Luciana Dornelles Venquiaruto

Qualitative lead extraction from recycled lead-acid batteries slag.

The pyrometallurgic process that the exhausted batteries are submitted for the recovery of metallic lead generates great amount of a by-product called slag. The slag is composed mainly of iron ( approximately 60%) and lead ( approximately 6%), and this residue cannot be disposed in conventional landfill due to the high lead content. This work presents a new methodology for the extraction of lead from slag, based on the complexing effect of EDTA, a chelating ligand that has the ability to solubilize several heavy metals. As the iron (Fe(2+)/Fe(3+)) have a formations constant with EDTA higher than the lead and is present in high concentrations in the samples, the fluoride ion (F(-)) was employed to mask the iron ions. The tests were carried out in a qualitative way, confirming the lead extraction by the formation of a yellow precipitate of lead iodide.

Optimization of the methodology for lead extraction from waste contaminated with heavy metals

A sequential experimental design strategy is used to optimize the extraction of lead from slag. The slag is composed mainly of iron (≈60%) and lead (≈6%), and cannot be disposed of in conventional landfill due to its high lead content. The extraction of lead is based on the complexing properties of ethylenediaminetetra‐acetic acid (EDTA), the iron being masked with fluoride ions. Atomic absorption spectroscopy (AAS) has been used for monitoring iron and lead concentrations. In a first step, Plackett–Burman PB‐12 experimental design was used for screening the variables and for selecting those to be used. Two central composite designs (CCDs) were then carried out to determine the optimal conditions for lead extraction. The optimized experimental conditions were established to be: contact time with the fluoride solution 30 min; particle size of slag between 150 and 600 µm; molecular concentration of fluoride solution 2.4 × 10−3 mol and of EDTA 5 × 10−4 mol; pH 1.5; 8 h contact time with the EDTA solution; and temperature 60°C. Under these experimental conditions the lead content was reduced by 57% compared with the raw sample.