Leaching of heavy metals stabilized in asphalt matrix

Long-term impact of stabilized/solidified hazardous waste on the environment was evaluated using a combination of long-term leaching tests and mathematical modeling. The waste used in this research is a dust collected from filters used in the production of nickel-cadmium accumulators. It contains nickel hydroxide, cobalt hydroxide, and cadmium oxide, and based on toxicity characteristic leaching procedure test it is a hazardous waste. This waste was stabilized using two different aqueous anionic asphalt emulsions. Several extraction tests were used to evaluate the long-term leaching of stabilized waste. Then using a mathematical model, the long-term leaching test data was analyzed to obtain mass transport parameters for the contaminants in the stabilized wastes. From the leaching test results mathematical model parameters needed to estimate the transport and release of contaminants to the real environment under alkaline pH from the stabilized waste were obtained. The model simulation of the performance of the stabilized waste under the actual environmental conditions of the disposal site showed that there is insignificant release of the contaminants from the stabilized waste. Hence it was concluded based on the experimental and modeling data that if the environment is able to maintain an alkaline pH condition, then the stabilized waste will not damage the environment.