A novel method to recover ammonia, manganese and sulfate from electrolytic manganese residues by bio-leaching

Abstract

The electrolytic manganese residues (EMRs) contain variable amounts of trace metals and valuable elements, which can negatively impact the environment. This research focused on recovering valuable elements (SO <inf>4</inf> ²⁻ , NH <inf>3</inf> –N, Mn, Mg, and Fe) from EMRs by bioleaching. Bacteria (Y1) were isolated from EMRs and then acclimated for bioleaching processes. The bacteria can grow with waste molasses as the only carbon/nutrient source. After bioleaching for 8 days, 78–88%, 85–98%, 75–85%, 88–95%, and 95–99% of SO <inf>4</inf> ²⁻ , Mn, Mg, Fe, and NH <inf>3</inf> –N were leached out from EMRs with a solid-to-liquid ratio of 1:2.5 kg of EMR powder L ⁻¹ of leaching liquid. Then, the elements of NH <inf>3</inf> –N, Mn, Mg, and Fe were separately precipitated as (NH <inf>4</inf> ) <inf>2</inf> Mn(SO <inf>4</inf> ) <inf>2</inf> 6H <inf>2</inf> O, (NH <inf>4</inf> ) <inf>2</inf> Mg(SO <inf>4</inf> ) <inf>2</inf> 6H <inf>2</inf> O and (NH <inf>4</inf> ) Fe(SO <inf>4</inf> ) <inf>2</inf> 6H <inf>2</inf> O by adjusting the pH of the bioleachate (i.e., the filtrate of the leachate solution) to 8.5–9.0. The process could be cost-effective due to the use of waste molasses (a low-cost product from sugar processes) as carbon sources and may have a great potential for industrial applications.