Imperial Chemical Industries Limited

Imperial Industries, Inc.

James H Steven

Graham W Scott

The ratio of silica to alkali in silicate liquors is increased, for example to convert alkaline grades to neutral grades, by passing the liquors through an electrodialysis stack comprising alternating cation exchange membranes and bipolar membranes mounted between an anode and a cathode, the membranes forming a concentrating cell between the anion exchange side of the bipolar membrane and the adjacent cation exchange membrane and a diluting cell between the cation exchange side of the bipolar membrane and the adjacent cation exchange membrane, the method comprising passing the silicate liquor through the diluting cells in the stack and passing water or an aqueous solution through the concentrating cells, whereby the silicate liquor is caused to lose alkali metal ions to the concentrating liquor and receive hydrogen ions from the bipolar membranes.

Method of concentrating silka in an aqueous alkali metal silicate

The ratio of silicate to alkali in silicate liquors is increased, for example to convert alkaline grades to neutral grades, by passing the liquors through an electrodialysis stack comprising alternating anion exchange membranes and cation exchange membranes mounted between an anode and a cathode, the membranes being spaced apart to provide cells through which a fluid can be passed, the method comprising passing the silicate liquor through those cells having their anion exchange membranes on the anode side and passing water or an aqueous solution through the other cells, whereby the silicate liquor is caused to lose alkali metal ions.

Method of concentrating silica in an aqueous alkali metal silicate

The ratio of silica to alkali in silicate liquors is increased, for example to convert alkaline grades to neutral grades, by passing the liquor through an electrodialysis stack comprising spaced ion-exchange membranes mounted between an anode and a cathode, the membranes forming cell triplets of a concentrating cell between an ion-exchange membrane and a fine cation exchange membrane, a diluting cell between the first cation exchange membrane and a second cation exchange membrane and a proton donor cell between the second cation exchange membrane and an adjacent anion-exchange membrane, the method comprising passing the silicate liquors through the diluting cells in the stack, passing water or an aqueous solution through the concentrating cells and passing an acidic solution through the proton donor cells whereby the silicate liquor is caused to lose alkali metal ions to the concentrating liquor and to receive hydrogen ions from the proton donor liquor.

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Runcorn, United Kingdom

James H Steven