Physico-chemical interpretation of the SRNF transport mechanism for solvents through dense silicone membranes

Mathematical Modelling of Molecular Separation Processes in Aggressive Solvent Systems

Research works on membrane technology, particularly molecular separation in solvent-based systems, has increased tremendously in recent years. In order to apply this technology at industrial scale, a suitable mathematical model for process design and optimisation must be developed. In the present study, mathematical models to describe process performance were developed with different levels of complexities. The models were developed based on two general transport mechanisms, pore-flow and solution-diffusion principles. Models with different complexity levels were developed, ranging from simple process models to a combination of transport, mass transfer and osmotic pressure effects. Series of molecular separation experiments were conducted to validate the models and to compare the difference among all models. The experimental system conducted in this study was a mixture of organic dyes in n-Dimethylformamide (DMF) solution, which mimics a typical industrial application where molecular purification in aggressive organic solvent is required. The filtration results obtained from any mathematical models are in good agreement with the experiments. The calculated purity of the organic dyes in the permeate ranging from 99.72 % to 100 % in comparison to 99.76 % from the experiments at 8000 s. The results obtained from this study can potentially be applied for industrial application as a prediction tool without conducting any excessive experiments.

Advances in Organic Solvent Nanofiltration Rely on Physical Chemistry and Polymer Chemistry

The vast majority of industrial chemical synthesis occurs in organic solution. Solute concentration and solvent recovery consume ~50% of the energy required to produce chemicals and pose problems that are as relevant as the synthesis process itself. Separation and purification processes often involve a phase change and, as such, they are highly energy-intensive. However, novel, energy-efficient technologies based on polymer membranes are emerging as a viable alternative to thermal processes. Despite organic solvent nanofiltration (OSN) could revolutionize the chemical, petrochemical, food and pharmaceutical industry, its development is still in its infancy for two reasons: (i) the lack of fundamental knowledge of elemental transport phenomena in OSN membranes, and (ii) the instability of traditional polymer materials in chemically challenging environments. While the latter issue has been partially solved, the former was not addressed at all. Moreover, the few data available about solute and solvent transport in OSN membranes are often interpreted using inappropriate theoretical tools, which contributes to the spread of misleading conclusions in the literature. In this review we provide the state of the art of organic solvent nanofiltration using polymeric membranes. First, theoretical models useful to interpret experimental data are discussed and some misleading conclusions commonly reported in the literature are highlighted. Then, currently available materials are reviewed. Finally, materials that could revolutionize OSN in the future are identified. Among the possible applications of OSN, isomers separation could open a new era in chemical engineering and polymer science in the years to come.

The Selectivity Challenge in Organic Solvent Nanofiltration: Membrane and Process Solutions

Recent development of organic solvent nanofiltration (OSN) materials has been overwhelmingly directed toward tight membranes with ultrahigh permeance. However, emerging research into OSN applications is suggesting that improved separation selectivity is at least as important as further increases in membrane permeance. Membrane solutions are being proposed to improve selectivity, mostly by exploiting solute/solvent/membrane interactions and by fabricating tailored membranes. Because achieving a perfect separation with a single membrane stage is difficult, process engineering solutions, such as membrane cascades, are also being advocated. Here we review these approaches to the selectivity challenge, and to clarify our analysis, we propose a selectivity figure of merit that is based on the permselectivity between the two solutes undergoing separation as well as the ratio of their molecular weights.

Mass Transport through Nanostructured Membranes: Towards a Predictive Tool

This study proposes a new mechanism to understand the transport of solvents through nanostructured membranes from a fundamental point of view. The findings are used to develop readily applicable mathematical models to predict solvent fluxes and solute rejections through solvent resistant membranes used for nanofiltration. The new model was developed based on a pore-flow type of transport. New parameters found to be of fundamental importance were introduced to the equation, i.e., the affinity of the solute and the solvent for the membrane expressed as the hydrogen-bonding contribution of the solubility parameter for the solute, solvent and membrane. A graphical map was constructed to predict the solute rejection based on the hydrogen-bonding contribution of the solubility parameter. The model was evaluated with performance data from the literature. Both the solvent flux and the solute rejection calculated with the new approach were similar to values reported in the literature.

EB depth-curing as a facile method to prepare highly stable membranes

Solvent resistant polymeric membranes were prepared via electron beam (EB) curing after adding acrylate monomers to the existing membrane casting solution.