Downstream recovery of Li and value-added metals (Ni, Co, and Mn) from leach liquor of spent lithium-ion batteries using a membrane-integrated hybrid system

초록

The end-of-life management of a large number of discarded lithium-ion batteries (LiBs) has become a global issue because of the steady increase in their usage every year. In this study, a novel membrane-integrated hybrid system was developed for recycling commercially valuable metals while treating acidic leach liquor obtained from spent LiBs (mostly LiFePO4 type). Alkaline (NaOH and NH4OH)-pretreated leach liquor (pH adjusted to 5.53) was ultrafiltered to ensure the effective removal of Fe and Al and reduce the turbidity (∼1.6 NTU) prior to processing in a nanofiltration system. The nanofiltration membrane (VNF2) was applied successfully to obtain the rejection values of 92.5% (Ni2+), 94.6% (Co2+), and 95.8% (Mn2+) while permeating > 89.6% of Li+ with 7.5 L/m2·h of flux under optimized conditions of transmembrane pressure (10 bar) and crossflow rate (2.25 m3/h) in the recirculation mode. The fractionation of monovalent ions from bivalent ions was performed in a concentrated mode to enrich the bivalent metal ions, Ni2+, Co2+, and Mn2+ from 0.74, 0.52, and 0.63 g/L to 6.14, 4.59, 5.62 g/L, respectively, at 90% recovery of the feed solution. The Li+ (21.1 g/L) that was contained in the nanofiltrate permeate stream was crystallized into Li2CO3; a purity of 99.5 wt% was obtained at 88.2% recovery using 4 M K2CO3 at an operating temperature of 70 °C. Hence, the proposed novel system can lead to the development of a clean and sustainable process for the recycling of precious metal ions from end-of-life LiBs for reuse on a commercial scale.

키워드