Inhibitory effects of CaO/Fe2O3 on arsenic emission during sewage sludge pyrolysis.

This work aimed to investigate effects and reaction mechanisms of CaO/Fe 2 O 3 on emission behaviors of arsenic during sewage sludge pyrolysis. The results showed that 24.8–54.2%, 26.4–60.4% and 27.7–63.1% of arsenic escaped from three samples when pyrolysis process happened at 723, 923 and 1123 K respectively. And the sludge which contained higher calcium and iron contents released less arsenic than others. External CaO and Fe 2 O 3 were added into the sewage sludge to study their effects on arsenic emissions during pyrolysis, where both of them inhibited arsenic emission effectively, especially at high temperatures. With the help of thermogravimetry analysis and X-ray fluorescence, inhibitory mechanisms of CaO/Fe 2 O 3 on arsenic emission during sewage sludge pyrolysis were studied. CaO could react with As 2 O 3 , As 2 S 3 and NaAsO 2 to form nonvolatile substances, such as Ca(AsO 2 ) 2 ; while Fe 2 O 3 could react with NaAsO 2 to generate certain substances which was stable below 1123 K. [ABSTRACT FROM AUTHOR]