THIOCYANATE-ASSISTED SOLID PHASE ENRICHMENT OF Cu(II) USING PYRIDINE DERIVATIVE WITH X-RAY CRYSTALLOGRAPHIC EVIDENCE

Abstract

Equimolar mixture of pyridine-2,6-dimethanol (PDM), and thiocyanate ion immobilized on silica serves as an efficient sorbent for selective retention of Cu(II) from other associated metal ions at µg g⁻¹ level. The maximum sorption capacity for Cu(II) was found as 2.44 mmol g⁻¹ at pH 6.0. The sorbed Cu(II) was completely eluted with 3 mol L⁻¹ HNO₃ and measured with a flame atomic absorption spectrometer (FAAS). The structure of the extracted Cu(II) complex was confirmed by single-crystal X-ray structure analysis and Fourier transform-infrared (FT-IR) spectroscopy. Thermogravimetric analysis (TGA) of the isolated Cu(II) complex was performed to determine its thermal stability at the extraction temperature. The three sigma detection limit (N = 15) of the method is 0.6 µ g mL⁻¹ with a relative standard deviation (RSD) of 0.1% (N = 15). Pre-concentration factor of the method is 133. Slight interference from Mn²⁺ ion was eliminated by prior oxidation with potassium periodate. The developed method was tested for trace level separation and estimation of Cu(II) in certified reference materials and environmental samples.

[Supplementary materials are available for this article. Go to the publisher's online edition of Chemical Engineering Communications for the following free supplemental resources: two tables providing details of the bond lengths and bond angles of the Cu(II) complex.]

Keywords:

• Copper(II)
• Crystal structure
• Flame atomic absorption spectroscopy
• Pyridine 2,6-dimethanol
• Thiocyanate

Acknowledgments

The authors are grateful to UGC-DAE, Kolkata Centre for funding. Animesh Sahana and Sisir Lohar are grateful to CSIR, New Delhi for fellowship. We are grateful to Prof. A. M. Z. Slawin and Dr. Yang Li of the School of Chemistry, University of St. Andrews, Scotland, for their help regarding X-ray structure analysis.

Notes

^a Coexisting ions are 200-fold to [Cu(II)].

FW = formula weight; Z = no. of molecules present per unit cell; a = crystallographic distance along x-axis in a unit cell; b = crystallographic distance along y-axis in a unit cell; b = crystallographic distance along z-axis in a unit cell; α= crystallographic angle in a unit cell between b and c; β= crystallographic angle in a unit cell between c and a; γ= crystallographic angle in a unit cell between a and b; V = volume; ρ= density; µ= molybdenum Kα radiation in wave number used in X-ray diffraction; F (000) = crystallographic (000) plane; R1, wR2 I  > 2(( I ) = goodness-of-fit; σ= standard deviation.

^a R1 = Σ||]^1/2.

NA = not available.