Reverse Osmosis Membrane

- Aug 13, 2020-

Materials

m-Phenylenediamine(>98%) (MPD) and trimesoyl chloride (>98%) (TMC) were acquired from Tokyo Chemical Industry Co. Inc. Hexane (>96%), sodium Chloride (>99.5%) and sodium hypochlorite solution (5.0 wt.%) were purchased from Kanto Chemical Co., Inc. (Purity>96%). All other reagents were of analytical grade or better. Surfactant dispersed MWCNT (Nanocyl NC-7000) were prepared as reported37. Polypropylene nonwoven supported porous polysulfone membranes (cut off Mw = 100,000) were acquired from Alfalaval DSS (Cat. No. GR40PP). We confirmed that the water permeability of the present thin-film nanocomposite membranes did not change due to compaction at pressures up to 5 MPa using 3.5 wt. % saline water at room temperature, as described in the following experimental methods.


Methods

Membrane synthesis

composite membranes consisting of porous polysulfone supported on nonwoven polypropylene (Alfa Laval ) were soaked in 2.0 wt. % MPD aqueous solution for 3 h and subsequently soaked in TMC-hexane solution (0.1 wt. %) for 2 min. The membranes were subsequently dried at room temperature for several hours. In the case of the MWCNT containing PA membrane, a MPD aqueous solution containing 1 wt.% of anionic surfactant stabilized MWCNT was used. In order to study the polymerization in presence of carbon nanotubes, an aqueous dispersion of MWCNT was added to a MPD aqueous solution to reach a 0.4/2.0/97.6 MWCNT/MPD/H2O ratio and weight. Then, the solution was filtered and the cake was re-dispersed in hexane by stirring and ultrasonication, stirred for 1 h and filtered again. These MWCNT were re-dispersed in hexane and then a small volume of this dispersion was added to a 0.1% solution of TMC in hexane. After 1 h the nanotubes were recovered by centrifugation, washed in hexane and analysed by HRTEM, XPS, FTIR and TGA. Bulk PA and MWCNT·PA samples were synthesized by interfacial polymerization of a 2% wt MPD solution in water and a 0.1% wt solution of TMC in hexane. Degradation by chlorine was also studied by exposing the bulk PA and MWCNT·PA samples to (200 ppm for 24 h ) and (5000 ppm for 30 min) chlorine solution at room temperature, followed by washing and drying. Fouling tests were carried out using room temperature crossflow filtration of an aqueous Bovine serum albumin (BSA) solution (200 ppm) at 1 MPa.