Research on a modified silica gel-based desiccant

Since the water absorption ratio of ordinary silica gel is not high and the regeneration temperature of silica gel modified separately by magnesium chloride or calcium chloride only is relatively high, a new kind desiccant was prepared by modifying the silica gel with magnesium chloride and calcium chloride simultaneously. Using the solution with appropriate ratio of magnesium chloride and calcium chloride as the composite modifier could make the modified silica gel have high hydroscopic ability and lower regeneration temperature. The differential scanning calorimeter (DSC) and the thermogravimetric analysis (TG) were used to investigate the regeneration performance, hydroscopic properties and the corresponding activation energies of water desorption of the silica gel modified by the composite modifier. The results show that, at the saturated air humidity corresponding to room temperature and using solution composed of 0.25 mol·L^-1 of calcium chloride and 0.25 mol·L^-1 of magnesium chloride as modifier, the water absorption capacity of the modified silica gel enhances greatly, which is about 2 times higher than that of the unmodified silica gel. Besides, the water absorption rate of the modified silica gel is significantly improved by 3.5 times and more, and its regeneration temperature is about 10°C lower. Moreover, after recycling for 6 times, the regeneration ratio of the modified silica gel is still as high as 92%, and which remains unchanged basically.