Adsorption Inhibition of the Growth of CaSO4 • 2H2O Crystals in Aqueous Solutions

The growth of gypsum CaSO4 center dot 2H(2)O crystals in aqueous solutions has been investigated, both on individual crystals and on crystals in a homogeneous suspension in the supersaturation range 1-20 and the temperature range 291-303 K. The dependence of the crystal growth rates on supersaturation is described by an S-shaped curve, which is due (i) to the specific features of CaSO4 self-adsorption on the surface of growing gypsum crystals and (ii) to the multistage character of dehydration of Ca2+ and ions at the transition from the solution to the solid. At solution supersaturations of similar to 20, at which the adsorption layer is close to saturation, the growth rate weakly depends on supersaturation, approaching the limit value G(jp). A model of the crystal hydrate growth in the kinetic mode is constructed which reveals the conditions at which the growth rate reaches the limit value G(jp) and does not change with a further increase in supersaturation.