Patent ID: 9745193
Date: 2017-08-29
CPC Classifications: C01B,C01F,C01G,C25B

Claim:
1. A method for manufacturing phosphoric acid from ore comprising phosphorus, calcium, and iron, the method comprising the following steps: a) preparing an aqueous mixture comprising the ore; b) adding sulfuric acid to the aqueous mixture thereby digesting the phosphorus, calcium, and iron and producing a solution comprising phosphoric acid and dissolved iron, and a precipitate comprising calcium sulfate; c) separating the precipitated calcium sulfate from the phosphoric acid and dissolved iron solution; d) reducing at least a portion of the phosphoric acid and dissolved iron solution wherein the reducing lowers the EMF of the solution relative to the standard hydrogen electrode to less than about 450 mV; e) adding oxalic acid to the portion of the phosphoric acid and dissolved iron solution; whereby iron oxalate precipitate and phosphoric acid solution is produced by the combination of steps d) and e); and f) separating the precipitated iron oxalate from the phosphoric acid solution.