Aqueous Solution System Research Articles

Time-programmed release of fluoroscein isocyanate dextran from micro-pattern-designed polymer scrolls

In this article we present a relevant strategy for a non-trivial time-programmed release of water-soluble macromolecules from biocompatible μ-containers. The system is based on self-scrolled chitosan acetate (CA) fibers, encapsulated in a poly(dimethylsiloxane) matrix. Mass transfer between a fiber and the external environment takes place via the only opened extremity of the fiber. Fluoroscein isocyanate dextran (FID) is initially deposited at the inner surface of the CA fiber according to a programmed pattern. The FID molecules became mobile after the arriving of the swelling front, which propagates along the fiber's axis upon the immersion of the system in aqueous solution. Diffusion of the macromolecules into the environment is enabled by the open-tube geometry of the swollen part of the fiber, while a programmed kinetics of the drug release is due to patterning of the polymer film prior to rolling. The release of the macromolecules can be retarded by a few hours according to the placement of the FID spot with respect to the fibers orifice. A pulsatile release kinetics is demonstrated for a discrete pattern. A few millimeter spacing of the FID spots results in a few hours time interval between the release impulses. Random walk model is plugged in the effective diffusion coefficient for Fick's law and the release kinetics are simulated.

Effective removal of tetracycline from aqueous solution using activated carbon prepared from tomato (Lycopersicon esculentum Mill.) industrial processing waste

Activated carbon (TAC) prepared under optimized conditions with ZnCl2 activation from a new precursor; tomato industrial processing waste (TW), was applied as an adsorbent to remove tetracycline (TC) from aqueous solution. The factors (TAC dosage, initial TC concentration, contact time, ionic strength and solution temperature) affecting the adsorption process were examined at natural pH (5.7) of TAC-TC system in aqueous solution. Kinetic data was found to be best complied by the pseudo-second order model. The isotherm analysis indicated that the equilibrium data could be represented by the Langmuir model. The maximum adsorption capacity was identified as 500.0mgg−1 at 308K.

Phase Behavior of Ascorbyl Palmitate Coagels Loaded with Oligonucleotides as a New Carrier for Vaccine Adjuvants

AbstractIn this work, the phase behavior variations of an ascorbyl palmitate (Asc16) system in aqueous solution were analyzed when immunologically active hydrophilic compounds (CpG and OVA) were introduced. This study was carried out through optical polarizing microscopy (OPM) and differential scanning calorimetry (DSC) at different temperatures and over a broad range of concentrations. The combination of both techniques allowed the determination of a complete phase diagram which was compared with those built for Asc16‐water system and it was demonstrated that fixed concentrations of hydrophilic compounds (300 and 24 µg/g for CpG‐ODN and OVA respectively) generate two lamellar liquid crystals, a cubic liquid crystal phase, and also other aggregates. However, no changes were observed in the phase diagram in terms of formation of new mesophases. The aqueous phase behavior was also studied as a function of surfactant and temperature. DSC and Fourier transform infrared spectroscopy (FT‐IR) measurements show differences in the free water and mainly in the secondary hydration layer, which confirm that the studied compounds are situated in the aqueous domain. The construction and analysis of Asc16 phase diagrams with a fixed concentration of CpG‐ODN/OVA allows the comprehension of Asc16 phase behavior and could be easily adapted to other concentrations. Moreover, these findings could be extrapolated to other hydrophilic substances in aqueous solution introduced in liquid crystal phases since they follow a similar behavior as those reported in the literature.

Diffusion and adsorption of uranyl ion in clays: Molecular dynamics study

Molecular dynamics (MD) simulations were performed to study the diffusion and adsorption behaviors of aqueous uranyl species in interlayer space of clay minerals, which are key processes in the safety assessment for geological disposal of radioactive waste. The diffusion behaviors of UO22+, K+, CO32− and Cl− and H2O were evaluated for the aqueous solution system. The diffusion coefficients of these species decreased with increasing solutes concentration, and that of UO22+ was much smaller than others. In the aqueous solution with higher concentration of carbonate ions, uranyl carbonate complexes such as UO2CO3 and UO2(CO3)22− could be observed. For the clay-aqueous solution system (clay: montmorillonite or illite), the adsorption and diffusion behaviors of UO22+ and K+ were evaluated by MD calculations. The distribution coefficients (KD) of these solutes increased with the layer charge of clay, and the KD value of UO22+ might be smaller than that of K+. Further, the diffusion coefficients in the adsorption layer on the basal plane were relatively small and decreased with increasing the layer charge of clay.

Fabrication of Aunanoparticle@mSiO2@Y2O3:Eu nanocomposites with enhanced fluorescence

Herein, Aunanoparticle@mSiO2@Y2O3:Eu nanocomposites are synthesized through layer-by-layer assembly technology. Aunanoparticle@mSiO2 core–shell nanospheres were prepared at first in the presence of CTAB in aqueous solution system by the modified one-pot method. A chemical precipitation method and a succeeding calcination process were adopted to the growth of Y2O3:Eu shells on the surfaces of Aunanoparticle@mSiO2 core–shell nanospheres. The structure, morphology and composition of the nanocomposites were confirmed by XRD, TEM and UV–vis absorption spectrum. The prepared Aunanoparticle@mSiO2@Y2O3:Eu nanocomposites have showed the emission intensity enhances to 6.23 times at 30 nm thickness of the silica spacer between the core of Au nanoparticle and the shell of Y2O3:Eu. According to the observations of fluorescent lifetime and the modeling of local electric field, the metal-enhanced and quenched fluorescence is closely related with the enhancement of excitation and radiative decay rate and the quenching by NRET comes as a result of competition between the distance-dependent mechanisms. This kind of multifunctional inorganic material will be widely used in electronics, biology and medical drug loading, etc.

Improvement of synthesis conditions of dispersed polymetallic Fe–Al–Mo systems in aqueous solutions

Kinetic dependences describing the processes occurring on aluminum microparticles in aqueous solutions containing iron and molybdenum ions were determined. It was shown that the samples obtained contain iron, molybdenum, and aluminum in the elementary state in the absence of an oxide phase.

Morphological control of hybrid amphiphilic poly(N-isopropylacrylamide)/metal cyanide complexes

A number of amphiphilic N-isopropylacrylamide (NIPAAm) oligomers and polymers with a S-1-dodecyl-S′-trithiocarbonate (DTC) and an amino terminal group were prepared using RAFT polymerization: DTC-NIPAAm13-NH3Cl (1), DTC-NIPAAm61-NH3Cl (2), DTC-NIPAAm78-NH3Cl (3), DTC-NIPAAm119-NH3Cl (4). and DTC-NIPAAm274-NH3Cl (5). Aqueous solutions of 1–5 became cloudy upon heating at pH 10, while 1–4 did not exhibit thermosensitivity at pH 7.0, instead forming stable rods and vesicles in aqueous solution. Nanorods and nanosquares were obtained from metal cyanide complexes of 1 and 2, both of which had low degrees of polymerization, and aqueous solutions of these nanocomposites became cloudy at pH 7.0. The electrostatic interactions between the amine segments and the anionic metal cyanide complexes as well as the low degree of polymerization in the vicinity of approximately 100 were both found to have a significant role in the morphology and thermoresponsiveness of the hybrids. These hybrid NIPAAm oligomer/metal cyanide complexes may allow the design of flexible, functional supramolecular systems in aqueous solutions. A number of amphiphilic N-isopropylacrylamide (NIPAAm) oligomers and polymers with a S-1-dodecyl-S′-trithiocarbonate (DTC) and an amino terminal group has been designed. The electrostatic interactions between the amine segments and the anionic metal cyanide complexes have a significant role in the morphology and thermoresponsiveness of the hybrids. The hybrids of PNIPAAms and metal complexes can lead not only to nanostructures in water but also to cylindrical aggregates (or spherical aggregates) assembled in rod, square and sheet structures.

An approach to determine the efficiency of LIBS system in aqueous solution using optical instruments

An approach to determine the efficiency of LIBS system in aqueous solution using optical instruments

Probing acid/base chemistry and adsorption mechanisms of hydrolysable Al(iii) species with a clay system in aqueous solution

The acid/base chemistry of hydrolysable Al(iii) species with a clay (bentonite and kaolin) system was investigated at 35 °C in the expanded solution pH range from 1 to 9.

Photocatalytic reduction of CO2 over Ag/TiO2 nanocomposites prepared with a simple and rapid silver mirror method.

The photocatalytic reduction of CO2 over Ag/TiO2 composites prepared with a simple silver mirror reaction method was investigated under UV-visible irradiation in both gas-phase (CO2 + water vapor) and aqueous solution (CO2-saturated NaHCO3 solution) systems. The as-prepared Ag/TiO2 nanocomposite exhibits efficient photocatalytic activity due to the surface plasmonic resonance and electron sink effect of the Ag component, which was found to be closely related to the size and loading amount of Ag. The rapid silver method is effective at curbing the size of Ag, so photocatalytic activity can be improved. Diverse organic chemical products were detected, including mainly methane and methanol as well as a small amount of C2 and C3 species such as acetaldehyde and acetone. Possible photocatalytic mechanisms were proposed. This artificial photosynthesis process may give a prosperous route to the removal of CO2 while simultaneously converting CO2 to valuable fuels based on highly efficient photocatalysts.

ChemInform Abstract: Water Mediated Domino Knoevenagel‐Michael‐Cyclocondensation Reaction of Malononitrile, Various Aldehydes and Barbituric Acid Derivatives Using Boric Acid Aqueous Solution System Compared with Nano‐Titania Sulfuric Acid.

Nano-titania sulfuric acid (TSA) and boric acid [B(OH)3] were efficiently utilized for domino Knoevenagel-Michael-cyclocondensation reaction of malononitrile, various aldehydes and barbituric acid derivatives to synthesis of pyrano[2,3-d]pyrimidine diones. It is interesting that in boric acid aqueous solution system, H+ which abstracted from water by the interaction with B(OH)3, efficiently catalyzed the reaction.

On the Acceleration of CO2 Reaction with N-Ethyldiethanolamine in Aqueous Solutions by the Addition of Promoters

Focusing on renewable resources, such as ethanol, for producing CO2-capturing solvents can stimulate a big change in the gas purification industry by creating a smaller environmental footprint. One such solvent showing great potential is the tertiary amine N-ethyldiethanolamine (EDEA). In this work, the reaction kinetics of the CO2-EDEA system in aqueous solutions (2–3 M) was determined from the absorption rate measurements in a stirred cell reactor under fast pseudo-first order conditions. We discovered that EDEA reacts with CO2 faster (rate constant kEDEA = 19 M–1 s–1 at 303 K) than other tertiary amines, such as N-methyldiethanolamine (MDEA), N-propyldiethanolamine (PDEA), and N-butyldiethanolamine (BDEA). When the performance of different absorption promoters in aqueous EDEA solutions was tested, it was found that piperazine (PZ) was more effective than monoethanolamine (MEA) and diethanolamine (DEA). Therefore, the influence of PZ on the equilibrium and kinetic characteristics of aqueous EDEA solutio...

Formation of a disperse Fe–Al–Cr system in aqueous solutions and its physical properties

We have demonstrated the feasibility of producing a disperse Fe–Al–Cr polymetallic system through a contact exchange in chloride-containing aqueous solutions and investigated the processes that take place on aluminum microparticles in aqueous solutions containing ions of appropriate metals. It has been shown that the system is a precursor of intermetallic phases that result from high-temperature processes, in particular from spark plasma sintering.

Transfer across goatskin barrier of 2-butanone, 2,3-butanedione and 2-butanol during maturation of traditional Lebanese cheese, Darfiyeh: Comparison between experimental aqueous model solution and goatskin system

Darfiyeh cheese is a Lebanese traditional variety made from raw goat’s milk and ripened in goatskin. Ripening tools and conditions play the role of a barrier to protect the foodstuff against deterioration. This function requires the control of small volatile molecules transfer, such as aroma compounds.Several methods have been used for the measurement of diffusion of aroma volatile compounds. Few selected aroma compounds have been employed in more or less complex food model systems. Aqueous models containing some of the food components have been adopted as appropriate models given the complexity of food matrices.In this study, we characterized fragments of goatskin microbiologically, physico-chemically and qualitatively. Furthermore, we followed the transfer of three model aroma compounds (2-butanone, 2,3-butanedione and 2-butanol) in an experimental aqueous model solution/goatskin system at 20, 40 and 60 days of exposure.The barrier properties of goatskin were assessed for aroma model molecules through permeability and sorption tests. Therefore, the behavior/distribution of diffusing molecules was discussed on the basis of the physico-chemical properties of these molecules, the properties of the barrier material, as well as the food matrix (aqueous dilute model solution in the case of our study).Until 40 days, the transfer of model molecules was dependent on their physico-chemical properties and exposure time. After 60 days, the molecules tended to migrate from the goatskin back to the aqueous dilute model solution. In such a model, there was evidence of a tendency towards the diffusion of aroma model molecules in a cyclic way.

Degradation of carbofuran by V(IV)/H2O2 system in aqueous solution

Carbofuran is a kind of carbamate pesticide commonly used on major crops. The degradation of carbofuran by V (IV)/H2O2 system was investigated. The degradation system was strongly influenced by the pH, and initial concentration of VO2+. The degradation efficiency of carbofuran at the difference pH with the initial concentration of VO2+ in system was observed. An initial carbofuran concentration of 10 mg L–1 was 95% degraded within 10 min at pH 2.6 with original VO2+ concentration of 5×10–4 M. The decrease of TOC content was observed during the catalytic process and the removal percentage was obtained about 20% after 24 h. Furthermore, therefore, this process based on the catalytic reaction of VO2+ and VO2 +, and was responsible for the continuous production of hydroxyl radicals in such system. It has also proven that the degradation percentage increase when a little amount of L-ascorbic acid of 5×10–4 M was applied, the degradation increase up to 20% more at 10 min. A gas chromatography-mass spectrometry analysis showed the formation of seven products, on the basis of formation of time and its abounded, of all these intermediate products, a reaction mechanism path was submitted.Bangladesh J. Sci. Ind. Res. 50(3), 211-218, 2015

Thermodynamic Modeling of Surface Tension of Aqueous Electrolyte Solution by Competitive Adsorption Model

Thermodynamic modeling of surface tension of different electrolyte systems in presence of gas phase is studied. Using the solid-liquid equilibrium, Langmuir gas-solid adsorption, and ENRTL activity coefficient model, the surface tension of electrolyte solutions is calculated. The new model has two adjustable parameters which could be determined by fitting the experimental surface tension of binary aqueous electrolyte solution in single temperature. Then the values of surface tension for other temperatures in binary and ternary system of aqueous electrolyte solution are predicted. The average absolute deviations for calculation of surface tension of binary and mixed electrolyte systems by new model are 1.98 and 1.70%, respectively.

ChemInform Abstract: Catalysts for C‐H Functionalization: Platinum, Gold and Even Nanodiamonds

AbstractReview: 194 refs.

The clouding phenomena of mixed surfactant (non-ionic Triton X-114 + cationic gemini 16-5-16) solutions: Influence of inorganic and organic additives on the cloud point

In this investigation, we have studied the micellization of non-ionic surfactant, Triton X-114 (by surface tension measurement) and cationic gemini surfactant, pentanediyl-1,5-bis(dimethylcetylammonium bromide) (16-5-16) by surface tension, conductivity and dye solubilization methods and the clouding phenomena of mixed surfactant (non-ionic Triton X-114+cationic gemini 16-5-16) system in aqueous solution. The critical micelle concentration (CMC) of Triton X-114 and 16-5-16 were measured and their surface properties and thermodynamics were evaluated. In aqueous solution, non-ionic surfactant, Triton X-114 undergoes phase separation or cloud point (CP). Herein, we also report the influence of additives (e.g., electrolytes, sugars, amino acids, etc.) on the CP of Triton X-114 in aqueous solutions. The CP showed a concentration dependent variation in the absence of any added compound (additives). With the addition of additives, the CP values were found to decrease and increase. It is found that the CP of pure Triton X-114 is concentration dependent; and the presence of gemini surfactant (16-5-16) increases the CP. However, all additives in the presence of the gemini surfactant (i.e., Triton X-114+16-5-16 system) decrease the CP. The results are discussed by taking into consideration the nature of the additives. The thermodynamic parameters are also evaluated at CP.

Advanced oxidation processes for the treatment of chlorpyrifos, dimethoate and phorate in aqueous solution

Photo-chemical-transformations of organophosphate pesticides, chlorpyrifos, dimethoate and phorate, using advanced oxidation processes (AOPs) namely UV photolysis, UV/H2O2, UV/Fenton and Fenton systems in aqueous solution were investigated in this work. A laboratory set-up was designed to evaluate and select the optimal oxidation process. Results show that addition of hydrogen peroxide/Fenton's reagent increased the UV degradation rates of all pesticides, and data were simulated through kinetic modeling. Kinetic results evidence pseudo first-order degradation, with the rate constant of reaction as 3.3 × 10–4, 2.07 × 10–2 and 1.88 × 10–2 for chlorpyrifos, dimethoate and phorate, respectively. Furthermore treatment efficiencies obtained for the studied AOPs indicate that UV/Fenton was most efficient for chlorpyrifos (50.3% degradation) and UV/H2O2 for dimethoate (96.9%) and phorate (89.6%). Finally, the identification of degradation products indicated that the UV/H2O2 technique results in the formation of fewer end products, with low toxicity. However, UV irradiation of phorate results in information of more toxic degradation end products such as phorateoxonsulfone.

Influence of temperature on adsorption mechanism of anionic polyacrylamide in the Al2O3 –aqueous solution system

The influence of temperature on the adsorption mechanism of anionic polyacrylamide (PAM) on the alumina surface was studied in the temperature range 15–35 °C. The structure of polymer adsorption layer was determined from spectrophotometric, surface charge and zeta potential measurements. These methods enable determination of the following parameters: adsorbed amount of polymer, surface charge density and zeta potential of Al2O3 particles in the absence and presence of PAM. The influence of carboxyl groups content in the polyacrylamide macromolecules (varying from 5 to 50%) was also examined. The obtained results indicate that temperature influences the adsorption behaviour of anionic polyacrylamide on the Al2O3 surface. Slight increase of PAM adsorbed amounts with the temperature rise was obtained for the polymer samples characterized by the higher anionic group content (20, 30 and 50%). In the case of PAM with 5% content of these groups significantly larger adsorption was observed at 25 °C. The PAM presence causes also changes in electrokinetic properties (zeta potential and surface charge density values, as well as pHpzc and pHiep positions) of the examined system in the temperature range 15–35 °C.