Evaluation of Pyrite Dissolution Rates by Two-step Leaching Model.

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  • ２段階溶出モデルによる黄鉄鉱の酸化・溶解速度の評価
  • 2 ダンカイ ヨウシュツ モデル ニ ヨル オウテッコウ ノ サンカ ヨウカイ ソクド ノ ヒョウカ

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Abstract

Batch leaching experiments in aerated conditions for two different types of crushed pyrite were carried out by measuring changes in pH and concentrations of Fe and SO4 for leachate. The results showed that leachate pH depended on the solid-liquid ratio and leaching period as well as the pyrite used, and that the electric conductivities and the concentrations of Fe and SO4 increased with the decrease in leachate pH. The chemicalforms of iron and sulfur in the leachate were identified as ferrous ions and sulfate ions, respectively. The concentrationchanges observed illustrated that the initial leaching rates of ferrous and sulfate ions from both pyrite samples were demonstrated by a first-order reaction with respect to the solid-phase concentration. This indicates that the initial dissolution process was governed by a surface reaction. On the other hand, the subsequent dissolution of one of the samples was expressed by a function of the square root of the leaching period, suggesting that the rate-determining process was diffusion in the crushed pyrite sample. These two different mechanisms were found to affect the dissolution rate of pyrite. Therefore, the initial leaching may be expected to be more critical to the chemical properties of leachate than the following leaching, due to the estimated diffusion coefficient within the pyrite being as low as 10-16 cm2/s. In addition, the diameter of the crushed pyrite affected the chemical properties of the leachate, but not the leaching rate.

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