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As a refractory industrial solid waste, high-alumina fly ash is discharged into nature in large quantities, causing serious environmental harm. The extraction of valuable components, such as aluminum, from high-alumina fly ash has become a research hotspot at home and abroad. The shortcomings of traditional alumina extraction from high-alumina fly ash include long technological processes, large amounts of waste acid and alkali, and serious equipment corrosion. A novel method for alumina preparation by electrotransformation AlCl3 solution(EAS) under NH4Cl catalysis with injected CO2 has been proposed by Northeastern University. The process has advantages, such as short flow and no waste acid discharge. In this study, the influence of initial NH4Cl concentration in the cathodic chamber on solution pH, phase and morphology of electrotransformation products, phase, D(50) and D(90) of roasting products, and Al recovery rate were examined. Simultaneously, EAS was examined and compared with and without injected CO2, as well as EAS under NH4Cl catalysis with and without injected CO2. The results showed that, when the solution in the cathodic chamber was NH4Cl with CO2 injection, with electrotransformation time extension, pH increased slowly and the morphology of electrotransformation products were all rough and fluffy block structures. Increasing initial NH4Cl concentration effectively improved the product crystallization states, roasting products D(50) and D(90), and Al recovery rate.

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The present study attempts to prepare Al-substituted α-Ni(OH)2 and Al-substituted α-Ni(OH)2 with modified interlayer anions by directly immersing pure α-Ni(OH)2 into AlCl3-containing solutions. XRD and FT-IR analysis demonstrated Al-substituted α-Ni(OH)2 can be prepared directly by soaking pure α-Ni(OH)2 into AlCl3 solution. Al-substituted α-Ni(OH)2 with S2O32− as the primary anion in the interlayer can be obtained by immersing pure α-Ni(OH)2 into AlCl3-Na2S2O3 solution. The analysis of Al content in samples demonstrated the Al content in the Al-substituted α-Ni(OH)2 was regulated by adjusting the molar ratio of pure α-Ni(OH)2 soaked in the solution and Al3+ dissolved in the solution. The Al element entered the lattice of pure α-Ni(OH)2 through a process of pure α-Ni(OH)2 dissolved followed by the precipitation of Al3+, Ni2+ and OH−. The S2O32− entered the interlayer of Al-substituted α-Ni(OH)2 through the formation process of the Al-substituted α-Ni(OH)2 or though ion exchange with the intercalated Cl−. The strongly alkaline solution soaking results demonstrated that Al-substituted α-Ni(OH)2 prepared by soaking pure α-Ni(OH)2 into AlCl3-containing solutions could preliminary get stabilized in the strongly alkaline solution.

• Al-substituted α-Ni(OH) 2 was prepared by immersing pure α-Ni(OH) 2 into AlCl 3 -containing solution. • Al atom and S 2 O 3 2- were incorporated in the lattice of α-Ni(OH) 2 by immersing pure α-Ni(OH) 2 into AlCl 3 -Na 2 S 2 O 3 solution. • Al-substituted α-Ni(OH) 2 prepared by soaking pure α-Ni(OH) 2 into AlCl 3 -containing solutions can get a preliminary stability in the strong alkali. The present study attempts to prepare Al-substituted α-Ni(OH) 2 and Al-substituted α-Ni(OH) 2 with modified interlayer anions by directly immersing pure α-Ni(OH) 2 into AlCl 3 -containing solutions. XRD and FT-IR analysis demonstrated Al-substituted α-Ni(OH) 2 can be prepared directly by soaking pure α-Ni(OH) 2 into AlCl 3 solution. Al-substituted α-Ni(OH) 2 with S 2 O 3 2− as the primary anion in the interlayer can be obtained by immersing pure α-Ni(OH) 2 into AlCl 3 -Na 2 S 2 O 3 solution. The analysis of Al content in samples demonstrated the Al content in the Al-substituted α-Ni(OH) 2 was regulated by adjusting the molar ratio of pure α-Ni(OH) 2 soaked in the solution and Al3+ dissolved in the solution. The Al element entered the lattice of pure α-Ni(OH) 2 through a process of pure α-Ni(OH) 2 dissolved followed by the precipitation of Al3+, Ni2+ and OH−. The S 2 O 3 2− entered the interlayer of Al-substituted α-Ni(OH) 2 through the formation process of the Al-substituted α-Ni(OH) 2 or though ion exchange with the intercalated Cl−. The strongly alkaline solution soaking results demonstrated that Al-substituted α-Ni(OH) 2 prepared by soaking pure α-Ni(OH) 2 into AlCl 3 -containing solutions could preliminary get stabilized in the strongly alkaline solution. [ABSTRACT FROM AUTHOR]