Inhibitor effects on calcite growth at low supersaturations

Abstract

The effect of the inhibitors sodium triphosphate (STP) and poly(maleic) acid (PMA) on the crystal growth kinetics of calcite has been studied in the supersaturation range 0.6 < σ < 2.5 using the constant composition technique. In the absence of inhibitor, constant growth rates to high outgrowths are observed.

Both inhibitors give rise to reproducible reductions in growth rate and reproducible inhibition periods. Recovery of growth rate following inhibition is essentially complete for STP but not for PMA. Up to a critical inhibitor concentration the growth rate can be described by an expression based on the Langmuir isotherm and inhibition periods are linearly dependent on inhibitor concentration. At higher inhibitor concentrations growth rates become very insensitive and inhibition periods very sensitive to inhibitor concentration. These two regions of inhibitor behaviour are also observed when supersaturation is varied at constant inhibitor concentration.