Channel flow cell studies of the inhibiting action of gypsum on the dissolution kinetics of calcite: A laboratory approach with implications for field monitoring
Sj. Wilkins et al., Channel flow cell studies of the inhibiting action of gypsum on the dissolution kinetics of calcite: A laboratory approach with implications for field monitoring, J COLL I SC, 236(2), 2001, pp. 354-361
The rate of dissolution of surface-treated calcite crystals in aqueous acid
ic solution has been studied using an adaptation of the channel how cell me
thod with microdisc electrode detection. Surface treatments of calcite with
sulfuric acid lead to the nucleation of gypsum overgrowths, which reduce t
he rate of dissolution of calcite. Rate constants for untreated calcite and
calcite pretreated with sulfuric acid conditions of 0.01 M for 1 h, 0.05 M
for 5 h, and 0.1 M for 21 h are found to be 0.035, 0.018, 0.006, and 0.004
cm s(-1), respectively, Deterioration of calcite materials caused by acid
deposition was investigated by held exposure of untreated and sulfate pretr
eated calcite racks under urban conditions for 12 months. The rate constant
for both pretreated and untreated calcite exposed to weathering is 0.003 c
m s(-1). This suggests that calcite self-passivates the surface from furthe
r reaction when exposed to acid deposition. However, surface studies indica
te that the surface undergoes erosion and dissolution before passivation, P
retreatment of the surface with sulfate protects the surface from acid depo
sition so it remains less reactive toward acid compared with untreated calc
ite. (C) 2001 Academic Press.