Cake Resistance (cake + resistance)

Distribution by Scientific Domains


Selected Abstracts


Formation and ageing of L-glutamic acid spherulites

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 7 2010
R. Beck
Abstract Polycrystalline spherulites of L-glutamic acid have been crystallized by pH-shift precipitation from stirred aqueous solutions. The time dependent behaviour of the spherulites has been studied during the crystallization process and batch filtration tests have been performed. It has been shown that the FBRM mean chord length of the investigated spherulites decreases in the course of time. The fact that the size reduction progresses faster at higher temperature and the solubility of resuspended polycrystalline particles decreasing with time, implies an ageing mechanism to be responsible for the observed changes in the particle size. It has been shown that the surface area decreases with time, ruling out particle breakage as a possible explanation for the decrease in particle size. XRD and Raman studies of L-glutamic acid, however, show only marginal differences in the crystalline structure of particles obtained from different time stages. The ageing may occur due to several different mechanisms like phase transformation and Ostwald ripening. L-glutamic acid spherulites after 3 h exhibit a 3-fold higher value for the cake resistance as compared to particles after 0.5 h. However, particles obtained after 22 h exhibit an 8-fold lower cake resistance as compared to the initially obtained spherulites, The increase in the cake resistance is attributed to the appearance of small plate-like crystals and a change in the interaction between the crystal surface and the solution. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Influence of citric acid on calcium sulfate dihydrate crystallization in aqueous media

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2007
S. Titiz-Sargut
Abstract The crystallization of Calcium sulfate dihydrate produced by the reaction between pure Ca(OH)2 suspension and H2SO4 solution was investigated at different pH values, temperatures and citric acid concentrations. Crystal size distributions, filtration rates and zeta potentials of gypsum were determined as a function of citric acid concentrations at pH 3.5 and 65°C. The influence of citric acid on the morphology of gypsum was also investigated and discussed. The average particle size of gypsum was reached to maximum in the presence of approximately 2500 ppm citric acid concentration, where the minimum cake resistance and maximum filtration rate were obtained. In the presence of citric acid, various crystal morphologies such as tabular, plate-like, double-taper leaf-like and flower-like, etc., were obtained. The change of morphology is related to the preferential adsorption of citric acid on different crystallographic faces. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Centrifugal drum filtration: I. A compression rheology model of cake formation

AICHE JOURNAL, Issue 2 2006
John D. Barr
Abstract A compression rheology model is used to describe the behavior of networking solids undergoing centrifugal filtration under batch operation. A description of the batch filtration process is accomplished through the use of the rheologic functions for compressive yield stress py(,) and the hydrodynamic resistance R(,), with a characteristic pressure scaling, timescaling, and membrane resistance. Comparison of the results of this model to those found in engineering text books indicates that noncompression models fail to describe the variation in the cake resistance. The compression rheology model also predicts that the effective cake resistance is approximately 20% larger than that predicted by conventional theory. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source]


Broth conditions determining specific cake resistance during microfiltration of Bacillus subtilis

BIOTECHNOLOGY & BIOENGINEERING, Issue 2 2006
Kevin Graves
Abstract The effects of broth pH, pressure, temperature, and fermentation medium on specific cake resistance were studied for dead-end microfiltration of Bacillus subtilis. Decreases in pH and transmembrane pressure decreased the specific cake resistance for cells grown in both complex and defined media. With the complex medium, the reduction in resistance with temperature decrease did not offset the flux decrease caused by the increase in viscosity. The greatest decrease in specific cake resistance occurred with adjustment of pH to 7.5 for cells grown in defined medium. For those cells the change in pH resulted in aggregation leading to a large increase in flux. © 2006 Wiley Periodicals, Inc. [source]


Effects of Ionic Environments on Bovine Serum Albumin Fouling in a Cross-Flow Ultrafiltration System

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 2 2007
S. Salg
Abstract The influence of electrostatic interactions on membrane fouling during the separation of bovine serum albumin (BSA) from solution was studied in a cross-flow ultrafiltration system. Experiments were carried out at different pH values between 3.78 and 7.46; and for different ionic strengths between 0.001,M and 0.1,M. The changes in permeate flux, cake layer resistance, zeta potentials of BSA and polyether sulfone (PES) membranes, and electrostatic interaction energies, were evaluated. At all of the ionic conditions studied, PES membranes are negatively charged. However, BSA molecules are either negatively or positively charged depending on the ionic environment. Whereas the cake layer resistance decreased with increasing pH and ionic strength, the permeate fluxes increased. The calculated electrostatic energy was a minimum at the isoelectric point (IEP) of BSA. However, at this point, the cake resistances corresponding to fouling at each ionic strength, were not minimized. Below the IEP of BSA, the electrostatic forces were attractive, while above the IEP, repulsive electrostatic forces were dominant. [source]