*4.4. Route for the Recovery of Arsenic from Arsenic-Bearing Dust Ash*

The arsenic recovery experiment by roasting in the atmosphere of air, anaerobic and reducing, was carried out with the dust ash containing 10% As2O3 powder [20]. The experiment confirms that arsenic recovery from dust ash by roasting in the atmosphere of air or an anaerobic atmosphere is difficult, and that arsenate easily remains in the dust ash. Figure 7 shows the effect of temperature on arsenic-containing products in dust ash by reduction roasting. Thermodynamic calculation of arsenic recovery by roasting under a reduction environment shows that arsenic is not easy to be removed from dust and that arsenate is easy to be formed when the roasting temperature is below 390 ◦C. The arsenic is easily volatilized and recovered when the dust is roasted above 390–890 ◦C, but it is easy to produce arsenate when the dust ash is roasted above 890 ◦C, which affects the recovery of arsenic.

**Figure 7.** Effect of temperature on arsenic-containing products in dust ash by reduction roasting.
