperature-gradient thermal annealing technique, accompanied by the kinetic evolution of single crystallization of Cu. The success of purification mainly relies on (i) the segregation of elements with low effective distribution coefficient driven by grain-boundary movements and (ii) the high-temperature evaporation of elements with high saturated vapor pressure. The purified Cu foils display higher flexibility (elongation of 70%) and electrical conductivity (104% IACS) than that of the original commercial rolled Cu foils (elongation of 10%, electrical conductivity of ∼100% IACS). Our results provide an effective strategy to optimize the as-produced metal medium, and therefore will facilitate the potential applications of Cu foils in precision electronic products and high-frequency printed circuit boards.

Development of mechanistic models for the description of radionuclide retention onto calcareous gravels

The retention capacity of natural calcareous gravels used as a filling material between the packages containing radioactive waste materials in the disposal cells was evaluated for Sr, U, Ni, Ag, 14C, 99Tc, 239Pu, 228Th and 152Eu. The thermodynamic calculations performed considering repository conditions indicated that the chemistry of most of these elements was dominated by neutral or cationic species, this is the case of 238Pu 152Eu, 228Th, Ni and Ag. The studied gravels presented high sorption capacities for these cationic or neutral species, but they are not efficient on retaining anionic species as in the case of 99Tc or Sr, which is already present in the composition of the studied gravels. For those elements where the predominant species are carbonated (14C and U) low distribution coefficients were obtained. A preliminary mechanistic sorption model was developed for each radionuclide considering carbonate (>CO3H) and calcium hydroxide (>CaOH) sites. Our preliminary model allowed to successfully reproduce the experimental trend of the data obtained in this work.

New Trends in Separation Techniques of Lithium Isotopes: A Review of Chemical Separation Methods.

In terms of isotopic technologies, it is essential to be able to produce materials with an enriched isotopic abundance (i.e., a compound isotopic labelled with 2H, 13C, 6Li, 18O or 37Cl), which is one that differs from natural abundance. The isotopic-labelled compounds can be used to study different natural processes (like compounds labelled with 2H, 13C, or 18O), or they can be used to produce other isotopes as in the case of 6Li, which can be used to produce 3H, or to produce LiH that acts like a protection shield against fast neutrons. At the same time, 7Li isotope can be used as a pH controller in nuclear reactors. The COLEX process, which is currently the only technology available to produce 6Li at industrial scale, has environmental drawbacks due to generation of Hg waste and vapours. Therefore, there is a need for new eco-friendly technologies for separation of 6Li. The separation factor of 6Li/7Li with chemical extraction methods in two liquid phases using crown ethers is comparable to that of COLEX method, but has the disadvantages of low distribution coefficient of Li and the loss of crown ethers during the extraction. Electrochemical separation of lithium isotopes through the difference in migration rates between 6Li and 7Li is one of the green and promising alternatives for the separation of lithium isotopes, but this methodology requires complicated experimental setup and optimisation. Displacement chromatography methods like ion exchange in different experimental configurations have been also applied to enrich 6Li with promising results. Besides separation methods, there is also a need for development of new analysis methods (ICP-MS, MC-ICP-MS, TIMS) for reliable determination of Li isotope ratios upon enrichment. Considering all the above-mentioned facts, this paper will try to emphasize the current trends in separation techniques of lithium isotopes by exposing all the chemical separation and spectrometric analysis methods, and highlighting their advantages and disadvantages.

Continuous Counter-Current Multistage Microextraction in a Novel Tube-In-Tube Microextractor

Counter-current operation has been widely applied to enhance the extraction efficiency for systems with low distribution coefficients, which was hindered in microextraction because viscous force and surface tension dominate over gravity and inertial force. In this study, a novel design of a tube-in-tube microextractor relying on a poly tetra fluoroethylene membrane to construct a stable interface was proposed to conduct continuous counter-current extraction. Extraction kinetics for two systems with different distribution coefficients, membranes with different pore radii, and three flow rate ratios were measured as a function of residence time. For the system that toluene was used to extract 0.06 wt % phenol in water, 4.1 stages of extraction efficiency were achieved at a residence time of 9.8 min. A challenging case study (50 wt % acetone–water–toluene) was subsequently conducted to prove the high applicability for emulsion systems of this special microextractor. Lastly, a mathematical model was established and the predicted results of three flow rate ratios are in good agreement with experimental results.

Refined W-3.5Nb alloy fabricated by electron beam melting via doped carbon

Electron beam melting (EBM) is a promising powder bed fusion additive manufacturing (AM) technology for the preparation of complex refractory components due to the significant advantages of vacuum environment and high level in energy utilization, scanning speed and temperature in the build chamber. However, the fabrication of crack-free and refined W-based alloy remains a challenge. This study aims to address this problem by introducing 0.7 wt% carbon in EBM W-3.5Nb alloy. Results revealed that the as built W-3.5Nb alloy had a typical columnar structure with obvious solidification cracks along the grain boundary. Doping 0.7 wt% carbon generated refined microstructure, which was composed of the initial dendrite of tungsten and the eutectic phase in the dendrites gap. Due to the low distribution coefficient of carbon, the nucleation at the bottom of the molten pool was caused by constitutional supercooling in the front of liquid solidification in a single molten pool, and velocity of the solidification front was reduced by carbon concentration leading increased thermal supercooling. Supercooling (thermal supercooling together with constitutional supercooling) refined the microstructure of W-3.5Nb alloy effectively. Meanwhile, due to the formation of eutectic phase with low melting point, the fluidity of liquid phase at the terminal solidification was improved and the solidification cracks along the grain boundary were reduced. The carbon addition also played a significant role in alloy strengthening. The microhardness of the alloy increased from 382 HV to 696 HV, and the compressive strength increased from 962.89 MPa to 1892.56 MPa. These findings offer a new perspective on the AM fabrication of high-quality W-based alloys.

Separation of Alcohols from n-Tetradecane Using 1-Ethyl-3-methylimidazolium Hydrogensulfate

Extraction of alcohols from n-tetradecane using various extraction solvents has been investigated at a range of temperatures from 295 to 393 K under ambient pressure. On the basis of the experimental liquid–liquid equilibrium data, the distribution ratio and selectivity were calculated for the extraction of 1-octanol, 1-decanol, and 1-dodecanol (C8–C12) in 1-ethyl-3-methylimidazolium hydrogensulfate [C2mim][HSO4] and sulfolane. Results showed that moderate selectivities were obtained in sulfolane with very low distribution coefficients. In contrast, [C2mim][HSO4] showed similar selectivity values with higher distribution coefficients. A study of a number of different 1-alcohols (C4–C12) showed that the decrease in hydrogen bonding compared to the increased van der Waals interactions between n-tetradecane and the higher-chain alcohols decreased the extraction selectivity in [C2mim][HSO4]. Increasing the temperature of the ionic liquid extraction medium resulted in increased chemical extraction for 1-butanol and 1-hexanol due to the formation of the corresponding alkylsulfate ionic liquid. In contrast, the selectivity decreased for 1-octanol, 1-decanol and 1-dodecanol due to the partial dissolution of the corresponding alkylsulfate ionic liquid into the n-tetradecane phase.

Screening of Double Solvents Based on Multi-Index Evaluation Method for the Selective Separation m-Cresol from Model Oil.

Ionic liquid (IL) as an extractant is an effective method for separating oil–phenol mixtures. However, relatively high neutral oil entrainment can lead to oil loss and a remarkable reduction in phenol purity. To reduce the entrainment of neutral oil in the extraction process, a double-solvent extraction system composed of IL 1-ethyl-3-methyl imidazolium acetate ([C2mim][Ac]) and an organic solvent was investigated. The multi-index evaluation method was used to screen the conventional organic solvent. The double-solvent extraction experiments were employed to verify the accuracy of the COSMO-RS prediction. Eighteen organic solvents, the interaction energy with m-cresol and cumene (neutral oil), their extraction ability, and mutual solubility with [C2mim][Ac], were calculated by COSMO-RS. Alkane and cycloalkane were screened due to their strong interaction and low distribution coefficient with cumene, as well as the low mutual solubility with [C2mim][Ac]. The experimental results were in good agreement with the COSMO-RS prediction, and cyclopentane as an organic solvent had the lowest distribution coefficient and entrainment of cumene because of its strong nonpolarity and hydrogen-bond repulsive interaction, which was explained by the σ-profile and σ-potential analysis. When the cyclopentane-to-[C2mim][Ac] mass ratio increased from 0.0 to 3.0, the entrainment of cumene was evidently declined from 39.5 to 5.8% and the selectivity to m-cresol was improved from 378.0 to 1058.5.

Anion exchange separations to produce a suitable electrolyte for the electrodeposition of pure zinc

Anion exchange separations have been devised to purify model solutions of the usual pickling liquor (SPL) obtained from hot dip galvanization to produce a suitable ZnCl2 electrolyte for electrodepositing pure Zn. The method was based on the established anion-exchange distribution functions in chloride media. Both the simple batch and the more accurate chromatographic methods of separation were examined. The loaded solutions contained Zn, Fe, Mn, Ni and Pb of different concentrations with 1.8 - 2 M NaCl or HCl as the background. The resin bed primarily retained Zn while divalent Fe, Mn and Ni were removed in the loading and the continued rinsing steps with the mobile phase at the initial level of Cl- ion concentration. The elution of Zn was carried out by a significantly reduced Cl- ion concentration. The preliminary reduction of the iron to its divalent state was found of utmost importance. The only difficulty arises from the separation of Pb, which has an equilibrium distribution function comparable to the anion exchange of Zn, however in Europe this minor impurity should not be present at disturbing levels. Kinetic examination of the batch process revealed that Zn sorption is virtually complete within 20 minutes, however despite the low distribution coefficients, some 10 % of iron is also sorbed. Almost 90 % of the retained iron could be in the Fe(III) state caused by aerial oxidation. It was also found that the elution of Zn in the batch technique was not possible by just lowering the Cl- ion concentration. Therefore, the chromatographic method is the only possible way if only chloride media are to be applied.

Multiple geochemical factors may cause iodine and selenium deficiency in Gilgit-Baltistan, Pakistan

Deficiencies of the micronutrients iodine and selenium are particularly prevalent where populations consume local agricultural produce grown on soils with low iodine and selenium availability. This study focussed on such an area, Gilgit-Baltistan in Pakistan, through a geochemical survey of iodine and selenium fractionation and speciation in irrigation water and arable soil. Iodine and selenium concentrations in water ranged from 0.01–1.79 µg L−1 to 0.016–2.09 µg L−1, respectively, which are smaller than levels reported in similar mountainous areas in other parts of the world. Iodate and selenate were the dominant inorganic species in all water samples. Average concentrations of iodine and selenium in soil were 685 µg kg−1 and 209 µg kg−1, respectively, much lower than global averages of 2600 and 400 µg kg−1, respectively. The ‘reactive’ fractions (‘soluble’ and ‘adsorbed’) of iodine and selenium accounted for < 7% and < 5% of their total concentrations in soil. More than 90% of reactive iodine was organic; iodide was the main inorganic species. By contrast, 66.9 and 39.7% of ‘soluble’ and ‘adsorbed’ selenium, respectively, were present as organic species; inorganic selenium was mainly selenite. Very low distribution coefficients (kd = adsorbed/soluble; L kg−1) for iodine (1.07) and selenium (1.27) suggested minimal buffering of available iodine and selenium against leaching losses and plant uptake. These geochemical characteristics suggest low availability of iodine and selenium in Gilgit-Baltistan, which may be reflected in locally grown crops. However, further investigation is required to ascertain the status of iodine and selenium in the Gilgit-Baltistan food supply and population.

Manipulation of pore structure during manufacture of agarose microspheres for bioseparation.

Agarose microspheres with a controllable pore structure were manufactured by varying agarose types and crosslinking degrees. Various agarose could tailor the gel formation of microspheres matrix and thus affect the final pore structures. Small pores in microspheres could be fabricated by agarose with a higher molecular weight, which was demonstrated by the packed column with lower distribution coefficient (Kav) values measured by gel filtration chromatography. Further, higher Kav values also demonstrated that more and larger pores were formed with increasing the crosslinking degree of agarose microspheres. Either using agarose with a high molecular weight or increasing the crosslinking degree would finally lead to the enhancement of the flow rate during flow performance of packed column as necessary for improving separation efficiency. This provides a foundation for high‐resolution chromatography with a controllable separation range as beneficial for downstream process.

Kinetically selective preparative chromatography of biologically active substances on polymeric sorbents

A technique of preparative adsorption chromatography, according to which the separation of substances is determined by the effect of kinetic selectivity of sorption (KSS), is discussed. Unlike traditional chromatography methods, in which separation is determined by the difference in the binding strength of the separated components (distribution coefficients), in kinetically selective chromatography, the separation parameters can be controlled by changing the ratios between the distribution coefficients and the sorption rate of components (effective diffusion coefficients). The necessary and sufficient prerequisites for the inversion of the selectivity of sorption of the components of sorption systems are identified, when the order of components coming off the column is reversed and a component with a higher equilibrium distribution coefficient comes out of the column first. The KSS effect consists in the fact that a component with a higher distribution coefficient is more selectively adsorbed before the selectivity inversion point and a component with a lower distribution coefficient is preferably absorbed after the inversion point. The prospects of practical use of kinetically selective chromatography are considered using systems important for biotechnology and pharmaceutics. The use of the KSS effect allowed us to optimize the separation of a number of biologically active substances both in the case of the inversion of sorption selectivity of the separated components and in those cases when the conditions of the inversion of sorption selectivity were not met.

Meta-Analysis of Nanoparticle Delivery to Tumors Using a Physiologically Based Pharmacokinetic Modeling and Simulation Approach.

Numerous studies have engineered nanoparticles with different physicochemical properties to enhance the delivery efficiency to solid tumors, yet the mean and median delivery efficiencies are only 1.48% and 0.70% of the injected dose (%ID), respectively, according to a study using a nonphysiologically based modeling approach based on published data from 2005 to 2015. In this study, we used physiologically based pharmacokinetic (PBPK) models to analyze 376 data sets covering a wide range of nanomedicines published from 2005 to 2018 and found mean and median delivery efficiencies at the last sampling time point of 2.23% and 0.76%ID, respectively. Also, the mean and median delivery efficiencies were 2.24% and 0.76%ID at 24 h and were decreased to 1.23% and 0.35%ID at 168 h, respectively, after intravenous administration. While these delivery efficiencies appear to be higher than previous findings, they are still quite low and represent a critical barrier in the clinical translation of nanomedicines. We explored the potential causes of this poor delivery efficiency using the more mechanistic PBPK perspective applied to a subset of gold nanoparticles and found that low delivery efficiency was associated with low distribution and permeability coefficients at the tumor site (P < 0.01). We also demonstrate how PBPK modeling and simulation can be used as an effective tool to investigate tumor delivery efficiency of nanomedicines.

Modified Physicochemical Properties of Acidic Model Drugs Immobilized on Fe3O4Magnetic Iron Oxide Nanoparticles

Nanoparticles are now extensively evaluated as drug carriers. The main objective of the present work was to evaluate the difference in physicochemical properties (solubility, permeability, lipophilicity) between acidic drugs immobilized on magnetic iron oxide nanoparticles and the same drugs in their unbound form. Synthesis of Fe3O4 magnetic iron oxide nanoparticles coated with (3-aminopropyl)triethoxysilane (APTES) was carried out with the chosen drugs attached. The obtained nanostructures were characterized using IR spectroscopy, atomic force microscopy (AFM), vibrating sample magnetometry (VSM) and dynamic light scattering (DLS) techniques, and physicochemical properties of the immobilized drugs were studied. The drug solubility was measured using the saturation shake-flask method. The permeability was measured using dialysis membranes, MWCO 50 kD with pores <10 nm. The lipophilicity was measured by partitioning in octanol. The drugs showed excellent solubility and permeability at low pH values (pH 2.0 and 5.0) and low solubility and permeability at higher pH values (pH 6.5 and 7.5) in comparison to the corresponding unbound drugs. The MNP[APTES]-immobilized drugs diffused to the organic phase very poorly, even in their non-ionized form (pH 2.0) and showed extremely low distribution coefficients. It was concluded that the immobilization of drugs on MNP[APTES] particles strongly modifies their physicochemical properties such as solubility, permeability and lipophilicity. This circumstance should be taken into account in designing new drug delivery systems, as the immobilization may strongly influence passive absorption. Extremely high release and dissolution rates of the tested drugs, followed by their efficient permeability through membrane pores at low pH, is the reason why the oral administration of therapeutic agents immobilized on MNPs should be considered as a method for more efficient drug delivery.

Enhancement of sorption capacity to Sr and Cs of a cement composite by addition of brick powder

Concrete is a suitable material for secondary casings in multi-barrier systems used in radioactive waste repositories, because it is durable and radiation- and thermal resistant and it has good mechanical properties. The casings should also limit possible leaching of radionuclides in case of failure of inner barriers. An efficient way to tackle this problem is the addition of a sorption material in the concrete mixture. Here mechanical and thermal properties of concrete containing different amounts of brick powder are studied in relation to the concrete mixture porosity. It is found out that, as expected, the bulk density and compressive and bending strengths decreased with an increasing amount of the brick powder. In addition, the sorption of cesium and strontium chlorides into the mixtures was analyzed under laboratory conditions, and their sorption isotherms and distribution coefficients were calculated. The results indicate that brick has higher sorption capacity for Sr than for Cs. Relatively low distribution coefficients indicate, however, that the studied brick is not a very suitable additive material for sorption of Sr and Cs elements.

Effects of porous media on extraction kinetics: Is the membrane really a limiting factor?

Porous media in extraction and especially pertraction are often suspected to add unnecessary diffusive resistance and considerably slow down extraction kinetics. This work presents a miniaturized pertraction device and simulation of diffusive and reactive solute transport. Kinetics are experimentally observed and numerically fitted. Reaction rates – or solute transfer rates – are estimated via this fit on a numerical basis. The work shows that the diffusive resistance created by a porous medium is prevalent only at low distribution coefficients. At high distribution coefficients as is the case of quasi all industrial processes, the porous membrane does not interfere with overall kinetics. Instead, the diffusive resistance is shared between feed and extraction phases, and interface transfer, depending on the value of transfer rate. Overall, this work can be generalized as enabling the measurement of solute transfer rates at the liquid-liquid interface, a key parameter in pertraction and membrane separation which is difficult to measure using classic methods of extraction.

Liquid–Liquid Equilibria of Formic Acid and Furfural in a Biphasic Aqueous–Organic System: Optimization of Solvent and Amine Extractant

Liquid–liquid equilibria of formic acid (FA) and furfural in a biphasic aqueous–organic system were studied. Fourteen kinds of samples with a high boiling point and a large density difference with water were first screened to measure the distribution coefficient of furfural. Eight solvents with a high furfural distribution coefficient were further screened for FA extraction. Six solvents (1,2-dimethoxybenzene, 2,4-dimethyl-1-nitrobenzene, diethyl phthalate, tributyl phosphate, dibutyl phthalate, and dibutyl sebacate) with a low FA distribution coefficient were then selected to measure the mutual solubilities at 298.15 K. Furthermore, two amine extractants (tri-n-octylamine and amine N235) were diluted in six solvents for the extraction of FA and furfural from aqueous solutions to optimize the solvent and extractant. 2,4-Dimethyl-1-nitrobenzene or diethyl phthalate was proven to be more suitable for this system. Effects of the amine extractant concentration in solvents were evaluated to balance the furfura...

Prediction Model for Antimalarial Activities of Hemozoin Inhibitors by Using Physicochemical Properties.

The rapid spread of strains of malaria parasites that are resistant to several drugs has threatened global malaria control. Hence, the aim of this study was to predict the antimalarial activity of chemical compounds that possess anti-hemozoin-formation activity as a new means of antimalarial drug discovery. After the initial in vitro anti-hemozoin-formation high-throughput screening (HTS) of 9,600 compounds, a total of 224 hit compounds were identified as hemozoin inhibitors. These 224 compounds were tested for in vitro erythrocytic antimalarial activity at 10 μM by using chloroquine-mefloquine-sensitive Plasmodium falciparum strain 3D7A. Two independent experiments were conducted. The physicochemical properties of the active compounds were extracted from the ChemSpider and SciFinder databases. We analyzed the extracted data by using Bayesian model averaging (BMA). Our findings revealed that lower numbers of S atoms; lower distribution coefficient (log D) values at pH 3, 4, and 5; and higher predicted distribution coefficient (ACD log D) values at pH 7.4 had significant associations with antimalarial activity among compounds that possess anti-hemozoin-formation activity. The BMA model revealed an accuracy of 91.23%. We report new prediction models containing physicochemical properties that shed light on effective chemical groups for synthetic antimalarial compounds and help with in silico screening for novel antimalarial drugs.

Charge Separation at the Evaporation (Condensation) Front of Water and Ice. Charging of Spherical Droplets

Charge separation at evaporation (condensation) front of water and ice is analyzed. Relatively low distribution coefficient of protons and hydroxide ions between vapor and condensed phase that is less than the distribution coefficient of water molecules leads to accumulation of protons and hydroxide ions at the phase front upon evaporation and a decrease in the amount of such species upon condensation. Interphase charge separation is caused by the subsequent diffusion of nonequilibrium protons and hydroxide ions. The charge separation is also affected by the double electric layer generated by orientation defects at the water and ice surfaces. Dependences of electric field at a plane surface of water and ice on the rate of phase transformation are calculated. Electric charges of spherical water droplets are estimated at different field strengths and droplet radii.

Trace element partitioning in fluvial tufa reveals variable portions of biologically influenced calcite precipitation

The formation of tufa is essentially influenced by biological processes and, in order to infer environmental information from tufa deposits, it has to be determined how the geochemistry of biologically influenced tufa deviates from equilibrium conditions between water and calcite precipitate. We investigated the evolution of the water and tufa geochemistry of consecutive tufa barrages in a small tufa-depositing creek in Southern Germany. High incorporation of divalent cations into tufa is ubiquitous, which is probably promoted by an influence of biofilms in the tufa element partitioning. The distribution coefficients for the incorporation of Mg, Sr and Ba into tufa at the Kaisinger creek D(Mg), D(Sr) and D(Ba) are 0.020–0.031, 0.13–0.18 and 0.26–0.43, respectively. This agrees with previous research suggesting that biofilm influenced tufa will be enriched in divalent cations over equilibrium values in the order of Mg < Sr < Ba. Furthermore, the incorporation of Mg, Sr and Ba into tufa of the Kaisinger creek decreases downstream, which can be attributed to changes of the relative portions of bio-influenced tufa formation with likely higher distribution coefficients and inorganically-driven tufa formation with likely lower distribution coefficients. Additionally, the distribution coefficients of metals in tufa of the Kaisinger creek D(Cd), D(Zn), D(Co) and D(Mn) show values of 11–22, 2.2–12, 0.7–4.9 and 30–57, respectively. These metals are highly enriched in upstream tufa deposits and their contents in tufa strongly decrease downstream. Such highly compatible elements could therefore be used to distinguish easily between different lateral sections in fluvial barrage-dam tufa depositional systems and could serve as a useful geochemical tool in studying ancient barrage-dam tufa depositional systems.