Lead Chemical Dissolution in Acidic Medium in the Presence of Citrate [Dissolu o Química do Chumbo em Meio ácido na Presen a de Citrato]

Lead is metal of great interest to scientific community due to the toxicity of its compounds against living beings. Otherwise, the citrate ion is a complexing agent with the ability to solubilize many metallic ions in solution. However, a few works are reported in the literature upon the dissolution of metallic lead in the presence of citrate ions in acidic solutions. The present work aims to study the lead dissolution into acidic solutions (pH 4) in the presence of citrate ions. It was observed the formation of insoluble lead citrate on the metal surface and its stoichiometric structure is Pb3(C6H5O7).4 H2O. The lead dissolution is affected to the concentration of citrate ions in the medium and to the buffering solution characteristics. When increasing citrate ions concentration in solution, the formation of insoluble lead citrate on the metal surface does not occur. Probably this compound is precipitated due to the pH increase nearby the metal surface. The lead dissolution kinetics and the lead citrate morphology are influenced by the stirring of the solution. However, the mechanism of dissolution is practically unchanged.