RI 8661 Anion Characterization of Florida Phosphate Rock Mining Materials and U.S. Cement Kiln Dust by Ion Chromatography

The Bureau of Mines has developed a rapid analytical method for the determination of anions by ion chromatography (IC) in phosphate rock mining materials and cement kiln dust (CKD). The procedure employs an Na2C03 fusion of the sample, followed by a water extraction that allows direct injection of the sample into an ion chromatograph without separator column poisoning by the transition metal ions. Fluoride (F-) and phosphate (P043-) were determined in 24 phosphate rock processing and waste material samples by the IC method. The results were compared with a pyrohydrolytic distillation-titration method for F-and a colorimetric procedure for P043-. Excellent analytical agreement was obtained for F-and p043-values determined by IC and the comparable wet chemical methods. Fluoride values ranged from 0.3 wt-pct in the filter cake to 3.6 wt-pct in phosphate rock concentrate. Phosphate values ranged from 1.2 wt-pct in the filter cake to 33.8 wt-pct in the rock concentrate. Fluoride, chloride, phosphate, nitrate, and sulfate in several CKD samples were determined by the IC method and standard wet chemical techniques. Excellent agreement was obtained between the two methods for all anions. A total of 113 CKD samples from all areas of the United States was analyzed by the IC method. Fluoride values ranged from <0.01 to 0.36 wt-pct. Chloride values ranged from <0.01 to 12.5 wt-pct. Sulfate values ranged from 0.41 to 31.6 wt-pct. Phosphate and nitrate were detected in only about 25 pct of the samples at >0.02 wt-pct. Maximum phosphate and nitrate values were 1.0 and 1.6 wt-pct, respectively.