Effects of Temperature and pH on the Transformation of Ferric Arsenate to Scorodite in Acidic Solution

Scorodite is an important arsenic carrier for the immobilization of arsenic generated in the metallurgical industries. The transformation of the amorphous ferric arsenate into scorodite was investigated in a mixed sulfate media (pH 1-2) and elevated temperature (80-95 °C). This transformation process has been traced via scanning electron microscopy (SEM) and X-ray diffraction (XRD). Thus, it was found that lower pH and higher temperature was favored to generate more stable scorodite. The scorodite with TCLP leachability of 3.58 mg/L As was produced at 95 °C and initial pH 1.2 for 12 h.