Zeolite sieve can dry continuously
15 Jan 2000
Christison Scientific Equipment, based in Gateshead, has announced the introduction of a novel molecular sieve technology called Z-Mem, which is capable of continuous drying.
Conventional zeolite structures only absorb 10-15 per cent of their weight of water before the membrane needs to be separated from the sample and regenerated.
The development of the continuous Z-Mem overcomes this limitation. Aluminosilicate crystals containing alkali metal ions form zeolite molecules, a three-dimensional, crystalline solid with a central cavity. Z-Mem is a lattice of such molecules, deposited onto a porous support in effect, a sub-nanometer-scale molecular sieve.
The metal counter-ion used to balance the electro-negativity of the crystal structure determines the exact nature of the sieve. Potassium and Sodium give pore diameters of 3.2A and 4.2A respectively. The variation in Z-mem pore size is typically 0.1A.
When a sample is placed in contact with the membrane, water molecules are absorbed into the zeolite pores. A vacuum applied downstream of the membrane draws out any water absorbed; thus the membrane's active surface is constantly rejuvenated as the water is removed.
