Leaching behavior of zinc and lead from electric arc furnace dust – Poly(vinyl) chloride residues after oxidative thermal treatment

Oxidative thermal treatment of electric arc furnace dust (EAFD) mixed with poly(vinyl) chloride (PVC) was carried out to study the impact of oxidizing environment on the extraction of valuable metals. The effect of oxygen partial pressure, temperature and holding time of the thermal treatment, as well as the pH of the leaching solution were considered as operational variables in this study. HCl evolved during PVC decomposition was found to react with the metal oxides present in EAFD producing metal chlorides. It was found that thermal treatment above 350 °C caused significant vaporization of lead and zinc chlorides. After thermal treatment, the residue was leached in water, the cheapest available leaching reagent. Zinc and lead were extracted with recoveries up to ∼100%, while iron recovery was as low as 12.5% being suppressed by oxidation of ferrous iron. Operating under oxidative conditions supresses the post dissolution of iron in water by oxidizing Fe₃O₄ to Fe₂O₃ and by oxidizing any formed FeCl₂ back to Fe₂O₃. The solution pH was also found to significantly affect the extraction of both lead and iron, especially at pH values above 4.0 where a sharp drop in metals recovery was observed. The obtained results present base for development of sustainable solution for treatment of PVC and EAFD wastes.