Method for producing pure boric acid
AssigneeSocieta Chimica Larderello S.p.A.
InventorsPaolo Bertocci, Paolo Mazzinghi
Life of this patent
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Abstract
Pure boric acid is obtained by a high-yield method with a non-pollutant effluent discharge, comprising the following stages carried out in succession: a) dissolving impure boric acid in an aqueous vehicle to form an aqueous solution of impure boric acid; b) separating pure crystalline boric acid from the aqueous solution of stage a) by crystallization; c) treating the discharge liquor from the crystallization of stage b) firstly through a strong cation exchange resin and then through a weak anion exchange resin; d) recycling the discharge liquor treated in stage c) for use as the aqueous vehicle for dissolving the impure boric acid in stage a).
Claims9
A method for preparing boric acid having a purity exceeding 99.99% by weight by crystallization of impure boric acid of purity from about 99% up to 99.9% by weight and substantially eliminating effluent pollutant discharge, comprising:
- (a) dissolving the impure boric acid in an aqueous vehicle to form an aqueous solution of impure boric acid;
- (b) separating pure crystalline boric acid from the aqueous solution of step (a) by crystallization;
- (c) purifying the discharge liquor substantially depleted in boric acid from the crystallization step (b) through a strong cation exchange resin and then through a weak anion exchange resin;
- and
- (d) recycling the discharge liquor treated in step (c) for use as the aqueous vehicle for dissolving the impure boric acid in step (a).
A method for preparing boric acid having a purity exceeding 99.99% by weight by crystallization of impure boric acid of 99.9% purity by weight and substantially eliminating effluent pollutant discharge, comprising:
- (a) dissolving boric acid of 99.9% purity by weight in an aqueous vehicle containing about 8% boric acid by weight to form an aqueous solution of impure boric acid having a boric acid concentration of between 18% to 22% by weight;
- (b) separating pure crystalline boric acid from the aqueous solution of step (a) by crystallization;
- (c) purifying the discharge liquor containing about 8% by weight of boric acid from the crystallization step (b) through a strong cation exchange resin and then through a weak anion exchange resin;
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- (d) recycling the discharge liquor treated in step (c) for use as the aqueous vehicle for dissolving the impure boric acid in step (a).
Dependencies are inferred from the claim text.