1. Introduction to colloid science and rheology 2. Hydrodynamic effects 3. Brownian hard spheres 4. Stable colloidal suspensions 5. Non-spherical particles 6. Weakly flocculated suspensions 7. Thixotropy 8. Shear thickening 9. Rheometry of suspensions 10. Suspensions in viscoelastic media 11. Advanced topics.

Colloidal Suspension Rheology

Colloidal behavior of aqueous montmorillonite suspensions: The specific role of pH in the presence of indifferent electrolytes

pH-dependent surface charging and points of zero charge. IV. Update and new approach.

Application of filtration aids for improving sludge dewatering properties – A review

The role of reactive surface sites and complexation by humic acids in the interaction of clay mineral and iron oxide particles

To characterize and optimize the compressi®e dewatering of suspensions, rapidly determinable material parameters are required. A mathematical framework exists for char() acterization of dewatering using three parameters: the compressi®e yield stress P , the y () ( ) hindered settling function r , and a solids diffusi®ity D .An ew®ariation on traditional constant pressure, batch filtration tests is described along with a computer-controlled filtration apparatus that enables complete characterization of a suspension with respect to dewatering in a matter of hours. The testing methods are ®alidated experimentally on flocculated zirconia suspensions along with calculation of the material dewatering parameters. Application of the calculated parameters to modeling of a real filtration test shows excellent agreement. Practical implications of the modeling are also discussed.

Rapid filtration measurement of dewatering design and optimization parameters

Characterization of the compressibility and permeability of flocculated suspensions is a time-consuming experimental process that often takes days to perform. A new pressure filtration method developed characterizes a sample only in hours. Using stepped pressure filtration, the compressive yield stress Py (ϕ) and a hindered settling function R(ϕ) of flocculated suspensions are determined as a function of the solids volume fraction ϕ. Traditional pressure filtration experiments involve the pressure filtration of a particulate suspension in which the time of filtration t is monitored as a function of piston height from which the specific volume of filtrate V is determined. Py (ϕ) is determined from the equilibrium solids volume fraction. The gradient d(t/V)/dV is traditionally used to determine R(ϕ) using a suspension filtration theory developed by Landman and White. The new method uses only one stepped pressure compressibility filtration test and one stepped pressure permeability filtration test to determine Py (ϕ) and R(ϕ) for multiple solids volume fractions and substantially decreases the time required for sample characterization. To eliminate the influence of a stepped pressure on calculated permeabilities, the analysis of experimental results was modified using the gradient dt/dV2. Results are presented for a zirconia suspension comparing both single and stepped pressure filtration.

Validation of a new filtration technique for dewaterability characterization

The role of swelling clays in hindering the compressional dewatering characteristics of coal-mine tailings is examined. The effects of electrolyte concentration and ion exchange in improving the shear and compressional rheology are compared. Suspensions studied include actual mine tailings (thickener feed and thickener underflow) as well as synthetic clay dispersions made from clay collected from the coal seam. It was shown that the most important parameter in controlling the properties of the tailings suspension is controlled dispersion in the presence of a Ca{sup 2+} electrolyte concentration in excess of that required to (1) prevent initial swelling and (2) provide full cation exchange of the clay. Under these electrolyte conditions, complete delamination of the clay did not occur, and both the dewatering and handling characteristics of the resultant suspensions improved dramatically.

Improving clay-based tailings disposal: Case study on coal tailings

Surface chemistry-rheology inter-relationships in clay suspensions

Compressive rheology, or the behaviour of suspensions in sedimentation and compression has been widely studied and many theories, using different physical quantities, have evolved in parallel. This review article provides a basis for the reconciliation of these approaches via presentation of the Buscall-White (1987) approach to consolidation, which uses a compressive yield stress, Py(φ), and a hindered settling factor, R( φ), to quantify the strength of a particle network in compression and the inter-phase drag respectively, and linking it to other theories and related de-watering parameters available in the literature. The links between behaviour of a concentrated particle system in shear and compression are then discussed and a review of the various experimental methods available for determination of the dewatering parameters is presented. The final section overviews the practical application, benefits and limitations of models for real de-watering processes.

Ross G. de Kretser

Papers

Rapid filtration measurement of dewatering design and optimization parameters

Validation of a new filtration technique for dewaterability characterization

Improving clay-based tailings disposal: Case study on coal tailings

Surface chemistry-rheology inter-relationships in clay suspensions

Compressive rheology : an overview