Hydrolysis Of Ions Research Articles

금속이온에 의한 조류 응결에 관한 연구

Studies on the flocculation of algae using various metal ions were carried out by measurements of optical density(OD) and zeta potential. Cyanobacteria were used as algaes. Flocculation efficiencies of cyanobacteria by an addition of metal ions were determined from OD values, and the effect of metal ions was greater in the order of >>>>. Especially for trivalent metal ions, percentages of metal removed from cyanobacteria solutions on flocculation were measured, showing the same order as in flocculation efficiencies. Zeta potentials of cyanobacteria alone were measured with increasing the concentration, found to be all negative voltages, and were increased with increasing the concentration. The effect of pH on zeta potential of cyanobacteria solution was investigated. Below pH 5.5, the zeta potentials were steeply decreased with increasing pH, whereas in the range of they were almost constant () even with increasing pH. At a constant concentration of cyanobacteria (), an increase in concentration of metal ions caused an increase in zeta potential of cyanobacteria solution, showing that the effect was greater in the order of >>. At a constant metal concentration, zeta potentials were measured with increasing cyanobacteria concentration, showing that zeta potentials for , and ions were negligibly changed, whereas those of and ions were decreased. Moreover, the effect of ion on decreasing zeta potential was smaller than that of ion. ions showed quite a different behavior that with increasing cyanobacteria concentration the zeta potentials increased and decreased thereafter. Hydrolysis of ions caused a difficulty to investigate coagulation or flocculation of cyanobacteria by measurement of zeta potential.

Modeling of 4-Carboxyl-2,6-dinitrobenzenediazonium Ion (CDNBD) Hydrolysis Through Addition of Water and Alkaline Buffer in a Strongly Acidic Medium

The transition from aryl diazonium reagent solution to a crystalline form has substantial merits, namely augmented stability and versatility. Absorbance decay data was from photometric titration with hydroxyl ion, supplied incrementally by water and alkaline buffer (pH 12.0), to 4-carboxyl-2,6-dinitrobenzenediazonium ion (CDNBD) and simpler analogs in a strongly acidic medium. The data were fitted to nested models (mono- and bi-exponential decay). Akaike’s Information Criterion was used for statistical model comparison. Preferred model identification shows simpler diazonium analogs are less reactive towards hydroxyl ion when alkaline buffer solution is the diluting medium. In contrast, CDNBD hydrolysis is faster when an alkaline diluting medium is added, owing to profound positive effect of strong electron withdrawing groups on its electrophilic reactivity. Acidic diluting medium was shown, unambiguously, as a critical requirement for maintaining CDNBD, in an acidic solution as the cation species. Key input process variables were reliably predicted, using model parameters like $$ V_{1/2}$$ and $$ V_{1/2}^{T} $$ , thus giving direction for optimal synthesis of crystalline CDNBD.

Stability of cefozopran hydrochloride in aqueous solutions

The influence of pH on the stability of cefozopran hydrochloride (CZH) was investigated in the pH range of 0.44–13.00. Six degradation products were identified with a hybrid ESI-Q-TOF mass spectrometer. The degradation of CZH as a result of hydrolysis was a pseudo-first-order reaction. As general acid–base hydrolysis of CZH was not occurred in the solutions of hydrochloric acid, sodium hydroxide, acetate, borate and phosphate buffers, kobs = kpH because specific acid–base catalysis was observed. Specific acid–base catalysis of CZH consisted of the following reactions: hydrolysis of CZH catalyzed by hydrogen ions (kH+), hydrolysis of dications (k1H2O), monocations (k2H2O) and zwitter ions (k3H2O) and hydrolysis of zwitter ions (k1OH−) and monoanions (k2OH−) of CZH catalyzed by hydroxide ions. The total rate of the reaction was equal to the sum of partial reactions: . CZH similarly like other fourth generation cephalosporin was most stable at slightly acidic and neutral pH and less stable in alkaline pH. The cleavage of the β-lactam ring resulting from a nucleophilic attack on the carbonyl carbon in the β-lactam moiety is the preferred degradation pathway of β-lactam antibiotics in aqueous solutions.

Aqueous Brønsted-Lowry Chemistry of Ionic Liquid Ions.

Ionic liquids have become commonplace materials found in research laboratories the world over, and are increasingly utilised in studies featuring water as co-solvent. It is reported herein that proton activities, aH (+) , originating from auto-protolysis of H2O molecules, are significantly altered in mixtures with common ionic liquids comprised of Cl(-), [HSO4 ](-), [CH3SO4 ](-), [CH3COO](-), [BF4](-), relative to pure water. paH (+) values, recorded in partially aqueous media as -log(aH (+)), are observed over a wide range (∼0-13) as a result of hydrolysis (or acid dissociation) of liquid salt ions to their associated parent molecules (or conjugate bases). Brønsted-Lowry acid-base character of ionic liquid ions observed is rooted in equilibria known to govern the highly developed aqueous chemistry of classical organic and inorganic salts, as their well-known aqueous pKs dictate. Classical salt behaviour observed for both protic and aprotic ions in the presence of water suggests appropriate attention need be given to relevant chemical systems in order to exploit, or avoid, the nature of the medium formed.

ChemInform Abstract: Am(II‐VII) Species in Aqueous Solutions and Mechanisms of Reactions Involving Them

AbstractReview: 210 refs.

Process of Salicylic Acid-Type Composite for Rare Earth Ions

The chelation adsorption behavior of a salicylic acid-type composite ASA-PGMA/SiO2for rare earth ions of the rare earth ore mud leaching solution in Mianning was studied in the present work. The effect of the reaction temperature and medium pH on adsorption properties of the ASA-PGMA/SiO2particle was examined. The concentrations of REEs were determined by ICP-MS. The results showed that the ASA-PGMA/SiO2possessed strong chelation adsorption ability for rare earth ions. The reaction temperature was 50°C, the adsorption properties of the composite were the best and the adsorption rate of rare earth ions reached above 90%. In the pH range where the hydrolysis of rare earth ions was inhibited, an increase in the pH value of the medium strengthened the chelation adsorption ability of the ASA-PGMA/SiO2particle for rare earth ions. The rare earth ions desorption from the ASA-PGMA/SiO2particle is effective when using 0.2mol/L of hydrochloric acid solution as the eluent.

Structure, function, evolution, and application of bacterial Pnu-type vitamin transporters.

Many bacteria can take up vitamins from the environment via specific transport machineries. Uptake is essential for organisms that lack complete vitamin biosynthesis pathways, but even in the presence of biosynthesis routes uptake is likely preferred, because it is energetically less costly. Pnu transporters represent a class of membrane transporters for a diverse set of B-type vitamins. They were identified 30 years ago and catalyze transport by the mechanism of facilitated diffusion, without direct coupling to ATP hydrolysis or transport of coupling ions. Instead, directionality is achieved by metabolic trapping, in which the vitamin substrate is converted into a derivative that cannot be transported, for instance by phosphorylation. The recent crystal structure of the nicotinamide riboside transporter PnuC has provided the first insights in substrate recognition and selectivity. Here, we will summarize the current knowledge about the function, structure, and evolution of Pnu transporters. Additionally, we will highlight their role for potential biotechnological and pharmaceutical applications.

Structure, function, evolution and application of bacterial Pnu-type vitamin transporters

AbstractMany bacteria can take up vitamins from the environment via specific transport machineries. Uptake is essential for organisms that lack complete vitamin biosynthesis pathways, but even in the presence of biosynthesis routes uptake is likely preferred, because it is energetically less costly. Pnu transporters represent a class of membrane transporters for a diverse set of B-type vitamins. They were identified 30 years ago and catalyze transport by the mechanism of facilitated diffusion, without direct coupling to ATP hydrolysis or transport of coupling ions. Instead, directionality is achieved by metabolic trapping, in which the vitamin substrate is converted into a derivative that cannot be transported, for instance by phosphorylation. The recent crystal structure of the nicotinamide riboside transporter PnuC has provided the first insights in substrate recognition and selectivity. Here, we will summarize the current knowledge about the function, structure and evolution of Pnu transporters. Additionally, we will highlight their role for potential biotechnological and pharmaceutical applications.

分散粒子を含まない溶液からの Zn-Zr 酸化物複合電析

Electrodeposition of Zn-Zr oxide composite was examined from an unagitated sulfate solution containing Zn2+ and Zr ions at pH 1 to 2 and 313 K under galvanostatic conditions. Zr content in deposits was higher in pH 2 than that in pH 1, and decreased for the moment with increasing current density, but the further increase in current density brought about the increase in Zr content in deposits. This increase in Zr content in deposits is attributed to the acceleration of the hydrolysis of Zr ions by means of an increase in hydrogen evolution in the cathode layer. In solution containing Zr ions, Zn deposition was significantly polarized due to the film resistance of Zr oxide formed by the hydrolysis of Zr ions. The pH in the vicinity of the cathode, as measured by an Sb microelectrode, was approximately 2.2, which is close to the critical pH for the formation of ZrO2. SEM and EDX point analysis of deposits revealed that the granular Zr oxide deposited at the surface of Zn platelet crystals and at the void between the Zn platelet crystals. It was found from the polarization curves in 3 mass% NaCl solution that the corrosion potential of deposited Zn-1.1 mass% Zr oxide films was more noble than that of pure Zn, and the corrosion current density of Zn-1.1 mass% Zr oxide films was lower than that of pure Zn.

Synthesis and thermal properties of low melting temperature tin/indium (Sn/In) lead-free nanosolders and their melting behavior in a vapor flux

Low melting temperature tin/indium (Sn/In) nanosolders with a wide composition range were synthesized by a surfactant-assisted chemical reduction method in an aqueous solution at ambient conditions. The parameters that affect the synthesis process were studied to control the size, shape and composition of the Sn/In nanosolders. It was found that hydrolysis of the metal ions significantly affected the nanosolder formation and inhibition of hydrolysis resulted in better nanosolder quality. Under optimized conditions, the Sn/In nanosolders around 50/50 (wt%) composition had a size range of 30–90nm. SEM, TEM, EDS and XRD were used to determine the morphology, composition, and crystal structure of the nanosolders. It was found that the Sn/In nanosolders were mainly composed of InSn4 at low In content (30wt% In). When the In content further decreased to 20%, a mixture of InSn4 and β-Sn exist; however, when the In content increased to 40% or higher, pure In appeared in the nanosolders, and the nanosolders have an increasing amount of In nanocrystals with the increase of the In ratio. DSC measurements have been conducted to understand the melting behavior of the nanosolders, and low melting temperatures were achieved at a wide range of In compositions (from 30% to 70%). The lowest melting temperature was found to be 115.5°C, indicating a new eutectic point around 30% In. Finally, the temperature and time effects on the melting behavior and solder reflow property of the nanosolders have been investigated in a vapor flux environment.

Mesoporous nanoscale ceria: synthesis from cerium (III) acetylacetonate and mechanism

Ceria nanopowders with crystallite size of about 10 nm have been prepared by the sol-gel method form cerium (III) nitrate or acetylacetonate. Dimethyloc- tylamine was used as low molecular weight stabilizer and hydrolyzing agent and acetylacetone as a chelating ligand to prevent a rapid hydrolysis of cerium ions. Ceria obtained had a mesoporous structure. It is shown that the presence of acetylacetonate ligands in solution promotes the obtaining of mesoporous ceria with a narrow pore size distribution (2-4 nm). The method of matrix assisted laser desorption/ ionization time of flight mass spectrometry was used to establish the composition of intermediate complexes in solution, sol, and xerogel of ceria. Mixed ligand complexes of cerium b-diketonates were found; key intermediates Ce- O linear structural fragments have been also found in all spectra.

Surface Chemistry of Calcium Aluminosilicate Glasses

The surface chemistry of synthetic calcium aluminosilicate glasses exposed to aqueous solutions of varying pH was described using zeta potential measurements and batch surface titrations. Element release and proton consumption were measured to characterize the reactions at the surface as a function of pH. It was found that proton–metal exchange or leaching was the dominant proton consumption process at low pH. The exchange reaction was observed to maintain charge balance, indicating that over the limited duration of the experiments no repolymerization of the silica‐rich leached layer occurred. At high pH, dissolution and hydrolysis of aqueous ions controlled the proton mass balance, no evidence for the formation of leached layers was found. Silica‐rich glasses were found to be more resistant to corrosion by either proton–metal exchange or dissolution than CaO‐rich glasses. Glass basicity was found to be reflected in the establishment of a higher pH when immersing the glass in neutral aqueous solutions and in a reduced stability of the glass surface toward aqueous solutions. High pH, high surface charge and reduced glass network polymerization act together in enhancing the reaction of CaO‐rich glasses with aqueous solutions.

In situ monitoring of the electrochemical reactivity of aluminium alloy AA6060 using the scanning vibrating electrode technique

Localized electrochemical activation of aluminium alloy AA6060 surfaces during immersion in chloride-containing aqueous solution has been characterised using the scanning vibrating electrode technique (SVET). Ionic current flows in the electrolyte phase adjacent to corroding microcells are imaged in situ, allowing their evolution with time to be monitored with spatial resolution. A heterogeneous response due to the presence of intermetallic inclusions in the material is found on AA6060 surfaces. The highly localized anodic activity was thus detected, which has been interpreted as a result of the galvanic coupling between the matrix and the intermetallic particles. Metallic inclusions behave cathodically whereas the aluminium matrix undergoes metal dissolution due to the activation of anodic sites in the proximity of those inclusions. Hydrolysis of aluminium ions leads to local acidification of the electrolyte adjacent to the anodic sites, and it is accompanied by hydrogen evolution.

Electrochemical desalination of solutions, containing hardness ions

Processes of the electrochemical desalination of solutions with high content of hardness ions in three-chamber electrolyzer with two anionic membranes MA-41 were studied. On the example of model solutions of magnesium sulfate, it was shown that, in this electrolyzer there is desalination of the solution, placed in the working chamber between the anionic membranes due to diffusion of sulfate anions to the anodic region and hydrolysis of magnesium ions in the working area due to diffusion of hydroxide anions from the cathode chamber to the working. The peculiarity of the electrolyzer is using anionic membrane from the cathode side. This prevents the migration of cations, including hardness ions, to the cathode region and protects the cathode from the formation of hardness ions hydrolysis products on its surface, especially from deposits on the magnesium hydroxide cathode surface, which significantly increases the electrical resistance of the system. Electrical conductivity in the electrolyzer is maintained by the migration of hydroxide anions, generated at the cathode, from the cathode chamber to the working chamber, thus compensating for the migration of chlorides and sulfates from the working chamber to the anode region. It was shown that hydroxide anions virtually do not pass to the anode chamber since they are bound in the working chamber during the hydrolysis of magnesium ions, and with the presence of hydrocarbons during their conversion into carbonates. This promotes the mitigation of the solution in the working chamber and its purification from chlorides and sulfates. In the anode chamber during the separation of oxygen and protons on the anode there is the formation of sulfuric acid. Chlorine after oxidation at the anode is separated from the acidic medium in the form of gas and is absorbed by an alkali solution with the formation of sodium hypochlorite. Similar processes are implemented during mine water desalination in this electrolyzer when adding magnesite to the working chamber near mine water.

A Chemical Sensing Plate for Simultaneous Measurements of pH and Cl− Concentration Inside Crevice of Stainless Steel

The decrease in pH caused by the hydrolysis of metal ions inside crevice is widely accepted to be the predominant factor affecting crevice corrosion for stainless steels. The accumulation of chloride ions inside crevice is also thought to be of great importance for the initiation of crevice corrosion. Kaji et. al. 1 fabricated a glass plate with a sol-gel SiO2 sensing layer, which contains a pH indicator or a Cl−-sensitive florescent dye, and the H+ and Cl− distributions in the crevice solution for stainless steel were visualized. They demonstrated the crevice corrosion was initiated when the H+ and Cl− concentrations inside the crevice reached the conditions for metastable pit formation. However, their experiments were not simultaneous measurements for pH and Cl− concentration, so that the combination between the pH decrease and the Cl− accumulation remains unclear. In this study, a simultaneous measurement technique for pH and Cl− was developed and applied to the visualization of pH and Cl− distribution inside crevice in the initial stage of crevice corrosion. A sensing layer with fluorescent dyes was made on one side of a SiO2 plate using the sol-gel SiO2 coating technique. Quinine sulfate (fluorescent dye) was use to measure Cl− concentration. 1 The excitation wavelength was 350 nm. The emitted light was filtered through a 420-nm long-pass filter, since quinine sulfate has a peak wavelength of 451 nm (blue fluorescence). A metal-organic complex (a fluorescent dye) was used as the sensing dye for pH measurements. The excitation wavelength of this dye was 270 nm, and the emitted light was filtered through a 510–550-nm band-pass filter. In this case, green fluorescence was observed. The sensing plate fabricated in this study was colorless and transparent to visible light, and hence the surface appearance of the steel could be observed through the plate clearly. The fluorescence images of the sensing plate placed on a Pt sheet were taken by a fluorescence microscope. The solutions with different pH and Cl− concentrations were used as calibration standards. Figure 1 shows the fluorescence of the Cl−-sensitive dye (quinine sulfate) in the sensing layer on the SiO2 plate. As seen in this figure, the brightness of the blue fluorescence depends on Cl− concentration but is independent of pH. Figure 2 shows the fluorescence of the H+-sensitive dye in the sensing layer on the SiO2 plate. In this case, even though Cl− concentration slightly affects the brightness; however, the brightness of the green fluorescence mainly depends on pH. Therefore, pH can be measured by previously obtaining the Cl− concentration from the brightness of the blue fluorescence. A Mn-containing austenitic stainless steel (Fe-18Cr-10Ni-5.5Mn) was used for crevice corrosion tests. Crevice (3 mm × 3 mm) was made between the surface of the stainless steel and that of the sensing plate. 1 Crevice corrosion tests were carried out in a naturally aerated 0.01 M NaCl solution (298K) of pH 3.0 adjusted with HCl, and the specimen was polarized at 0.3 V (vs. Ag/AgCl, 3.33 M KCl). Figure 3 shows the surface appearance of the initiation site of crevice corrosion (micro pit) and the fluorescence images corresponding to pH and Cl− concentration. It was confirmed that both the pH decrease and the Cl− accumulation occurred at the initiation site of crevice corrosion.Reference:1. T. Kaji, T. Sekiai, I. Muto, Y. Sugawara, N. Hara, J. Electrochem. Soc., 159, C289-C297 (2012).

Surfactant Assisted Dispersion and Adhesion Behavior of Carbon Nanotubes on Cu–Zr and Cu–Zr–Al Amorphous Powders

Carbon nanotubes (CNTs) were dispersed in gas atomized Cu47.5Zr47.5Al5 (CZA) and Cu50Zr50 (CZ) amorphous powders, in an effort to elucidate the mechanisms of adhesion of CNTs onto amorphous metallic powders. CNTs were homogenously dispersed in water using a zwitterionic (ZW) surfactant. Then CZA and CZ powders were submersed in the ZW-CNT suspensions with varying amounts of dwell time in an ultrasonic bath. The ZW-CNT-metal powder suspensions were dried, and CNT-metal composite powders were obtained after decomposition of the surfactant by calcination. Zeta potential measurements on ZW-CNT-metal powder suspensions and scanning electron microscopy investigation into the CNT-metal composite powders both indicated an ideal dwell time, for a specific alloy composition, of metallic powders in ZW-CNT suspension to achieve optimal adhesion of CNTs onto amorphous metallic powder surfaces. The results are rationalized on the basis of hydrolysis of metal ions into suspension creating a net positive charge on the metallic powder surfaces, and the interaction between the charged powder surfaces and the charged hydrophilic head groups of ZW, which has the other end attached to CNTs.

Am(II–VII) species in aqueous solutions and mechanisms of reactions involving them

Published data on the structure of americium ions in aqueous solutions are analyzed. The hydrolysis of americium ions, their complexation with certain inorganic and organic anions, disproportionation, and reactions with oxidants and reductants are considered.

The Borohydride Oxidation Reaction on La–Ni‐Based Hydrogen‐Storage Alloys

This work provides insights into the processes involved in the borohydride oxidation reaction (BOR) in alkaline media on metal hydride alloys formed by LaNi(4.7)Sn(0.2)Cu(0.1) and LaNi(4.78)Al(0.22) with and without deposited Pt, Pd, and Au. The results confirm the occurrence of hydrolysis of the borohydride ions when the materials are exposed to BH(4)(-) and a continuous hydriding of the alloys during BH(4)(-) oxidation measurements at low current densities. The activity for the direct BOR is low in both bare metal hydride alloys, but the rate of the BH(4)(-) hydrolysis and the hydrogen-storage capacity are higher, while the rate of H diffusion is slower for bare LaNi(4.78) Al(0.22). The addition of Pt and Pd to both alloys results in an increase of the BH(4)(-) hydrolysis, but the H(2) formed is rapidly oxidized at the Pt-modified catalysts. In the case of Au modification, a small increase in the BH(4)(-) hydrolysis is observed as compared to the bare alloys. The presence of Au and Pd also leads to a reduction of the rates of alloy hydriding/de-hydriding.

Fabrication of Composite Polymer Foam Films at the Liquid/Liquid Interface through Emulsion-Directed Assembly and Adsorption Processes

The foam films of polystyrene-b-poly(acrylic acid)-b-polystyrene (PS-b-PAA-b-PS) doped with Cd(II) or Pb(II) species were fabricated at the planar liquid/liquid interfaces between a DMF/chloroform (v/v: 1/1) solution of the polymer and aqueous solutions containing cadmium acetate or lead acetate at ambient temperature. Optical microscopic observation shows the thin film is uniform on a larger length scale. Transmission electron microscopic (TEM) investigations reveal that the foam films are made up of microcapsules with the size of several hundreds of nanometers to micrometers. The walls of the microcapsules have a layered structure decorating with nanofibers and hollow nanospheres, where numerous inorganic fine nanoparticles are dispersed homogeneously. The film formation is a result of emulsion droplet-templated assembly and adsorption of the formed microcapsules at the planar liquid/liquid interface. Because of the miscibility of DMF with chloroform and water, DMF migrates to the aqueous phase while water migrates to the organic phase across the interface, resulting in the formation of a W/O emulsion, as revealed by optical microscopic observation, freeze fracture transmission electron microscopic (FF-TEM) observation, and dynamic laser scattering (DLS) investigation. The triblock copolymer molecules and the inorganic species adsorb and self-assemble around the emulsion drops, leading to the formation of the composite microcapsules. X-ray photoelectron spectroscopic (XPS) and FTIR spectroscopic results indicate that two kinds of Cd(II) or Pb(II) species, metal oxide or hydroxide, resulting from the hydrolysis of the metal ions and the coordinated metal ions to the carboxyl groups coexist in the formed thin films, which transform to metal sulfide completely after treating with hydrogen sulfide to get metal sulfide nanoparticle-doped polymer thin films.

A facile in situ fabrication and visible-light-response photocatalytic properties of porous carbon sphere/InOOH nanocomposites

Visible-light-response porous carbon sphere/InOOH nanocomposites were synthesized through a facile hydrothermal process. The grain size of the crystalline InOOH is estimated around 14 nm, and the nanocomposites show a size range from 100 to 200 nm. The as-prepared nanocomposites possess a porous structure and a specific surface area of 45 m2 g−1. A possible in situ formation process was proposed after conducting a series of contrast experiments. Carbon spheres (CSs) were suggested to act as spherical templates and reducing reagents during the synthesis process of nanocomposites. The whole process involves the hydrolysis of indium ions, the redox reactions on surfaces groups of the CSs, and the dehydration of indium hydroxide. UV–Vis diffuse reflectance spectrum revealed a red shift of light absorption of the nanocomposites to about 600 nm compared with pure InOOH. The photocatalytic degradation for methylene blue was performed under visible light irradiation, 90 % of methylene blue was degraded after reacting for 6 h. We propose that the red shift was attributed to the interaction between carbon sphere and InOOH, and the CSs may act as photosensitizers.