Abstract
-. A ststistic~ sensitiviw ~alysis was conduct~ to idcnt~ predotit factors ~ntrolling leachate quality hm humidity cell, soxhlet, and column overburden leaching tests. Soxhlet and weathering cell tests exhibited the greatest sensitivity to(1) storage condition (temperature and humidity); and (2) leaching inferwaf (time between lewhinga). The factors ofp~”cle size and Ieachanf temperature played secondary roles in influencing lcachate quality. High temperature, oven sample storage selectively promoted pyrite oxidation over carbonate dissolution, with pyrite oxidation reactions that were continuous and thermally enhanced, and discontinuous calcium carbonate dissolution which varied with the water content of the overburden sample. For short leaching intervals, (2 days), pore water was retained fm a greater percentage of the total storage internal, and acidity produced by pyrite oxidation was neutralized by carbonate dissolution. For longer leaching intervals (7 days), pore water was retained for a smaller portion of the total storage interval, and acidity was not neutralized by carbonate dissolution. Weathering cells and columns exhibited sensitivity to particfe size which controlled the rate of water movement through the overburden material. Short residence times fm pore water in the large grained overburden samples favored low alkalinity production. Fine graimd overburdens, with small pore sizes, resulted in slower water movement favoring greater alkalinity production and acid neutralization. Acid and sulfate production ratea exhibited logarithmic correlation with particle size. Acid production rates for high NP overburdens were positively comelated with the logarithm of particle size, while acid production rates for low NP overburdens were negatively correlated with particle size. Sulfate production rates were negatively correlated with particle size. The results of this study aid in the selection and design of overburden leach tests for acid mine drainage prediction.
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More From: Journal American Society of Mining and Reclamation
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