3-Mercaptopropyltrimethoxysilane-modified multi-walled carbon nanotubes as a new functional adsorbent for flow injection extraction of Pb(II) from water and sediment samples

In the present study, a novel synthesized adsorbent material based on 3-mercaptopropyltrimethoxysilanefunctionalized multi-walled carbon nanotubes was used to increase the Pb²⁺ adsorption from aqueous solutions in a flow injection solid-phase extraction system coupled to flame atomic absorption spectrometry. Spectroscopic and microscopic techniques (Fourier transform infrared spectroscopy, energy dispersive spectroscopy, and scanning electronmicroscopy) were employed to confirm the chemical modification of the adsorbent surface. Preconcentration conditions (sample pH, flow rate, buffer solution, and eluent concentrations) were optimized using factorial and Doehlert matrix designs that made it possible to construct a linear graph in the 5.0- to 130.0-μgL^-1 range (r0 0.9999) and estimate detection and quantification limits (1.7 and 5.7 μgL^-1, respectively). The method precision was found to be 4.20 and 1.97%for 5.0 and 100.0 μgL ^-1 Pb²⁺ solutions, respectively. When using the 3-mercaptopropyltrimethoxysilane-functionalized multiwalled carbon nanotubes, the sensitivity for the Pb²⁺ trace determination was improved to 95 % compared with the oxidized multi-walled carbon nanotubes, thus evidencing the significant enhancement of the adsorption capacity. The developed method was successfully applied to the analysis of Pb²⁺ species in different water samples and the PACS-2 marine sediment-certified reference material.