## 3 Results and Discussion  
### Distribution of Components between Phases at Precipitation of Ammonium Alum  
When processing nepheline with a solution of ammonium bisulfate, along with aluminum, a large number of components are leached, including iron compounds, alkaline and alkaline earth elements, and trace amounts of gallium, zirconium rare earth and other elements. After the stage of hot filtration with the separation of undecomposed residues and subsequent cooling with the release of aluminum ammonium alum, these components are partially co-precipitated together with alum and partially remain in the mother liquor 2 (Figure 2). The study of the distribution patterns of the components is extremely important for the subsequent deep purification of the aluminum-containing intermediate compound in accordance with the requirements for alumina as the final product. This is also important for the coarse purification of circulating solutions from impurities in order to prevent their accumulation during the cyclic closed-loop process. Figures 5-7 show data on the distribution of components between the residual solution and alum crystallized from primary filtrates and washing solutions. On the ordinate axes, the values of the distribution coefficients between the phases are plotted, namely, the ratio of the content of a given element in alum (mol/kg) to its total content in an equilibrium solution (mol/L). On the abscissa axes are the values of the total sulfate content in the equilibrium solution. As can be seen from the dependences presented in Figure 5, iron and aluminum behave in opposite ways in terms of their distribution between phases. With an increase in the total sulfate concentration in mother liquor solution (correlating to the concentration leaching agent), aluminum more and more selectively precipitates in the form of alum and, starting from the concentration of ammonium bisulfate in the solution of 3 mol/L, practically quantitatively precipitates with a distribution coefficient of more than 100. At the highest concentration of ammonium bisulfate, about 7.5 mol/L, the distribution coefficient reaches into the several hundreds. At the same time, with an increase in the concentration of sulfate, an increasing proportion of iron remains in the mother liquor;at ammonium bisulfite concentrations of more than 4 mol/L, the distribution coefficient between the phases becomes less than one unit. The observed effect can be explained by the significantly higher solubility of double ammonium-iron sulfate [10] compared to the similar aluminum compound, the solubility of which decreases with increasing ratio NH\({}_{4}\)/Al in the system [23]. Gallium is similar in its chemical properties to aluminum, and its distribution depends on the concentration of total sulfate in a similar way. Figure 5: Distribution of trivalent metals: aluminum, iron, and gallium between the phases of ammonium album and the residual solution depending on the total concentration of sulfate. Figure 6: Distribution of alkali metal and ammonium ions between the solid alum and the liquid phases (dashed lines—theoretical dependencies). The patterns of distribution of singly charged alkali metal ions between the phases are very interesting (Figure 6).