The residue generated in the crystallization stage of the Bayer process to obtain alumina may be used for sodium recovery. The addition of calcium hydroxide (Ca(OH)₂) to the residues of the Bayer process may become an alternative study for recovering the caustic soda (NaOH) inserted in the process, so the objective of this work is to utilize the causticization technique in a real residue obtained from the crystallization step of the Bayer liquor. The residue characterized presented 13% Al, so this indicated that there were losses of this element in the Bayer process. Also, the presence of Na₂C₂O₄, Na₂CO₃, and NaAlO₂ were observed. The total sodium recovery was 87%, and the best condition for causticization to occur was in the use of a 1:1 molar ratio (Na₂C₂O₄ and Ca(OH)₂), during 6 h of reaction, and at 80°C, with the conversion of 96% of the organic carbons present in the solution. The causticization was effective in separating sodium from residue in the removal of oxalates, organics, and aluminium, and it provided a reaction that separated oxalates and carbonates that are harmful to the aluminium obtaining process.

中文翻译：

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氧化铝选矿拜耳液结晶废液中钠回收

在拜耳法获得氧化铝的结晶阶段产生的残渣可用于钠回收。将氢氧化钙 (Ca(OH) ₂ ) 添加到拜耳工艺的残留物中可能成为回收工艺中插入的苛性钠 (NaOH) 的替代研究，因此本工作的目的是利用苛化技术在从拜耳液的结晶步骤中获得的真实残留物。残留物表征为 13% Al，因此这表明在拜耳法中该元素有损失。此外，Na ₂ C ₂ O ₄、Na ₂ CO ₃和 NaAlO _2的存在被观察到。总钠回收率为 87%，发生苛化的最佳条件是使用 1:1 的摩尔比（Na ₂ C ₂ O ₄和 Ca(OH) ₂），在反应 6 小时期间，在80°C，溶液中 96% 的有机碳被转化。苛化在去除草酸盐、有机物和铝的过程中有效地将钠从残渣中分离出来，并且它提供了分离对铝制取过程有害的草酸盐和碳酸盐的反应。