A new treatment process to recover magnetite, zinc and lead from iron and steelmaking dusts and sludges

Steelmaking dusts are frequently classified as hazardous residues, due to their eco-toxicity characteristics. This derives mainly from the presence of heavy metals like zinc, lead and cadmium in their compositions, in forms that are easily leachable by water or slightly acidic or alkaline media. Following the most employed eco-toxicity standard tests, like DIN 38414-S41) from Germany, and TCLP (Toxicity Characteristic Leaching Procedure)2) from the United States, steelmaking dusts present a high level of mobility of heavy metals, what is relevant for the evaluation of their environmental impact, when disposed in controlled landfills. In the present project (contract number ERB IC 15CT97-0704), a new process is being developed to recover valuable metals and products from steelmaking dusts and sludges. Two different process routes are being evaluated, both from the technical and from the economic points of view. A pre-treatment stage, based on water leaching of the dusts, is, in both cases, studied, to remove alkalis present in the wastes