Functionalized carbon nanotubes for dispersive solid-phase extraction and atomic absorption spectroscopic determination of toxic metals ions

A nanosorbent for dispersive solid-phase extraction was fabricated by functionalizing multiwalled carbon nanotubes with sulfosalicylic acid after oxidation and thiolation followed by decoration with Fe ₃ O ₄ nanoparticles. Incorporation of hydrophilic carboxylic and sulfonic acid groups introduces coordinating ability and accessibility for cadmium and lead, resulting in high sorption capacity of 217.39 and 454.54 mg g ⁻¹ , respectively. Decoration by magnetic nanoparticles enhances its dispersibility and facilitates the separation of solid phase without tedious centrifugation or filtration processes, which is the exclusive objective of dispersive solid-phase extraction. The functionalized sorbent was characterized by FT-IR, SEM and TEM. The uniform and monolayer sorption behavior of the sorbent was proved by an evident fit of the equilibrium data to Langmuir isotherm model. The analytical method developed after optimizing the experimental variables such as solution pH, sorption time, amount of sorbent, desorption condition for preconcentration and separation enables the use of an economically viable less sensitive AAS for trace determination due to the improved detection limit of 0.13 and 1.21 µg L ⁻¹ for cadmium and lead, respectively. Commonly occurring concomitant ions in the real samples was not found to interfere in the trace determination of analyte. The good precision was assessed by the determined average day-to-day coefficient of variation of 3.02% for cadmium and 2.29% for lead. The accuracy and applicability of the present method for sequential cadmium and lead determination are substantiated by the analysis of Standard Reference Material and environmental water samples from electroplating industries, river water and tap water.