Metal Recovery Using Polyphenols Prepared by Enzymatic Reactions of Horseradish Peroxidase

Enzymatic reactions of horseradish peroxidase were used to polymerize phenols in various substrates, and the polyphenols were used for precious metal recovery. The phenol groups in polyphenols can reduce gold ions to gold particles at high capacities. Increasing the phenol group density in the polyphenol enhances the gold-reducing ability in acidic media. Poly(tyramine) produced by polymerization with horseradish peroxidase has oxidation and ion-exchange abilities and good solubility. Palladium and platinum ions were adsorbed on poly(tyramine) via ion-exchange interactions. Using the solubility of poly(tyramine), we propose a novel recovery system for gold ions. Because of the hydroxyl groups in the polymer, base metal ions, such as copper ions, were adsorbed in the pH region of 2-5.