Decolorization of orange II DYE using bacteria immobilized onto multi-walled carbon nanotube cement composite

Abstract

In this study, decolorization of Orange II dye using Enterococcus faecalis immobilized onto multi-walled carbon nanotube (MWCNT) cement composite was assessed. Multi-walled carbon nanotube (MWCNT) cement composites were made by mixing zeolite (40g), cement (12g), water (8ml) and MWCNT (0.6g) for attachment of biofilm. Biofilm was allowed to develop on the biocomposites for 7 days. The efficiency of decolorization of orange II dye was examined in the presence and absence of biofilm. By comparing the system with and without biofilm, the system without biofilm (using free suspended cells) achieved the highest percentage removal of orange II dye (97.69%). Unexpectedly the lowest percentage of dye decolorization was achieved for the system using cells immobilized onto Hardened Cement Paste + MWCNT (72.74%). This was most likely due to the cytotoxic effect of MWCNT on the bacterial cells. As expected maximum decolorization for all the systems occurred in anaerobic condition and after entering the aerobic condition decolorization had reached a steady state because of the competition between oxygen and dye.