Multi-scale features including water content of polymer induced kaolinite floc structures

Despite their many uses, fine clay particles, such as kaolinite, present a problem in the management of tailings in various mineral industries such as the oil sands and phosphate processing industries. The effective flocculation, sedimentation and consolidation of these fine particles are major challenges. The structure of the flocs and the water entrapped within the flocs determine floc behavior and settling characteristics. The quantification of water entrapped within the kaolinite flocs has not been reported previously. In this research, a new technique was developed for water content and size analysis of sedimented kaolinite flocs using High Resolution X-ray Microtomography (HRXMT). The results suggest a normal distribution of water content for these flocs, with mean water content of 53.9% by volume and a standard deviation of 11.8%. About 98% of the flocs were found to have water content in the range 30-80%. The size analysis revealed that about 90% of the flocs are less than 1.5 mm in size. The water content was found to decrease with an increase in size of the floc. The floc shape analysis was done for selected flocs. The flocs were found to be fairly irregular, with sphericity values around 0.1. In addition to macroscopic analysis of individual flocs, flocs were also analyzed for their microstructure by cryo-SEM. Visualization of floc microstructure and polymer chains revealed the stabilization of kaolinite microflocs in the web formed by polymer chains. The structure of the polymer chains as well as the interaction between microflocs and polymer chains is a key to understanding floc growth and stability. (C) 2016 Elsevier Ltd. All rights reserved.