Cyclic olefin polymer as a novel membrane material for membrane distillation applications

A first attempt was made to prepare cyclic olefin polymer/copolymer (COP/COC) flat-sheet porous membranes by the well-known non-solvent induced phase separation method. In this study, two solvents (chloroform and 1,2,4-trichlorobenzene), different additives (polyvinylpyrrolidone, PVP, polyethylene glycol, PEG400, polyethylene oxide, PEO, and Sorbitan monooleate, Span 80) and coagulants (acetone and 70/30 wt% acetone/water mixture) were employed. The prepared membranes were characterized in terms of the thickness (70–85 μm), porosity (~50–80%), liquid entry pressure (1.16–4.55 bar), water contact angle (~86° - 111°), mean pore size (158–265 nm), mechanical properties (tensile strength: 0.74–5.51 MPa, elongation at break: 3.34%–7.94% and Young's modulus: 29–237 MPa), morphological and topographical characteristics. Short-term direct contact membrane distillation (DCMD) tests showed maximum permeate fluxes of 20 kg m−2h−1 and 15 kg m−2h−1 when using as feed distilled water and 30 g/L sodium chloride aqueous solution, respectively, with a high salt separation factor (99.99%). Long-term DCMD tests of some selected membranes carried out during 24–50 h showed that the membranes prepared with PEG additive exhibited more stable DCMD performance. In general, it was proved that COP can be successfully used as a novel polymer candidate in membrane distillation (MD) applications.