EXAFS and FTIR studies of selenite and selenate sorption by alkoxide-free sol–gel generated Mg–Al–CO 3 layered double hydroxide with very labile interlayer anions

Handle URI:
http://hdl.handle.net/10754/598263
Title:
EXAFS and FTIR studies of selenite and selenate sorption by alkoxide-free sol–gel generated Mg–Al–CO 3 layered double hydroxide with very labile interlayer anions
Authors:
Chubar, Natalia
Abstract:
© the Partner Organisations 2014. Current research on Layered Double Hydroxides (LDHs, also known as hydrotalcites, HTs) is predominantly focused on their intercalations, but the industrial application of LDHs for anion exchange adsorption has not yet been achieved. It was recently recognized that, to develop LDH applications, these materials should be produced using methods other than direct co-precipitation. Mg-Al-CO3LDH produced using an alkoxide-free sol-gel synthesis showed exceptional removal properties for aqueous selenium species. Se K-edge EXAFS/XANES and FTIR studies (supporting the data by XRD patterns) were performed to explain the unusual adsorptive performance of Mg-Al LDH by revealing the molecular-level mechanism of HSeO3 -, SeO4 2-and {HSeO3 -+ SeO4 2-} uptake at pH 5, 7 and 8.5. The role of inner-sphere complexation (exhibited by inorganic adsorbents with good performance) in adsorption of both selenium aqueous species was not confirmed. However, Mg-Al LDH fully met the other expectations regarding the involvement of the interlayer anions. The interlayer carbonate (due to its favorable speciation and generous HT hydration) gave a "second breath" to selenite sorption and was the only mechanism that controlled the removal of Se(vi). Because inner sphere complexation was the leading mechanism for selenite removal, ion exchange via surface OH-and interlayer CO3 2-species was the only mechanism for selenate removal; both of these species were easily bound to Mg-Al LDH (on its surface and gently parked into the interlayer forming a multilayer without violation of the structure of Mg-Al-CO3LDH). This work provides the first theoretical explanation of why it is more difficult to sorb selenate than selenite and which material should be used for this purpose. This journal is
Citation:
Chubar N (2014) EXAFS and FTIR studies of selenite and selenate sorption by alkoxide-free sol–gel generated Mg–Al–CO 3 layered double hydroxide with very labile interlayer anions . J Mater Chem A 2: 15995–16007. Available: http://dx.doi.org/10.1039/c4ta03463e.
Publisher:
Royal Society of Chemistry (RSC)
Journal:
J. Mater. Chem. A
KAUST Grant Number:
KUK-C1-017-12
Issue Date:
8-Aug-2014
DOI:
10.1039/c4ta03463e
Type:
Article
ISSN:
2050-7488; 2050-7496
Sponsors:
A major part of the work was funded by King Abdullah University of Science and Technology (KAUST) through Center-in-Development award no. KUK-C1-017-12. The EXAFS research at DUBBLE at ESRF was funded by NWO (Dutch Ministry of Scientific Research). The authors gratefully thank Dr Harrison (University of Aberdeen) and Prof. Krivovichev (St. Petersburg State University) for providing the crystallography data.
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DC FieldValue Language
dc.contributor.authorChubar, Nataliaen
dc.date.accessioned2016-02-25T13:17:37Zen
dc.date.available2016-02-25T13:17:37Zen
dc.date.issued2014-08-08en
dc.identifier.citationChubar N (2014) EXAFS and FTIR studies of selenite and selenate sorption by alkoxide-free sol–gel generated Mg–Al–CO 3 layered double hydroxide with very labile interlayer anions . J Mater Chem A 2: 15995–16007. Available: http://dx.doi.org/10.1039/c4ta03463e.en
dc.identifier.issn2050-7488en
dc.identifier.issn2050-7496en
dc.identifier.doi10.1039/c4ta03463een
dc.identifier.urihttp://hdl.handle.net/10754/598263en
dc.description.abstract© the Partner Organisations 2014. Current research on Layered Double Hydroxides (LDHs, also known as hydrotalcites, HTs) is predominantly focused on their intercalations, but the industrial application of LDHs for anion exchange adsorption has not yet been achieved. It was recently recognized that, to develop LDH applications, these materials should be produced using methods other than direct co-precipitation. Mg-Al-CO3LDH produced using an alkoxide-free sol-gel synthesis showed exceptional removal properties for aqueous selenium species. Se K-edge EXAFS/XANES and FTIR studies (supporting the data by XRD patterns) were performed to explain the unusual adsorptive performance of Mg-Al LDH by revealing the molecular-level mechanism of HSeO3 -, SeO4 2-and {HSeO3 -+ SeO4 2-} uptake at pH 5, 7 and 8.5. The role of inner-sphere complexation (exhibited by inorganic adsorbents with good performance) in adsorption of both selenium aqueous species was not confirmed. However, Mg-Al LDH fully met the other expectations regarding the involvement of the interlayer anions. The interlayer carbonate (due to its favorable speciation and generous HT hydration) gave a "second breath" to selenite sorption and was the only mechanism that controlled the removal of Se(vi). Because inner sphere complexation was the leading mechanism for selenite removal, ion exchange via surface OH-and interlayer CO3 2-species was the only mechanism for selenate removal; both of these species were easily bound to Mg-Al LDH (on its surface and gently parked into the interlayer forming a multilayer without violation of the structure of Mg-Al-CO3LDH). This work provides the first theoretical explanation of why it is more difficult to sorb selenate than selenite and which material should be used for this purpose. This journal isen
dc.description.sponsorshipA major part of the work was funded by King Abdullah University of Science and Technology (KAUST) through Center-in-Development award no. KUK-C1-017-12. The EXAFS research at DUBBLE at ESRF was funded by NWO (Dutch Ministry of Scientific Research). The authors gratefully thank Dr Harrison (University of Aberdeen) and Prof. Krivovichev (St. Petersburg State University) for providing the crystallography data.en
dc.publisherRoyal Society of Chemistry (RSC)en
dc.titleEXAFS and FTIR studies of selenite and selenate sorption by alkoxide-free sol–gel generated Mg–Al–CO 3 layered double hydroxide with very labile interlayer anionsen
dc.typeArticleen
dc.identifier.journalJ. Mater. Chem. Aen
dc.contributor.institutionGlasgow Caledonian University, Glasgow, United Kingdomen
dc.contributor.institutionUtrecht University, Utrecht, Netherlandsen
kaust.grant.numberKUK-C1-017-12en
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