Search results for "Ultrafiltration"
showing 10 items of 68 documents
Zr, Hf and REE distribution in river water under different ionic strength conditions
2018
International audience; The Platani River flowing in south-central Sicily, interacting with evaporite rocks, generates a wide range of ionic strength in the water catchment from 0.1 to 5.0 mol kg−1. We sampled 38 river sites and analysed the composition for the dissolved fraction filtered through 0.45 μm, the truly dissolved fraction obtained through ultrafiltration (10 kDa) and the relative included colloidal fraction.This study was focused on the recognition of Zr, Hf and REE behaviour under changing ionic strength conditions, since this is one of parameters responsible for colloid stability in natural waters. In turn, this phenomenon leads to REE release from the colloidal fraction and t…
Protein diffusion through charged nanopores with different radii at low ionic strength
2014
[EN] The diffusion of two similar molecular weight proteins, bovine serum albumin (BSA) and bovine haemoglobin (BHb), through nanoporous charged membranes with a wide range of pore radii is studied at low ionic strength. The effects of the solution pH and the membrane pore diameter on the pore permeability allow quantifying the electrostatic interaction between the chargedpore and the protein. Because of the large screening Debye length, both surface and bulk diffusion occur simultaneously. By increasing the pore diameter, the permeability tends to the bulk self-diffusion coefficient for each protein. By decreasing the pore diameter, the charges on the pore surface electrostatically hinder …
Performance Comparison of Alternative Hollow-Fiber Modules for Hemodialysis by Means of a CFD-Based Model
2022
Commercial hemodialyzers are hollow-fiber cylindrical modules with dimensions and inlet–outlet configurations dictated mostly by practice. However, alternative configurations are possible, and one may ask how they would behave in terms of performance. In principle, it would be possible to depart from the standard counter-flow design, while still keeping high clearance values, thanks to the increase in the shell-side Sherwood number (Sh) due to the cross-flow. To elucidate these aspects, a previously developed computational model was used in which blood and dialysate are treated as flowing through two interpenetrating porous media. Measured Darcy permeabilities and mass transfer coefficients…
Polymer-enhanced ultrafiltration for heavy metal removal: Influence of chitosan and carboxymethyl cellulose on filtration performances
2018
Abstract Reclaiming of wastewaters contaminated by heavy metals has become a major challenge over the last decades. For this reason, nanoporous membrane processes have awaken the interest of industry and local community, and the possible ways to improve their performances has become a priority goal for researchers. Metal removal enhancement by polymer addition is a potential way that is deeply investigated herein on nickel ion rejection with chitosan and carboxymethyl cellulose addition. Due to the vanishing of electrostatic interactions induced by the large amount of salt usually contained in effluents, ion rejection consequently drastically drops. However, it is highlighted that a suffici…
Taste active compounds in a goat cheese water-soluble extract 1. Development and sensory validation of a model water-soluble extract
2000
The aim of this study was to evaluate the impact of the components of a goat cheese water-soluble extract (WSE) on its flavor by both physicochemical and sensory techniques with special emphasis on taste. After characterization of the organoleptic properties of the cheese, the WSE was extracted with pure water and submitted to successive tangential ultrafiltrations and nanofiltration. The physicochemical assessment of these fractions led to the constitution of a model mixture (MWSE) compared by sensory evaluation to the crude WSE, using a panel of 16 trained members. The results of both sensory profile and triangular tests indicate no significant difference, therefore proving that the recon…
P1082COMPARISON OF THE REMOVAL OF PROTEIN-BOUND TOXINS AND LARGE MIDDLE MOLECULES WITH HIGH-FLUX PMMA AND MEDIUM CUT-OFF DIALYZERS
2020
Abstract Background and Aims Dialytic clearance of protein-bound toxins and large middle molecules is poor by diffusive treatment and limited by high-flux hemodialysis (HD) and on-line hemodiafiltration (OL-HDF), and only a few studies have examined how to improve their removal by other extracorporeal strategies. Since 2017, there is a new generation of polymethyl methacrylate (PMMA) membranes that suppress platelet adhesion on the membrane surface improving hemocompatibility and permeability, while also maintaining adsorption properties related to conventional PMMA membranes. Expanded HD (HDx) with medium cut-off (MCO) membranes has also recently been incorporated into clinical practice an…
Ultrasound-Assisted Extraction, Centrifugation and Ultrafiltration: Multistage Process for Polyphenol Recovery from Purple Sweet Potatoes
2016
This work provides an evaluation of an ultrasound-assisted, combined extraction, centrifugation and ultrafiltration process for the optimal recovery of polyphenols. A purple sweet potato (PSP) extract has been obtained using ultrasonic circulating extraction equipment at a power of 840 W, a frequency of 59 kHz and using water as solvent. Extract ultrafiltration, using polyethersulfone (PES), was carried out for the recovery of polyphenol, protein and anthocyanin. Pre-treatment, via the centrifugation of purple sweet potato extract at 2500 rpm over 6 min, led to better polyphenol recovery, with satisfactory protein removal (reused for future purposes), than PSP extract filtration without cen…
Ultrafiltration as a Means to Investigate Copper Resistance Mechanisms in Soil Bacteria
1999
Copper is a trace element of major concern for agricultural soils. It exhibits a high toxicity against microorganisms and is widely introduced into soils as a component of pesticide treatments or urban wastes such as sewage sludges or refuse composts. In most French vineyards, “Bordeaux mixture” (copper sulfate) has been applied for more than a century, sometimes leading to copper concentrations in soils much higher than the threshold values (100 mg kg−1 in France). Microorganisms exposed to high concentrations of copper or other trace elements are known to develop resistance mechanisms and represent a suitable material for the study of such processes, both at a physiological and molecular …
Determination of taste-active compounds of a bitter camembert cheese by omission tests
2001
The taste-active compounds of a Camembert cheese selected for its intense bitterness defect were investigated. The water-soluble fraction (WSE) was extracted with pure water and fractionated by successive tangential ultrafiltrations and nanofiltration. The physicochemical assessment of these fractions led to the construction of a model WSE which was compared by sensory evaluation to the crude water-soluble extract, using a panel of 16 trained tasters. As no significant difference was perceived, this model WSE was then used directly or mixed with other cheese components for omission tests. Among the main taste characteristics of the WSE (salty, sour, umami and bitter), bitterness was found t…
Isolation of a peptidic fraction from the goat cheese water-soluble extract by nanofiltration for sensory evaluation studies
1997
Abstract The effect of the small water-soluble peptides on the taste of cheeses has not been clarified yet because of the high difficulties to isolate them from the other water-soluble compounds. A new filtration method, nanofiltration, using ionizable membranes, allowed us to purify a peptidic fraction prepared from the permeate obtained by ultrafiltration (MWCO=1000) of a goat cheese water-soluble extract. A large proportion of mineral salts and a part of amino acids were eliminated from the nanofiltration retentate where a majority of small peptides were concentrated. The peptidic fraction was incorporated in a cheese model with known synergistic effectors such as mineral salts and amino…