High Efficiency of Multiwalled Carbon Nanotubes Filters for Benzene Removal from Aqueous Solutions: Quantitative Analysis using Raman Spectroscopy

High Efficiency of Multiwalled Carbon Nanotubes Filters for Benzene Removal from Aqueous Solutions: Quantitative Analysis using Raman Spectroscopy

The environmental application of multiwalled carbon nanotubes (MWCNTs) as a new type of filters to remove benzene from aqueous solutions was investigated. The surface functionalization of MWCNTs enhances their performance for this application. Arrays of MWCNTs were synthesized via chemical vapor deposition (CVD) by spray-pyrolysis method. An aliquot of these MWCNTs array was oxidized by concentrated nitric acid. The Fourier transform infrared analysis showed that the peaks corresponded to the hydroxyl and carboxylic acid groups in oxidized MWCNTs (O-MWCNTs) are more intense than that in raw MWCNTs (R-MWCNTs). The images of scanning electron microscopy indicated that the O-MWCNTs have a lower degree of entanglement and decreased nanotubes diameters. Energy dispersive X-ray spectroscopy showed high oxygen content for O-MWCNTs compared to R-MWCNTs. In order to estimate the removal efficiency of MWCNTs filters, Raman spectroscopy as a quantitative technique to make concentration measurements of benzene in water solutions was conducted and used to estimate the purification efficiency. The removal efficiency of benzene by O-MWCNTs was found to reach 99% for concentration of 500 ppm, indicating the existence of specific π-π electronic interactions between benzene molecules and the surface of O-MWCNTs. Functionalized MWCNTs possess good potential applications to water and wastewater treatment, maintaining a high qualityof water, and could be used for cleaning up environmental pollution.