Kinetics and Mechanism of the Ammonia Pressure Leaching of Laterite Ore Containing Nickel

• Shimakage Kazuyoshi

  Department of Metallurgy, Faculty of Engineering, Tohoku University

• Hoshi Masayoshi

  Department of Metallurgy, Faculty of Engineering, Tohoku University

• Ejima Tatsuhiko

  Department of Metallurgy, Faculty of Engineering, Tohoku University

抄録

In the presence of oxygen more than an atmospheric pressure, laterite ore containing nickel which is previously reduced dissolves in a NH₃–(NH₄)₂SO₄ solution by the following reaction: Ni·Fe+O₂+(n+m−4)NH₃+4NH₄⁺→Ni(NH₃)_n²⁺+Fe(NH₃)_m²⁺+2H₂O where n and m are the integral numbers between 1 and 6, respectively. In the current investigation, the kinetics of this reaction has been examined by changing the concentrations of NH₃ and NH₄⁺ ion, partial pressure of oxygen, stirring velocity, temperature, and surface area. The leaching reaction of laterite ore in a solution containing both ammonia and ammonium sulfate is shown to be the zero-th order, because of the linearity found in the leaching time curve. The leaching reaction is accelerated by increasing temperature and stirring the leaching solution. The apparent activation energy calculated from the Arrhenius plots is 4690 cal/mol. The leaching rate is also proportional to the surface area and the partial pressure of oxygen. Therefore, the transport process of the dissolved oxygen in the leaching solution is assumed to be the rate-determining step of the leaching reaction and the chemical process may be much faster than the diffusion rate of oxygen. In addition, the leaching reaction of laterite ore is well explained by an electrochemical mechanism, and the cathodic reaction of oxygen is found to be the rate-determining step of the leaching reaction.<BR>According to the experimental results obtained, the leaching rate equation for laterite ore containing nickel in a NH₃–(NH₄)₂SO₄ solution under the presence of pressurized oxygen is as follows:<BR>Leachingrate=K·S·Po₂·V(x)·e^−4690⁄RT<BR>where K is the rate constant, S the surface area of the laterite ore reduced, Po₂ the partial pressure of oxygen, kg/cm², V(x) the stirring velocity, rev/min (x is unknown because the sample is in the pulverized state), R the gas constant, and T the absolute temperature.

収録刊行物

• Transactions of the Japan Institute of Metals

  Transactions of the Japan Institute of Metals 15 (2), 121-128, 1974

  社団法人 日本金属学会

キーワード

• General Engineering

詳細情報

• CRID: 1390282680095893760
• NII論文ID: 130003485277
• DOI: 10.2320/matertrans1960.15.121
• ISSN: 24324701
• ISSN: 00214434
• Web Site: https://www.jstage.jst.go.jp/article/matertrans1960/15/2/15_2_121/_pdf
• 本文言語コード: en
• データソース種別:
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