In this work, we report atomic-scale reconstruction processes in Fe-Ce oxide-based composites (hydrothermally precipitated at Fe-to-Ce dosage ratios of 1:0, 2:1, 1:1, 1:2, and 0:1), upon treatment at 300 °C. The structural changes are correlated with the adsorptive removal of arsenate, phosphate, fluoride, bromide, and bromate. The presence of the carbonate-based Ce-component and surface sulfate in precursor samples creates favorable conditions for phase transformation, resulting in the formation of novel (unknown) layered compounds of Fe and Ce. These compounds are of the layered double hydroxide type, with sulfate in the interlayer space. In spite of general awareness of the importance of surface area in adsorptive removal, the increase in surface area upon thermal treatment did not increase adsorption of the studied anions. However, EXAFS simulations and the adsorption tests provided evidence of regularities between local structures of Fe in composites obtained at 80 and 300 °C and adsorption performance of most studied anions. The best adsorption of tetrahedral anions was demonstrated by samples whose simulated outer Fe shells resulted from oscillations from both O and Fe atoms. In contrast, the loss of extended x-ray absorption fine structure was correlated with the decrease of adsorptive removal. Both Fe K-edge and Ce L3 -edge EXAFS suggested the formation of solid solutions. For the first time, the utilization of extended x-ray absorption fine structure is suggested as a methodological approach (first expressed in the companion paper) to estimate the surface reactivity of inorganic materials intended for use as anion exchange adsorbents.
|Original language||English (US)|
|Number of pages||12|
|Journal||Journal of Colloid and Interface Science|
|State||Published - Dec 7 2016|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUK-C1-017-12
Acknowledgements: This work was funded by King Abdullah University of Science and Technology (KAUST) via the Global Research Partnership Programme, award N° KUK-C1-017-12, and Netherlands Organization for Scientific Research (NWO) for EXAFS/XANES studies at the Dutch-Belgian Beamline (DUBBLE) at the European Synchrotron-Radiation Facilities (ESRF). The authors are grateful to Dr. Andrey Shchukarev (Umea University) for XPS measurements and consideration of the results and to Ms. Helen de Waard, Ms. Dineke van de Meent-Olieman, Ms. Anita van Leeuwen-Tolboom, Mr. Pieter Kleingeld, Mr. Piet Peereboom, and Mr. Ton Zalm (Utrecht University) for excellent technical support during their research. The authors gratefully acknowledge the anonymous Reviewers and Editor Prof. Teresa Bandosz for helping improve this work.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.