| Research Abstract |
This study investigates dissolition of calcite at pH5 over a wide range of phosphate concentration (1.0x10^<-6>-5.0x10^<-1> molar). The result is that the phosphate ions act as an inhibitor on the dissolution rate of calcite at low concentration, but at high concentration (about upper 10^<-4> molar), the calcite dissolution rate increases as phosphate ions increasing. From the experiments at various phosphate concentration, also SEM photomicrographs of the calcite surface under high concentration of phosphate, it was concluded : (1) for low concentration of phosphate ion, its chemical adsorption, which can be described by a Langmuir isotherm equation, to the calcite surface makes the reaction area smaller, and the dissolution rate of calcite slower, (2) phosphate ions act as a buffer of the hydrogen ion concentration at the calcite surface and its effect appears as rate increasing of the calcite dissolution.
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