Patent ID: 7232554

Claim:
A process for recovering arsenic from an aqueous acid solution, the process comprising: heating said aqueous acid solution in one or more evaporators in series to concentrate said aqueous acid solution and obtain a concentrated acid solution; preparing a crystallized solution by cooling said concentrated acid solution to crystallize arsenic contained in said concentrated acid solution as arsenic trioxide crystals; separating the crystallized solution to obtain a solid phase comprising impure arsenic trioxide crystals and a residual liquid phase; and purifying said solid phase to obtain a purified crystal product comprising arsenic trioxide; wherein said solid phase comprising impure arsenic trioxide crystals is purified by contacting said solid phase comprising impure arsenic trioxide crystals with a lixiviant to remove arsenic trioxide from said solid phase, thereby producing a purified liquid phase comprising arsenic trioxide; contacting said purified liquid phase with an acid to lower the pH of said purified liquid phase to a value of 10 or below, thereby crystallizing arsenic trioxide to produce a purified solid phase comprising arsenic trioxide in said purified liquid phase; and separating said purified solid phase comprising arsenic trioxide from said purified liquid phase to produce a purified crystal product comprising arsenic trioxide.