Chemistry of the Acid Neutralization Capacity of Bauxite Residue
Chemistry of the Acid Neutralization Capacity of Bauxite Residue
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DOI：
10.1089/ees.2007.0228
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发表时间：
2009-05-01
影响因子：
1.8
通讯作者：
Lowry, Gregory V.
中科院分区：
文献类型：
--
作者：
Khaitan, Sameer;Dzombak, David A.;Lowry, Gregory V.
铝土矿残渣（红泥-RM）是拜耳法将铝土矿精炼为氧化铝的副产品，具有强碱性（pH值接近13），其处理和储存带来了独特的废物管理挑战。在这项工作中，酸中和能力（ANC）的牙买加RM从存储设施在得克萨斯州的舍温，进行了测量，并通过分析的RM组合物和化学平衡建模的固体和水相的贡献ANC进行了研究。RM的ANC通过RM浆料的快速和长期酸滴定至4.5、6、8和10的pH终点来测量。发现牙买加RM的ANC对于长期滴定至pH 4.5和10分别为1.8和0.5 mEq/g RM。使用RM组成的信息，在MINEQL+中制定了化学模型，并用于研究负责向RM浆料中添加强酸的pH值变化的反应。通过建模，确定ANC主要归因于方解石（CaCO 3（s））、铝酸三钙（Ca 3Al 2 O 6（s）; C3 A）、硅酸铝钠（NaAlSiO 4（s））的溶解，以及残余孔隙水中Al（OH）（4）（-）、NaOH和NaCO 3-的中和。通过对铝土矿残渣滴定前后的X射线衍射分析，证实了矿物的存在。该化学模型提供了关于控制RM的酸碱行为的反应以及在各种pH值下从RM浆料中浸出金属的可能性的见解。它可用于估计中和给定量RM所需的酸剂量。
Bauxite residue (red mud-RM), a byproduct of the Bayer process for refining bauxite to alumina, is highly alkaline (pH similar to 13) and its treatment and storage poses unique waste management challenges. In this work, the acid neutralizing capacity (ANC) of Jamaican RM from a storage facility in Sherwin, Texas, was measured, and the solid and aqueous phase contributions to the ANC were investigated through analyses of the RM composition and chemical equilibrium modeling. The ANC of RM was measured by both rapid and long-term acid titration of RM slurries to pH endpoints of 4.5, 6, 8, and 10. The ANC of Jamaican RM was found to be 1.8 and 0.5 mEq/g RM for long-term titration to pH 4.5 and 10, respectively. Using information on RM composition, a chemical model was formulated in MINEQL+ and used to investigate reactions responsible for the changes in pH for strong acid additions to RM slurry. Through modeling, the ANC was determined to be attributable primarily to dissolution of calcite (CaCO3(s)), tricalcium-aluminate (Ca3Al2O6(s); C3A), sodium-aluminum-silicate (NaAlSiO4(s)), and to the neutralization of Al(OH)(4)(-), NaOH, and NaCO3- in the residue porewater. The presence of the minerals was confirmed through X-ray diffraction analyses of the bauxite residue before and after titration. The chemical model provided insights about the reactions controlling acid-base behavior of RM and the potential for metal leaching from the RM slurry at various pH values. It can be used to estimate the dose of acid required to neutralize a given quantity of RM.