Sedimentation particle size analysis, methods

In the paper presented here I intend to describe some of the methods for sedimentation particle size analysis in current use. Although I do not intend to cover operating procedures it would be remiss of me not to mention the two factors which, more than anything else, lead to incorrect analyses. The first is incorrect sampling analyses are carried out on from a... 

The choice of method from available resources depends largely upon the properties of the material to be analyzed, the basic significance or physical wearing of the measurement, and the purpose for which the information is required. For example, failure to disperse the particles as discrete entities is the biggest single problem in all size analysis methods that depend on individual particulate behavior. With microscopic techniques particles must be dispersed on the slide to permit observation of individual particles, and in sedimentation techniques the material must be suspended in the fluid so that the particles behave as individuals and not as floes. 

Turbidimetric methods for particle size analysis (Refs 10, 16 27) are used in conjunction with sedimentation procedures to determine the concn of particles at given distances below the surface at successive time intervals. From these data, and Stokes law, particle size distribution can be calculated... 

US Dept of Commerce (1967) 37) R. Abbott, N. Gelber N. Liszt, Particle Size Analysis of Ammonium Perchlorate by the MSA Sedimentation Method", PATM 1778 (1967) 38) C.E. 

Sedimentation runs should be conducted at a constant temperature, not only so that Ap and T7 are known, but also to minimize disturbances due to convection. Any sort of disturbance will obviously disrupt the segregation of the particles by size that has occurred as a result of sedimentation. An intrinsic difficulty with the balance method lies in the fact that the liquid below the balance pan is less dense than the liquid with dispersed particles above the pan. Thus, there is a tendency for a counterflow of pure solvent to arise, which would introduce an error in the particle size analysis. 

NFX 11-681 Test Methods for Particle Size Analysis-Particle Size Analysis by Gravity Sedimentation in a Liquid Medium, 360... 

II ASTM C958 (1997), Standard Test Method for Particle Size-Analysis of Alumina or Quartz by X-ray Monitoring of Gravity Sedimentation, 360... 

Mueller, R., Kammler, H.K., Wegner, K., and Fkatsinis, S.E., The OH-surface density of SiOj and TiOj by thermogravimetric analysis, Langmuir, 19, 160, 2003. Bernhardt, C., Particle Size Analysis, Classification and Sedimentation Methods, Chapman Hall, London, 1994. 

Other samples of alkaline slurry were subjected to particle size analysis by sedimentation. With the —43 xm + 1.2 [im fraction this analysis was done in a 50-mm-diameter settling column of dilute slurry with a tared pan at the base to record continuously the mass of sedimented solid. The data were analyzed by the method of Oden (8), and the particle size distribution (Stokesian diameter), expressed on a mass percent basis, was calculated. 

Some advantages of disc centrifuge sedimentation method include (1) the disc centrifuge allows a wide dynamic range of particle size analysis, depending on particle density, from 30 jun down to 0.01 pm (2) any particle which can be centrifuged can be analysed (3) large representative sample (lO particles) (4) requires only 0.5-1.0 ml sample of 0.05-0.5% concentration. 

BS ISO 13317 (2000) Particle size analysis - gravitational sedimentation methods. British Standards Institution, London. 

Bernhardt C (1994) Particle Size Analysis, Classification and Sedimentation Methods. London Chapman Hall. 

Cummings Sedimentation Method. An approximate method of particle-size analysis having the merit of giving a weight/size distribution directly. (D. E. Cummings, J. Industr. Hyg. Toxicol., 11, 245,1929.)... 

Allen, T., Particle Size Measurement (Powder Technology Series), 5th edn, Chapman Hall (November 1997), ISBN 0 41275 350 2 Bernhardt, 1. C., Particle Size Analysis—Classification and Sedimentation Methods, Chapman Hall (September 1994), ISBN 0 41255 880 7 Gy, P. and Royle, A. G. (translator). Sampling for Analytical Purposes, John Wiley Sons Ltd (abridged 153 pages) (July 1998), ISBN 0 47197 956 2 Kaye, B. H., Characterization of Powders and Aerosols, John Wiley Sons Ltd (January 1999), ISBN 3 52728 853 8... 

If, for instance, the separation effect is influenced only by the mobility of particles in fluids, the terminal setding velocity or Stokes diameter could be used for the size x and the method of particle size analysis would be chosen accordingly (sedimentation or elutriation). 

The main advantage of particle size analysis by ultracentrifugal sedimentation over other methods such as dynamic light scattering is the enhanced resolution precision (typically 0.25%) and accuracy. Particle bands differing by only 5% in size may be differentiated. 

A Review of Sedimentation Methods of Particle Size Analysis... 

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