Lead Recovery From PbO Using Hydrogen as a Reducing Agent

A systematic isothermal reduction study was carried out on pure PbO pellets using 15 pct H2/85 pct N2 gas. The reduction was carried out at 350 °C to 800 °C at different reaction times (30 minutes to 4 hours) with gas flowrate of 500 mL/min. The kinetics of the reaction were evaluated by measuring the mass change and applying kinetic models to the data. The results from microstructure observation showed that globular and non-wetting lead droplets form on the surface of PbO samples. The droplet's diameter was observed to increase with increasing temperature and reduction time. It was observed that this lead droplets layer, once covers the whole surface, appears to reduce the overall reduction rate. The kinetics analysis showed that PbO pellet reduction is a diffusion-controlled process as supported by the SEM (scanning electron microscope) micrographs, samples’ cross-section observation, and phase analyses using EDS (energy-dispersive spectrometry) and XRD (X-ray diffraction). The energy activation, Ea, was calculated for two temperature ranges, i.e., 61 kJ/mol (for 350 °C to 450 °C) and 224 kJ/mol (for 600 °C to 800 °C), respectively. These results suggest that, in an industrial context, continued reduction process will require constant removal of lead product from the surface of the lead monoxide.