Electron transmission microscopy of charcoals impregnated with ammonium salts Of Cu(II) and Cr(VI)
✍ Scribed by Victor R. Deitz; Jean N. Robinson; Edward J. Poziomek
- Publisher
- Elsevier Science
- Year
- 1975
- Tongue
- English
- Weight
- 606 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0008-6223
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✦ Synopsis
Gas adsorbent charcoals were impregnated with simplified whetleriring solutions and the results compared with commercial whetlerites. Electron micrographs of the products showed a segregation of a considerable fraction of the added salts into crystalline areas, the latter ranging from 50 to 200 A in the short dimension. Impregnation with ammonium chromate alone gave single-crystal electron diffraction patterns having planar separations corresponding almost entirely to Cr20,, hexagonal rhombic. The spacings for charcoals impregnated with ammoniacal basic copper carbonate agreed best with alimited defect structure of CuZO. An ammoniacal solution of the crystals, formed in the slow evaporationof awhetlerizingsolution, wasimpregnatedoncharcoal;theresultantplanarseparationscouIdbecorrelated with known X-ray diffraction spacings of (NH&CrO,. CuzO and Cr20,. The impregnated copper salts thus appear to protectthechromateiontoaconsiderableextent.OneASCcommercial whetleritegavespacingsprincipallyofCr,O,and Cu,O.Thereisgoodevidencethatimpregnatedcharcoaldriedbelow ISO'isnotaninert support,butittakespart inaredox system in which 0(I) and Cr(III) are formed and the carbon networks oxidized. When a whetlerite was exposed to intensified beam current for short periods, small particles were observed to deposit on the support film. The particle5 ranged in size from about 100 A to much smaller diameters; the diffraction patterns were polycrystalline Cu,O and Cu. Theresidueleftinthecharcoalgave 19interplanarspacingsthatcloselycorrelated withCr,O,hexagonal rhombic.