Combinatorial Screening of NADES for Sustainable Lead Recovery from Untreated Lead-Acid Battery Waste

Lead acid batteries (LABs) continue to pose a persistent threat to human health on disposal due to informal pyrometallurgical recycling in low and middle income countries. In this paper Natural Deep Eutectic Solvents (NADES) are put forward as highly effective solvents to dissolve and sequester lead by exploiting the same mechanisms that make lead so toxic to living beings. This paper screens Type V NADES made of a variety of amino acids and organic acids, as well as traditional Type III NADES for comparison. To avoid pre-treating the battery waste, solvents were first optimised for dissolving PbSO4 (80 g/L achieved after 18 hours at room temperature) and PbO2 (700 g/L achieved after 18 hours at room temperature) before being mixed together combinatorially to achieve a solvent capable of dissolving 350 g/L after 18 hours at room temperature of untreated lead acid battery waste with a 1:1 solid : liquid loading ratio. This solvent is made from naturally occurring compounds (β-alanine, glycolic acid and betaine) and contains little water making the solvent both sustainable and appropriate for use in water-scarce regions, where much of the informal battery recycling that endangers public health takes place.