Osmotic drying of gelcast bodies in liquid desiccant

Osmotic drying of gelcast alumina bodies was carried out in water solutions of various polyethylene glycols (PEGs) with molecular weight ranging from 1000 to 80,000 g/mol. Up to 30% of the water content could be removed from the gelcast bodies immersed in a 43 wt% solution of PEG 80000. It was found that PEG 1000 was a less effective desiccant than the PEGs with higher molecular weights, even if the osmotic pressure was similar (4.9 MPa). The smaller PEG molecules penetrated the gelled bodies and reduced the dewatering. Moreover, the penetrated PEG molecules affected the pore structure of green bodies and in this way influenced the sintering behaviour. The time dependence of dewatering and the effect of the size of gelcast bodies were investigated and correlated with the green body structure and sintering behaviour in order to optimize the osmotic drying process.