Search results for "Separation process"
showing 10 items of 21 documents
Dynamic Structural Changes and Thermodynamics in Phase Separation Processes of an Intrinsically Disordered–Ordered Protein Model
2021
Elastin-like proteins (ELPs) are biologically important proteins and models for intrinsically disordered proteins (IDPs) and dynamic structural transitions associated with coacervates and liquid-liquid phase transitions. However, the conformational status below and above coacervation temperature and its role in the phase separation process is still elusive. Employing matrix least-squares global Boltzmann-fitting of the circular dichroism spectra of the ELPs (VPGVG) 20 , (VPGVG) 40 and (VPGVG) 60 , we found that coacervation occurs sharply when a certain number of repeat units has acquired β-turn conformation (in our sequence setting a threshold of ~20 repeat units). The differential scatter…
Size-Exclusion Chromatographic Determination of Polymer Molar Mass Averages Using a Fractal Calibration
2005
The characterization of polymers by size-exclusion chromatography basically consists of the determination of the weight-average molar mass (Mw), number-average molar mass (Mn), and polydispersity index (I). An accurate estimation of these magnitudes requires the use of a reliable and trusted calibration curve. Three procedures for building up a calibration curve are analyzed in this work. The first is the classical universal calibration (UC), based on the elution of tetrahydrofuran-polystyrene in a system as reference. The second is based on the proper calibration curve made with standards of the sample under study. However, two main drawbacks arise when using these methodologies: the nonfu…
Flow-through pore characteristics of monolithic silicas and their impact on column performance in high-performance liquid chromatography
2008
Abstract In order to elucidate the role of the flow-through characteristics with regard to the column performance in high-performance liquid chromatography (HPLC) native and n -octadecyl bonded monolithic silica rods and columns, respectively of 100 mm length and 4.6 mm ID with mesopores in the range between 10 and 25 nm and macropores in the range between 0.7 and 6.0 μm were examined by mercury intrusion/extrusion, scanning electron microscopy, image analysis and permeability. The obtained data of the flow-through pore sizes and porosity values as well as surface-to-volume ratio of the stationary phase skeleton enabled to predict their influence to the chromatographic separation efficiency…
A no-carrier-added 72Se/72As isotope generator
2001
Siinznrary A no-carrier-added 72Se/72As generator has been developed for the isolation of 72As, relevant for eventual application in the syntheses of 72As-labelled radiophamaceuticals. Avoiding the addition of Se carrier and using a thennochromatographic destillation process, no-carrier-added 72As is nearly quantitatively released within 10 min. 72Se remains almost quantitatively (> 99.7%) in solution when a temperature of the separation process of 100°C is applied. Introdiiction Arsenic-72 is a positron emitting isotope with properties which are promising for eventual application in 72As-labelled radiopharmaceuticals. It has n positron emission rate of 88% and positron energies of EP+,,,,~…
Effective Cahn-Hilliard Equation for the Phase Separation of Active Brownian Particles
2014
The kinetic separation of repulsive active Brownian particles into a dense and a dilute phase is analyzed using a systematic coarse-graining strategy. We derive an effective Cahn-Hilliard equation on large length and time scales, which implies that the separation process can be mapped onto that of passive particles. A lower density threshold for clustering is found, and using our approach we demonstrate that clustering first proceeds via a hysteretic nucleation scenario and above a higher threshold changes into a spinodal-like instability. Our results are in agreement with particle-resolved computer simulations and can be verified in experiments of artificial or biological microswimmers.
Sulfonation of Triphenylphosphines and Separation of Sulfonated Triphenylphosphines by Crystallization and Solvent Extraction
2007
Abstract The effect of sulfonation conditions on the formation of sulfonated triphenylphosphines and their separation from the post‐reaction mixture, containing concentrated sulphuric acid, was studied. The solvent extraction was found to be a suitable technique to separate sulfonated triphenylphosphines from concentrated sulphuric acid, and the purity and yield was higher than obtained by crystallization from various solvents. Tributyl phosphate was a suitable extractant. Sodium salts of sulfonated triphenylphosphines could then be recovered as precipitates by treating the organic phase with the sodium hydroxide solution and separation by crystallization. The solvent extraction simplified …
Photocatalytic process intensification by coupling with pervaporation
2011
The integration of photocatalysis with a membrane separation process, in particular pervaporation, permits the recovery of valuable intermediate compounds (aromatic aldehydes) while they are produced avoiding their further degradation in the reactive ambient. In this way the yield and the conversion are enhanced. The coupling of the two processes is straightforward and the integration is complete even maintaining pervaporation and photocatalysis in two separate apparatuses provided that the process stream is continuously recycled at a sufficiently high flow rate. Additional advantages are: higher degree of purification of the aldehyde in the powder-free product stream, semicontinuous produc…
Poly-left-lactic acid tubular scaffolds via diffusion induced phase separation: Control of morphology
2013
n this work, tubular poly-left-lactic acid scaffolds for vascular tissue engineering applications were produced by an innovative two-step method. The scaffolds were obtained by performing a dip-coating around a nylon fiber, followed by a diffusion induced phase separation process. Morphological analysis revealed that the internal lumen of the as-obtained scaffold is equal to the diameter of the fiber utilized; the internal surface is homogeneous with micropores 1–2 μm large. Moreover, a porous open structure was detected across the thickness of the walls of the scaffold. An accurate analysis of the preparation process revealed that it is possible to tune up the morphology of the scaffold (w…
Heat-transfer performance comparison between overlapped and woven spacers for membrane distillation
2016
Sustainable production of fresh water from seawater desalination is a problem of crucial importance nowadays. Recently, some desalination technologies are taking advantage from the coupling with renewable resources. Among emerging technologies, Membrane Distillation (MD) is considered as one of the most promising as it can be easily powered by solar thermal energy or waste-heat. As an emerging technology, efforts are required to optimize MD unit geometry and operating conditions in order to reduce fresh water production specific cost. Temperature polarization phenomenon is a well-known detrimental effect for the MD process. Spacers are traditionally used to enhance mixing and shrink tempera…
CFD simulation of a membrane distillation module channel
2009
The interest towards the use of membrane distillation (MD) processes for seawater desalination has been rising recently due to the ease of coupling MD with waste and/or solar thermal energy. Notwithstanding the flexibility of the process and its potential for further developments in membrane performances, one of the main drawbacks is the thermal efficiency reduction caused by temperature polarization. Because of such phenomenon, only a small amount of the driving force potentially available for the separation process, i.e. the temperature difference between evaporating and condensing fluids, is actually used for the separation. In order to reduce temperature polarization a study on the effe…