Chemistry of the M (M=Fe, Ca, Ba)-Se-H2O Systems at 25 °C

The chemistry of the M (M=Fe, Ca, Ba)-Se-H2O systems at 25 degrees C is reviewed based on our previous papers. In this paper, the phase equilibria in the Fe(III)-Se(IV)-H2O, Ca-Se(IV,VI)-H2O and Ba-Se(IV,VI)-H2O systems at 25 degrees C are discussed. Then, the three-stage process for removal of selenium from industrial waste water [Se(IV,VI) < 1,500 mg/L] containing sulfuric acid was introduced. This seems to be a promising process for selenium removal from acidic sulfate waste water containing high concentration levels of selenium to below 0.1 mg/L.