An Integrated Experimental-Modeling Approach To Study The Acid Leaching Behaviour Of Lead From Sub-Micrometer Lead Silicate Glass Particles

This work focuses on the development of a procedure to study the mechanism of leaching of lead from sub-micrometer lead glass particles using 0.3 mol I-1HNO3 as a leachant. Glass particles with an effective size distribution range from 0.05 to 1.4 um were generated by laser ablation (213 nm Nd: YAG laser) and collected on an inline 0.2um syringe filter. Subsequently, the glass particles on the filter were subjected to online leaching and continuous monitoring of lead (Pb-208) in the leachate by quadrupole ICP-MS. The lead leaching profile, aided by the particle size distribution information from cascade impaction, was numerically fitted to a mathematical model based on the glass intraparticle diffusion, liquid film distribution and thermodynamic glass-leachant distribution equilibrium. The findings of the modelling show that the rate-limiting step of leaching is the migration of lead from the core to the surface of the glass particle by an ion-exchange mechanism, governed by the apparent intraparticle lead diffusivity in glass which was calculated to be 3.1 x 10-18 m2s-1. Lead leaching is illustrated in the form of graphs and animations of intraparticle lead release (in time and intraparticle position) from particles iwth sizes of 0.1 and 0.3 um.