Speciation of citric acid on anatase (TiO2)–water interface and its effect on Eu(III) sorption
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Sharayu Kasar
Abstract
Citric acid is one of the low molecular weight organic acids which are ubiquitous in nature. In this study the sorption of citric acid at titania (anatase)/water interface was investigated using batch adsorption experiment and attenuated total reflectance – Fourier transform infrared spectroscopy (ATR-FTIR) over wide experimental conditions of pH, surface loading and ionic strengths. The batch adsorption experiment showed typical anionic characteristics; higher sorption was observed at lower pH values and sorption decreases with increasing pH. Strong dependence of sorption on ionic strength shows formation of citrate surface species in outer-sphere binding mode. At lower pH, ATR-FTIR spectra of aqueous citrate differs from that of sorbed citrate ions indicating lowering of pKa values of surface sorbed citrate compared to that present in solution. Detailed analysis of FTIR spectra of sorbed citrate in light of that of aqueous and Ca(II)/Eu(III) complexed citrate revealed formation of an inner sphere complex of citrate on anatase surface along with the outer sphere complex. Wavenumber difference between the asymmetric and symmetric COO– peaks (Δυ = 159 cm–1) implies inner-sphere complex in bidentate bridging mode. These results help in explaining the sorption behaviour of Eu(III) on anatase in presence of citric acid.
Supplementary material
the online version of this article (DOI: 10.1515/ract-2014-2320) provides supplementary material for authorized users.
Acknowledgement
Authors thank Dr. Abhinav Dubey and Mr. C. V. Chaudhary, RTDD, BARC for their support during ATR-FTIR spectroscopic experiments. Support from Dr. N.K. Kulkarni and Dr. K.S. Krishnan during TGA and XRD measurements of anatase is gratefully acknowledged.
©2015 Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Frontmatter
- Preface
- Separation Science in Nuclear Technology in India
- Studies on extraction of actinides by unsymmetrical diamylbutyl phosphonate
- Supercritical fluid extraction of uranium and thorium from nitric acid medium using organophosphorous compounds
- Novel polymer inclusion membranes containing T2EHDGA as carrier extractant for actinide ion uptake from acidic feeds
- Studies on the feasibility of using completely incinerable reagents for the single-cycle separation of americium(III) from simulated high-level liquid waste
- Phosphonates as alternative to tributyl phosphate for the separation of actinides from fission products
- Actinides draw down process for pyrochemical reprocessing of spent metal fuel
- Spectroscopic investigations on sorption of uranium onto suspended bentonite: effects of pH, ionic strength and complexing anions
- Speciation of citric acid on anatase (TiO2)–water interface and its effect on Eu(III) sorption
- Separation of 134Cs and 137Cs from 125I solution for medical applications
- Optimization of 210Po estimation in environmental samples using an improved deposition unit
