Microchemical Investigations of Dust Emitted by a Lead Smelter

Abstract

Dusts emitted by an important pyrometallurgical lead smelter have been sampled within the pipes of the grilling and furnace working units before and after the filtering systems, respectively. Particle size distribution, elementary analyses, and X-ray powder diffraction analysis indicate PbS, PbSO4, PbSO4·PbO, Pb, ZnS small particles less than 5 μm in size to contribute mainly to the current atmospheric pollution. Although at least 90% of dust are retained on the filters, the amounts of the respirable smaller particles are significantly larger in the current emission. The average chemical speciation was found to be analogous for the dust samples collected before and after the filters. The scanning electron microscopy associated with energy-dispersive X-ray analysis and Raman microspectrometry established the morphology and chemical composition at the level of individual particles. A lot of minor compounds (α-PbO, β-PbO, FeS2, FeO, Fe3O4, α-Fe2O3, FeCO3, CaSO4·2H2O, CaCO3, CdS, ...) were found as small heterogeneous individual particles (less than 5 μm) in the heterogeneous particles of grilling dust. Among the homogeneous particles of furnace dust, amorphous C, β-PbO, PbO·PbCl2, FeO, CdS, CdSO4 were often detected as homogeneous mixtures with the major compounds within the particles.