Toxic substances, like fluoride salts present in spent cathode carbon (SCC), have been a great risk to the environment and public health. Our approach involves alkali leaching to eliminate soluble fluoride, followed by microwave hydrothermal acid leaching to efficiently remove insoluble CaF from SCC. The optimized conditions, including a temperature of 353 K, a solid–liquid ratio of 1:20, and a 60-minute reaction time, resulted in an impressive 95.6 % removal of fluoride from SCC. Various characterization techniques were employed to analyze the composition, micro-morphology, and elemental content of the materials before and after the leaching process. Furthermore, critical process parameters on the leaching separation of insoluble CaF during microwave hydrothermal acid leaching were systematically investigated. The study removal mechanism revealed the transformation of insoluble CaF in the process of microwave oxidation insertion-hydrothermal acid leaching for SCC. The kinetic characteristics of the two-stage leaching process of CaF at different temperatures were analyzed according to the shrinkage kernel model. The results indicate that the two-stage leaching process of CaF is affected by mixing control and by diffusion control, severally. The expansion of the graphite flake layer of SCC through oxidative intercalation was identified as a critical process for the thorough removal of CaF. Microwave hydrothermal acid leaching demonstrated a 17 % improvement over traditional hydrothermal acid leaching within the same reaction time, showcasing a noteworthy enhancement in fluoride removal. Consequently, the microwave oxidizing intercalation-hydrothermal acid leaching treatment of SCC, as explored in this study, offers an effective approach for achieving deep defluoridation of SCC.

中文翻译：

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微波水热硫酸浸出铝电解废阴极炭高效去除不溶性氟化钙

废阴极碳 (SCC) 中存在的氟化物盐等有毒物质对环境和公众健康构成了巨大风险。我们的方法包括碱浸以消除可溶性氟化物，然后通过微波水热酸浸以有效去除 SCC 中的不溶性 CaF。优化的条件（包括 353 K 的温度、1:20 的固液比和 60 分钟的反应时间）使 SCC 中氟化物的去除率达到了令人印象深刻的 95.6%。采用各种表征技术来分析浸出过程前后材料的成分、微观形貌和元素含量。此外，系统研究了微波水热酸浸过程中不溶性CaF浸出分离的关键工艺参数。研究的去除机理揭示了SCC微波氧化插入-水热酸浸过程中不溶性CaF的转化。根据收缩核模型，分析了不同温度下CaF两阶段浸出过程的动力学特征。结果表明，CaF的两阶段浸出过程分别受到混合控制和扩散控制的影响。通过氧化插层膨胀 SCC 的石墨片层被认为是彻底去除 CaF 的关键过程。微波水热酸浸在相同的反应时间内比传统水热酸浸提高了 17%，显示出显着的除氟效果。因此，本研究探索的微波氧化插层-水热酸浸处理SCC为实现SCC深度除氟提供了一种有效的方法。