Extraction of mercury (II) from sample water by Schiff base-chitosan grafted multi-walled carbon nanotubes

Abstract

A functionalized Schiff base-chitosan-grafted multi-walled carbon nanotubes (S-CS-MWCNTs) material has been studied on pre-concentration and determination of trace mercury. In this process, the effects of solution pH solution, elution conditions on pre-concentration of trace mercury were studied and the effect of interfering ions was also investigated. A novel S-CS-MWCNTs solid-phase extraction adsorbent was synthesized by covalently grafting a Schiff base-chitosan (S-CS) onto the surfaces of oxidized MWCNTs. The stability of chemically modified S-CS-MWCNTs especially in concentrated hydrochloric acid was then used as a recycling and pre-concentration reagent for further uses of S-CS-MWCNTs. The application of S-CS-MWCNTs for sorption of a series of metal ions was performed by using different controlling factors such as the pH of metal ion solution and the equilibration shaking time by the static technique. Hg(II) was found to exhibit the highest affinity towards extraction by these S-CS-MWCNTs phases. The pronounced selectivity was also confirmed from the determined distribution coefficient or dissociation constant (Kd) of all the metal ions, showing the highest value reported for Hg(II) to occur by S-CS-MWCNTs. The potential applications of S-CS-MWCNTs for selective extraction of Hg(II) to occur from aqueous solution were successfully accomplished as well as pre-concentration of low concentration of Hg(II) (60 pg ml-1) from natural tap water with a pre-concentration factor of 100 for Hg(II) off-line analysis by cold vapor atomic absorption analysis. Key words: Pre-concentration, Hg(II), Schiff base-chitosan-grafted multiwalled carbon nanotubes (S-CS-MWCNTs).