THERMAL ENCAPSULATION OF TOXIC METAL SALTS

The need for alternative treatments for hazardous waste disposal is rapidly growing as landfilling is being phased out by regulatory actions. The objective of this research was to demonstrate that toxic metal salts (cadmium salts) can be encapsulated by slagging. Mixtures of a base material (1 part coal, 1 part limestone, 1 part cadmium salt, and 0.5 part silica) were added to various amounts of borax. These mixtures were heated in a tube furnace. The slag that was formed was subjected to the EPA leaching test (TCLP). The resulting extracts were analyzed for cadmium concentration using an atomic absorption spectrophotometer. For this method to comply with federal standards, cadmium concentration in the extract must be below 1 ppm. The results indicate that mixtures of 1 part cadmium to 5 or more parts borax complied with the regulatory level. Extract concentrations ranged from 0.01 ppm to 0.43 ppm. The optimal mix was determined to be a 1:8 mixture of cadmium to borax.