Study on harmless and resources recovery treatment technology of waste cathode carbon blocks from electrolytic aluminum

The paper provides a brief introduction in the physical and chemical properties of waste aluminum cathodes, and its harmless treatment technology and resource comprehensive utilization technology. The main chemical composition of the waste cathode carbon blocks of electrolytic aluminum are carbon, fluorine, sodium, aluminum, calcium, silicon and etc. The main mineral components of waste cathode carbon include sodium fluoride, cryolite, calcium fluoride, silicate minerals and so on, therein the fluorine content is about 9.86%, and the content of cyanide ions (CN-) is 0.82ppm, which are the most important reasons leading serious environmental hazards caused by the waste aluminum cathodes; and in which carbon has been graphitized mostly and the content of it is up to 58.56%, having a high recycling value. Using the flotation-chemical treatment process to recover fluorine and carbon, carbon powder was obtained with the carbon content of 88.00%, recovery of 95.90%; and the content of sodium and fluoride in sodium fluoride product are 49.33% and 38.53% respectively, the total recovery of fluorine in fluoride sodium and other products is 90.10%. It proves that the cyanide in the waste cathode carbon block of electrolytic aluminum has been completely decomposed. The process takes fully the factors of crushing, grinding, flotation, chemistry, waste gas absorption technology into account, and achieves the purpose of harmless treatment and comprehensive utilization of resources (C) 2012 Selection and/or peer-review under responsibility of Basel Convention Coordinating Centre for Asia and the Pacific and National Center of Solid Waste Management, Ministry of Environmental Protection of China.