Environmental Contamination by Cobalt in the Vicinity of a Cemented Tungsten Carbide Tool Grinding Plant

Abstract

Surface soil and dust samples have been collected from the vicinity of a hard metal (cemented tungsten carbide) tool grinding factory. As a result of poor waste management practices, dusts generated by the grinding operation were, for the most part, swept from the interior of the building onto open ground at the rear of the plant. The potential for contamination of the local environment with cobalt, tungsten, and other metals as a result of dust being either resuspended from the resulting uncontrolled mound of debris or emitted from the factory vents was considerable. Levels of cobalt in local soils were found to be as high as 12,700 mg kg−1; almost 2000 times higher than the average value for in the United States. Scanning electron microscopy and energy dispersive X-ray microanalysis examination of the waste dust particles revealed that the individual particles were, in general, composites containing variable quantities of tungsten, cobalt, calcium, titanium, and iron. Individual particles in soil samples collected at some distance from the plant were less heterogenous, and fewer particles contained detectable quantities of cobalt. This would suggest that a degree of disassociation had occurred in the soil environment resulting in a mobilization of the cobalt.