Mass transfer process and separation mechanism of sulfuric acid and aluminum sulfate mixture based on IEC technology: Modeling

[Display omitted] •A cooperative adsorption isotherm was proposed for H2SO4 and Al2(SO4)3.•A dynamic model was proposed to interpret the mass transfer process.•A column model was developed to describe the separation mechanism.•Metal-ions of different valence affected the H2SO4 ‘concentration’. Ion exclusion chromatography (IEC) is an efficient technique used for the separation of strong electrolytes from weak electrolytes and nonelectrolytes. This work focuses on the assessment of mass transfer process and separation mechanism of H2SO4 and Al2(SO4)3 on the strong base quaternary ammonium I anion exchange resin A-853E. A dynamic model for IEC was proposed and explicitly taken into account the Donnan equilibrium. The result showed that Donnan effect played a significant role in the mass transfer process of ionic species, which was interpreted as the inability of co-ion (Al3+) to pass through Donnan membrane, while the counterion (SO42-) can enter resin pores due to electrostatic attraction. Meanwhile, a column model, based on Donnan equilibrium and cooperative adsorption isotherm, was then developed. The model successfully predicted the concentration profiles of mixed-ion (Al3+ and SO42-) at the outlet of the fixed-bed in the dynamic separation process. The results indicated that the Al3+ promoted the adsorption of SO42- on the resin in view of presence of ‘concentration’ phenomenon. The separation mechanism of Al3+ and SO42- was presented combining model prediction and experimental results. Finally, the influence of three different valence states of metal ions (Na+, Fe2+, Al3+) on the degree of H2SO4 ‘concentration’ was investigated to further verify the Donnan effect.