Effect of Salicylic and Picolinic Acids Acids on the Adsorption of U(VI) onto Oxides

산화물 표면의 U(VI) 흡착에 미치는 살리실산과 피콜린산의 영향

  • Published : 2009.12.31

Abstract

The effect of organic acids on the adsorption of U(VI) onto oxide surfaces ($TiO_2)$(anatase), $SiO_2$(amorphous) and $Al_2O_3$(amorphous)) has been investigated. Two different organic acids, salicylic and picolinic acids, were used. Changes of adsorption ratio of U(VI), which depend on the existence of organic acids in a sample, were measured as a function of pH. Quantities of adsorbed organic acids, which depend on the existence of U(VI) in a sample, were also measured as a function of pH. It is confirmed that the soluble complex formation of U(VI) with organic acids can deteriorate the adsorption of U(VI) onto $TiO_2$ surface. It is noteworthy that salicylic acid does not affect the adsorption of U(VI) onto $SiO_2$ surface, however, picolinic acid enhances the adsorption of U(VI) onto $SiO_2$ surface. The latter effect can be understood by considering the formation of a ternary surface complex on $SiO_2$ surface, which was confirmed by the co-adsorption of picolinic acid with U(VI) and the change in a fluorescence spectra of U(VI) on surface, In the case of $Al_2O_3$, organic acids themselves were largely adsorbed onto a surface without deteriorating the adsorption of U(VI). This would support the possibility of a ternary surface complex formation on the $Al_2O_3$ surface, and an additional spectroscopic study is required.

세 종류의 산화물($TiO_2$(아나타제), $SiO_2$(비결정성) 및 $Al_2O_3$(비결정성)) 표면에 U(VI)이 흡착될 때 유기산이 미치는 영향을 연구하였다. 유기산으로는 살리실산과 피콜린산을 사용하였다. 유기산의 존재 여부에 따라 달라지는 U(VI)의 흡착률 변화를 pH 함수로 측정하였다. 또한 U(VI)의 존재 여부에 따라 달라지는 유기산의 흡착량을 pH 함수로 측정하였다. $TiO_2$의 경우, 살리실산과 피콜린산이 U(VI)과 수용성 착물을 형성함으로써 U(VI)의 흡착률을 저하시킨다. $SiO_2$의 경우, 살리실산은 U(VI) 흡착에 영향을 주지 않지만, 피콜린산은 오히려 U(VI) 흡착을 증가시킨다. 이 현상을 삼성분 표면착물(ternary surface complex) 생성으로 해석하였으며 U(VI) 흡착에 의존하는 피콜린산의 흡착량 변화, 그리고 흡착된 U(VI)의 형광 특성 변화로 이를 확인하였다. $Al_2O_3$의 경우, 살리실산과 피콜린산 모두 U(VI) 흡착과 무관하게 높은 흡착량을 보였으나 U(VI) 흡착을 감소시키지는 않았다. 따라서 삼성분 표면착물 생성을 배제할 수 없으나 이를 확인하기 위해서는 분광 분석과 같은 추가 연구가 필요하다.

Keywords

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