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Activated Carbon
Cavbon, 1972, Vol IO, pp 117-l 18
Pergamon
Press.
Pnnted ,n Great Bntam
BOOK
REVIEWS a comment on the recent proliferation of knowledge about the many aspects of carbon and graphite. The section on the reactions of gas with carbon and graphite together with its extensive bibliography should be a very useful beginning point for those interested in particular or general problems associated with the topic. While consistent results and interpretations are now being obtained for many simple carbon-gas reactions at low temperatures, the chapter reflects the fact that while this whole area is the most thoroughly worked over in the science of carbon, it is still less than completely understood. Mechanical properties are not given the broad coverage that is maintained in other sections. The reader will have to look elsewhere to find up-todate accounts of this important subject. The editor is to be congratulated for including a chapter on “fraction and wear”, an area which is seldom included formally in books on carbon and graphite. Perspectives of the relative Importance of the many applications of carbon and graphite cited in the last chapter may be gained by carefully studying Table I of that chapter before its reading. Those interested in the science and technology of carbon will find this book easy to read and a valuable reference.
Modern Aspects of Graphite Technology (Edited by L. C. F. Blackman) Academic Press, London and New York (1970), vii + 320 pp. $14.
Contents: I. Polycrystalline Carbon and Graphite, J. M. Hutcheon. II. Manufacturing Technology of Baked and Graphitized Carbon Bodies, J. M. Hutcheon. III. Electron Transport in Graphites and Carbons, G. A. Saunders. IV. Thermal Gas Reactions of Graphite, J. B. Lewis. V. Mechanical Properties, H. H. W. Losty. VI. Friction and Wear, D. V. Badami and P. K. C. Wiggs. VII. Industrial Applications of Carbon and Graphite, A. R. Ford and E. Greenhalgh. The first two chapters, dealing with the several solid forms of carbon and how they are prepared, provide a very lucid and comprehensive account, complete with an extensive bibliography. An excellent summary of electron transport in graphites and carbons is given even though recent work in this area [namely that of Schroeder et al., Phys. Rev.Lett. 20, 1292 (1968), and Woollam, Phys. Lett. 32A, 115 (1970)] has rendered parts of the interpretation of the band structure obsolete. This latter remark is not intended as a criticism but as
J. T.
Activated Carbon by James S. Mattson and Harry B. Mark, Jr., Marcel Dekker, New York (1971), vii +237 pp. $19.75.
MEERS
About 50 per cent of this valuable volume of 237 pages is concerned with a good critical review of selected topics in solution adsorption. About 25 per cent of the volume discusses important recent infrared spectroscopic investigations, mainly by the internal reflection technique; the remaining 25 per cent leaves something to be desired. In the opening paragraphs it is stated that the emphasis of the book would be on the mterpretation of data obtained with well-characterized carbon samples, namely, laboratory-activated sugar carbons. The reviewer looked in vain for a justification of this statement and concluded that such characterization is presently not possible. It is true that with careful choice of starting material, the ash content can be made quite small.
Shortly after World War I it was maintained by some that solid carbon existed in three forms: graphite, diamond and active carbon. Those responsible for the purveyance of the new article of commerce invented the term “activated carbon”, but nothing has since developed to justify the claim for such a species. The reviewer presumes that the authors, Dr. J. S. Mattson and Professor H. B. Mark, Jr., are really concerned with the properties of highly-adsorbent carbonaceous residues obtained empirically from various organic source materials, 117
118
BOOK REVIEWS
However, the molecular structure of a carbonaceous residue has a built-in variability, formed as it is by the run-away reactions during pyrolysis of the source material. The authors do not make it clear how the chemical reactions of a carbon surface, in which they are interested, can be independent of this factor. Many of the results reported in this volume were obtained for systems that used commercial carbon adsorbents by trade names with little reference as to the source materials. There is a good discussion of the role that surface oxygen groups play in carbon adsorbents as shown (1) from the behavior observed during thermal breakdown at various temperatures into CO, COz and Hz0 and (2) from the reactions of the adsorbents in solution with acids and bases. To these the authors have added their own direct observations of surface oxygen groups employing the internal reflection infra-red techniques. Although the new tool has great potential in identifying and dealing with specific chemical groups in the surface, the present stage of the observations are largely descriptive. The reported results do demonstrate that careful and patient research will be needed to unravel the complicated molecular structure of carbon surfaces from measurements of infra-red active vibrations. At present there are many cases where the total oxygen content exceeds the oxygen in the identified surface groups. It is regretable that the current exciting progress in laser Raman scattering from adsorbed films was not developed sufficiently to be included in this publication. Although the volume as a whole may lack a Chapter 6 (Adsorption of coherent theme,
Electrolytes) and Chapter 7 (Adsorption of Weak and Non-electrolytes from Aqueous Solutions) are valuable contributions to solution adsorption. It is challenging to learn that in spite of considerable effort by many investigators, the chemistry of the surface functional groups cannot account for even the elementary behavior of the primary adsorption of acids at pH > 2. Adsorption studies in solution have, in general, been handicapped by the inability to differentiate between a diffusion-controlled process and one dealing with a specific chemical reaction. The authors prefer not to classify solution adsorption processes on carbon adsorbents in terms of “chemisorption” and “physical adsorption”. The presentation is in terms of either a direct interaction of the solute with the surface involving the chemical characteristics of each or by an indirect process which does not involve direct surface interaction. This is an interesting point of view for long range attractions involving charged species. Many of the systems discussed were obviously selected for pertinency to the physicochemical treatment of waste water. The scolding given to the producers of commercial carbon adsorbents (see page 7) does not appear to the Reviewer to be entirelyjustified. Surely after reading and studying this volume, it is doubtful whether producers will be in a much better position “to do additional research into the whys and wherefores of their products.” The elementary facts have yet to be discovered by those skilled in the pursuit of fundamental research. VICTOR
R. DEITZ
Pergamon
Press.
Pnnted ,n Great Bntam
BOOK
REVIEWS a comment on the recent proliferation of knowledge about the many aspects of carbon and graphite. The section on the reactions of gas with carbon and graphite together with its extensive bibliography should be a very useful beginning point for those interested in particular or general problems associated with the topic. While consistent results and interpretations are now being obtained for many simple carbon-gas reactions at low temperatures, the chapter reflects the fact that while this whole area is the most thoroughly worked over in the science of carbon, it is still less than completely understood. Mechanical properties are not given the broad coverage that is maintained in other sections. The reader will have to look elsewhere to find up-todate accounts of this important subject. The editor is to be congratulated for including a chapter on “fraction and wear”, an area which is seldom included formally in books on carbon and graphite. Perspectives of the relative Importance of the many applications of carbon and graphite cited in the last chapter may be gained by carefully studying Table I of that chapter before its reading. Those interested in the science and technology of carbon will find this book easy to read and a valuable reference.
Modern Aspects of Graphite Technology (Edited by L. C. F. Blackman) Academic Press, London and New York (1970), vii + 320 pp. $14.
Contents: I. Polycrystalline Carbon and Graphite, J. M. Hutcheon. II. Manufacturing Technology of Baked and Graphitized Carbon Bodies, J. M. Hutcheon. III. Electron Transport in Graphites and Carbons, G. A. Saunders. IV. Thermal Gas Reactions of Graphite, J. B. Lewis. V. Mechanical Properties, H. H. W. Losty. VI. Friction and Wear, D. V. Badami and P. K. C. Wiggs. VII. Industrial Applications of Carbon and Graphite, A. R. Ford and E. Greenhalgh. The first two chapters, dealing with the several solid forms of carbon and how they are prepared, provide a very lucid and comprehensive account, complete with an extensive bibliography. An excellent summary of electron transport in graphites and carbons is given even though recent work in this area [namely that of Schroeder et al., Phys. Rev.Lett. 20, 1292 (1968), and Woollam, Phys. Lett. 32A, 115 (1970)] has rendered parts of the interpretation of the band structure obsolete. This latter remark is not intended as a criticism but as
J. T.
Activated Carbon by James S. Mattson and Harry B. Mark, Jr., Marcel Dekker, New York (1971), vii +237 pp. $19.75.
MEERS
About 50 per cent of this valuable volume of 237 pages is concerned with a good critical review of selected topics in solution adsorption. About 25 per cent of the volume discusses important recent infrared spectroscopic investigations, mainly by the internal reflection technique; the remaining 25 per cent leaves something to be desired. In the opening paragraphs it is stated that the emphasis of the book would be on the mterpretation of data obtained with well-characterized carbon samples, namely, laboratory-activated sugar carbons. The reviewer looked in vain for a justification of this statement and concluded that such characterization is presently not possible. It is true that with careful choice of starting material, the ash content can be made quite small.
Shortly after World War I it was maintained by some that solid carbon existed in three forms: graphite, diamond and active carbon. Those responsible for the purveyance of the new article of commerce invented the term “activated carbon”, but nothing has since developed to justify the claim for such a species. The reviewer presumes that the authors, Dr. J. S. Mattson and Professor H. B. Mark, Jr., are really concerned with the properties of highly-adsorbent carbonaceous residues obtained empirically from various organic source materials, 117
118
BOOK REVIEWS
However, the molecular structure of a carbonaceous residue has a built-in variability, formed as it is by the run-away reactions during pyrolysis of the source material. The authors do not make it clear how the chemical reactions of a carbon surface, in which they are interested, can be independent of this factor. Many of the results reported in this volume were obtained for systems that used commercial carbon adsorbents by trade names with little reference as to the source materials. There is a good discussion of the role that surface oxygen groups play in carbon adsorbents as shown (1) from the behavior observed during thermal breakdown at various temperatures into CO, COz and Hz0 and (2) from the reactions of the adsorbents in solution with acids and bases. To these the authors have added their own direct observations of surface oxygen groups employing the internal reflection infra-red techniques. Although the new tool has great potential in identifying and dealing with specific chemical groups in the surface, the present stage of the observations are largely descriptive. The reported results do demonstrate that careful and patient research will be needed to unravel the complicated molecular structure of carbon surfaces from measurements of infra-red active vibrations. At present there are many cases where the total oxygen content exceeds the oxygen in the identified surface groups. It is regretable that the current exciting progress in laser Raman scattering from adsorbed films was not developed sufficiently to be included in this publication. Although the volume as a whole may lack a Chapter 6 (Adsorption of coherent theme,
Electrolytes) and Chapter 7 (Adsorption of Weak and Non-electrolytes from Aqueous Solutions) are valuable contributions to solution adsorption. It is challenging to learn that in spite of considerable effort by many investigators, the chemistry of the surface functional groups cannot account for even the elementary behavior of the primary adsorption of acids at pH > 2. Adsorption studies in solution have, in general, been handicapped by the inability to differentiate between a diffusion-controlled process and one dealing with a specific chemical reaction. The authors prefer not to classify solution adsorption processes on carbon adsorbents in terms of “chemisorption” and “physical adsorption”. The presentation is in terms of either a direct interaction of the solute with the surface involving the chemical characteristics of each or by an indirect process which does not involve direct surface interaction. This is an interesting point of view for long range attractions involving charged species. Many of the systems discussed were obviously selected for pertinency to the physicochemical treatment of waste water. The scolding given to the producers of commercial carbon adsorbents (see page 7) does not appear to the Reviewer to be entirelyjustified. Surely after reading and studying this volume, it is doubtful whether producers will be in a much better position “to do additional research into the whys and wherefores of their products.” The elementary facts have yet to be discovered by those skilled in the pursuit of fundamental research. VICTOR
R. DEITZ