Selective detection and recovery of gold at tannin-immobilized non-conducting electrode

Abstract

A tannin-immobilized glassy carbon electrode (TIGC) was prepared via electrochemical oxidation of the naturally occurring polyphenolic mimosa tannin, which generated a non-conducting polymeric film (NCPF) on the electrode surface. The fouling of the electrode surface by the electropolymerized film was evaluated by monitoring the electrode response of ferricyanide ions as a redox marker. The NCPF was permselective to HAuCl4, and the electrochemical reduction of HAuCl4 to metallic gold at the TIGC electrode was evaluated by recording the reduction current during cyclic voltammetry measurement. In the mixed electrolyte containing HAuCl4 along with FeCl3 and/or CuCl2, the NCPF remained selective toward the electrochemical reduction of HAuCl4 into the metallic state. The chemical reduction of HAuCl4 into metallic gold was also observed when the NCPF was inserted into an acidic gold solution overnight. The adsorption capacity of Au(III) on tannin-immobilized carbon fiber was 29 ± 1.45 mg g−1 at 60 °C. In the presence of excess Cu(II) and Fe(III), tannin-immobilized NCPF proved to be an excellent candidate for the selective detection and recovery of gold through both electrochemical and chemical processes.

Sustainable Electropolymerization of Zingerone and Its C2 Symmetric Dimer for Amperometric Biosensor Films

“…The As shown in Panel A of Figure 5, the formation of the PPD polymer gave the formation of a non-conductive polymer, as widely reported in the literature [49][50][51]. As previously reported [52], this phenomenon was further highlighted by the disappearance of the oxidation and reduction peaks of the ferricyanide, which instead are clearly visible from the voltammograms obtained on bare platinum. The same behavior was displayed by polyZING (Panel B) and polyZINGDIM (Panel C) when monomers were polymerized in N 2 -(blue plot) and O 2 -(green plot) saturated conditions.…”

“…Surprisingly, when ZING and ZING DIM polymerization were carried out in air-saturated conditions, the reversible peaks of potassium ferricyanide were conserved with the same potentials and amplitudes monitored on bare platinum. In the literature, the ferricyanide is used to study the electrochemical characteristics of non-conductive polymers [ 52 ]. In fact, the polymeric films presented in this work, in addition to interfering with the diffusion of ferricyanide, could also interact with it.…”

Preparation of Polyurethane Monolithic Resins and Modification with a Condensed Tannin-Yielding Self-Healing Property

“…Hydrolysable tannin is made up primarily of gallic acid while condensed tannin is made up from three-ring flavanols [31] and is largely used to produce adhesives, foams, biofoams [32] and many tannin-based polymers using different hardeners [33]. Tannins are natural polyphenolic antioxidants [34] and contain multiple adjacent hydroxyl groups and exhibit specific affinities for many metal ions [34]. Tannin, when added to the electrolyte or in the primer, protects metallic surfaces against corrosion [35,36,37,38,39,40,41], and when encapsulated tannin was added to sol–gel films of methyltrimethoxysilane and tetraethylorthosilicate, but when directly added to the sol–gel film was leaching [42].…”

Recovery and investigation of Cu(II) ions by tannin immobilized porous membrane adsorbent from aqueous solution

“…Tannins(Tan), a natural biopolymer, contain high content of multiple adjacent phenolic hydroxyls in their molecules (refer to Scheme 1), and thus they have strong chelating ability towards many heavy metal ions and organic mater [18][19][20][21][22][23][24]. Therefore, they promise to be used as effective adsorbent for removing of copper ions from wastewater.…”