Metal Recovery from Bottom Ash of an Incineration Plant: Laboratory Reactor Tests

The bottom ashes, produced by the industrial incinerators, are an essential secondary raw material resource that has been drawing attention to recover economically important metals. In the present study, a hydrometallurgical process (chemical leaching) has been discussed to recover some economically important metals using lab scale reactors (600 mL and 2L capacity). Prior to the leaching tests, the material was characterized for chemical composition and mineralogical phase analysis through XRD. In addition, the conventional process of magnetic separation was applied before leaching tests to remove some easily separable parts. Two acidic reagents (HCl and H2SO4) and an alkali reagent (NaOH) have been used to compare the recovery of metal values from the pre-treated bottom ash samples at varying concentrations. Process parameters such as acid/alkali concentration, working volume and temperature have been optimized and the recoveries of metal values under optimum conditions were recorded. The studies showed that 3M H2SO4, 1.5 L working volume and 80 degrees C were sufficient to leach 88% Mo, 82% V, 37% Ni, 37% Fe, and 28% Cu. Acid leaching tests using H2SO4 were found to be an economical and appropriate solvent for metal recovery from bottom ash.