NMR Characterization of 13C-Benzene Sorbed to Natural and Prepared Charcoals
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- 作者：Ronald J. Smernik ; Rai S. Kookana ; and Jan O. Skjemstad
- 刊名：Environmental Science & Technology
- 出版年：2006
- 出版时间：March 15, 2006
- 年：2006
- 卷：40
- 期：6
- 页码：1764 - 1769
- 全文大小：144K
- 年卷期：v.40,no.6(March 15, 2006)
- ISSN：1520-5851
文摘
We investigated how the NMR properties of uniformly13C-labeled benzene molecules are influenced by sorptionto charcoals produced in the laboratory and collectedfrom the field following wildfires. Uniformly 13C-labeledbenzene was sorbed to two charcoals produced in thelaboratory at 450 and 850 
C. The chemical shift of benzenesorbed to the higher-temperature charcoal was 5-6ppm lower than that of benzene sorbed to the lower-temperature charcoal. This difference was attributed tostronger diamagnetic ring currents (which cause a shift tolower ppm values) in the more condensed or "graphitic" high-temperature charcoal. The chemical shift of benzenesorbed to two charcoals collected from the field followingwildfires indicated a degree of charcoal graphitizationintermediate between that of the two laboratory-preparedcharcoals. Variable contact time and dipolar dephasingexperiments showed that the molecular mobility of sorbedbenzene molecules increased with increasing charcoalgraphitization, and also increased with increasing benzeneconcentration. We propose that the chemical shiftdisplacement of molecules sorbed to charcoal could beused to identify molecules sorbed to black carbon inheterogeneous matrixes such as soils and sediments, andto establish how condensed or "graphitic" the blackcarbon is.
C. The chemical shift of benzenesorbed to the higher-temperature charcoal was 5-6ppm lower than that of benzene sorbed to the lower-temperature charcoal. This difference was attributed tostronger diamagnetic ring currents (which cause a shift tolower ppm values) in the more condensed or "graphitic" high-temperature charcoal. The chemical shift of benzenesorbed to two charcoals collected from the field followingwildfires indicated a degree of charcoal graphitizationintermediate between that of the two laboratory-preparedcharcoals. Variable contact time and dipolar dephasingexperiments showed that the molecular mobility of sorbedbenzene molecules increased with increasing charcoalgraphitization, and also increased with increasing benzeneconcentration. We propose that the chemical shiftdisplacement of molecules sorbed to charcoal could beused to identify molecules sorbed to black carbon inheterogeneous matrixes such as soils and sediments, andto establish how condensed or "graphitic" the blackcarbon is.