Borax recovery using sodium metaborate and boric acid intermediates

A process for recovering sodium tetraborate from boron-containing feed solutions which comprises:

• contacting a first feed solution having a pH of between about 5 and about 8 in a first separation zone with an aliphatic 1,3-diol to produce a boron-rich first organic phase and a boron-depleted first aqueous phase;
• separating the first aqueous phase from the first organic phase;
• extracting the boron values from the boron-rich first organic phase with an aqueous solution comprising an alkali metal hydroxide in a second separation zone, to produce a second aqueous phase rich in sodium metaborate and a boron-depleted second organic phase;
• separating the second aqueous phase from the second organic phase;
• contacting a second feed solution having a pH of greater than about 7 with a water-insoluble aromatic polyol in a third separation zone, to produce a boron-depleted third aqueous phase and a boron-rich third organic phase;
• separating the third aqueous phase from the third organic phase;
• contacting the third organic phase with mineral acid in a fourth separation zone, to produce a fourth aqueous phase rich in boric acid and a boron-depleted fourth organic phase;
• separating the fourth aqueous phase from the fourth organic phase;
• and
• reacting sodium metaborate from the second aqueous phase with boric acid from the fourth aqueous phase to produce a fifth aqueous phase rich in sodium tetraborate.