Effect of flocculating agents on solubility behavior of calcium sulfate dihydrate (gypsum) in aqueous sodium chloride system and solution properties at 35 °C

摘要

The effect of addition of flocculatingagents, viz., alum (KAl(SO4)2·12H2O) (up to 10wt%) and polyaluminum chloride ([Al(OH)aClb]n,a >1.05; n~15) (up to 6 wt%) on the solubility behavior of calcium sulfatedihydrate (gypsum, CaSO4·2H2O) in aqueous NaCl solutions hasbeen examined at 35 °C. The solubility of CaSO4·2H2Odecreases with the addition of alum while it increases with the addition ofpolyaluminum chloride without any significant shift in solubility maximum.Density (ρ) and speed of sound (u) have also been determined for thequaternary systems (CaSO4·2H2O+NaCl+alum/PAC+H2O)at 35 °C and used to estimate solution isentropic compressibility (κs) and ion-hydration (nh)characteristics. Empirical equations describing the s, ρ, u and κs as a function of solution composition are presented.