Analysis of the effect of temperature, pH, CO_2 pressure and salinity on the olivine dissolution kinetics

摘要

The dissolution kinetics of olivine has been extensively studied under several temperatures, CO_2 pressures, and solution compositions. Dissolution is an important mechanism in the aqueous mineral carbonation process. The overall carbonation reaction consists of dissolution of mineral silicate, e.g. olivine, serpentine and wollastonite, followed by carbonate precipitation, thus fixing CO_2 into naturally occurring stable solids, such as magnesite and calcite. The slowness of the dissolution kinetics hinders the overall carbonation reaction and in order to make the process technically and economically feasible, such a reaction should be sped up by finding the optimum operating conditions. Experiments were performed in a flow-through reactor at 90- 120-150°C. The pH was adjusted by adding either acids (e.g., HCl, citric acid) or LiOH, and by changing PCO_2. The salinity was changed by adding NaCl and NaNO_3. From the experimental data, the dissolution rate was estimated by using the population balance equation (PBE) model coupled with a mass balance, and the obtained values were regressed with a linear model log (r) = -n pH - B, where r is the specific dissolution rate (mol s~(-1) cm~(-2)).