| Description |
Despite their many uses, fine clay particles such as kaolinite are a nuisance in management of tailings in various industries such as the oil sands and phosphate processing industry. The effective flocculation, sedimentation, and consolidation of these fine particles are a major challenge. In industries, polymers are added to tailings suspension to facilitate formation and eventual sedimentation of flocs. The structure of floc and the water entrapped within the floc determine floc behavior and settling characteristics. The quantification of water entrapped within the kaolinite flocs has not been reported before. The information on kaolinite floc size and shape is also limited due to the challenges in experimental procedures for these delicate structures. In this thesis research, operating conditions for kaolinite flocculation were determined and a suitable polymer was chosen by settling experiments. Further investigation of the floc formed was done in suspended state as well as in sedimented state. The flocs were analyzed for their size, shape, water content, and microstructure. A pool of analytical techniques like the Particle Vision & Measurement (PVM), Dynamic Image Analysis (DIA), Scanning Electron Microscopy (SEM), High Resolution X-ray Microtomography (HRXMT), and image processing software like Fiji, Medical Image Processing Analysis & Visualization (MIPAV), and Drishti were used. The analysis of suspended flocs by PVM and DIA revealed a mean floc size of about 225 µm for high molecular weight, 5% anionic polyacrylamide-induced flocs. The low molecular weight, 70% cationic polymer-induced flocs were found to be smaller in size (145 µm). DIA was used to analyze the flocs at different solid concentration. It was found that the increase in solid concentration leads to increase in floc size. Floc circularity was also analyzed by using both these methods. Most flocs were irregular in shape with circularity ranging between 0.2-0.3. However, the circularity results from both these methods do not agree well due to the difference in methods of detection and different definitions used for circularity/sphericity. Major contribution of this thesis work includes development of a new technique for water content and size analysis of sedimented kaolinite flocs. The sediment bed was segmented into about 13 thousand individual flocs and each floc was analyzed for its size and water content. The results suggest a normal distribution of water content for these flocs, with mean water content of 53.9% and standard deviation of 11.8%. About 98% of the flocs 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 increase in size of the floc. The flocs were found to be fairly irregular, with sphericity values around 0.1. The floc shape analysis was also done but limited to 10 flocs. In addition to macroscopic analysis of individual flocs, flocs were also analyzed for their microstructure. Visualization of floc microstructure and polymer chain was done with the help of SEM. Microstructures of up to 10 µm in size were revealed along with the web formed by polymer chain. |
