School of Metallurgical Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, Shaanxi, China.
School of Metallurgy and Environment, Central South University, 410083, Changsha, China.
J Environ Manage. 2022 Sep 15;318:115503. doi: 10.1016/j.jenvman.2022.115503. Epub 2022 Jun 22.
Spent carbon cathode (SCC) as a hazardous solid waste produced in aluminum electrolysis industry, contains plenty valuable components but generate a seriously threat to the environment. This paper focus on a closed-circuit cycle process for direct treatment of SCC based on the hydrothermal acid-leaching method. Thermodynamic calculation, single factor experiment, orthogonal experiment and kinetic study are utilized to obtain the leaching properties of impurities, optimize the leaching conditions, study the influence of conditions on leaching, and capture the restriction factors of leaching. The results indicate that the carbon content of the treated SCC can reach 97.3% when the leaching condition attach the optimal (liquid-solid ratio of 25 mL/g, temperature of 413 K, time of 270 min and acid concentration of 4 mol/L), and liquid-solid ratio is regarded as the crucial factor influencing on that. In addition, the activation energy of impurities reaches 6.25 kJ/mol and the whole leaching process is controlled by the diffusion extent. Finally, the filtrate after the hydrothermal acid leaching is treated, and calcium fluoride, cryolite and sodium chloride are successfully separated. The proposed process eliminates the harm of SCC to the environment, and completes a closed-circuit cycle for the treatment of SCC and recovery of valuable components. It enriches the hydrometallurgical processes of SCC, and provides an attractive scheme for the treatment of SCC.
废炭阴极（SCC）是铝电解工业产生的一种危险固体废物，含有大量有价值的成分，但对环境造成严重威胁。本文聚焦于基于水热酸浸法的 SCC 直接处理闭路循环工艺。通过热力学计算、单因素实验、正交实验和动力学研究，获得了杂质的浸出特性，优化了浸出条件，研究了条件对浸出的影响，并捕捉了浸出的限制因素。结果表明，在最优浸出条件（液固比 25mL/g、温度 413K、时间 270min 和酸浓度 4mol/L）下，处理后的 SCC 的碳含量可达到 97.3%，而液固比被认为是影响浸出的关键因素。此外，杂质的活化能达到 6.25kJ/mol，整个浸出过程受扩散程度控制。最后，对水热酸浸后的滤液进行处理，成功分离出氟化钙、冰晶石和氯化钠。该工艺消除了 SCC 对环境的危害，完成了 SCC 处理和有价值成分回收的闭路循环。它丰富了 SCC 的湿法冶金工艺，为 SCC 的处理提供了一个有吸引力的方案。
