ANODE DISSOLVING TIN AND LEAD IN METHANESULFONATE SOLUTIONS

Abstract

An important applied problem today is the selective separation of tin, lead, copper and other valuable elements from alloys obtained in the process of recycling used electronic and computer equipment. The volume of such waste is growing rapidly due to the rapid development of information technology and materials science, which causes a constant need to update electronic devices. The recycling of non-ferrous metals is economically profitable, contributes to environmental safety and provides industry with critically important metals. An energy-efficient method of separating metals in such waste is their hydrometallurgical processing. Multicomponent alloys are dissolved in acidic or alkaline media, after which the individual components are selectively separated. For the simultaneous dissolution of tin and lead from scrap electrical alloy, it is advisable to use leaching solutions in which soluble compounds of these metals are formed. One of the most promising in this aspect are solutions based on methanesulfonic acid. For controlled and selective dissolution of alloys, the anodic dissolution method is used. In this work, a study of the anodic dissolution of tin and lead in a methanesulfonic acid solution was conducted. The study used membrane electrolysis, in which the anolyte was separated from the catholyte by an anion exchange membrane. It was established that one hundred percent dissolution of tin with the formation of tin(II) ions occurs in a 1 mol/l methanesulfonic acid solution in the range of current densities of 0.5–3 A/dm2. In the range of current densities of 3–6 A/dm2, the current yield of tin(II) ion formation decreases due to the parallel anodic oxidation process of tin to tin(IV). The current yield of anodic dissolution of lead with the formation of plumbum(II) ions in the studied range of current densities is 100 %. It has been established that when concentrating the anolyte during the membrane electrolysis of tin and lead, water is observed to move from the catholyte to the anolyte under the influence of osmotic pressure. To eliminate this effect, it is proposed to maintain the acid concentration in the catholyte at 3.5 mol/l while concentrating the anolyte in terms of metal ions at 1.85 mol/l.