Detoxification and Recovery of Spent Carbon Cathodes via NaOH–Na 2 CO 3 Binary Molten Salt Roasting–Water Leaching: Toward a Circular Economy for Hazardous Solid Waste from Aluminum Electrolysis

作者：Zhen Yao, Jin Xiao, Qiuyun Mao, Gang Wang, Lei Tang, Zihan You, Qifan Zhong · 发表于：ACS Sustainable Chemistry & Engineering · 年份：2020 · DOI：10.1021/acssuschemeng.0c06067 · 被引用次数：54 · 研究领域：Recycling and Waste Management Techniques、Extraction and Separation Processes、Molten salt chemistry and electrochemical processes

The conversion of solid waste into secondary resources has become a prerequisite for the sustainable development of the industry. This study focused on the development of the detoxification process for spent carbon cathode (SCC) without environmental pollution risks and the exploration of the recycling direction of recovered carbonaceous materials. First, the mechanism of thermodynamic conversion and decomposition of toxic substances was explored. Parameters of NaOH–Na 2 CO 3 binary molten salt roasting were optimized through an orthogonal design and a single-factor experiment, and gas release behavior during detoxification treatment was investigated. Results showed that most of the fluoride and cyanide were dissociated and decomposed, and the leaching concentration of fluoride and cyanide was as low as 7.58 and 0.12 mg/L after detoxification treatment, respectively. Then, a multistage recovery process of fluorine from fluorine-containing leachate was designed, and the comprehensive utilization of exhaust gas and the recycling of the reaction reagent were realized simultaneously. The possibility of recovering graphitized carbon blending to prepare carbon anodes was discussed in detail, and the catalytic mechanism of main impurity elements on the O 2 /CO 2 reactivity of carbon anodes was investigated via density-functional-based tight binding (DFTB). The results showed that the Boudouard reaction and carbon–O 2 reaction were affected because of the presence of Ca or Na, and th...