Use, Preparation, and Characterization of Copper-Containing Silica Gel

Abstract

The preparation and characterization of humidity-indicating silica gel containing copper sulfate were aimed at in the present study. The equilibrium and kinetics of Cu­(II) sorption were investigated by contacting 200–1600 mg dm–3 Cu ion-containing solutions with silica hydrogel slabs having 10% silica. The diffusion coefficient of Cu­(II) in silica hydrogel was determined to be on the order of 10–10 m2 s–1. X-ray diffraction indicated that the gels contained mainly CuSO4·3H2O, CuSO4·H2O, and small amounts of CuSO4 and CuSiO3·2H2O. The silica gel with Cu­(II) can be used as a humidity indicator since its color changes from light blue to dark blue upon moisture adsorption.

Microencapsulation of Copper(II) Sulfate in Ionically Cross-Linked Chitosan by Spray Drying for the Development of Irreversible Moisture Indicators in Paper Packaging

“…Some trials, however, have been performed to develop colorimetric humidity-indicating sensors based on copper. For instance, indicating agents of interest in humidity-adsorbing columns were recently prepared by Ulutan et al [ 45 ] by drying silica hydrogels impregnated with a saturated copper sulfate solution at 100 °C. The prepared dried copper sulfate-containing gels containing light blue CuSO 4 ·H 2 O were transformed upon moisture adsorption at 25 °C into dark blue CuSO 4 ·3H 2 O, as clearly shown using visible spectroscopy.…”

The copper sulfate hydration cycle. Crystal structures of CuSO4 (Chalcocyanite), CuSO4·H2O (Poitevinite), CuSO4·3H2O (Bonattite) and CuSO4·5H2O (Chalcanthite) at low temperature using non-spherical atomic scattering factors

“…12 The anhydrous powder is used as a laboratory desiccant and as an indicator in other drying agents such as silica gel. 13 The hydration/dehydration mechanism and energetics of copper sulfate remain of significant interest with recent reports from Raman and teraHertz spectroscopies 14,15 and older studies of differential thermal analysis from the decomposition of 4. [16][17][18] Dehydration by shock waves has recently been investigated.…”