Silica-gel Particles Loaded with an Ionic Liquid for Separation of Zr(IV) Prior to Its Determination by ICP-OES

Abstract

A new ionic liquid loaded silica gel amine (SG-APTMS-N,N-EPANTf₂) was developed, as an adsorptive material, for selective adsorption and determination of zirconium, Zr(IV), without the need for a chelating intermediate. Based on a selectivity study, the SG-APTMS-N,N-EPANTf₂ phase showed a perfect selectivity towards Zr(IV) at pH 4 as compared to other metallic ions, including gold [Au(III)], copper [Cu(II)], cobalt [Co(II)], chromium [Cr(III)], lead [Pb(II)], selenium [Se(IV)] and mercury [Hg(II)] ions. The influence of pH, Zr(IV) concentration, contact time and interfering ions on SG-APTMS-N,N-EPANTf₂ uptake for Zr(IV) was evaluated. The presence of incorporated donor atoms in newly synthesized SG-APTMS-N,N-EPANTf₂ phase played a significant role in enhancing its uptake capacity of Zr(IV) by 78.64% in contrast to silica gel (activated). The equilibrium and kinetic information of Zr(IV) adsorption onto SG-APTMS-N,N-EPANTf₂ were best expressed by Langmuir and pseudo second-order kinetic models, respectively. General co-existing cations did not interfere with the extraction and detection of Zr(IV). Finally, the analytical efficiency of the newly developed method was also confirmed by implementing it for the determination of Zr(IV) in several water samples.

Keywords: Zr(IV) detection; adsorption isotherm; inductively coupled plasma-optical emission spectrometry (ICP-OES); ionic-liquid; solid-phase extraction.

Scheme 1

Synthetic route of SG-APTMS-N,N-EPANTf₂ phase.

Figure 1

FT-IR spectra of activated SG and SG-APTMS-N,N-EPANTf₂ phases.

Figure 2

SEM images of (a) activated SG and (b) SG-APTMS-N,N-EPANTf₂ phases.

Figure 3

Effect of pH on the adsorption of 2 mg·L⁻¹ Zr(IV), Au(III), Cu(II), Co(II), Cr(III), Pb(II), Se(IV) and Hg(II) on 20 mg SG-APTMS-N,N-EPANTf₂ at 25 °C.

Figure 4

Adsorption profile of Zr(IV) on 20 mg activated SG and SG-APTMS-N,N-EPANTf₂ in relation to the concentration at pH 4.0 and 25 °C.

Figure 5

Langmuir adsorption isotherm model of Zr(IV) adsorption on 20 mg SG-APTMS-N,N-EPANTf₂ at pH 4.0 and 25 °C. Adsorption experiments were performed using different concentrations (0–200 mg·L⁻¹) of Zr(IV) under batch conditions.

Figure 6

Effect of contact time on 150 mg·L⁻¹ Zr(IV) adsorption by 20 mg SG-APTMS-N,N-EPANTf₂ at pH 4.0 and 25 °C.

Figure 7

Pseudo second-order adsorption kinetic model of Zr(IV) uptake on 20 mg SG-APTMS-N,N-EPANTf₂ at pH 4.0 and 25 °C.