Comparison of Drying Method on Acid-functionalized Multi-walled Carbon Nanotube and their Application for Dye Removal

Abstract

The application of surface modified multi-walled carbon nanotube is one of the emerging adsorbents for removal of pollutants from wastewater, particularly dye pollutants. In this study, the effects of drying methods on acid functionalized MWCNT (f-MWCNT) by using freeze dry or oven dry treatment methods were investigated and compared. It is vital to have a proper drying method in order to attain desired particles sizes and properties. Freeze-dried MWCNT (FD-MWCNT) were more desirable than oven-dried MWCNT (OD-MWCNT), as they were in soft flake form, with no formation of aggregates. Besides, characterization studies were performed to analyze the surface morphology and chemical compositions of the f-MWCNTs. Results revealed that FD-MWCNT has less structural damaged and higher oxygenated functional groups than OD-MWCNT. As for batch dye adsorption experiments, FD-MWCNT has higher performances compared to OD-MWCNT. The maximum dye removal efficiency that FD-MWCNT can achieve was 99% at pH 7, 90 min, 10 mg/L dye initial concentration and 150 rpm. It has been proved that freeze dry treatment is more favorable than oven dry method as the dried MWCNT obtained has superior structure properties and adsorption capability for dye removal.