Influence of Functionalized Multiwall Carbon Nano-Tube on the Structure and Performance of Cellulose Di-Acetate Based Forward Osmotic Membrane for Desalination Process

Jianfang Sheng,Xiulan Zhao

doi:10.4172/2155-9589.1000135

Abstract

To improve the performance of Cellulose di-acetate (CDA) based forward osmotic (FO) membrane in sea water desalination process, functionalized multi-walled carbon nano-tubes (MWCNTs) were blended as additives at varied compositions, from 0 to 5 wt%, into the solutions to prepare FO membranes using a classical phase-inversion method. The structure and property of the formed membranes were characterized by Fourier transfer infrared (FTIR) spectroscopy, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Transitional Electron Microscopy (TEM), Water Flux and Reverse Solute Flux Tests. It was found that the content of functionalized MWCNTs was an important factor influencing the morphology, porous structures and properties of the blend membranes. SEM, AFM and TEM images of the blend membranes showed that the surface morphology and the cross-sectional morphology changed with the content of functionalized MWCNTs. It is interesting to see that at the presence of functionalized MWCNTs, the surface contact angle and the reverse solute flux of the FO membranes could be greatly improved without significantly affecting the pure water flux. With the addition of only about 1 wt% MWCNTs, the water flux of CDA based FO membrane was increased from 10.5 to 12.5 L/m2h while its reverse solute flux was reduced from 1.8 to below 0.3 mol/m2h. Desalination tests with 3.5 wt% simulated seawater feed solution had shown that the blend membrane with 1 wt% MWCNTs, was 366% higher in water flux and 53% lower in reverse solute flux than those of pure CDA FO membrane. These results suggest that CDA bases FO membranes modified with functionalized MWCNTs could possess good potential to be further developed for practical applications in the sea water desalination processes.

Highlights

In recent years, Forward Osmosis (FO), as an emerging water treatment technology, has gained increasing interest
Compared with pure Cellulose di-acetate (CDA) membrane, M-1 has higher water flux and lower reverse solute flux, which may be attributed to the combined effects from the existence of longer central porous section, the relatively more uniform distribution of multi-walled carbon nano-tubes (MWCNTs), rougher top surfaces and denser top skin layer with more hydrophilic MWCNTs nano-channels
scanning electron microscopy (SEM), Optical Microscopy, and Atomic Force Microscopy (AFM) images of the blend membranes showed that the cross-section morphology changed with the content of functionalized MWCNTs

Summary

Introduction

Forward Osmosis (FO), as an emerging water treatment technology, has gained increasing interest. To evaluate osmosis performance of membranes with MWCNTs, an aqueous solution of NaCl at an initial concentration of 2.0M was used as the draw solutions, whereas the feed solution was de-ionized water.

Results

Conclusion