Recovery of lead, tin and indium from alloy wire scrap

Abstract

Lead, tin and indium were successfully recovered from alloy wire scrap containing these metals by acid/alkali leaching. The scrap material was leached with hot HCl-HNO3 solution. Upon cooling down to 10°C, 71.8% of lead initially present was separated as lead chloride. The major part of the remaining lead content (22.9%) was recovered by cementation with indium powder of 1.5 equivalents per equivalent of lead at 45°C. Tin was recovered from the acidic solution as hydrated tin oxide by using NaOH at pH 2.0-2.8. Indium was recovered from the remaining solution by two different methods. The first method involved precipitation of indium as phosphate using H3PO4 at pH 3.91, converting the phosphate to the oxide by leaching with NaOH solution. In the second method, sponge metallic indium was recovered by cementation with zinc powder of 1.2 equivalents per equivalent of indium at 30°C. Parameters controlling the recovery processes, such as temperature, time, pH and metal equivalent were investigated. ICP and X-ray analysis were carried out to estimate the purity of the products. Results obtained are explained, knowing that the stated salts have the least solubility and highest purity under the given experimental conditions. Lead, tin and indium, having purities of > 99, 99.7 and 99.8%, respectively, are obtained. The recovery of these metals are found to be 94.7, 99.5 and 99.7%, respectively. The recovery processes are favored at a temperature of ≤ 45°C for a maximum duration of 8 h and at a pH ≤ 2.4. © 1998 Elsevier Science B.V. All rights reserved.