Poly(vinylidene fluoride-co-hexafluoro propylene) membranes prepared via thermally induced phase separation and application in direct contact membrane distillation

Abstract

A non-toxic and environmentally safe diluent, acetyl tributyl citrate, was employed to prepare poly(vinylidene fluoride)-co-hexafluoropropylene membranes via thermally induced phase separation. Effects of the polymer concentration on the phase diagram, membrane morphology, hydrophobicity, pore size, porosity and mechanical properties (tensile stress and elongation at break) were investigated. The results showed that the pore size and porosity tended to decrease with increasing polymer concentration, whereas the contact angle, liquid entry pressure and mechanical properties showed the opposite trend. In direct contact membrane distillation operation with 3.5 wt-% sodium chloride solution as the feed solution, the prepared membranes performed high salt rejection (>99.9%). Furthermore, the prepared membranes retained excellent performance in long-term stability tests regarding the permeate flux and salt rejection.

Graphical abstract

Keywords

poly(vinylidene fluoride)-co-hexafluoropropylene / thermally induced phase separation / non-toxic diluent / direct contact membrane distillation

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Acknowledgments

This work was supported by the National Natural Science Foundation of China (Grant No. 22078146), the National Key R&D Program of China (Grant No. 2020YFC0862903), the Natural Science Foundation of Jiangsu Province (Grant No. BK20200091), the Jiangsu Province Department of Human Resources and Social Security (Grant No. JNHB-036), the Materials-Oriented Chemical Engineering State Key Laboratory Program (Grant No. KL19-04) and the Priority Academic Program Development of Jiangsu Higher Education Institution (PAPD). N. Tavajohi is grateful for financial support by the Kempe Foundation (Grant No. SMK-1850) and Bio4energy program (Grant No. B4E3-TM-1-01).

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