Structural Changes in Boehmite Slurries Due to Shear Forces

There are currently 300 million liters of radioactive waste from the Cold War era being managed by the U.S. Government. This radioactive waste is stored in many tanks that consist of highly basic slurries made up of oxyhydroxides and aluminum hydroxides, such as boehmite. These slurries have unique properties that make moving and treating the waste a difficult task. In this study, suspensions of synthetic boehmite are used to mimic the behavior of the radioactive waste slurries. Rheometry techniques are used to investigate the particle interactions in the slurry. The investigation is conducted using a rheometer with several different techniques used to determine how these rheological properties change with increased flow. The properties of these slurries are investigated at many different conditions including varying pH of solution and concentration of boehmite. Results from these rheological experiments show that the slurries experience a structural change after a certain shear rate, with the largest changes occurring at a ‘critical’ pH. The structural changes induced by shearing lead to changes in the bulk rheological properties of the slurries. Frequency sweeps were conducted before and after shear rate ramp tests to conclude the final changes in slurry properties. The combination of these two types of measurements reveals that pH of solution has an impact on when the structural change occurs, as well as the magnitude of change. This study reveals a rheological trend that can be observed with multiple measurement techniques in slurries near pH 12.