Determination of the solubility limiting solid of selenium in the presence of iron under anoxic conditions

Iida, Yoshihisa ; Yamaguchi, Tetsuji ; Tanaka, Tadao ; Kitamura, Akira  ; Nakayama, Shinichi 

We performed dissolution experiments of iron-selenium compounds from both undersaturation and oversaturation directions to determine the solubility limiting solid of selenium in the presence of iron under anoxic conditions. The solid products was identified to be iron diselenide but the concentration of selenium was 9 orders of magnitude higher than the value calculated from the existing thermodynamic data of FeSe, therefore FeSe was not considered to be the solubility limiting solid. The pH and Eh dependencies of the concentration of selenium were best interpreted as the dissolution reaction of Se(cr), but the concentration of selenium was still 3 orders of magnitude higher than the value calculated from the existing thermodynamic data of Se(cr). Because any selenium compounds other than FeSe was not detected by XRD and the concentration of selenium was higher than the solubility of Se(cr), the solubility limiting solid was considered to be amorphous selenium.