Development of Zr/polyoxometalate/carbon nanotube ternary composite for the efficient dispersive micro solid-phase extraction of phenolic derivatives

In this work, a tri-component composite containing zirconium nanoparticles/polyoxometalate/carbon nanotube (ZrNP@SiW₁₂-CNT) was developed as sorbent for the dispersive micro solid-phase extraction (D-μSPE) of phenolic derivatives (i.e. phenol, 2-chlorophenol, 3-chlorophenol, and 4-nitrophenol) from water samples. The structure and morphology of the sorbent were studied by different techniques in which the Zr nanoparticles were chosen to be encapsulated by Keggin-type polyoxometalate [SiW₁₂O₄₀]⁴⁻ (SiW₁₂) units to form ZrNP@SiW₁₂ clusters. Then, these clusters are assembled on the surface of oxidized carbon nanotube (CNT) by many types of electrostatic interactions to form ZrNP@SiW₁₂-CNT composites. Therefore, ZrNP@SiW₁₂-CNT with aromatic and oxygen-rich surface (oxo-groups from polyoxometalate (POM) clusters, carboxylate, and hydroxy groups of oxidized CNT) can be a suitable sorbent to anchor phenolic pollutants (containing aromatic ring, hydroxyl group, and halogen or nitro groups) via electrostatic interactions like π-stacking, hydrogen and halogen bonding. The extracted phenolic derivatives were analyzed using a gas chromatography-flame ionization detector (GC-FID) with linear calibration plots in the concentration range of 0.03–200 ng mL⁻¹. The limits of detection (LODs) were determined as 0.01–0.02 ng mL⁻¹ which showed that the D-μSPE-GC-FID method is valid for the extraction of phenolic derivatives from water samples with relative recovery values of 96.6–99.9 %. Also, the relative standard deviation (RSD) range was 3.6–4.7 %.