Development of a methodic process to recycle spent alkaline batteries

Abstract

Selective dismantling of spent alkaline batteries was conducted, followed by neutral leaching of the black mass at room temperature and gravity concentration to recover KOH and metallic Zn, respectively. A counter current washing process at two different S/L ratios of 1:3 and 1:5 was evaluated and a Wilfley shaking table was employed aiming metallic Zn recovery. Neutral leaching could be effectively conducted at a 1:5 S/L ratio (17 rpm, 20 min, room temperature), using four cycles with fresh water, leading to less than 1% of the black mass K in the final water. Although less effective in terms of K recovery, the use of 1:5 S/L ratio or lower seems more technically feasible for future application of the methodic washing (34 g KOH/L in the washing water). Gravity concentration requires further optimization to effectively concentrate metallic Zn and Mn appears to be present in the fractions of higher caliber (>850μm).