I= SURFACE STUDIES OF CARBON IMPREGNATED WITH VARIOUS METALS
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Title of Thesis
SURFACE STUDIES OF CARBON IMPREGNATED WITH VARIOUS METALS

Author(s)
Fazal Mahmood
Institute/University/Department Details
Department of Chemistry/ Quaid-i-Azam University Islamabad
Session
1992
Subject
Chemistry
Number of Pages
217
Keywords (Extracted from title, table of contents and abstract of thesis)
carbon, metal impregnated carbons, metal doping, chemisorption, adsorbate, mercury porosimetry, nitrogen adsorption measurements, temperature programmed reduction, gas adsorption, isosteric heats

Abstract
The first part of the thesis deals with the work on structural investigation of metal impregnated carbons (Ni, Cu, Zn and Cd) using different techniques such as nitrogen adsorption, mercury Porosimetry, temperature programmed reduction(TPR), X-ray diffraction, thermal analysis and scanning electron microscopy. The effects of metal doping on the surface area, pore size distribution and discussed. DR analysis of nitrogen adsorption isotherms indicates that the microporsity of the active carbon decreases as the metals are supported on the surface of the carbon. Results reveal that metal resides are present on the surface of active carbon in the dispersed forms leading to an appreciable pore blockage. The metal resides which are present at the micropore entrance of the active carbon reduce the empty space available for the adsorption of nitrogen. X-ray diffraction and temperature programmed reduction (TPR also confirm the above findings.

The second part deals with the adsorption of methanol, acetone, methyl formate and acetaldehyde on active carbon and metal doped carbons between 273 and 303K. The heats of adsorption are calculated at a number of temperatures and coverages from the resulting adsorption isotherms. The vales of isosteric heats of adsorption are generally found to be higher for metal doped carbons which may be due to chemisorption of adsorbate molecules on metal resides present on the surface of active carbon. The heats of adsorption are shown to be generally consistent with the idea of two adsorption processes occurring simultaneously, one with a small activation energy and the other with a large activation energy. Some unexplained results were also obtained

Thermodynamic parameters such as free energy, enthalpy and entropy of adsorption are also computed using a virial isotherm expression and are interpreted. It is observed that metal dopant/ active carbon systems are synergic, exhibiting more adsorption affinity for different organic vapors than the sum of the individual constituents Results show that an increase in adsorption affinity for metal doped carbon is not due to configurational factors affecting the entropy of adsorption but because of large exothermicity in the enthalpy of adsorption.

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6088.78 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
311.09 KB
2 1 Introduction 1
1165.68 KB
  1.1 Active Carbon 1
  1.2 Adsorption At Gas-Solid Interface 8
  1.3 Aim Of The Present Work 25
3 2 Preparation Of Materials 27
387.86 KB
  2.1 Chemicals And Reagents 27
  2.2 Preparation And Analysis Of Metal 31
  2.3 Determination Of Doped Metals In Carbon Samples 34
4 3 Characterization 39
2218.69 KB
  3.1 Nitrogen Adsorption Measurements 39
  3.2 Mercury Porosimetry 57
  3.3 Temperature Programmed Reduction 72
  3.4 X-Ray Diffraction 92
  3.5 Thermal Analysis 101
  3.6 Electron Microscopy 111
  3.7 References 117
5 4 Thermodynamic Of Surfaces 126
508.55 KB
  4.1 One Component System With Plane Interface 126
  4.2 Two Component System With Plane Interface 136
  4.3 Thermodynamics Of Gas Adsorption 137
6 5 Procedure €“Calculation And Results 144
785.17 KB
  5.1 Procedure For Taking Adsorption Isotherms At Different Temperatures 144
  5.2 Calculation Of Isosteric Heats Of Adsorption 147
  5.3 Virial Isotherms Expression 148
7 6 Discussion 191
971.66 KB
  6.1 Size Of Q st €˜ The Heat Of Adsorption 191
  6.2 Surface Porosity 196
  6.3 Heat Of Adsorption As A Function Of Coverage And Temperature 197
  6.4 Thermodynamic Parameters Calculated From Virial Isotherm Expression 206
  6.5 References