Selective Recovery of Gold from Electronic Circuit Board Waste with Pyrogallol-Formaldehyde Polymer

Electrical and electronic waste (e-waste) has become one of the largest solid waste problems today, as it contains valuable recyclable materials like gold, platinum, and silver. Recycling of precious metals is important in terms of re-using the high precious metal content wastes. In this study, pyrogallol-formaldehyde polymer (PGNR) material was synthesized as an adsorbent. The obtained PGNR was characterized by Brunauer-Emmett-Teller (BET), Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetry analysis (TGA) and nuclear magnetic resonance (NMR) analyses. The adsorption performance of solutions containing gold (III) ions was evaluated under variables such as different pH values, adsorbent amounts, initial concentrations, time and temperature. Data obtained from the experiments were used to perform adsorption isotherm, kinetic, and thermodynamic calculations. The results indicated that the "Pseudo Second Order Equation" provided the best fit for the kinetic data, while the "Langmuir Equation" was the most suitable for the isotherm data. The Langmuir isotherm revealed that the monolayer saturation capacity for Au(III) ions on the PGNR polymer was found to be 2456.78 mg/g at a temperature of 328 K. The FTIR analysis conducted after adsorption revealed that polyphenolic groups played a key role in the adsorption of Au(III) species. XRD and XPS characterization studies showed that nearly all of the Au(III) ions were reduced to metallic gold following adsorption. It was found that the PGNR polymer chosen as the adsorbent exhibited a high efficiency in adsorbing Au(III) from the actual leach solution derived from electronic waste. PGNR polymer particles are a potential adsorbent for the selective recovery of gold metal in leach solutions of electronic waste containing high concentrations of base metals.