ABSTRACT
In the recent years, we have obtained plenty of data of the mineral dissolution rates in aqueous solutions based on the kinetic experiments of the open-flow system. The experiments suggest that the kinetic processes of the mineral dissolutions have non-linear behavior, particularly in the reaction system far removed from equilibrium state. It has been found that the reaction rate is only stable in a short period of time, when the experimental conditions are fixed. The time for keeping the steady state of the kinetic process depends on the different minerals, the different solutions, and the physical conditions. The rates of the mineral dissolutions were measured by using a packed bed reactor and in an open-flow system. The experiments in the mineral-aqueous solution system indicate that the output concentrations of the dissolving species of the reactant products from the open flow system are not stable in some cases, in a very long term experiment, while maintaining the constant chemical and hydrodynamic conditions. The observation of the output products is carried by using an electronic conductivity detector, and recording the electronic conductivity of the output solutions continuously. And also we take the liquid example for chemical analysis. The experimental results also indicate that the reaction rates were weakly waving within a long time period. The phenomena of the non-linear behavior have been found in the fluorite-HCl-H2O system, such as the multi-steady states, self-transient of the state, and complex chaotic oscillation of the concentrations of the dissolving species in the output solutions. When change the input from water to HCl-aqueous solution in a continuous flow system, the reaction system will have a response in the output solutions for this change. This is a step change of an input solution, which can drive a non-linear response of the output solution. For instance, a temporary complex oscillation of the output solution appears in that case. This study suggests a solid-liquid interface pattern to illustrate this non-linear behavior. This model describes the coupling processes of adsorption, surface reaction, surface ion exchange and diffusion or transportation processes. And also, the multi-steps of the reaction and intermediate products on surface involve in the kinetic process, which can derive a non-linear kinetic processes.
