Characterisation of the fouling of an ultrafiltration polyethersulfone membrane fouled by an emulsion modelling lipids issued from Microalgae

International audienc

Study of transfer of alcohol (methanol, ethanol, isopropanol) during nanofiltration in water/alcohol mixtures

International audienceThis study aimed at studying the impact of alcohol presence in water/alcohol mixtures on the performances of the NF 270 polypiperazine amide nanofiltration membrane (Dow Filmtec). Three alcohols of different physico-chemical characteristics were selected methanol, ethanol and isopropanol. NF was achieved for several water/alcohol mixtures of different viscosity (up to twice that of water) and dielectric constant, both known to play a role in separation performances. In presence of alcohol (up to 23 vol%, 30 vol% and 21 vol% for methanol, ethanol and isopropanol, respectively) the flux significantly decreased when compared to that of water. This study provides insights in the alcohol transfer mechanisms allowing to select Spiegler and Kedem and reject Solution-Diffusion, both coupled with the film theory. Discussion highlights how surprisingly the membrane swelling can sometimes have no significant impact on the membrane resistance because opposite phenomena can be compensated such as pore radius increase simultaneously with membrane thickness increase. © 202

Design of membrane cascades according to the method of McCabe-Thiele: An organic solvent nanofiltration case study for olefin hydroformylation in toluene

International audienceThe method of McCabe-Thiele is widely used for the design of distillation columns. At a given pressure, this graphical method is only based on 3 equations: (i) the partitioning curve linking the liquid and gas phases for a given component at a given plate thanks to a unique set of thermodynamic data and (ii) two operating lines, each one describing the liquid/gas equilibrium of two consecutive plates either in the enrichment section or in the stripping one. In this paper, the method has been adapted to the membrane separation processes aiming at the easy selection of a first set of appropriate designs of cascades that fulfill given separation targets, especially in the case of a binary mixture of components having both intermediate rejections and very different concentrations. Membrane cascades involving several recyclings of the permeate and retentate streams are proposed according to a similar but more sophisticated methodology than for distillation, since for a selected membrane and for given hydrodynamic conditions (pressure, velocity, temperature), several proposals can be made for each equation mentioned above. In short, a set of operating lines is generated varying with the volume reduction ratio (VRR) either for the permeate or the retentate retreatment sections. The method is applied to the OSN separation of a final synthesis medium of a homogeneous catalyzed reaction, namely olefin hydroformylation achieved in toluene. This example is a typical one dealing with the more general case of a product to be extracted in the permeate and a catalytic system to be recovered in the retentate for further recycling in the synthesis reactor aiming at a greener production process. The initial concentration ratio of the two components to separate in OSN is 1/1000 and both compounds have intermediate rejections of 30% and 88%. Thanks to this method, the design of several membrane cascades is proposed and discussed according to different goals of separation (target product purity or recovery, enrichment of component to be recycled, energy consumption, etc.)

Synthesis and characterization of new ultrafiltration ceramic membranes for water treatment

International audienc

Separation of solutes with an organic solvent nanofiltration cascade: Designs, simulations and systematic study of all configurations

Due to the lack of efficient membranes to achieve subtle separations in a single step, membrane cascades appear as an alternative to improve the separation of solutes, especially in the case of close rejections. However, there is still a need for their rational design. In this work, a systematic study of all configurations up to seven stages is proposed through a unique and flexible simulation architecture. Different recycling modes in between stages are detailed and developed. The same VRR is imposed at each stage, ranging from 2 to 10. The case study is the olefin hydroformylation catalytic reaction, for which the simulations aim at the separation of two components, one modelling all organic products to extract in the permeate and the other one modelling the catalytic system to recover in the retentate for its further re-use in the synthesis reactor. Input data for the simulations (rejections and fluxes) are obtained from preliminary experimental studies. The separation performances are evaluated through seven criteria, amongst which the outflows extraction/recovery and the membrane area. The analysis of the simulation results allows to determine the optimal configuration that fulfills the targeted criteria or to fine tune these separation criteria according to the potentialities or the limitations of the membrane cascades. Even though focusing a priori on specific criteria, a careful attention should be paid to all parameters to ensure realistic proposals of cascades or to revise the objectives for more realistic ones