160 servation and automotive transport, environmental protection, and oil spills on land and water. This is quite a mixed bag, some of it rather spec...

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servation and automotive transport, environmental protection, and oil spills on land and water. This is quite a mixed bag, some of it rather specialised. Perhaps of most general interest is the section on environmental protection which contains reviews by Jimeson and by Ecke and Dreyhaupt of governmental environmental policy in the U.S.A. and in W. Germany, respectively, and a paper by Sutton on the evaluation and control of noise in process plant. F. P. Lees

Flocculation by R. J. Akers, published by 1. Chem. E. Services, London, 1975; 32 pages; Price E4.00. This review stems from an Institution of Chemical Engineers Industrial Research Fellowship in Flocculation which was held by Dr. Richard Akers. Dr. Akers is one of the very few British academics who specialize in the applied colloid chemistry of dispersions. The fellowship enabled him to see, at first hand, how flocculation is being employed in a wide range of industries, as well as to discuss the basic scientific problems with other specialists. The objectives of the enquiry were defined as: “(i) to survey the current state of flocculation in terms of current scientific knowledge and the application of that knowledge to flocculation technology, and (ii) to report and make recommendations as to those aspects of the subject that merit particular attention and into which useful research might be conducted”. The present publication is the resulting report. It reveals, only too clearly, that treating slimes and sludges is still a “messy” and formidable problem of


considerable economic and environmental importance. Although colloid chemists have progressed significantly with the theory of electrolytic coagulation of model lyophobic colloids and have introduced a range of new polymeric flocculants, methods of thickening and de-watering real sludges are still largely in the hit-or-miss testing stage. Even the machinery used for these operations gives the impression of having been invented by amateurs, rather than of having been designed according to professional engineering principles. Dr. Akers has collected a great deal of technical “know-how” in the course of his enquiry and he sets it out in a plain, competent and unpretentious manner. He covers inorganic coagulation as well as flocculation by polymers, and briefly summarizes current practice in various industries in which these troublesome suspensions are encountered. He concludes with a baker’s dozen of recommendations for research into chemical, engineering and plant design problems related to flocculation. The final recommendation is that “any syllabus on solid-liquid separation in a chemical engineering course should include a section on the principles and applications of flocculation”. The report itself would provide an ideal study guide, as it includes about 100 references to selected literature on particular aspects. There is a useful appendix on coagulants and flocculants and suppliers of proprietory cures for all manner of slurries. The overall exercise has done valuable service in drawing the attention of chemical engineers to the problems which need research in order to raise flocculation to a more respectable technological status. J. A. Kitchener