Chelation extraction of lead from soil using pyridine-2,6-dicarboxylic acid
Abstract
Pyridine-2,6-dicarboxylic acid (PDA) was employed as a lead-complexing agent. Batch testing involving PDA extraction of lead from spiked soils showed PDA to be an effective lead solubilizing agent across a wide pH range. Lead extraction efficiency was independent of the total carbonate concentration, competing cations, or the soil aging period. In addition, PDA compared favorably with EDTA as a lead-complexing agent, while behaving more desirably than EDTA in releasing the extracted lead. PDA was effectively reclaimed and reused in four successive extraction procedures, achieving in each run a lead extraction efficiency that exceeded 80% recovery of the total lead present in the spiked soil. In recovery procedures, the complex solution was elevated to a pH of about 10, separating the lead as a hydroxide precipitate, and allowing for virtually complete recovery of the PDA in solution.