Aggregate structures and solid-liquid separation processes

Solid-liquid separation processes for dispersions of fine particles continue to present significant challenges in many areas. As an example, in filtration it is usually possible to achieve either fast filtration or a dry cake, but rarely both. To achieve both a compact dry cake and rapid filtration will rely upon an increased ability to control the particle network structure of the filter cake throughout the whole process, with a probable requirement being a controlled structural change from the beginning to the end of the filtration. An obvious pre-requisite is a detailed knowledge of how to control the structure of sediment beds during flocculation processes. Recent advances in measurement technology have provided unique insights of the relationship between the mechanism (bridging, depletion, charge neutralisation) and conditions of flocculation and resultant aggregate structures. As a consequence, the link between aggregate structures and sediment bed properties is also being investigated with renewed interest. Clearly, the link between flocculation, aggregate structure and sediment bed is vital in the understanding and control of solid-liquid separation processes. This paper will present a review of recent research linking aggregate formation and characterisation of solid-liquid dispersions to subsequent physical properties of the sediments and filter cakes that they produce.