Mylonite rocks of the Abu Rusheid area, Southeastern Desert of Egypt, were physically upgraded producing Zr, Ti, Nb, and REEs concentrate. Comparative fusion digestion studies of the concentrate using NaOH and KOH were carried out. Dissolution efficiencies of 83.4%, 99.8%, 69.7%, and 97.1% for Zr, Nb, Ti, and REEs, respectively, were accomplished using NaOH under 1023 K, 90 min, 1:1.25 ratio, and 74 µm particle size. However, 79.5, 87.3, 90.5, and 97.4% were achieved using KOH under 1023 K, 90 min, 1:1.75 ratio, and 44 µm particle size. Suggested pseudo-reversible first-order, uptake general, and shrinking core models fitted well with the experimental results using the two alkalis. Convergent activation energies were calculated using the three models. A suggested Floatotherm including the Van’t Hoff parameters model showed endothermic and spontaneous behavior with a decrease in the randomness at the solid/solution interface during the attack of fused alkali on the concentrate particles.

埃及东南部沙漠 Abu Rusheid 地区的糜棱岩经过物理升级，生产出 Zr、Ti、Nb 和 REE 精矿。使用 NaOH 和 KOH 对浓缩物进行了比较融合消化研究。Zr、Nb、Ti 和 REE 的溶解效率分别为 83.4%、99.8%、69.7% 和 97.1%，使用 NaOH 在 1023 K、90 分钟、1:1.25 比率和 74 µm 粒径下完成。然而，在 1023 K、90 分钟、1:1.75 比率和 44 µm 粒径下使用 KOH 实现了 79.5、87.3、90.5 和 97.4%。建议的伪可逆一阶、吸收一般和收缩核心模型与使用两种碱的实验结果非常吻合。使用这三个模型计算会聚活化能。