REJECTION OF MINERAL SALTS ON A GAMMA-ALUMINA NANOFILTRATION MEMBRANEAPPLICATION TO ENVIRONMENTAL PROCESS

Nanofiltration of salt solutions through an alumina membrane prepared by a sol gel process was investigated: rejections depend on the charge of the ions and decrease in the order: (divalent cation, monoanion)>( monocation, monoanion) or (dication, dianion)>(monocation, dianion). T he surface charge of the membrane in the investigated solutions was sh own to be positive over a very large pH range. The rejection of ionic species can be rationalised by taking into account the low pore diamet ers of the membrane and its surface charge: as in the case of organic nanofiltration membranes, the rejection mechanism depends on the relat ive ratio of the coulombic, dielectric and hydration interactions betw een the membrane material and the ionic species. The use of nanofiltra tion through the alumina nanofiltration membrane for denitration of wa ter is also presented.