Solubility and reaction rates of oxides and hydroxides to high temperatures with in situ pH measurement

摘要

Summaries of experimental studies involving the equilibrium solubility of the crystalline solid phases boehmite (AlOOH), zincite (ZnO), and neodymium hydroxide (Nd(OH)_3), and the dissolution/precipitation rates of aluminum solid phases (boehmite and gibbsite, A1(OH)_3) are presented. These experiments were performed over a wide range of pH (2-10), temperature (30 to 290°C), and ionic strength (0.03-5.0), using a hydrogen-electrode concentration cell (HECC). This cell provides continuous, accurate in situ pH measurements of solid/solution mixtures to 295°C. Some of the potentiometric investigations were complemented by batch (AlOOH and ZnO), and flow-through column (ZnO) experiments. This research represents the first studies ever reported of mineral solubility profiles across the entire pH range of natural waters, and their precipitation/dissolution rates at temperatures above 100°C, involving direct pH monitoring.