scholarly journals Electrostatic Potential Analysis in Polyelectrolyte Brush-Grafted Microchannels Filled with Polyelectrolyte Dispersion

Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1475
Author(s):  
Byoungjin Chun ◽  
Myung-Suk Chun
Keyword(s):  
Charge Density ◽  
Electrostatic Potential ◽  
Ion Concentration ◽  
Solution Ph ◽  
Model Framework ◽  
Fixed Charges ◽  
Modeling And Experiments ◽  
Monomer Distribution ◽  
Almost All ◽  
Brush Layer

In this study, the model framework that includes almost all relevant parameters of interest has been developed to quantify the electrostatic potential and charge density occurring in microchannels grafted with polyelectrolyte brushes and simultaneously filled with polyelectrolyte dispersion. The brush layer is described by the Alexander-de Gennes model incorporated with the monomer distribution function accompanying the quadratic decay. Each ion concentration due to mobile charges in the bulk and fixed charges in the brush layer can be determined by multi-species ion balance. We solved 2-dimensional Poisson–Nernst–Planck equations adopted for simulating electric field with ion transport in the soft channel, by considering anionic polyelectrolyte of polyacrylic acid (PAA). Remarkable results were obtained regarding the brush height, ionization, electrostatic potential, and charge density profiles with conditions of brush, dispersion, and solution pH. The Donnan potential in the brush channel shows several times higher than the surface potential in the bare channel, whereas it becomes lower with increasing PAA concentration. Our framework is fruitful to provide comparative information regarding electrostatic interaction properties, serving as an important bridge between modeling and experiments, and is possible to couple with governing equations for flow field.

Electrostatics of soft charged interfaces with pH-dependent charge density: effect of consideration of appropriate hydrogen ion concentration distribution

RSC Advances ◽  
2015 ◽  
Vol 5 (6) ◽  
pp. 4493-4501 ◽  
Author(s):  
Guang Chen ◽  
Siddhartha Das
Keyword(s):  
Charge Density ◽  
Concentration Distribution ◽  
Density Effect ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Explicit Consideration ◽  
Ph Dependent ◽  
Monomer Distribution

Explicit consideration of hydrogen ion concentration for describing the electrostatics of grafted polyelectrolyte layers with pH-dependent charge density exhibits the necessity of considering a non-uniform depth dependent monomer distribution.

What Kind of Friction Model Is Needed to Predict Brake Squeal?

2012 ◽  
Author(s):  
Tore Butlin ◽  
Jim Woodhouse
Keyword(s):  
Large Scale ◽  
Dynamic Properties ◽  
Theoretical Work ◽  
Friction Model ◽  
Coupled Systems ◽  
Brake Squeal ◽  
Model Framework ◽  
Wide Range ◽  
Pin On Disc ◽  
Almost All

Predictive models of friction-induced vibration have proved elusive despite decades of research. There are many mechanisms that can cause brake squeal; friction coupled systems can be highly sensitive to small perturbations; and the dynamic properties of friction at the contact zone seem to be poorly understood. This paper describes experimental and theoretical work aimed at identifying the key ingredients of a predictive model. A large-scale experiment was carried out to identify squeal initiations using a pin-on-disc test rig: approximately 30,000 squeal initiations were recorded, covering a very wide range of frequencies. The theoretical model allows for completely general linear systems coupled at a single sliding point by friction: squeal is predicted using a linearised stability analysis. Results will be presented that show that almost all observed squeal events can be predicted within this model framework, but that some subsets require innovative friction modelling: predictions are highly dependent on the particular choice of friction model and its associated parameters.

scholarly journals Biosorption of Cadmium by Fucus spiralis

2004 ◽  
Vol 1 (3) ◽  
pp. 180 ◽  
Author(s):  
Manuel Esteban Sastre de Vicente ◽  
Roberto Herrero ◽  
Pablo Lodeiro ◽  
Bruno Cordero
Keyword(s):  
Heavy Metals ◽  
Metal Removal ◽  
Heavy Metal Removal ◽  
Biological Materials ◽  
Ion Concentration ◽  
Adsorption Parameters ◽  
Solution Ph ◽  
Biosorption Process ◽  
Fucus Spiralis ◽  
Biosorption Kinetics

Environmental Context. Conventional processes for the removal of heavy metals from wastewaters generally involves chemical precipitation of metals (changing the pH) followed by a period to allow the metal precipitates to settle and be separated. These processes are inefficient when the metals are at a low concentration and still demand handling and disposal of toxic metal sludges. An alternative method for heavy metal removal is adsorption onto a biological material, biosorption. The biological materials, including agricultural byproducts, bacteria, fungi, yeast, and algae, all which take up heavy metals in substantial quantities, are relatively inexpensive, widely available, and from renewable sources. However, biological materials are complex and the active mechanisms often unclear. Abstract. Cadmium biosorption properties of nonliving, dried brown marine macroalga Fucus spiralis from Galician coast (northwest Spain) have been investigated. The biosorption capacity of the alga strongly depends on solution pH; the uptake is almost negligible at pH ≤ 2 and reaches a plateau at around pH 4.0. Cadmium biosorption kinetics by F. spiralis is relatively fast, with 90% of total adsorption taking place in less than one hour. A pseudo second order mechanism has been proved to be able to predict the kinetic behaviour of the biosorption process. The effect of initial cadmium ion concentration, alga dose, solution pH, and temperature on the biosorption kinetics has been studied. The Langmuir, Freundlich, Langmuir–Freundlich, and Tóth isotherms were used to fit the experimental data and to find out the adsorption parameters. Acid–base properties of the alga have been studied potentiometrically in order to calculate the number of acidic groups and the apparent pK value by using Katchalsky model. The pK obtained is comparable with typical values associated to the ionization of carboxyl groups of alginates, supporting the implication of these groups in the biosorption process.

Effect of pH and Concentration of Ca2+ on Spherical Calcium Carbonate Crystallization by Continuous CO2 Gas Bubbling into Phosphogypsum Leaching Solution

2015 ◽  
Vol 814 ◽  
pp. 552-558
Author(s):  
Ya Qing Liang ◽  
Hong Juan Sun ◽  
Tong Jiang Peng
Keyword(s):  
Grain Size ◽  
Calcium Carbonate ◽  
Particle Dispersion ◽  
Ion Concentration ◽  
High Grade ◽  
Solution Ph ◽  
Salt Leaching ◽  
Novel Approach ◽  
Different Temperatures ◽  
Leaching Solution

Spherical calcium carbonate (CaCO3) is a potential component in many industrial fields such as high-grade papermaking, high-grade painting, environment, and pesticide. This paper describes a novel approach to synthesize spherical calcium carbonate (CaCO3) particles via passing CO2 bubbles into phosphogypsum salt leaching solution (CaSO4) in the presence of ammonia (NH3) at different temperatures. The influence of the initial solution pH and concentration of calcium ions on the polymorph and morphology of CaCO3 was studied. The physical characteristics of the precipitate were evaluated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that compared with different calcium sources the phase and morphology of CaCO3 synthesized by phosphogysum leaching solution had some regularity. The grain size of spherical CaCO3 became bigger, surface became smoother, and particle dispersion became better with the increase of calcium ion concentration. The content of vaterite increased and particle grain size changed a little with the increase of pH. The research results had important environmental significance for phosphogysum resource utilization and CO2 fixation.

scholarly journals Reduced hæmatin and hæmochromogen

1929 ◽  
Vol 105 (735) ◽  
pp. 112-130 ◽  
Keyword(s):  
Carbon Monoxide ◽  
Helix Pomatia ◽  
Nitrogen Compound ◽  
Strong Solutions ◽  
Ion Concentration ◽  
Free Oxygen ◽  
Hydrogen Ion Concentration ◽  
Naturally Occurring ◽  
Chemical Combination ◽  
Almost All

Hæmochromogen, which originally was known only as an artificial degradation product of hæmoglobin, has since been found to occur in almost all organisms. Helicorubin, a hæmochromogen occurring in the intestinal fluid of snails (such as Helix pomatia ) was described by Krukenberg (1884), and its properties examined by Dhéré (1917). Cytochrome has been shown by Keilin (1925) to be a mixture of at least two, possibly three, hæmochromogens. Just as hæmoglobin differs in its behaviour towards oxygen from any of the other compounds of hæmatin at present known, so most of the naturally occurring hæmochromogens differ in properties from any of the artificial hæmochromogens. Ordinary hæmochromogen, obtained directly from hæmoglobin, combines with carbon monoxide to give CO-hæmochromogen, and is rapidly oxidised under all conditions by free oxygen to hæmatin. The hæmochromogens of cytochrome do not combine with carbon monoxide, and with the exception of component b (Keilin, 1929) are not rapidly oxidised by free oxygen over definite ranges of hydrogen-ion concentration. Originally hæmochromogen was only a name for the spectrum of reduced hæmatin under special conditions. Zeynek (1920) had shown by an analysis of solid pyridine hæmochromogen that it contains 2·2 molecules of pyridine. Anson and Mirsky (1925) were the first to show that this particular type of hæmatin spectrum is due to chemical combination of reduced hæmatin with substances containing nitrogen, and that each nitrogen compound gave its characteristic hæmochromogen. They showed that these compounds were dissociable in solution, and also that the various nitrogen compounds were in equilibrium with the hæmochromogen according to their relative affinities. Late I (1926) measured the minimum quantity of pyridine required to change completely the spectrum of reduced hæmatin into hæmochromogen, using strong solutions of hæmatin, and found that 2 molecules per molecule of reduced hæmatin were required, which agreed with Zeynek's analysis.

Charge Density and Electrostatic Potential Study of 16α,17β-Estriol and the Binding of Estrogen Molecules to the Estrogen Receptors ERα and ERβ

2016 ◽  
Vol 120 (34) ◽  
pp. 8882-8891 ◽  
Author(s):  
Elizabeth A. Zhurova ◽  
Vladimir V. Zhurov ◽  
Poomani Kumaradhas ◽  
Simone Cenedese ◽  
A. Alan Pinkerton
Keyword(s):  
Charge Density ◽  
Estrogen Receptors ◽  
Electrostatic Potential ◽  
Potential Study

scholarly journals Adsorption of Pollutants from Aqueous Solutions Using Activated and Non-Activated Oak Shells: Parametric and Fractional Factorial Design Study. Part I. Removal of Copper

2003 ◽  
Vol 21 (2) ◽  
pp. 177-188 ◽  
Author(s):  
Sameer Al-Asheh ◽  
Fawzi Banat ◽  
Nagham Al-Hamed
Keyword(s):  
Aqueous Solutions ◽  
Factorial Design ◽  
Contact Time ◽  
Fractional Factorial Design ◽  
Ion Uptake ◽  
Fractional Factorial ◽  
Ion Concentration ◽  
Batch Adsorption ◽  
Solution Ph ◽  
Operating Variables

Non-activated and chemically activated oak shells were evaluated for their ability to remove Cu2+ ions from aqueous solutions. Batch adsorption experiments were conducted to investigate the effect of contact time, sorbent concentration, Cu2+ ion concentration and the pH of the solution on the sorption process. The Cu2+ ion uptake by oak shells increased with decreasing sorbent concentration or with an increase in Cu2+ ion concentration or solution pH. The fractional factorial design technique was applied in order to determine the average Cu2+ ion uptake, the contribution of each operating variable to the value of the uptake and the interaction among the operating variables when the sorbent type, sorbent concentration, Cu2+ ion concentration, pH, contact time and salt were all varied from one level to another. Application of this technique showed that the sorbent concentration had the largest influence on the value of the Cu2+ ion uptake followed by Cu2+ ion concentration and sorbent type. Interaction among the different operating variables played an important role in the adsorption process.

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