title: 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.
authors.affiliation: Department of Molecular & Medical Pharmacology, University of California, Los Angeles, CA 90095, United States; Venture Business Laboratory, Center for Advanced Science and Innovation, Osaka University, Suita, Osaka 565-0871﻿, Japan. Electronic address: kbanu@ucla.edu.
authors.forename: Khaleda
authors.initials: K
authors.lastname: Banu
authors.affiliation: Venture Business Laboratory, Center for Advanced Science and Innovation, Osaka University, Suita, Osaka 565-0871﻿, Japan; Department of Material & Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, Japan.
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Shimura
authors.affiliation: Department of Molecular & Medical Pharmacology, University of California, Los Angeles, CA 90095, United States. Electronic address: samsadeghi@mednet.ucla.edu.
authors.forename: Saman
authors.initials: S
authors.lastname: Sadeghi
mesh_terms: D002712:Chlorides / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D055664:Electrochemical Techniques; D004566:Electrodes; D005290:Ferric Compounds / Q000737:chemistry; D006046:Gold / Q000032:analysis*; D017612:Gold Compounds / Q000737:chemistry; D010084:Oxidation-Reduction; D013634:Tannins / Q000737:chemistry*
chemical_list: D002712:Chlorides; D005290:Ferric Compounds; D017612:Gold Compounds; D013634:Tannins; D006046:Gold; D003300:Copper; C024568:gold tetrachloride, acid; C029892:cupric chloride; C024555:ferric chloride
keywords: Gold; Non-conducting electrode; Permselective diffusion; Selective detection; Selective recovery; Tannin