SELENOCYANATE (SeCN-) CONTAMINATED WASTEWATER TREATMENT USING TiO2 PHOTOCATALYSIS: SeCN- COMPLEX DESTRUCTION, INTERMEDIATES FORMATION, AND REMOVAL OF SELENIUM SPECIES

Removal of selenocyanate (SeCN-) complex from synthetic wastewater was investigated using TiO2 based photocatalytic degradation (PCD) process. Using only UV-light showed no change in SeCN- however adding TiO2 to the same reactor system caused near complete disappearance of SeCN-. Also selenocyanate disappearance was noted at both acidic and basic pH values and over a wide concentration range. At pH 4 a gradual buildup of cyanide species along with disappearance of SeCN-, and formation of selenite (SeO32-) and selenate (SeO42-) supported SeCN- complex destruction. The selenite results showed an initial increase followed by a gradual decrease. Similar was noted at pH 6 and pH 10. However at pH 12 a larger buildup of selenite was explained based on reduced selenite adsorption on to TiO2 surface and consequently selenite's reduced oxidation to selenate. In any case the respective results showed that noted selenocyanate disappearance occurs because of SeCN- complex destruction. Furthermore