Some electrokinetic behaviour of tin tailing slimes

Tin tailing slimes from three ex-mining ponds located in different parts of Malaysia and with different clay compositions were studied. Pengkalan slime contained about 8% of montmorillonite clay; Serendah (SH) slime had a high content of amorphous materials (24%) while the main constituents of all samples were kaolinite and illite with a small amount of organic materials and microorganisms as exemplified by Malim Nawar slime. The surface nature of the clay minerals in these slimes was characterised using the particle microelectrophoresis technique. The electrokinetic behaviour of the slime basically followed that of kaolinite but differences due to compositional variations were evident. This is especially so for the SH slime where the amorphous materials present completely modified the surface property of the kaolinite. The magnitude of the electrophoretic mobility depended strongly upon the exchangeable cations associated with the clay particles and pore fluid chemistry of the slime samples. The evaluation of the isoelectric point of the edges of clay particles by the electrokinetic method is discussed. The importance of understanding the charged surfaces of the clay minerals in the slimes in relation to the design of an efficient dewatering programme is briefly discussed.