Fabrication and characterization of functionalized multi-walled carbon nanotube mixed-matrix membrane for treating biochemical and chemical oxygen demands of surface waters

Abstract

In this work, a mixed-matrix (MM) membrane consisting of functionalized multi-walled carbon nanotube (MWCNT), polyethersulfone (PES) and polyester non-woven fabric was fabricated using immersion precipitation. The membrane capability in reducing the biochemical oxygen demand (BOD) and chemical oxygen demand (COD) levels of the surface water samples collected from rural areas in Sarawak, Malaysia are tested. MWCNTs were functionalized using chemical oxidation to promote functional group onto their sidewalls. Raman analysis reveals a higher peak in D-band than G-band in the functionalized CNT but the higher ID/IG intensity ratio was demonstrated by CNT treated with strong acid. Surface morphological characterization verified the existence of the defects in CNT structures, which was reflected on the sidewall defects, debundling and shortening of the MWCNTs. Meanwhile, the surface waters were tested for BOD and COD levels and treated with three different types of membrane by conventional vacuum filtration. Membrane of raw MM displayed the best treatment capability which is reflected on its ability to maintain the BOD level and reduce the COD level with a consistent percentage. Thus, this work provides a different insight in membrane capability in treating BOD and COD levels in surface waters.