Sorption of Sb(III) and Sb(V) to Goethite: Influence on Sb(III) Oxidation and Mobilization
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- 作者：Ann-Kathrin Leuz ; Hermann Mö ; nch ; C. Annette Johnson
- 刊名：Environmental Science & Technology
- 出版年：2006
- 出版时间：December 1, 2006
- 年：2006
- 卷：40
- 期：23
- 页码：7277 - 7282
- 全文大小：281K
- 年卷期：v.40,no.23(December 1, 2006)
- ISSN：1520-5851
文摘
Antimony is an element of growing interest for a varietyof industrial applications, even though Sb compounds areclassified as priority pollutants by the EnvironmentalProtection Agency of the United States. Iron (Fe) hydroxidesappear to be important sorbents for Sb in soils and sediments, but mineral surfaces can also catalyze oxidationprocesses and may thus mobilize Sb. The aim of this studywas to investigate whether goethite immobilizes Sb bysorption or whether Sb(III) adsorbed on goethite is oxidizedand then released. The sorption of both Sb(III) and Sb(V)on goethite was studied in 0.01 and 0.1 M KClO4 M solutionsas a function of pH and Sb concentration. To monitor oxidation processes Sb species were measured in solutionand in the solid phase. The results show that both Sb(III)and Sb(V) form inner-sphere surface complexes at thegoethite surface. Antimony(III) strongly adsorbs on goethiteover a wide pH range (3-12), whereas maximum Sb(V)adsorption is found below pH 7. At higher ionic strength,the desorption of Sb(V) is shifted to lower pH values, mostlikely due to the formation of ion pairs KSb(OH)6
. Thesorption data of Sb(V) can be fitted by the modified triple-layer surface complexation model. Within 7 days, Sb(III)adsorbed on goethite is partly oxidized at pH 3, 5.9 and 9.7.The weak pH-dependence of the rate coefficients suggeststhat adsorbed Sb(III) is oxidized by O2 and that thecoordination of Sb(III) to the surface increases the electrondensity of the Sb atom, which enhances the oxidationprocess. At pH values below pH 7, the oxidation of Sb(III)did not mobilize Sb within 35 days, while 30% of adsorbedSb(III) was released into the solution at pH 9.9 within thesame time. The adsorption of Sb(III) on Fe hydroxidesover a wide pH range may be a major pathway for theoxidation and release of Sb(V).
. Thesorption data of Sb(V) can be fitted by the modified triple-layer surface complexation model. Within 7 days, Sb(III)adsorbed on goethite is partly oxidized at pH 3, 5.9 and 9.7.The weak pH-dependence of the rate coefficients suggeststhat adsorbed Sb(III) is oxidized by O2 and that thecoordination of Sb(III) to the surface increases the electrondensity of the Sb atom, which enhances the oxidationprocess. At pH values below pH 7, the oxidation of Sb(III)did not mobilize Sb within 35 days, while 30% of adsorbedSb(III) was released into the solution at pH 9.9 within thesame time. The adsorption of Sb(III) on Fe hydroxidesover a wide pH range may be a major pathway for theoxidation and release of Sb(V).