1994-02-28_REVISION - M1988112 (2)

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~~ The NEt.P is a relatively simple test which could be conducted quickly in the field (Coasteeh Research Inc., 1989; Miller et al., 1990), a distinct acl~~antage; over thz three previously mentioned tests. However, both Coa:tech Research Inc. (1989) and Miller et al. (1990) indicated that the NAP underestimated the capacity to produce acid. One possible explanation for this flaw is that the hydrogen peroxide "digestion" does not completely oxidize the iron sulphides present in the mine waste samp:.es. Consequently, the acid generatedi in the test is less than the actual acid production potential. The use of hydrogen peroxide to accelentte the oxidation of sulphide minerals was previously applied to determine the acid potential of soils (Sobek et al. 1978). Mirza et al. (1992) tested this method and reported incomplete ~~xidation of coal, coal pyrite, and ore pyrite. Finkelman and Griffin (1986) proposed another method, referred to a<; the Hydrogen Peroxide Test, for deternrining the pyrite content of coal related wastes. Coastex:h Research Inc. (1989) applied this technique to hard rock mine samples and concluded the method was "too inaccurate and erratic to be of real use." O'Shay et al. (1990) subsequently modified the method of Finkt;lman and Griffin (1986) and achieved pyrite recoveries on pyrite standards of 97 to 102%, as compared to 61 to 171% for the original method. Thus, the modified technique was highly accurate in determining the pyrite content of the standards, which suggests that similar modific;rttion may improve the accuracy of the NAP Test. This paper presents results from such a madificadon, and compares these results to those of other static tests and the Net NP determined by mineralogical analyses. Based on the results, field application of the test is discussed. Materials METHODS Four waste rock samples, identified as RK1 to RK4, and six tailing samples, identified as TLl to TL6, were collected for testing. The mine waste sample were split into different subsamples for subsequent chemical and mineralogical analysis and static testing. The splitting procedure was tested by analyzing the sulphur and cazbon dioxide content of three sample splits, to ensure uniformity of the samples generated. Sulphur was analyzed by LECO induction f~.rrnace and sulphate was analyzed following a sodium carbonate leach. Carbon dioxide was analyzed using a Coolermetrics carbon dioxide analyzer. Silica and major metal components were extracted using bor<<te fusion and analyzed using DC Plasma. X-ray diffraction (XRD), in ccmjunction with the chemical analyses, was used for mineral identification as well as for determination of the approximate modal composition. Static Test Procedures Standard Acid-Base Accounting, Modified Acrid-Base Accounting, and the B. C. Research initial Tests were conducted using the methods of Sobek et al. (1978), Iawrence (1990), and 147