Prodn. of V2O5 from a NaVO3 soln. by treatment with NH4Cl or (NH4)SO4 at a low temp. to ppte. ammonium vanadate, dissolution of the separated ppte. in hot water, treatment of the resulting soln. with a mineral acid, sepn. of the resulting ppte. and calcination thereof, is improved in that the treatment of the NaVO3 soln. with NH4Cl or (NH4)SO4 is effected at pH 6-4 (pref. 4.8-4.4). Utilisation of NaVO3 solns. obtained by processing the mud during the prodn. of alumina is imporved in that the precipitation of NH4VO3 is carried out under optimum conditions so that the loss of vanadium values is reduced to a minimum. High-purity V2O5 is obtained (e.g. 99.8% purity).
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