Method for preparing metal hydroxide from sparingly soluble salt, useful particularly for making lithium hydroxide, uses an electrodialysis cell, supplied with concentrated aqueous salt solution

摘要

Method for preparing a metal hydroxide (I) by electrolysis of a salt (II), where the concentration of (II) is as high as possible, without formation of a precipitate inside the cell. Method for preparing a metal hydroxide (I), with solubility in water at least 10 g/100 g (at 25[deg]C), from a metal salt (II), with maximum solubility in water 5 g/100 g (at 25[deg]C), in an electrodialysis cell, where the new feature is that the concentration of (II) is as high as possible, without formation of a precipitate inside the cell. The cell comprises an anode; cathode; bipolar membrane (M1; with its cation-selective side facing the cathode) or a bipolar electrode; and a membrane (M2), selectively permeable to cations, arranged on the cathodic side of M1 (or bipolar electrode). The solution of (II) is supplied to the space between M1 and M2; a potential is applied, and (I) recovered on the side of M2 that faces the cathode.