Determination and modeling of the solubilities of NH4Al(SO4)2•12H2O in the NH4+-Al3+-H3O+-HSO4--SO42--H2O system at different H2SO4 molalities and temperatures

Solubilities of NH4Al(SO4)(2)center dot 12H(2)O in the NH4+-Al3+-H3O+-HSO4--SO42--H2O system, as well as the densities of the saturated solution were measured at the temperature range from 293.15 to 323.15 K and at the H2SO4 molalities varying from 0.6 to 3.6 mol/kg. At the same temperature and H2SO4 molality, the solubilities of (NH4)(2)SO4 sharply deceased with the addition of Al-2(SO4)(3) from 0 to a turning point at first and then slightly decreased. The electrolyte NRTL model embedded in Aspen plus was applied to model the solubilities of NH4Al(SO4)(2)center dot 12H(2)O in the NH4+-Al3+-H3O+-HSO4--SO42--H2O system. The model parameters were obtained via regressing the experimental results and the total relative average deviation of temperature is 1.04%, indicating that the calculation values are good with experiment data. With the newly obtained model parameters, the fundamental solubilities of NH4Al(SO4)(2)center dot 12H(2)O in the NH4+-Al3+-H3O+-HSO4--SO42--H2O system can be calculated precisely for its crystallization process. (C) 2015 Elsevier B.V. All rights reserved.