Gold Recovery from HCl Solutions using Cyphos IL‐101 (a Quaternary Phosphonium Ionic Liquid) Immobilized in Biopolymer Capsules

Abstract

Tetraalkyl phosphonium chloride (Cyphos IL‐101), an ionic liquid (IL), was tested for gold recovery from HCl solutions: first in liquid/liquid extraction systems (using toluene and hexane as solvent) and in a second step, after being immobilized in a biopolymer composite matrix. SEM‐EDAX analysis was used for the characterization of the resins. The sorption capacity reached up to 140 mg Au(III) g⁻¹ in 1 M HCl solutions. Base metals that do not form anionic chlorocomplexes and nitrate or chloride ions (at 5 g L⁻¹) did not interfere with Au(III) binding. Gold binding probably occurs through the interaction of R₃R'P⁺ with AuCl₄ ⁻. The kinetics of sorption was carried out varying agitation speed, metal concentration, IL content, and resin drying. Intraparticle diffusion played an important role on the control of sorption kinetics. Gold could be desorbed from the loaded IL‐impregnated resin using thiourea (in HCl solutions). The resin could be re‐used for at least 4 cycles. The resins are specially adapted for the recovery of gold from low metal concentrations.

Keywords:

• Gold
• phosphonium ionic liquid
• sorption isotherms
• diffusion
• desorption

ACKNOWLEDGMENTS

The authors thank the Erasmus program for the financial support granted to P.B. during his stay at Ecole des Mines Alès. E.G. acknowledges the financial support from the Carnot program for the Project Bioencapsulation of Extractants. K.C. thanks the support of the Franco‐Peruvian collaboration program “Raul Porras Barrenechea.” The authors thank Jean‐Marie Taulemesse (Centre des Matériaux de Grande Diffusion, Ecole des Mines Alès) for his technical assistance for SEM and SEM‐EDAX analyses.