Process for producing low aluminum content phosphoric acid from high aluminum matrix

A process for producing phosphoric acid from unbeneficiated phosphate ore matrix containing tricalcium phosphate, clay, silica and trialuminum phosphate, said process comprising:

• (a) digesting said phosphate ore matrix in aqueous impure phosphoric acid containing as impurities dissolved ions of aluminum and fluorine, to produce undissolved solids and a solution comprising ions of calcium, phosphate, fluorine and aluminum;
• (b) adding a flocculant to consolidate said undissolved solids;
• (c) separating said flocculated undissolved solids from said solution comprising ions of calcium, phosphate, fluorine and aluminum;
• (d) adding sufficient sulfuric acid to said solution comprising ions of calcium, phosphate, fluorine and aluminum to cause the precipitation of substantially all of said ions of calcium as solid gypsum and producing an impure aqueous phosphoric acid solution containing ions of aluminum and fluorine.
• (e) reducing the amount of fluorine in said impure aqueous phosphoric acid by an amount sufficient to retard formation of solid aluminum fluorophosphate, AlFHPO.sub.4.2H.sub.2 O, therein.