Filtration and dewatering of the mixture of quartz and kaolinite in different proportions

Abstract Fine minerals, such as silicate and clay minerals are difficult to filtrate and dewater in mineral processing industry. In this study, quartz and kaolinite particles were mixed in different proportions to investigate the filtration and dewatering behavior difference. Combined with the calculation of DLVO theory, the particles size of quartz flocs, kaolinite flocs and the flocs of quartz and kaolinite mixture under pH of 7 and 11 were analyzed by focused beam reflectance measurement (FBRM). In addition, the structure of quartz/kaolinite flocs and the filter cake porosity were analyzed by 3D-high solution X-ray microanalyser (3D-XRM). The mixture of 80% quartz and 20% kaolinite had the maximum filtration velocity. The DLVO theoretical analyses show that the interaction between the aluminum-oxygen surface of kaolinite and silicon-oxygen surface of kaolinite/quartz particles is an attractive force at pH of 7, but repulsion force at pH of 11. The FBRM tests found that quartz and kaolinite tended to form relative larger agglomerates at pH of 7 when compared to a pH of 11. The results of 3D-XRM showed the kaolinite flocs were surrounded by amounts of quartz particles at pH of 7, which formed many quartz-kaolinite agglomerates, and therefore the porosity of the cake was increased for the water to easily pass through, which finally sped up the filtration process. However, quartz and kaolinite were evenly dispersed and had no obvious aggregates phenomenon at pH of 11, and the filtration velocity was slow because the kaolinite filled in the gap between quartz particles, which reduced the porosity of filter cake.