Evaluation of Neutralization Potential Determinations for Metal Mine Waste and a Proposed Alternative

Standard acid-base accounting (standard ABA), modified ABA, and B.C. Research initial static tests tended to overestimate the neutralization potential (NP) present as calcium carbonate and magnesium carbonate, with the extent of overestimation depending on the minerals present in the 10 metal-mine wastes examined.For 6 of the 10 samples the static test NP values were within about 10 kg/mt CaC0 3 of the calculated mineralogic NP.These samples were composed largely of qua1tz and sheet silicates (mica, chlorite, kaolinite, montrnorillonite).The excess acid neutralization measured for these samples was apparently due to the presence of some (less than 10 % ) calcium feldspar in the samples.For the standard ABA and modified ABA methods, the NP overestimation was higher (13 to 47 kg/mt CaC0 3 ) for samples containing larger amounts of calcium feldspar, pyroxene, olivine, or iron carbonate minerals.The extent of overestimation for the B.C. Research initial NP was typically slightly higher than the standard ABA and modified ABA and was greatest for samples containing iron carbonate.The maximum overestimations by the standard ABA, modified ABA, and B.C. Research initial test NP values were 33, 31, and 49 kg/mt CaC0 3 , respectively.A newly proposed method of NP determination, NP available above pH 6, was more accurate than these three methods.Six of the 10 NP values determined by this method were approximately equal to the mineralogic NP values.For the remaining 4 samples, this NP was within 3 kg/mt CaC0 3 of the mineralogic NP.