Determination of sulfur anions in spent oil shale leachates by ion chromatography

The leaching and transport of chemical constituents from spent oil shale disposal areas is an area of environmental concern at the present time. Sulfur-containing compounds are prevalent in spent oil shales and have the potential to leach into aqueous systems surrounding disposal sites. Computer modeling has been used in recent years to predict the transport of species in an aqueous environment. The quality of model predictions, however, depends on the validation steps taken in comparing model predictions with laboratory data on ion speciation. Further, the quality of the validation step depends on the reliability of laboratory methods in generating ion speciation data. The purpose of this study was to develop methods to separate and quantify sulfur-containing anions in spent oil shale leachates by suppressed ion chromatography. The anions studied were S2- (sulfide), SO2/3 (sulfite), SO2/4 (sulfate), SCN- (thiocyanate), S2O2/3 (thiosulfate), and S4O2/6 (tetrathionate). After the separations were developed, a series of method-challenging experiments were performed to test the reliability of the methods and assure the development of an analytically sound product.