Contaminant Leaching from Stabilized/Solidified Acid Tars

This work investigates the leachability-related properties of acid tars treated with portland cement (CEM I), with the addition of high carbon fly ash (HCFA), as a novel binder for the immobilization of hydrocarbons. The leachate pH, acid neutralization capacity (ANC), and leaching of metals and sulfates from the treated acid tars were investigated. The effect of acid tar type, CEM I:HCFA ratio, and curing time on hydrocarbon leaching was also studied using factorial design experiment. ANC results show that acid tars had detrimental effect on the formation of cement hydration products. The overall results indicate that metal was not released in high concentration from the stabilized/solidified acid tars; hence their leaching is not of great environmental concern. The amount of leached sulfates was significantly lower than untreated acid tars and was attributed to ettringite formation. Factorial analyses show that all studied factors significantly affected hydrocarbon leaching. HCFA addition resulted in reduction in hydrocarbon leaching but led to an increase in sulfate leaching. This work shows that HCFA improved the immobilization of hydrocarbons and may represent an inexpensive binder for stabilization/solidification of wastes containing organic contaminants.