Vaporization studies of calcium arsenate under neutral conditions and in contact with copper pyrometallurgical slags

The feasibility of capturing As as calcium arsenate in reverberatory and Mitsubishi converter slags used in copper pyrometallurgy was studied by torsion-effusion, thermogravimetric, and mass spectrometric methods. In the temperature range from 1376 to 1489 K pure Ca3 (AsO4)2 decomposed to yield very low equilibrium pressures of AsO and O2. Mixtures of Ca3 (AsO4)2 with slag exhibited rapid mass losses between 973 and 1173 K. The vapor phase species evolved under these conditions were As2 and As4, indicating that the arsenate had been reduced by the slag to volatile elemental arsenic.