Researchers from the Beijing Institute of Technology (BIT), led by Professor Zhao Zhiping from the School of Chemistry and Chemical Engineering, have made significant advances in understanding the mass transfer mechanisms of pervaporation for alcohol/water separation. Their findings were published in the prestigious AIChE Journal, under the title A computational study on molecular transport mechanisms and models for alcohol recovery by polymer pervaporation membranes.

Bioalcohols like ethanol and butanol are promising alternatives to fossil fuels, typically obtained by separating them from low-concentration fermentation solutions. Compared to traditional separation methods like distillation, membrane pervaporation (PV) offers advantages such as lower energy consumption and no azeotropic limitations with alcohol/water mixtures.

The classical solution-diffusion model describes the PV process as comprising three sequential steps: surface dissolution, diffusion through the membrane, and vaporization on the downstream side. However, this model lacks detailed insights into nanoscale phenomena such as molecular adsorption, diffusion modes, and dispersion forms, making it challenging to accurately describe molecular transport mechanisms.

In this study, the BIT team used molecular dynamics (MD) simulations to explore how the hydrophilicity and hydrophobicity of membrane surfaces affect the adsorption behavior of feed molecules (alcohol and water) at an atomic scale. The research visualizes how membrane pore structures influence the dissolution and diffusion of feed molecules and proposes a mathematical model for quantitatively comparing the separation performance of PV and distillation.

Through equilibrium MD simulations, the study systematically characterized the adsorption behavior of alcohol/water solutions on nine polymer membranes with varying hydrophilic and hydrophobic properties. The reliability of the polymer membrane models in describing surface hydrophilicity and hydrophobicity was validated by comparing experimental data on contact angles and surface energies.

This research provides deeper insights into the molecular transport mechanisms in membrane pervaporation, potentially leading to more efficient separation technologies for bioalcohol recovery.