Colloid science in solid/liquid separation technology: is it important?

Of the various fine particle/liquid separation techniques available to the process engineer the most commonly used are variants of filtration, expression and sedimentation. Their simple concept and apparent ease of operation enable the efficient separation of many solid/liquid systems. However, the separation of finer, near colloidal sized, particle suspensions using these techniques frequently poses problems which have undesirable consequences. For example, on occasions the wetness of filter cakes can be inexplicably high, with the result that thermal drying is the only viable method by which the required moisture removal can be achieved. With cost increases of energy forever pending, and demands for improved separation technologies, there is a growing interest in developing alternative and more cost effective methods of separation. To meet this goal it is necessary for both engineers and scientists to work together and to have a basic understanding of how the technology of one affects the science of the other (and vice-versa). This paper considers some of the implications of the work of colloid scientists for the separations technologist, with particular reference to sedimentation and filtration processes.