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Updated: Dec 5, 2025

Two-way Valorization of Blast Furnace Slag: Synthesis of Precipitated Calcium Carbonate and Zeolitic Heavy Metal Adsorbent
Published on: February 21, 2017
An environmental-friendly process for dissociating toxic substances and recovering valuable components from spent
Zhen Yao1, Qifan Zhong2, Jin Xiao2
1School of Metallurgy and Environment, Central South University, Changsha 410083, PR China; School of Materials and Architectural Engineering, Guizhou Normal University, Guiyang 550001, PR China.
Abstract:
Spent carbon cathode (SCC), a hazardous solid waste discharged from the aluminum electrolysis industry, has a serious environmental pollution risk. This study aims to explore an environmental friendly process for dissociating toxic substances and recovering valuable components from SCC. Parameters of molten salt-assisted roasting and water leaching were optimized. A possible dissociation mechanism of toxic substances was proposed. Results showed that 99.12% of cyanide was decomposed and 96.63% of fluoride was leached under optimal conditions. The recovery route of fluoride was designed according to the solution equilibrium chemical calculation and the difference in solubility and particle size between the recovered products. Exhaust gas with a high concentration of CO and CO2 was used for the carbonation of the leaching solution to recover cryolite. Effects of reaction conditions on precipitation mass and phase composition of recovered cryolite were investigated in detail. Characterization results indicated that the crystallinity and particle size of cryolite recovered under optimal conditions were extremely similar to those of commercial products. Finally, NaF and Na2CO3 were separated and recovered via evaporative crystallization combined with selective filtration. This proposed process with circular economy and green chemistry characteristics is expected to recover valuable components while minimizing environmental hazards of SCC.
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