Patent ID: 7615199

Claim:
A method for treating a material containing at least one valuable metal and arsenic to form a valuable metal-depleted scorodite sediment and a pure aqueous solution to be discharged, comprising: contacting with a dilute acid the material containing the valuable metal and arsenic to form a dilute acidic solution of components thereof; removing at least one valuable metal from the dilute acidic solution by liquid-liquid extraction to form a valuable metal-depleted solution; routing the valuable metal-depleted solution to a two-stage arsenic removal, comprising: in a first arsenic removal stage, precipitating arsenic as scorodite (FeAsO 4 2H 2 O), which is suitable for storing, and forming a first exiting solution; and in a second arsenic removal stage, precipitating arsenic from the first exiting solution as amorphous ferric arsenate (FeAsO 4 ), which is recycled to the first arsenic removal stage, and producing a second exiting solution, wherein the second exiting solution has an arsenic concentration of around 0.01-0.2 mg/l.