Holographic interferometry study of the dissolution and diffusion of gypsum in water

TL;DR

This study uses holographic interferometry to measure the dissolution rate and interdiffusion coefficient of gypsum in water, providing microscopic insights that differ from macroscopic measurements.

Contribution

It introduces a holographic interferometry method to directly measure microscopic dissolution parameters of gypsum in water.

Findings

Interdiffusion coefficient D = 1.0 x 10^-9 m^2/s

D value aligns with theoretical predictions

Dissolution rate constant k = 4 x 10^-5 mol/m^2/s, lower than macroscopic estimates

Abstract

We have performed holographic interferometry measurements of the dissolution of the (010) plane of a cleaved gypsum single crystal in pure water. These experiments have provided the value of the dissolution rate constant k of gypsum in water and the value of the interdiffusion coefficient D of its aqueous species in water. D is 1.0 x 10^-9 m2 s^-1, a value close to the theoretical value generally used in dissolution studies. k is 4 x 10^-5 mol m^-2 s^-1. It directly characterizes the microscopic transfer rate at the solid-liquid interface, and is not an averaged value deduced from quantities measured far from the surface as in macroscopic dissolution experiments. It is found to be two times lower than the value obtained from macroscopic experiments.