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

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 (SO42-, NH3-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 SO42-, Mn, Mg, Fe, and NH3-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 NH3-N, Mn, Mg, and Fe were separately precipitated as (NH4)(2)Mn(SO4)(2) 6H(2)O, (NH4)(2)Mg(SO4)(2) 6H(2)O and (NH4) Fe(SO4) (2)6H(2)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. (C) 2019 Elsevier Ltd. All rights reserved.