Hematite에 대한 Se(IV)의 흡착반응에 휴믹산이 미치는 영향.

Abstract

Selenium(Se) is an essential micronutrient that is necessary for cancer prevention and cure, heavy metal detoxication, body metabolism and so on in human and animal bodies. However, excessive intake of Se may cause severe reverse effect such as poisoning. In this study we investigated the adsorption of Se(Ⅳ) onto hematite, which usually exists in soils and rocks, focusing on the effect of NOM. In other words, we investigated the adsorption reactions of Se(Ⅳ) with the synthesized hematite under various physicochemical conditions (ionic strenth, pH, concentration of Se(Ⅳ)) in the presence of the NOM. Results show that the selenium adsorption onto hematite varies with the contact time, finally reaching an equilibrium state in 5 hours. By carrying out the modeling on the acquisited kinetic data, we found that the result is in good agreement with the Parabolic diffusion equation (R2 = 0.97). In addition, the adsorption with different initial selenium concentrations was also reproduced fairly with a Langmuir isotherm (R2 = 0.92). It was found that the adsorption efficiency of Se(Ⅳ) increased with decreasing pH, particularly at pH lower than pHpzc. The Se(Ⅳ) adsorption reduced by increasing ionic strength, is best modeled under the assumption that Se(Ⅳ) forms an outer-sphere surface complex. The adsorption of Se(IV) onto hematite in ternary system (Se-hematite-humic acid) decreased more than that in binary system (Se-hematite). Results obtained through this study would be helpful to understand the fate and transport of Se in natural environment and to remove selenium. In addition, it would provide an important basic reference in the field of geochemistry of metal oxyanions.