Reverse osmosis separation for a montmorillonite membrane

摘要

It has been known for a long time that a membrane made of a pure clay rejects ionic solutes. Its application in separation technology, however, has never been attempted. This study is to explore such a possibility by investigating the solute separation characteristics of a montmorillonite membrane. For this purpose, a montmorillonite membrane with a thickness of 0.5 mm was prepared by sandwiching purified clay paste between two millipore filters and reverse osmosis experiments were conducted for various inorganic and organic solutes under an operating pressure of 3 MPa. The membrane exhibited characteristics typical for a charged membrane by rejecting sodium chloride solute less effectively with increasing solute concentration. The rejection of small organic solutes was very low. It was also found that the separation of amino acids greatly depends on the net charge carried by the amino acid molecule. Thus, this membrane opens up a route to the effective fractionation of electrolyteonelectrolyte mixtures and amino acid mixtures.