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 mu m), porosity (-50-80%), liquid entry pressure (1.16-4.55 bar), water contact angle (similar to 86 degrees - 111 degrees), 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(-2) h(-1) and 15 kg m(-2) h(-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

Effects of halloysite nanotubes on the morphology and CO2/CH4 separation performance of Pebax/polyetherimide thin-film composite membranes

Enhancing the performance of gas separation membranes is one of the major concerns of membrane researchers. Thus, in this study, poly(ether-block-amide) (Pebax)/polyetherimide (PEI) thin-film composite membranes were prepared and their CO2/CH4 gas separation performance was investigated by means of pure and mixed gases permeation tests. To improve the properties of these membranes, halloysite nanotubes (HNT) were added to Pebax layer at different loadings of 0.5, 1, 2, and 5 wt % to form Pebax-HNT/PEI membranes. Scanning electron microscopy, gas sorption, X-ray diffraction, Fourier-transform infrared, and differential scanning calorimetry tests were also performed to investigate the impact of HNT on structure and properties of prepared membranes. Results showed that both CO2/CH4 selectivity and CO2 permeance increased by adding HNT to Pebax layer up to 2 wt %. By increasing HNT loading to 5 wt %, the CO2/CH4 selectivity decreased from 32 to 18, while CO2 permeance increased from 3.25 to 4.2 GPU. Pebax/PEI and Pebax-HNT/PEI membranes containing 2 wt % of HNT were tested using CO2/CH4 gas mixtures at different feed CO2 concentrations and feed pressure of 4 bar. The results showed that with increasing CO2 concentration from 20 to 80 vol %, CO2/CH4 selectivity of Pebax/PEI composite membranes increased by 19%, while, in Pebax-HNT/PEI membrane, CO2/CH4 selectivity decreased by 40%

A state-of-the-art protocol to minimize the internal concentration polarization in forward osmosis membranes

© 2020 Elsevier B.V. The main reason for the lower water flux, than expected, in the forward osmosis (FO) process, is the internal concentration polarization (DICP). Usually, the structural parameter (S) is used as an indicator of the intensity of DICP. Small S value is desirable for the FO membrane due to the low DICP. However, due to design and construction problems, structural parameter reduction has some drawbacks. In this work, DICP reduction in FO membranes will be investigated using an approach other than structural parameter reduction. Accordingly, during the FO process, the feed solution (FS) valve is opened and closed at a constant period of time (feed valve timing (FVT)). Four types of FO membranes with different S parameters were used. The effects of the implementation of the proposed protocol on the water flux (Jw), reverse salt flux (Js), specific reverse solute flux (Js/Jw) and effective driving force were investigated. The effects of the S parameter and draw solution (DS) concentration also investigated separately. The results showed that the proposed protocol significantly increased Jw. Also, the values of Js/Jw decreased with increasing the FVT values and reached the lowest level in the practical recovery time (PRT)