Thiol-functionalized multi-walled carbon nanotubes for effective removal of Pb(II) from aqueous solutions

In this study, thiol-functionalized multi-walled carbon nanotubes (MWCNT-SH) was synthesised using carboxy-functionalized multi-walled carbon nanotubes (MWCNT-COOH) as a precursor and 2-mercaptoethanol as a sulfur source. It was an effective adsorbent for Pb(II) removal. The SEM , TEM, FTIR, XPS , EDS , TGA and zeta potential analysis were used to characterize this adsorbent. The adsorption of Pb(II) mainly depends on the abundant functional groups on the surface of MWCNT-SH. Pb(II) adsorption experiments using MWCNT-SH and MWCNT-COOH showed that the adsorption capacity of the former was increased by approximately 30.5% compared to the latter at pH = 5. The increase in adsorption capacity was attributed to the higher adsorption activity of –SH compared to –COOH for Pb(II). The adsorption kinetics data is described well by the pseudo-second-order model, and this implies that the chemical adsorption process mainly determined the adsorption rate. The Pb(II) equilibrium data were highly consistent with the Langmuir adsorption isotherm , and the maximum adsorption capacity for Pb(II) was 144.9 mg g −1 . In addition, the adsorption was a thermonegative and spontaneous reaction. It can be verified by thermodynamic research (ΔG < 0, ΔH > 0, ΔS > 0). Finally, Pb (II) removal apply to three kinds of natural wastewater demonstrated the potential of MWCNT-SH. All the results showed that MWCNT-SH has broad application prospects in water treatment.