Chemical predictive modeling of acid mine drainage from waste rock: model development and comparison of modeled output to experimental data.
White-WW III; Trujillo-EM; Lin-C-K
Proceedings of the International Land Reclamation and Mine Drainage Conference and Third International Conference on the Abatement of Acidic Drainage, April 24-29, 1994, Pittsburgh, Pennsylvania. Washington, DC: United States Department of the Interior, SP 06D-94, 1994 Apr; 1:157-166
The U.S. Bureau of Mines (USBM) is developing a geochemical predictive model for acid mine drainage (AMD) from waste rock associated with metal mining. The model will identify AMD potential during property exploration and development and will facilitate planning of waste-rock handling. This paper presents results on model development and comparison of model output with 90 weeks of kinetic tests (humidity-cell data) for three selected samples. The existing model successfully matched experimental data collected from humidity-cell effluent during the 90-week period. The model (1) predicted the progressive development of acid as well as the decrease in aqueous sulfate and iron concentrations as jarosite precipitated and (2) demonstrated good agreement between modeled output and actual effluent pH, total iron, and sulfate concentrations from the three different samples of waste rock. Sulfide contents of these three samples were 3, 6, and 24 wt %. Although acid-base accounting classified all three samples as potential acid producers, effluent pH from the 3% pyrite sample was neutral to slightly basic during 90 weeks of accelerated weathering. Samples containing 6% and 24% pyrite continuously produced acidic effluent during the same 90-week period. Sulfate-release rates resulting from sulfide oxidation increased with solid-phase sulfide content and decreasing pH. Calcium and magnesium release-rates determined from accelerated weathering of the 3% pyrite sample were projected beyond 90 weeks. This projection suggests that the 3% pyrite sample should develop AMD after 110 to 130 weeks of laboratory-accelerated weathering. The mathematical model also predicts that AMD will occur after 130 weeks.
acid mine drainage; geochemical predictive model; laboratory-accelerated weathering; metal-mine waste rock
Proceedings of the International Land Reclamation and Mine Drainage Conference and Third International Conference on the Abatement of Acidic Drainage, April 24-29, 1994, Pittsburgh, Pennsylvania