New Approaches on non Ferrous Metals Electrolysis

Abstract

Engitec Technologies is a relatively young company active in the field of non ferrous metals recovery from diverse sources. Since the beginning, the company has studied systems based on innovative hydrometallurgical processes trying to avoid, when possible, the use of pyrometallurgical techniques.In particular, the company has developed two systems based on very different and unusual electrolytes: Fluoboric acid - for primary and secondary Pb and Cu. Ammonium chloride - for primary and secondary Zn and Pb. For the fluoboric acid system, a demo plant campaign on primary Pb concentrate was recently completed and we are currently preparing proposals for industrial plants. This electrochemical system is based on a diaphragm divided cell were Pb metal is plated at the cathode and Fe3+ is produced at the anode insteadof evolving oxygen. The Fe3+ produced is then used to leach the Pb from the mineral concentrate closing the process loop.For the ammonium chloride system, the electrolysis is run in a more traditional open cell. Unlike other chlorine electrolysis systems, this cell has no chlorine gas emissions. Instead, where chlorine is produced at the anode it is immediately converted to nitrogen by a chemical reaction with ammonia in the bulk solution. A small industrial plant was operated for several years in Italy producing Zn from electric arc furnace dust generated during the production of steel from steel scrap.In addition, we are electrowinning Pb from ammonium chloride electrolyte in a bi-polar flow cell working at 8,000-10,000 A/m2 without any need for cathode stripping. This is currently being piloted at our facility in Milan, Italy.This paper will describe these industrial electrochemical approaches in more detail.