A new and practical Se(IV) removal method using Fe3+ type cation exchange resin

Highlights: • Development of a practical column method to remove selenium (Se(IV)) from wastewater. • The Fe³⁺ type cation exchange resin is useful for removing Se(IV). • The Se(IV) is specifically adsorbed by the formation of an Fe-O-Se bond. • By 12.8 g of the resin, Se(IV) in 3 tons of 0.1 ppm Se solution can be removed. • Fe³⁺ and Se(IV) can be desorbed easily using a small amount of 6 mol/dm³ HCl. -- Abstract: An effective method for removing selenium (Se) from water is required from the viewpoint of environmental preservation. To establish this method, a cation exchange resin that adsorbed ferric ions was applied as an adsorbent. In this study, the adsorption behavior of Se to the adsorbent was examined by both batch and column methods. The batch experiment confirmed that selenite ions (Se(IV)) are effectively adsorbed but selenate ions (Se(VI)) are hardly adsorbed. To elucidate the adsorption mechanism, the Fe in the adsorbent and the Fe in the adsorbent after the adsorption of Se(IV) were characterized by Fe K-edge X-ray absorption spectroscopy and ⁵⁷Fe Mssbauer spectroscopy. The analytical result of Se K-edge EXAFS spectra for the Se(IV) adsorbed on the adsorbent suggests that Se(IV) are adsorbed specifically to the adsorbent through the formation of Fe-O-Se bonds. The breakthrough curve obtained by the column experiment showed that Se(IV) in 3 tons of synthetic solution containing 0.1 ppm Se can be efficiently removed using a column in which 12.8 g (10.4 cm³) of the adsorbent was packed.