Details
| Original language | English |
|---|---|
| Pages (from-to) | 17-30 |
| Number of pages | 14 |
| Journal | Applied clay science |
| Volume | 28 |
| Issue number | 1-4 SPEC. ISS. |
| Publication status | Published - Jan 2005 |
Abstract
Smectites and vermiculites modified with hexadecylpyridinium (HDPy+), hexadecyltrimethylammonium (HDTMA+), benzethonium (BE+) and dipyridinododecane (DPyDD2+) cations exhibit high adsorption capabilities for the anionic radionuclide 125I- (Part I of this article). In some cases, exposure to higher temperature decreased the anion adsorption. To clarify the mechanisms of temperature dependence of the investigated organo-clay minerals, structural properties and thermal stabilities were examined by in situ powder X-ray diffraction (XRD), thermogravimetry (TG), thermocalorimetry (DTA) and FTIR spectral analyses. The organic cations HDPy, HDTMA and BE form bilayers, pseudotrimolecular layers and paraffin-type structures. The basal spacings of DPyDD-smectite and DPyDD-vermiculite were more or less unchanged in comparison to the original clay minerals (∼1.4 nm). It is assumed that the anion adsorption is due to the uptake of organic cations in an excess of the CEC, predominantly in the interlayer spaces as ion pairs. The decreasing iodide adsorption with increasing temperature is probably due to conformational changes of the alkyl chains, which are most pronounced for DPyDD-vermiculite at 60 °C (1.48→1.20 nm). Additionally, dehydration reactions, which occur at distinct temperatures for the organo-vermiculites (HDPy, 71; HDTMA, 57, 72; BE, 61; DPyDD, 41 °C), may be another reason for a decrease in iodide adsorption. The thermal decomposition of the organic cation starts at 200 °C. The HDPy, HDTMA and DPyDD-smectites and the HDTMA and BE-vermiculites show a high thermal stability with the basal spacing remaining constant up to 150 °C, which recommends the use for anion retention in engineered barriers for heat-producing waste.
Keywords
- Anion adsorption, Organo-clay minerals, Thermal analysis
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geology
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
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In: Applied clay science, Vol. 28, No. 1-4 SPEC. ISS., 01.2005, p. 17-30.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Temperature effects on iodine adsorption on organo-clay minerals - II. Structural effects
AU - Dultz, Stefan
AU - Riebe, Beate
AU - Bunnenberg, Claus
N1 - Funding information: We thank Dr. C. Rüscher for helpful support with the FTIR analysis, R.M. Klatt for technical assistance and Prof. Lagaly for his constructive comments and helpful suggestions to the manuscript. The work was supported by the Federal Ministry for Economic Affairs and Employment (BMWA) under contract number 02E9481.
PY - 2005/1
Y1 - 2005/1
N2 - Smectites and vermiculites modified with hexadecylpyridinium (HDPy+), hexadecyltrimethylammonium (HDTMA+), benzethonium (BE+) and dipyridinododecane (DPyDD2+) cations exhibit high adsorption capabilities for the anionic radionuclide 125I- (Part I of this article). In some cases, exposure to higher temperature decreased the anion adsorption. To clarify the mechanisms of temperature dependence of the investigated organo-clay minerals, structural properties and thermal stabilities were examined by in situ powder X-ray diffraction (XRD), thermogravimetry (TG), thermocalorimetry (DTA) and FTIR spectral analyses. The organic cations HDPy, HDTMA and BE form bilayers, pseudotrimolecular layers and paraffin-type structures. The basal spacings of DPyDD-smectite and DPyDD-vermiculite were more or less unchanged in comparison to the original clay minerals (∼1.4 nm). It is assumed that the anion adsorption is due to the uptake of organic cations in an excess of the CEC, predominantly in the interlayer spaces as ion pairs. The decreasing iodide adsorption with increasing temperature is probably due to conformational changes of the alkyl chains, which are most pronounced for DPyDD-vermiculite at 60 °C (1.48→1.20 nm). Additionally, dehydration reactions, which occur at distinct temperatures for the organo-vermiculites (HDPy, 71; HDTMA, 57, 72; BE, 61; DPyDD, 41 °C), may be another reason for a decrease in iodide adsorption. The thermal decomposition of the organic cation starts at 200 °C. The HDPy, HDTMA and DPyDD-smectites and the HDTMA and BE-vermiculites show a high thermal stability with the basal spacing remaining constant up to 150 °C, which recommends the use for anion retention in engineered barriers for heat-producing waste.
AB - Smectites and vermiculites modified with hexadecylpyridinium (HDPy+), hexadecyltrimethylammonium (HDTMA+), benzethonium (BE+) and dipyridinododecane (DPyDD2+) cations exhibit high adsorption capabilities for the anionic radionuclide 125I- (Part I of this article). In some cases, exposure to higher temperature decreased the anion adsorption. To clarify the mechanisms of temperature dependence of the investigated organo-clay minerals, structural properties and thermal stabilities were examined by in situ powder X-ray diffraction (XRD), thermogravimetry (TG), thermocalorimetry (DTA) and FTIR spectral analyses. The organic cations HDPy, HDTMA and BE form bilayers, pseudotrimolecular layers and paraffin-type structures. The basal spacings of DPyDD-smectite and DPyDD-vermiculite were more or less unchanged in comparison to the original clay minerals (∼1.4 nm). It is assumed that the anion adsorption is due to the uptake of organic cations in an excess of the CEC, predominantly in the interlayer spaces as ion pairs. The decreasing iodide adsorption with increasing temperature is probably due to conformational changes of the alkyl chains, which are most pronounced for DPyDD-vermiculite at 60 °C (1.48→1.20 nm). Additionally, dehydration reactions, which occur at distinct temperatures for the organo-vermiculites (HDPy, 71; HDTMA, 57, 72; BE, 61; DPyDD, 41 °C), may be another reason for a decrease in iodide adsorption. The thermal decomposition of the organic cation starts at 200 °C. The HDPy, HDTMA and DPyDD-smectites and the HDTMA and BE-vermiculites show a high thermal stability with the basal spacing remaining constant up to 150 °C, which recommends the use for anion retention in engineered barriers for heat-producing waste.
KW - Anion adsorption
KW - Organo-clay minerals
KW - Thermal analysis
UR - http://www.scopus.com/inward/record.url?scp=11044219866&partnerID=8YFLogxK
U2 - 10.1016/j.clay.2004.01.005
DO - 10.1016/j.clay.2004.01.005
M3 - Article
AN - SCOPUS:11044219866
VL - 28
SP - 17
EP - 30
JO - Applied clay science
JF - Applied clay science
SN - 0169-1317
IS - 1-4 SPEC. ISS.
ER -