Adsorption of lithium in sea water on alumina—magnesia mixed-oxide gels

Abstract

Alumina—magnesia gel, which was prepared from a mixed solution of equimolar aluminum and magnesium chlorides by coprecipitation using sodium hydroxide as the precipitant, exhibited an ability to adsorb lithium from sea water. This was attributed to both the weak acidic sites and the micropores of diameter 20–30Å. The adsorption of lithium proceeded predominantly by the cation-exchange mechanism. The facility of ion exchange of lithium with monovalent cations located on the gel surface was shown to be in the order Na + ⪢ H + ⪢ NH + 4. The Freundlich-type adsorption isotherm was used to relate the amount of lithium adsorbed to the equilibrium concentration of lithium in sea water. The amount of lithium adsorbed on the best binary gel was 100μ g −1 at a lithium concentration in sea water of 0.17 mg dm −3. The elution of lithium adsorbed on the binary gel was achieved with a relatively small amount of 0.05 mol dm −3 hydrochloric acid. It has, therefore, been confirmed that the lithium in sea water can be concentrated up to 7 times using this technique.