The effect of the addition of the hygroscopic salt of MgSO₄ on the physicochemical properties of an aluminum oxide-based adsorbent

Two-component adsorbents “MgSO₄/Al₂O₃” with different hygroscopic salt contents in the structure were synthesized and studied. Samples were obtained by impregnation from an excess of MgSO₄ solution onto alumina adsorbent granules. The initial alumina sample was obtained by centrifugal thermal activation. The geometric mean values of the granules are l = 3,5 mm, d = 2,5 mm. Changes in the structure of the samples are presented after the stages of impregnation, drying and calcination: phase composition and texture characteristics. The bayerite phase is not detected in the composition after the main stages of the synthesis of the adsorbent. The specific surface area value decreases with increasing MgSO₄ concentration in the samples from 290 m²/g for the initial sample to 112 m²/g for the sample with the maximum salt content. Also, the average pore diameter in the samples increases and the value of the total pore volume decreases with increasing salt concentration. There are studied changes the trends in the strength of granules with increasing salt concentration. It is shown, the inflicted hygroscopic salt is evenly distributed over the volume of the porous matrix, with the exception of the sample with a content of 15,4% of the mass. MgSO₄. The values of the dynamic capacity of the samples increases after impregnation and decreases as the amount of introduced salt increases. In addition, the kinetics of water vapor absorption under dynamic conditions and the equilibrium adsorption capacity were studied. Samples with concentration 11,1% mass and lower has lower adsorbtion capacity than for the original sample. The sample with the highest salt content in the structure (15,4% wt. MgSO₄) during the kinetics experiment did not reach the equilibrium value of the adsorption capacity, however, even with incomplete saturation, it has a larger capacity for water vapor than the initial sample. An equation describing of the kinetics of adsorption on the obtained alumina samples is selected.

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