Selective removal of arsenic from crude antimony trioxide by leaching with nitric acid

Abstract

The presence of arsenic (As) in crude antimony trioxide (Sb2O3) impedes the Sb recovery and results in an environmental issue. Selective As removal from crude antimony trioxide would therefore enable using this residue in commercial Sb2O3 production. This work uses a nitric acid leaching method to remove As from crude antimony trioxide. Arsenic oxide and antimony oxide are respectively converted to soluble H3AsO4 and insoluble antimony(III) oxide hydroxide nitrate Sb(III)OHN during HNO3 leaching. The As content in the crude antimony trioxide decreases from 3.0 wt% to 0.4 wt%. The As removal ratio reaches 86%, while the Sb leaching ratio is limited to 0.3%, confirming the high selectivity of HNO3 leaching. The leaching residue is composed of cervantite (Sb2O4) and Sb(III)OHN. By calcining the leaching residue in the air at 200 °C, it can be converted to a mixture of cervantite and valentinite (Sb2O3). Finally, cervantite is decomposed above 1070 °C in N2 into Sb4O6 that can be condensed as Sb2O3. A novel flowsheet is proposed for both As removal and Sb recovery from the crude antimony trioxide.