An approach of the whiteness quantification of crushed and floated talc concentrate

The influence of the particles shape of crushed and floated talc for different size fractions on the whiteness index (parameter Y) was quantified by the fractal dimensions D-f of the contour roughness and D-g of the size distribution. Contours were obtained by an image analysis method and the fractal dimension D-f was calculated by the Richardson-Mandelbrot method. Frequency distributions of D-f for the talc particles < 20 mu m show higher values of D-f (between 1.25 and 1.35) after wet grinding in a ball mill with ceramic grinding media (Y = 85-86%) than after dry grinding with hammer mill Forplex (Y = 88.5%). This can be related to an increase of the number of particles with complex morphology that could influence the light distribution during the whiteness measurements. An increase in D-g values can be related to the presence of greater number of fine particles that could influence the quality of floated concentrates and then correlatively the whiteness of this concentrate.