Integration of H2S gas cleaning and bioleaching for zinc recovery from electric arc furnace dust

Electric arc furnace (EAF) dust is a by-product of the stainless-steel industry that contains significant amounts of zinc and iron as well as lead and is classified as hazardous waste. Recovering metals from the EAF dust would increase the zinc supply from waste and decrease the amount of hazardous waste. Cleaning of industrial gases using EAF dust is a potential low-cost alternative to non-regenerable primary ZnO adsorbents. The challenge is to develop further treatment methods for sulfide materials to recover their metal values and manage sulfur, by comparing the leaching of EAF before and after sulfidation with H₂S. This study shows the feasibility of integrating H₂S removal by adsorption at elevated temperatures using EAF dust with zinc recovery from the sulfide material of EAF after sulfidation (S-EAF) using bioleaching. In this process, sulfur- and iron-oxidizing microorganisms oxidize the sulfide mineral and leach zinc into the solution. Hydrometallurgical EAF dust recycling technologies require significant quantities of acid. A part of the acid used for leaching can be produced from the sulfide material itself, significantly reducing the need for external sulfuric acid. Integrating gas cleaning with bioleaching enables the utilisation of both the metal and captured sulfur content. The integrated sulfur capture-bioleaching concept has potential for adaptation to other oxidized waste materials beyond EAF dust.