Effect of hydroxyl alkyl amines on the solubility behavior of calcium sulphate dihydrate (gypsum) in the aqueous sodium chloride system at 35 °C

Shukla, Jignesh ; Kumar, Arvind

Abstract

The solubility behavior of calcium sulphate dihydrate (gypsum, CaSO4·2H2O) in aqueous NaCl solutions upon addition of hydroxyl alkyl amines, such as, ethanolamine (EA), diethanolamine (DEA), or triethanolamine (TEA) at 35 °C is reported.  The addition of hydroxyl alkyl amines alters the solubility of CaSO4·2H2O in NaCl solutions significantly. At any equal concentration of hydroxyl alkyl amines in the solution, the order of CaSO4·2H2O solubility enhancement is found to be: EA < DEA < TEA. A three-fold increase in CaSO4·2H2O solubility maximum is observed in the solutions containing 15 wt% TEA. The addition of hydroxyl alkyl amines shifts the solubility maximum of CaSO4·2H2O towards higher concentration of NaCl in solution. Solution properties such as density (ρ) and speed of sound (u) data have been measured for the quaternary systems (CaSO4·2H2O+NaCl+hydroxyl alkyl amines+H2O). All the measurements have been carried out at 35 °C under atmospheric pressure. Solution isentropic compressibility (κS) values have been derived from u and ρ data. Solubility, density, speed of sound, and isentropic compressibility data have been fitted with suitable polynomial equations in these systems.

Keyword(s)

Solution chemistry, Solubility, Density, Compressibility, Calcium sulphate, Gypsum, Hydroxyl alkyl amines

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