Functionalization of multiwalled carbon nanotubes with thiol groups for Lead adsorption

Water contaminated by heavy metal ions had become much more serious with a rapid development of industries and competitive use of fresh water in many parts of the world. Heavy metal ions are highly toxic even at low concentrations and can accumulate in living organisms, causing several disorders and diseases. The heavy metals hazardous to human health include Pb, Hg, Cd, As, Cu, Zn, and Cr. As and Cd cause cancer, Hg can cause mutations and genetic damage, while Cu, Pb, and Hg can cause brain and bone damage [1]. There are many conventional methods that are being used to remove the metal ions. Among the different physicochemical processes, adsorption offers the best prospects for overall treatment, especially for effluents that contains moderate and low concentrations of metals [2]. Due to a large surface area, small, hollow, and layered structures, carbon nanotubes have already been investigated as promising adsorbents for various organic pollutants and metal ions and can be easily modified by chemical treatment to increase their adsorption capacity. [3,4]. In this study, multi-walled carbon nanotubes (MWCNTs) were modified by strong oxidizing agents and were functionalized with thiol groups. These MWCNTs were used for adsorption of lead ions from aqueous solution. The pristine and functionalized MWCNTs were characterized by Fourier transform infrared, scanning electron microscopy and X-ray diffraction. In batch tests, the influences of solution pH, contact time, and amount of adsorbent were studied. The Langmuir and Freundlich isotherms were used to describe the adsorption behavior of heavy metal ions by CNTs. The results showed that functionalized MWCNTs have good potential application in environmental protection.