Selective dissolution of gold in an alkaline thiourea solution by electrolysis

Abstract

Anodic polarization behavior of gold, silver, copper, nickel and iron in potentiostatic condition has been examined in an alkaline aqueous thiourea solution, where gold is hardly dissoluble normally. The addition of Na₂SO₃ into the solution can accelerate anodic dissolution of gold. The factors affecting selective dissolution of gold in the alkaline thiourea solution by electrolysis have been studied, and the optimum condition was obtained. In 0.1 mol/L thiourea solution of pH 12.5 containing 0.5 mol/L Na₂SO₃ and 2.5% acetone, at the potential of 0.34 V vs NHE, at the temperature of 323 K, the dissolved mass of gold anode with the exposed area of 1.0 cm² reached more than 300 mg · dm⁻³ within 30 min, and other metals such as silver, copper, nickel and iron could hardly dissolve.

Keywords

polarization behavior / selective dissolution of gold / electrolysis / alkaline thiourea solution / sodium sulfite

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