Innovative Sulphite Method for Optimizing Aluminum Oxide Production from Alunite Ore

This study presents an innovative engineering process for extracting high-purity, siliconfree aluminum oxide from alunite ore using sulfurous acid.This method is distinct in its operation at lower temperatures and pressures, thus bypassing the need for high-pressure equipment, which typically increases production costs.The process flow has been optimized for efficiency, starting with alunite ore that is crushed and dewatered before treatment.When exposed to sulfurous acid, samples of alunite dehydrated at 823-858 K for two hours exhibit significantly improved solubility.Optimal dissolution conditions were identified as a temperature of 323 K, a solid-to-liquid ratio of 1:10, a maximum particle size of 2-310 m, and a stirring time of 120 minutes.Under these conditions, the alunite dissolves fully, producing a filtrate containing aluminum salts, sodium and potassium sulfates, and divalent iron salts.The subsequent steps involve heating the filtrate to 373 K, recycling excess SO, and treating the solution with a NaOH solution.This reaction precipitates Fe(OH) and Al(OH).A s more alkali is introduced, aluminum hydroxide dissolves as Na[Al(OH)], while Fe(OH) is filtered out.The Na[Al(OH)] is then hydrolyzed to yield high-purity Al(OH), which decomposes to form AlO with a notable yield of 92.39%.The process is environmentally friendly and waste-free: byproducts, such as NaSO and KSO, can be used in fertilizer production, and the residual sludge is suitable for construction material.Compared to conventional recycling methods that require costly solvents, this approach is economically viable and sustainable.Semiindustrial studies of this process are currently being conducted at the Ganja Aluminium Smelter to further assess its commercial feasibility.