Ion-containing Solutions Research Articles

Discovery of a hyperalkaline liquid condensed phase: significance toward applications in carbon dioxide sequestration.

Bicarbonate ion-containing solutions such as seawater, natural brines, bovine serum and other mineralizing fluids have been found to contain hyperalkaline droplets of a separate, liquid condensed phase (LCP), that have higher concentrations of bicarbonate ion (HCO3 -) relative to the bulk solution in which they reside. The existence and unique composition of the LCP droplets have been characterized by nanoparticle tracking analysis, nuclear magnetic resonance spectroscopy, fourier transform infrared spectroscopy, dissolved inorganic carbon analysis and refractive index measurements. Carbon dioxide can be brought into solution through an aqueous reaction to form LCP droplets that can then be separated by established industrial membrane processes as a means of concentrating HCO3 -. Reaction of calcium with the LCP droplets results in calcium carbonate precipitation and mineral formation. The LCP phenomenon may bear on native mineralization reactions and has the potential to change fundamental approaches to carbon capture, sequestration and utilization.

Protective performance evaluation of AT13 ceramic coatings sealed with organic and inorganic sealants in chloride-containing solutions at different temperatures

Exploring the sealing stability of different media to plasma-sprayed refractory Al2O3–13%TiO2 ceramic coatings is of guiding significance for rational application. Thus, the protective performance of commonly used organic and inorganic sealing agents under different environmental temperatures in chloride ion-containing solutions was investigated in this paper. Firstly, the corrosion resistance of each sample at different temperatures was characterized by potentiodynamic polarization studies. Then the effect of solution temperature was analyzed by Arrhenius equation. Moreover, the mechanism of solution temperature influence was discussed via electrochemical impedance spectroscopy, aiming to provide guidance on the selection of sealing agent types for different environments. The results indicated that both sealing agents provided corrosion resistance far beyond that of the as-sprayed coating at different temperatures. However, as the temperature increased, despite the stable behavior of the inorganic sealing coating itself, the organic sealing agent exhibited a more stable application effect in corrosion resistance, even at 80 °C, it can still show a corrosion current density in the order of 10−8 A cm−2.

Study on oxidation mechanism of aluminum surface under applied electric field

The oxidation behavior of aluminum alloy has a significant impact on its industrial application of aluminum alloy, and studying how aluminum alloy oxidizes in electrolyte solutions is crucial. However, current research predominantly focuses on aluminum anodization at higher voltages and the second-phase corrosion behaviors in halide ion-containing solutions. The research on the formation mechanism of the oxide film on the aluminum surface lacks in-depth analysis, and there is no unified opinion on the method of oxygen invasion into the oxide film. This study establishes an experiment on the corrosion of aluminum alloy in an oxygen-free water environment. By scrutinizing the oxidation behaviors of aluminum surface under conditions of no voltage and low voltage, we investigate the effect of applied electric field on the mode of oxygen invasion in alumina. The findings reveal that under the condition of no external voltage and an alkaline environment, self-passivation products of aluminum undergo a transformation from AlO(OH) to Al(OH)3 as the pH value increases. At a pH of 10, complete transformation into Al(OH)3 occurs. When external voltage is applied, Al(OH)3 is initially formed on the aluminum surface with an increase of potential. As the potential reaches a certain value, the potential energy barrier for the reaction of H and O in OH− is disrupted, leading to the reaction of Al3+ replacing H+ and generating an Al2O3 film, with the current on the membrane surface changes unevenly during this process, resulting in the emergence of a double-layer film structure on the aluminum surface. Therefore, under the electrochemical environment of applying a small current, the film formation process on the surface of aluminum alloy is carried out under the action of OH− heterocracking in water, and the O in the water molecule forms two distinct oxide films with the Al matrix in the form of O2− and OH−.

Biomimetic Organic-Inorganic Hybrid Membranes for Removal of Fluoride Ions.

Carbon nanofibers (CaNFs) exhibit promising applications in the fields of environmental science and nanotechnology, and self-assembled peptide nanofibers (PNFs) are useful for the biomimetic synthesis of organic-inorganic hybrid nanomaterials and the fabrication of functional hybrid membranes for the removal of various pollutants from water. In this work, we report the biomimetic synthesis of hybrid nanomaterials by the interweaving of CaNFs and PNFs. Using the biomimetic mineralization properties of PNFs, ZrO2 nanoparticles were synthesized along the nanofiber surface, and then functional nanohybrid porous membranes were prepared by the vacuum filtration technology. For the fabrication of membranes, the amount of PNFs and ZrO2 precursors in the hybrid membrane were optimized. The designed organic-inorganic hybrid membranes exhibited high removal performance for fluorine ion (F−) from water, and the removal efficiency of the fabricated membranes towards F− ion-containing aqueous solution with a concentration of 50–100 mg/L reached more than 80%. In addition, the nanofiltration membranes revealed good adsorption capacity for F− ions. It is expected that the strategies shown in this study will be beneficial for the design, biomimetic synthesis, and fabrication of nanoporous membranes for economic, rapid, and efficient water purification.

Characterization and electrochemical properties of stable Ni2+ and F- co-doped PbO2 coating on titanium substrate

• A stable Ni 2+ and F - co-doped PbO 2 coating was fabricated by tsition method. • The electrochemical behavior of un-doped and doped PbO 2 coatings was evaluated before and after ALT. • Simultaneously doping of F - and Ni 2+ ions in PbO 2 coating leads to the best electrocatalytic activity. • The service life of Ni 2+ and F - co-doped Ti/SnO 2 -Sb 2 O 3 /PbO 2 electrode was several times as much as that of the un-doped electrode. In the present work, a novel Ni 2+ and F - co-doped PbO 2 coating featuring high stability toward electrochemical degradation was fabricated on titanium substrate by anodic electrodeposition method. The microstructure of the coatings was characterized using scanning electron microscopy (SEM), energy-dispersive X-Ray spectroscopy (EDS), and X-ray diffraction (XRD). The results showed that the addition of dopants into PbO 2 coating, encourages the formation of a compact coating without any cracks and pores on its surface. The stability of the Ti/SnO 2 -Sb 2 O 3 /PbO 2 electrode was measured using the accelerated life test (ALT) in chloride ion-containing solution with a large current density of 2.5 A.cm −2 . Before and after ALT, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were utilized to evaluate the electrochemical behavior of the electrodes. It was found that the service life of Ni 2+ and F - co-doped Ti/SnO 2 -Sb 2 O 3 /PbO 2 electrode was 120 h, such that was several times as much as that of the un-doped electrode. The results of EIS and CV measurements indicated that Ni 2+ and F - co-doped anode compared to F - doped and the un-doped anodes has the lowest charge transfer resistance and also the best electrocatalytic activity. These characteristics are due to the simultaneously doping of F - and Ni 2+ , which inhibited the penetration of chloride ions toward the titanium substrate and also delayed the formation of the non-conductive TiO 2 layer at the coating/substrate interface.

Liquid metal enabled continuous flow reactor: A proof-of-concept

Liquid metal enabled continuous flow reactor: A proof-of-concept

Polymer Networks for Enrichment of Calcium Ions.

In this study, solvogels containing (2-((2-(ethoxycarbonyl)prop-2-en-1-yl)oxy)-ethyl) phosphonic acid (ECPA) and N,N′-diethyl-1,3-bis-(acrylamido)propane (BNEAA) as the crosslinker are synthesized by UV induced crosslinking photopolymerization in various solvents. The polymerization of the ECPA monomer is monitored by the conversion of double bonds with in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The morphology of the networks is characterized by in situ photorheology, solid state NMR spectroscopy, and scanning electron microscopy (SEM) of the dried gels. It is demonstrated that the storage modulus is not only determined by the crosslinker content in the gel, but also by the solvent used for preparation. The networks turn out to be porous structures with G′ being governed by a rigid, phase-separated polymer phase rather than by entropic elasticity. The external and internal pKa values of the poly(ECPA-co-BNEAA) gels were determined by titration with a specially designed method and compared to the calculated values. The polymer-immobilized phosphonic acid groups in the hydrogels induce buffering behavior into the system without using a dissolved buffer. The calcium accumulation in the gels is studied by means of a double diffusion cell filled with calcium ion-containing solutions. The successful accumulation of hydroxyapatite within the gels is shown by a combination of SEM, energy-dispersive X-ray spectroscopy (EDX) and wide-angle X-ray scattering (WAXS).

Novel and potent antimicrobial effects of caspofungin on drug-resistant Candida and bacteria

Echinocandins, including caspofungin, micafungin, and anidulafungin, are first-line antifungal agents for the treatment of invasive candidiasis. They exhibit fungicidal activity by inhibiting the synthesis of β-1,3-d-glucan, an essential component of the fungal cell wall. However, they are active only against proliferating fungal cells and unable to completely eradicate fungal cells even after a 24 h drug exposure in standard time-kill assays. Surprisingly, we found that caspofungin, when dissolved in low ionic solutions, had rapid and potent antimicrobial activities against multidrug-resistant (MDR) Candida and bacteria cells even in non-growth conditions. This effect was not observed in 0.9% NaCl or other ion-containing solutions and was not exerted by other echinocandins. Furthermore, caspofungin dissolved in low ionic solutions drastically reduced mature biofilm cells of MDR Candida auris in only 5 min, as well as Candida-bacterial polymicrobial biofilms in a catheter-lock therapy model. Caspofungin displayed ion concentration-dependent conformational changes and intracellular accumulation with increased reactive oxygen species production, indicating a novel mechanism of action in low ionic conditions. Importantly, caspofungin dissolved in 5% glucose water did not exhibit increased toxicity to human cells. This study facilitates the development of new therapeutic strategies in the management of catheter-related biofilm infections.

Influence of shot peening on corrosion behavior of low alloy steel

Surface modification is an important technique for maintaining relatively favorable mechanical properties to surface properties and corrosion resistance. In this study, Surface shot peening technology is applied to low alloy steel production nanocrystallines. The microstructure near the surface layer was characterized by x-ray diffraction, transmission electron microscopy and electron backscatter diffraction. The corrosion behavior of the shot-treated surface layer was analyzed by polarization and pitting test, and the surface morphology of the corroded sample was observed by a scanning electron microscope. The results showed that the surface layer of the alloy after shot peening can be divided into three parts: equiaxed nanoparticle layer (NG), ultrafine grain layer (FG) and elongated fine grain layer (EG). Surface nanocrystallization improved the potential polarization behavior of low alloy steel in 3.5% NaCl solution. The microhardness of the near surface region showed a significant increase compared to the as-received steel sample, showing a more stable electrochemical performance. Shot peening also significantly reduced the pitting rate and maximum pitting depth in 10% FeCl3 solution. The surface nano-layer structure produced by the shot peening process could provide more nucleation sites, thereby improving the uniformity and compactness of the passivation film, resulting in better corrosion resistance. The above experimental results clearly showed that the overall and local corrosion resistance of the low alloy carbon steel in the chloride ion-containing solution can be improved by shot peening.

Biocorrosion properties of Ti–3Cu alloy in F ion-containing solution and acidic solution and biocompatibility

Ti–3Cu alloy has shown low melting point and strong antibacterial properties against S. aureus and E. coli and thus has potential application as dental materials and orthopedic application. In this paper, the corrosion properties of Ti–3Cu alloy in five kinds of simulated solutions were investigated in comparison with cp-Ti (commercially pure titanium) by electrochemical technology and immersion experiment. Electrochemical results have demonstrated that Ti–3Cu alloy exhibited much nobler corrosion potential, lower corrosion current density and high corrosion resistance than cp-Ti in all solutions, especially in saliva-pH6.8 + 0.2F and saliva-pH3.5, indicating that Ti–3Cu alloy has much better anticorrosion properties than cp-Ti. Immersion results have shown that Ti ion and Cu ion were released from Ti–3Cu, especially in saliva-pH6.8 + 0.2F and saliva-pH3.5 solutions. Both electrochemical data and immersion results have indicated that high corrosion rate and high metal ion release rate were detected in F ion-containing solution and low-pH solution, displaying that F− and low pH had much strong aggressive attack to cp-Ti and Ti–3Cu alloy. The corroded surface morphology was observed by scanning electron microscopy (SEM), and the roughness was tested in the end. The good corrosion resistance of antibacterial Ti–3Cu alloy suggests its great potential as a long-term biomedical application.

A tandem photoelectrochemical water splitting cell consisting of CuBi2O4 and BiVO4 synthesized from a single Bi4O5I2 nanosheet template.

We report on a simple and facile synthetic approach for preparing both a CuBi2O4 photocathode and BiVO4 photoanode from a single Bi4O5I2 nanosheet template. A nanosheet structured Bi4O5I2 (nanoBi4O5I2) template, solvothermally deposited on a conducting glass substrate, can be converted to a textured CuBi2O4 photocathode and a BiVO4 photoanode with coral-like nanostructure by drop-casting a copper ion-containing and a vanadium ion-containing solution, respectively, with a follow-up heat treatment. UV-vis absorption spectra and Mott-Schottky analyses confirm CuBi2O4 and BiVO4 have well-suited band gaps for absorbing a large portion of visible light and complementary band structures for proton reduction and water oxidation, respectively. A photoelectrochemical tandem cell, consisting of a cobalt based catalyst modified CuBi2O4 photocathode and a cobalt based catalyst modified BiVO4 photoanode shows promising photoelectrochemical properties towards water splitting, and can be operated without an external bias. Factors limiting the performance of the tandem cell are also discussed.

Surface reactivity of octacalcium phosphate-derived fluoride-containing apatite in the presence of polyols and fluoride.

The present study was designed to characterize co-precipitated fluoridated apatitic materials from octacalcium phosphate (OCP) precursor and to investigate their surface reactions with polyols including glycerol in the presence of fluoride ions. Laboratory-synthesized fluoridated apatite crystals (LS-FA) were obtained in a solution containing fluoride (F) from 25 to 500 ppm. LS-FAs and commercially available fluoroapatite (FA) and hydroxyapatite (HA) were characterized by physical techniques, such as X-ray diffraction. LS-FA obtained in the presence of 100 ppmF (100 ppm-LS-FA) had an apatitic structure, but its solubility was close to HA in a culture medium (α-MEM) despite the fact it contains over 3 wt % of F. 100 ppm-LS-FA, FA, and HA were then subjected to the human serum albumin (HSA) adsorption test at pH 7.4 (in a 150 mM Tris-HCl buffer) and the dissolution and re-mineralization experiments in the presence of xylitol, D-sorbitol, or glycerol, and F under acidic and neutral conditions. Adsorption affinity of HSA was estimated as highest for FA and lowest for LS-FA. LS-FA, FA, and HA were immersed in a lactic acid solution with the polyols and/or F ion-containing solution up to 200 ppm to analyze the dissolution behavior. LS-FA had the highest dissolution tendency in the conditions examined. Glycerol enhanced the dissolution of phosphate from apatite crystals in particular from LS-FA. The results suggest that the apatite crystals, obtained through the hydrolysis of OCP in the presence of F, provide a more reactive surface than FA or HA under physiological environments. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2235-2244, 2018.

Polyelectrolyte-complex multilayer membrane with gradient porous structure based on natural polymers for wound care

Chitosan and alginate have been considered to be promising natural polymers for biomedical application because of their biocompatibility, biodegradability and similarity to macromolecules recognized by human body, which are extensively used in wounds and burns management. Here a sponge-like polyelectrolyte-complex multilayer membrane (PCMM) was prepared via freeze-drying method. The attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM) analysis revealed that chitosan/alginate layer exhibited gradient porous structure and interpenetrating polymer networks in PCMM. The porosity and swelling ratio of PCMM were evaluated. The results indicate that the prepared PCMM shows porosity up to 90% and equilibrium swelling ratio up to 22.4 in deionized water as well as 21.5 in ion-containing solution. Antibacterial activity evaluated in vitro shows the PCMM appears obviously antibacterial activity towards E. coli. Cytotoxicity study evaluated in vitro illustrates the nontoxic nature of the PCMM, and it is good for the cell attachment, growth, and proliferation. These results strongly support the possibility of using this novel PCMM for wound care.

Formation of Au nanoparticle arrays on hydrogel two-dimensional patterns based on poly(vinylpyrrolidone)

In this study, we demonstrated the formation of Au nanoparticle (NP) arrays on two-dimensional gel patterns based on poly(vinylpyrrolidone) (PVP), which were fabricated by electron beam (EB) lithography. Au NPs were preferentially formed on PVP patterns by photoreduction in HAuCl4-containing MeOH solutions without any surface treatment. The number density of the Au NPs was highly controlled by changing the UV irradiation time; therefore, increasing the UV irradiation time produced Au NP arrays with highly packed Au NPs on the PVP patterns. The size of the cross-linking networks of PVP, which depended on the cross-linking density induced by EB irradiation, plays a very important role in the formation of Au NPs in the Au ion-containing solution under UV irradiation. We discussed the difference in the fabricated Au NP arrays at different EB exposure doses in terms of the interaction between the gel networks and the Au NPs formed.

Calcium ion modification of TiO2 nanotube arrays to enhance apatite formation

Highly ordered TiO2 nanotube arrays were fabricated by anodisation of titanium, and then anodic TiO2 nanotubes were modified in calcium ion-containing solution using ultrasound-assisted impregnation. For reference, the experiments were also carried out by conventional impregnation. The ability to form apatite on specimens was examined upon exposure to modified simulated body fluids combined with FESEM, EDS, XRD, FTIR and Zeta potential investigations. The results reveal that it had a negligible effect on the morphology of nanotubes with varying calcium source and impregnation time using conventional impregnation. Nevertheless, TiO2 nanotubes were modified by the method of ultrasound-assisted impregnation, the mouth of nanotubes became glossy, the diameter of nanotubes became non-uniform and the amount of adsorbate in the inner wall of nanotubes increased. The calcium ion-modified nanotubes were more efficient in promoting apatite formation than the unmodified nanotubes, which may be attributed to the release of calcium ions and the significantly high amount of Ti–OH groups on its surface.

Analytical Results on the Behavior of a Liquid Junction across a Porous Diaphragm or a Charged Porous Membrane between Two Solutions According to the Nernst–Planck Equation

We model the behavior of an ideal liquid junction, across a porous and possibly charged medium between two ion-containing solutions, by means of the Nernst–Planck equation for the stationary state, in conditions of local electroneutrality. An analytical solution of the equation was found long ago by Planck for the uncharged junction with only ions of valences +1 and −1. Other analytical results, which have later been obtained also for more general situations, seem impractical for performing calculations. In this paper, we obtain analytical solutions for systems with up to three valence classes, which can be applied to perform numerical calculations in a straightforward way. Our method provides a much larger amount of information on the behavior of the system than the well-known Henderson’s approximation. At the same time, it is more simple and reliable, and much less demanding in terms of computational effort, than the nowadays commonly employed numerical methods, typically based on discrete integration and trial-and-error numerical inversions. We present some examples of practical applications of our results. We study in particular the uphill transport (i.e., the transport from the lower-concentration to the higher-concentration region) of a divalent cation in a liquid junction containing also other univalent anions and cations.

Translation of a solution-based biomineralization concept into a carrier-based delivery system via the use of expanded-pore mesoporous silica

Mineralization of collagen fibrils using solution-based systems containing biomimetic analogs of matrix proteins to stabilize supersaturated calcium phosphate solutions have been predictably achieved in vitro. Solution-based systems have limitations when used for in-situ remineralization of human hypomineralized tissues because periodic replenishment of the mineralizing solution is infeasible. A carrier-based platform designed for delivering mineral precursors would be highly desirable. In the present work, mesoporous silica nanoparticles with expanded pores (eMSN; 14.8nm) were synthesized. Polyacrylic acid–stabilized amorphous calcium phosphate (PA–ACP) was generated from a supersaturated calcium and phosphate ion-containing solution, and chosen as the model mineralizing phase. After amine functionalization (AF) of the eMSN through a post-grafting method, the positively-charged AF-eMSN enabled loading of PA–ACP by electrostatic interaction. In-vitro cytotoxicity testing indicated that PA–ACP@AF-eMSN was highly biocompatible. The release kinetics of mineralization precursors from PA–ACP@AF-eMSN was characterized by an initial period of rapid calcium and phosphate release that reached a plateau after 120h. Intrafibrillar mineralization was examined using a 2-D fibrillar collagen model; successful mineralization was confirmed using transmission electron microscopy. To date, this is the first endeavor that employs expanded-pore mesoporous silica to deliver polymer-stabilized intermediate precursors of calcium phosphate for intrafibrillar mineralization of collagen. The carrier-based delivery system bridges the gap between contemporary solution-based biomineralization concepts and clinical practice, and is useful for in-situ remineralization of bone and teeth. Statement of significanceConcepts of collagen biomineralization have been reasonably well established in the past few years and intrafibrillar mineralization of collagen fibrils can be predictably achieved with analogs of matrix proteins using solution-based systems. However, solution-based systems have their limitations in clinical applications that require direct application of mineralization precursors in-situ because periodic replenishment of the mineralizing solution is impossible. The present work presents for the first time, the use of amine-functionalized mesoporous silica with expanded pores for loading and release of polyacid-stabilized amorphous calcium phosphate mineralization precursors, and for intrafibrillar mineralization of type I collagen fibrils. This strategy represents an important step in the translational application of contemporary biomineralization concepts for in-situ remineralization of bone and teeth.

A Continuous Static-Mixer-Based Reactor for Preparing Calcium Phosphate Bioceramics

The common methods for synthesizing calcium phosphates include solid-state reaction, hydrothermal, sol–gel, and wet precipitation. The purpose of this study was to prepare various calcium phosphate bioceramics through a continuous reactor equipped with a static mixer. The precursors, amorphous calcium phosphate (ACP), and poor crystal hydroxyapatite (PC-HAp) were prepared using calcium and phosphate ion-containing solutions by adjusting the pH and the [Ca]/[P] input ratio. The phase transformation from precursors to HAp, alpha-tricalcium phosphates (α-TCP), beta-tricalcium phosphate (β-TCP), or biphasic calcium phosphate (BCP) was dependent on the sintering temperature.

Atomic Force Microscopy and Voltammetric Investigation of Quadruplex Formation between a Triazole-Acridine Conjugate and Guanine-Containing Repeat DNA Sequences.

The interactions of the Tetrahymena telomeric repeat sequence d(TG4T) and the polyguanylic acid (poly(G)) sequence with the quadruplex-targeting triazole-linked acridine ligand GL15 were investigated using atomic force microscopy (AFM) at a highly oriented pyrolytic graphite and voltammetry at a glassy carbon electrode. GL15 interacted with both sequences, in a time dependent manner, and G-quadruplex formation was detected. AFM showed the adsorption of quadruplexes as small d(TG4T) and poly(G) spherical aggregates and large quadruplex-based poly(G) assemblies, and voltammetry showed the decrease and disappearance of GL15 and guanine oxidation peak currents and appearance of the G-quadruplex oxidation peak. The GL15 molecule strongly stabilized and accelerated G-quadruplex formation in both Na(+) and K(+) ion-containing solution, although only K(+) promoted the formation of perfectly aligned tetra-molecular G-quadruplexes. The small-molecule complex with the d(TG4T) quadruplex is discrete and approximately globular, whereas the G-quadruplex complex with poly(G) is formed at a number of points along the length of the polynucleotide, analogous to beads on a string.

The research of precipitation process of calcium carbonate from liquid wastes of soda manufacture

The paper deals with solving environmental problems of soda producing enterprises. A promising direction is developing low-waste technologies, which consist in processing wastes with obtaining products that are in great demand. As a commercial product, it is proposed to obtain chemically precipitated calcium carbonate, which is widely used as a filler to create various composite materials.The most bulky waste of soda ash production using ammonia process is distiller slurry, which is formed in an amount of 8-10 m3 per 1 ton of product and contains calcium ions. According to the results of complex theoretical and experimental studies, it is found that the best way to produce synthetic calcium carbonate is its precipitation from distiller liquid (clarified part of distiller slurry) using carbonate ion-containing solutions. Excessive mother liquor of purified sodium bicarbonate production or sodium carbonate solution with a predetermined concentration can be used as precipitant.The paper presents the results of studies of the dependence of precipitation degree and basic physicochemical characteristics of calcium carbonate on the process parameters. Process conditions (temperature, reaction time, the ratio of reactants), which allow to obtain a product that meets modern requirements for filler, are defined.