Search results for "Surface charge"
showing 10 items of 86 documents
Fabrication of zinc doped aluminium oxide/polysulfone mixed matrix membranes for enhanced antifouling property and heavy metal removal
2021
International audience; Heavy metal removal from water resources is essential for environmental protection and the production of safe drinking water. In this direction, Zinc doped Aluminium Oxide (Zn:Al2O3) nanoparticles were incorporated into Polysulfone (PSf) to prepare mixed matrix membranes for the efficient removal of heavy metals from water. These Zn:Al2O3 nanoparticles prepared by the solution combustion method have a very high surface area (261.44 m2/g) with an approximate size of 50 nm. X-ray Photoelectron Spectroscopy analysis showed that the Al and Zn were in +3 and + 2 oxidation states, respectively. Cross-sectional Scanning Electron Microscopy images revealed the finger-like mo…
Dynamic evaluation of aggregation and agglutination of red blood cells.
1984
Viscoelastic evaluation of aggregation and agglutination of red blood cells was attempted. A concentric double cylinder viscoelastometer was used for determining the dynamic rigidity modulus and loss modulus of blood sample. The dynamic rigidity modulus of horse blood were measured over a wide range of hematocrit. The relation between the viscoelastic behavior and the erythrocyte sedimentation was examined. The change in the amount of surface charge of enzyme treated red blood cells was qualitatively estimated from the measurements of dynamic viscoelasticity of red blood cells suspension with added poly-L-lysine. The dynamic rigidity modulus of red blood cells agglutinated by adding lectin …
Interactions between bacterial surfaces and milk proteins, impact on food emulsions stability
2008
Bacteria possess physicochemical surface properties such as hydrophobicity, Lewis acid/base and charge which are involved in physicochemical interactions between cells and interfaces. Moreover, food matrices are complex and heterogeneous media, with a microstructure depending on interactions between the components in media (van der Waals, electrostatic or structural forces, etc.). Despite the presence of bacteria in fermented products, few works have investigated how bacteria interact with other food components. The objective of the present study was to determine the effects of the surface properties of lactic acid bacteria on the stability of model food emulsions. The bacteria were added t…
Novel polyaminoacidic copolymers as nonviral gene vectors
2000
Human gene therapy is one of the most promising methods developed in recent years, providing great potential for the treatment of a variety of diseases. Complexes formed between DNA and cationic polymers are attracting increasing attention as novel synthetic vectors for the delivery of genes. We have synthesized polycations with quaternary ammonium groups in their side chains for self-assembly with calf thymus DNA. This paper describes the functionalization of α,β-polyasparthydrazide (PAHy), a synthetic macromolecule having many potential applications in the field of biomedical sciences, with glycidyltrimethylammonuim chloride (GTA) in order to introduce positive charges into their chains. …
Preparation of novel high permeability and antifouling polysulfone-vanillin membrane
2020
International audience; A novel high-performance nanofiltration membrane was fabricated by a simple and scalable route involving in situ cross-linking of hydrophilic, cheap, and environmentally friendly vanillin as antifouling agent with polysulfone (PSf) for salt rejection performance. Vanillin acts as a porogen, which induces a negative surface charge on the membrane surface due to the presence of polar functional groups like alcohol and aldehyde. The surface properties, including charge, morphology, and hydrophilicity, were investigated in detail using analytical instruments. The nanofiltration performance of the fabricated PSf-vanillin membranes was dependent on the percentage of vanill…
Tetraalkylammonium Cations Conduction through a Single Nanofluidic Diode: Experimental and Theoretical Studies
2017
[EN] We describe experimentally and theoretically the concentration-dependent conduction of tetraalkylammonium (TAA+) cations through a nanofluidic diode fabricated in a polymer membrane via asymmetric track-etching techniques. This single-pore membrane exhibits current rectification characteristics because of the ionized carboxylate groups on the pore surface. We use aqueous solutions of potassium (K+ ), ammonium (A+ ), tetramethylammonium (TMA+ ), tetraethylammonium (TEA+ ), and tetrabutylammonium (TBA+ ) ions with concentrations ranging from 50 to 500 mM under acidic (pH 3.5) and physiological (pH 6.5) conditions. Compared with the K+ and A+ ions, the TMA+ , TEA+ , and TBA+ ions show rel…
Silicate adsorption by goethite at elevated temperatures
2009
Abstract Batch adsorption experiments with relatively low silica concentrations between 10 µM and 100 µM were conducted at three different ionic strength (0.01 − 0.1 M), and four different temperatures between 10 °C and 75 °C, yielding in a total of 550 experimental data points. The residual concentration of monosilicic acid is controlled by an adsorption equilibrium which is dependent on pH. The % Si adsorbed vs. − log[H + ] curves reveal an upward bend with a maximum at about a pH of 9. With acidification below pH 9 the residual Si concentration in the suspensions steadily increases, as well as in the increasingly alkaline pH range. The slope of the latter is becoming steeper with increa…
Orientation of charged clay nanotubes in evaporating droplet meniscus.
2015
© 2014 Elsevier Inc. During drying, an aqueous suspension of strongly charged halloysite clay nanotubes concentrates at the edge of the droplet ("coffee-ring" effect) which provides alignment of the tubes along the liquid-substrate contact line. First, the surface charge of the nanotubes was enhanced by polyanion adsorption inside of the lumen to compensate for the internal positive charges. This increased the magnitude of the ξ-potential of the tubes from -36 to -81mV and stabilized the colloids. Then, colloidal halloysite was dropped onto the substrate, dried at 65°C and after a concentration of ~0.05mgmL-1 was reached, the alignment of nanotubes occurred starting from the droplet edges. …
Surface complexation modeling of arsenate adsorption by akagenéite (β-FeOOH)-dominant granular ferric hydroxide
2014
Abstract A surface complexation model has been set up for the first time with akaganeite (β-FeOOH), a major compound of granular ferric hydroxide (GFH) used in groundwater purification units worldwide for arsenic and other toxic pollutant removal. Unlike the situation for the α-FeOOH polymorph goethite, there is yet no published surface complexation model to predict competing oxyanion effects. This is due to a linked bulk-surface reactivity by which excess protons released in an unknown amount from tunnel sites hamper quantification of surface protonation by acid titration. The measured proton uptake thus exceeds what can be expected from OH groups active in surface protonation. However, ch…
Impact of Surface Charge Directionality on Membrane Potential in Multi-ionic Systems
2020
The membrane potential (Vmem), defined as the electric potential difference across a membrane flanked by two different salt solutions, is central to electrochemical energy harvesting and conversion. Also, Vmem and the ionic concentrations that establish it are important to biophysical chemistry because they regulate crucial cell processes. We study experimentally and theoretically the salt dependence of Vmem in single conical nanopores for the case of multi-ionic systems of different ionic charge numbers. The major advances of this work are (i) to measure Vmem using a series of ions (Na+, K+, Ca2+, Cl-, and SO42-) that are of interest to both energy conversion and cell biochemistry, (ii) to…