Theoretical Analysis of Concentration Polarization Effect on VOC Removal by Pervaporation

Pervaporation is an innovative membrane-based separation technology for volatile organic compound (VOC) removal from contaminated groundwater. Concentration polarization is a process phenomenon occurring in pervaporation and several other membrane-based separation technologies. Concentration polarization, defined as concentration gradient of permeating solute between the bulk and the region near the membrane surface, becomes a limiting factor in pervaporation separations using high-performance membrane materials in VOC removal operations. Thus, the ability to predict the impact of concentration polarization upon process performance is highly desirable in process design and optimization. A mathematical model was developed to illustrate the interplay between concentration polarization and process performance in pervaporation operation of VOC removal in a membrane channel with rectangular cross section. By incorporating pervaporative mass transfer, laminar hydrodynamics, and boundary-layer theory, the model was built to allow theoretical analysis of the sensitivity of flow velocity, feed concentration, and concentration polarization index (CPI) upon the transmembrane flux and longitudinal mass flow

Membrane processes for the dehydration of organic compounds

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Polyether-block-amide thin-film composite hollow fiber membranes for the recovery of butanol from ABE process by pervaporation

This work reports the continuation of previous efforts to recover butanol from the ABE (acetone-butanol-ethanol) fermentation process by pervaporation (PV). A key aspect to improve the efficiency of the technology is the membrane used to perform the selective butanol separation; hence, this study focuses on the implementation of hollow fiber (HF) membrane configuration for the ABE separation by PV as opposed to flat sheet membrane configuration. The HF membrane preparation was done by dip coating, a frequently used process for the production of HF membranes, which involves the deposition of a thin film of a coating solution. Different thicknesses of the active layer were obtained by modifying the polymer content in the coating solution, allowing later to evaluate the influence of the thickness on the separation performance. This study includes a description of the procedure to prepare selective membranes, its characterization and an analysis of the influence of operating conditions on membrane separation performance. SEM and water contact angle were used to characterize the produced membranes. The mass transport phenomena in the pervaporation process were characterized using a resistances-in-series model. The results allow to adopt a criterion to select the most suitable thickness for the membrane active layer, which allows to achieve an adequate separation performance, and reveal the importance in the choice of the membrane support material. Finally, a comparative analysis of the self-made hollow fiber membranes performance in terms of flux, separation factor and PSI with respect to those found in the literature is presented.This research is being supported by the Spanish AEI under the projects PID2019-104369RB-I00 and RTI2018-093310-B-I00, and by the Project ENERGY PUSH SOE3/P3/E0865, which is co-financed by the European Regional Development Fund (ERPF) in the framework of the INTERREG SUDOE Programme. Carla Arregoitia also thanks for a FPI research scholarship (BES-2017-081708)

Concentration of aroma compounds from an industrial solution of soluble coffee by pervaporation process

AbstractPervaporation experiments with PDMS membrane have been performed in a plate and frame module to investigate its ability to concentrate volatile compounds identified in an industrial soluble coffee solution. Eight compounds were chosen to depict key aroma of soluble coffee. The effect of feed flow rate, temperature and permeate pressure on the pervaporation performance has been analyzed. Concentration polarization phenomena was not identified in the feed flow rate studied. The temperature effect showed a good agreement with the nonlinear Arrhenius equation. The permeate pressure followed the solution–diffusion model behavior. Results showed that pervaporation is a promising alternative to concentrate aroma compounds from soluble coffee