Recovery of lead from smelting fly ash of waste lead-acid battery by leaching and electrowinning

摘要

Fly ash that was enriched with lead (Pb), formed as an intermediate in waste lead-acid battery (WLAB) smelting, was recycled by the hydro-electrometallurgy. Characterization of fly ash thereof indicated that the Pb was in the forms of PbSO_4 (anglesite) and Pb_2OSO_4 (lanarkite). Nitric acid and sodium hydroxide were firstly used to study the leaching of the fly ash sample, which was affected by leachant dosage and solid-to-liquid ratio (S/L). At an S/L of 60 g L~(-1), the leachability of Pb was 43% and 67% in 2 M acidic and basic solutions, respectively, based on an average 70 wt% of Pb in the original fly ash. Anglesite was completely soluble in NaOH and lanarkite was mildly soluble in HNO_3. Pb was recovered from the pregnant leach solution within an electrolytic cell constructed with graphite or RuO_2/IrO_2-coated titanium (Ti-DSA) anodes and a stainless steel cathode. Properties of anodes deposited with lead dioxides were analyzed by cyclic voltammetry. The optimized parameters of electrowinning were 2 M NaOH leachant, a current density of 0.75 A dm~(-2) and an electrolytic process duration of 120 min, which yielded a Pb removal of higher than 99% and a specific energy consumption of 0.57 W h g~(-1). This process constitutes an eco-friendly and economic alternative to the presently utilized secondary pyrometallurgy for treating lead-containing fly ash.