Postgraduate Seminar Presentation : Organic Nanofiltration of the Probe Dyes through 2D Zn-TCPP(Fe) Membrane – Solvation and Fluid Effects on Separation Performance

Speaker Lei Xiangting (Supervisor: A/Prof Hong Liang)

Host Department of Chemical and Biomolecular Engineering

Date/Time 20 Nov - 20 Nov, 2.00pm

Venue E5-02-32 , Faculty of Engineering, National University of Singapore


This study investigates organic solvent nanofiltration (OSN) of 2D Zn-TCPP(Fe) membrane on a submicron Nylon filtration sheet, which is fabricated by the vacuum-assisted deposition. Two organic dyes, Rose Bengal (RB) and Brilliant Blue G, were selected to examine the performance of the membrane in various dye solutions, where ethanol, isopropanol and ethyl acetate are the solvents used. Unlike aqueous solution, interactions of organic solvent, dye and 2D nanosheets at the molecular level profoundly influence the separation performance. They can be expressed by an interaction triangle, in which the solvent-dye, dye-nanosheet and nanosheet-solvent relations vary with the molecular structures. Typically, the solvent-dye association, or solvation, favors rejection but both solvent-nanosheet and dye-nanosheet associations demolish the laminate structure of membrane. 
In addition, the study invented a remedy to tackle the instability of the 2D membrane caused by the above two factors. The remedy involves the use of an ethanol suspension containing Zn-TCPP(Fe) and ZIF-8 in an optimal dose to conduct membrane deposition. The attractiveness is that ZIF-8 grains only overlying the 2D-membrane, plugging those surface perforations. These surfaces distributed and implanted grains are identified as stabilizing spots offering multiple stabilization roles. They include preventing feed streams from direct intrusion via defective loops, creating transverse fluid field on membrane surface to weaken solvent-solute interactions, and buffering dislocations of 2D sheets underneath due to mass transfer. The three types of organic dyes and three common organic solvents were used to assess OSN performance of the membrane. The presence of ZIF-8 spots on the membrane dramatically enhances the NF performance by about 40%. In conclusion, the novelty of this study is presumed to look at the chemical mechanical effect on the OSN performance of the selected systems.