Extraction of Tetrahydrofuran and Ethylene Dichloride Solvents from Aqueous Solutions by Pervaporation through Thin Film Composite PDMS Membranes

Abstract

Thin film composite (TFC) hydrophobic PDMS membrane of 5 µm active layer thickness supported on Polyethersulfone (PES) ultraporous substrate was synthesized and thermally crosslinked for the pervaporation based extraction of organic solvents such as Tetrahydrofuran (THF) and Ethylenedichloride (EDC) for the first time. The study was extended to acetone, ethanol, t-butanol, Iso-butanol, and acetic acid. Membranes were characterized by SEM, TGA, XRD, and FTIR to study the surface and cross-sectional morphology, thermal stability, crystalline nature, and structural properties, respectively. High selectivities of 868, 72, and 31 were observed at organic feed concentrations of 0.68, 3.42, and 9.38 wt% in water with reasonable fluxes of 0.2, 0.16, and 0.31 kg m⁻² h⁻¹ for EDC, THF and acetone, respectively at a downstream vacuum of 0.5 mmHg. The estimated mass transfer coefficients (MTCs) were found to be 9.11 × 10⁻⁶, 11.77 × 10⁻⁶, and 10.73 × 10⁻⁶ m s⁻¹ for THF, EDC, and acetone extraction, respectively. The membrane exhibited considerable feasibility for scale-up due to its composite nature with significant potential for extraction of volatile organic solvents present in low concentrations. A comparison with previous values reported in literature revealed higher selectivities for extraction of EDC, THF and acetone using the present membrane.

Keywords:

• mass transfer coefficient
• PDMS membrane
• pervaporation
• solvent extraction

ACKNOWLEDGEMENTS

The authors are thankful to the Council of Scientific and Industrial Research (CSIR), New Delhi, for funding this project study under the XIIth five year plan network project.

Notes

(VTES-Vinyltriethoxysilane; PVDF – Polyvinyledenefluoride; CA – Cellulose Acetate; PES-Polyethersulfone, PEBA – Polyetherblockamide, *Sulzer chemtech, Switzerland, ^@ Pervatech, Netherlands).