Apparent Dissolution Kinetics of Diatomite in Alkaline Solution

The dissolution kinetics of diatomite in alkaline solution is the theoretical basis for the process optimization of alkali-diatomite reaction and its applications. In this study, the dissolution kinetics of diatomite in NaOH solution is investigated. The results indicate that the dissolution reaction fits well the unreacted shrinking core model for solid-liquid heterogeneous reactions. The apparent reaction order for NaOH is 2 and the apparent activation energy for the reaction (Ea) is 28.06 kJ·mol−1. The intra-particle diffusion through the sodium silicate layer is the rate-controlling step. When the dissolution reaction occurs at the interface of unreacted diatomite solid core, the diffusion in the trans-layer (the liquid film around the wetted particle) reduces the rate of whole dissolution process.