Research Progresson Harmless Treatment and Resource Utilization of Spent Cathode Carbon from Aluminum Electrolysis
Spent cathode carbon(SCC)is a solid hazardous waste generated during the dismantling of aluminum electrolytic cells,in which toxic substances such as cyanide can cause irreversible harm to the environment,but large-scale SCC is rich in carbonaceous components and fluoride,which has high recycling value and green significance as an important secondary resource.The harmless treatment of SCC is mainly to detoxify cyanide and fluoride,while cyanide is easy to decompose,but the high content and reactivity of fluoride makes it easy to produce secondary fluorinated solid waste through pyrometallurgical treatments,while hydrometallurgical treatment make it difficult to completely dissolve fluoride in the carbon block,resulting in low purity of recovered carbon.HF and fluo-ride produced in the process of SCC treatment have serious corrosion on equipment,and have high requirements on equipment perfor-mance and high maintenance cost.Overcoming this technical difficulty provides favorable conditions for the realization of large-scale treatment of SCC.At present,the harmless treatment of SCC in aluminum electrolysis mainly includes pyrometallurgical treatment,hy-drometallurgical treatment and combined treatment.Combustion treatment to achieve the decomposition of cyanide and fluoride,the emitted fluoride can be collected and treated on the one hand,and on the other hand it can be detoxified and converted for recovery,carbonaceous components are generally used as fuel to provide a heat source,with low resource utilization and added value,making it difficult to meet the current demand for green cycle development.The recovery of spent cathode by high-temperature processes of oxy-gen-controlled treatment and vacuum treatment,these processes have good effect of fluoride removal and simple operation,but gener-ally high energy consumption.The vacuum distillation process has the advantages of simple process and low production cost.Carbon and electrolyte can be recovered from spent cathode carbon block,but refractory substances are difficult to separate from SCC,so the quality of recovered carbon needs to be improved.The quality of carbon recovered by chemical leaching process or alkali fusion process is better,but the treatment process is complicated and the waste water is difficult to be treated.Many studies have shown that the use of microwave,ultrasonic,mechanical activation and other auxiliary means to cooperatively treat SCC can achieve high efficiency and remarkable recycling effect.However,higher technical requirements,treatment costs,batch volumes and difficulties in the recycling field limit the advancement of industrial treatment and resource recycling of spent cathode carbon in aluminum electrolytic,and the de-velopment of efficient,low-cost and high-utilization treatment methods are essential.This review introduced the technical methods,process characteristics and development status of harmless treatment of SCC from aluminum electrolysis in recent years,as well as the ways of resource utilization and value-added development direction of SCC,such as preparation of lithium battery electrode materials,synthesis of silicon carbide,used as a reducing agent recovery of valuable metals from the by-products of metallurgical industry produc-tion,etc.,which could provide technical reference for harmless treatment and resource utilization of SCC in aluminum electrolysis.The recycling of SCC in aluminum electrolytic and the broadening of its applications was the mainstream development trend now and in the future.The current recycling of SCC mainly included:the use of high temperature roasting process,alkali fusion process or high temperature graphitization process to prepare electrode materials for lithium batteries,but the initial Coulomb efficiency and cycle per-formance and other properties needed to be improved to meet the practical application.SCC was co-processed with coal gangue to pre-pare silicon carbide,and the solid waste could be effectively converted into raw materials for production.SCC could be used as a reduc-ing agent to recover valuable metals from red mud,electroplating sludge and copper slag without purification of valuable components,which was one of the lower treatment cost ways.The preparation of graphene oxide from SCC as an organic pollutant absorber in water,and the oxidative exfoliation of SCC exhibited a defected structure with enhanced specific surface areas and plenty of oxygen-contained functional groups,thus making it an excellent absorber of organic pollutants in water.
spent cathode carbon(SCC)resourcefulness recyclingharmless treatmenthigh temperature roasting processchemi-cal leaching
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