Role of metastable phases in the spontaneous precipitation of calcium carbonate

摘要: This paper reports a study of the spontaneous precipitation calcium carbonate from aqueous solutions which are very supersaturated with respect to calcite, both in absence inhibitors, and presence triphosphate as inhibitors. The sequence events during is governed strongly by initial supersaturation, temperature, or triphosphate.At high first-formed phase an amorphous carbonate. It observed only above well defined ionic activity product, homogeneously nucleated, its formation not inhibited triphosphate. Over temperature range 289–333 K, this has solubility K1, equation: log K1=(1247.0/T)– 10.224, At concentrations insufficient produce phase, solid nucleates heterogeneously. In it calcite. triphosphate, first hexahydrate at lower temperatures, vaterite/calcite mixture higher temperatures. CaCO3·6H2O formed temperatures below ca. 25 °C, decomposes vaterite. These crystalline phases also result decomposition CaCO3 supersaturation.In course work, product for (K2) was measured 277–312 K as: K2=(1696/T)+ 0.9336 quantitative basis consistent re-evaluation CaCO03 pair constant K3, K3= 7.722 –(1347.2/T). results show that °C binding CO2–3 significantly greater than earlier publications have suggested: implication distribution species oceans yet be fully assessed.