Some different possible solutions to the problem of industrial waste originating from primary aluminium production (also known as SPL) have been investigated. The latest techniques to treat SPL are presented, with the highlight being flotation and chemical treatment technology. Laboratory tests confirmed that the SPL treatment model is not feasible and viable within partial solutions. Only the systematically achieved solution can be in accordance with a wide range of contemporary demands. Partly, the cause is the allotropic form of the carbon cathodes produced and partly also the impurities in the waste material that prevent an effective one-phase treatment. Laboratory investigations of reactive extraction open up the possibilities for wide SPL material utilization. The preliminary inquiry confirms that the interdisciplinary approach leads to open solutions leading to possible market interest or generated value from the waste as the main goal of a circular economy.

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Spent Pot Lining (SPL) cathode pot, waste from the aluminium smelting process needs detoxification from cyanides, washing out water-soluble salts and extraction of the cryolite (Na3AlF6) decomposition products to be recycled. Revealed cryolite decomposition mechanism with NaOH opens possibilities to explore its critical role in the reactive extraction process. Common Na+ ion from NaOH hinders the solubility of the product but also drives mass transfer to the reaction site. Reaction mass balance provides adequate liquid to solid ratio (L/S) and NaOH concentration range. A newly developed kinetic model based on Whitman film theory and NaOH mass flow enables prediction of the reaction time to decompose cryolite to a low enough level. Results show that the internal particle resistance to transport (1/ks) is 19 times larger than the external (1/kl) one and governs the whole process.