Effect of Ionic Liquid Additives on the Solubility Behavior and Morphology of Calcium Sulfate Dihydrate (Gypsum) in the Aqueous Sodium Chloride System and Physicochemical Solution Properties at 30 °C

Abstract

We have investigated the solubility behavior of calcium sulfate dihydrate (gypsum, CaSO 4 •2H 2 O) in aqueous NaCl solutions upon the addition of ammoniumor imidazolium-based ionic liquids (ILs), viz., ethylammonium lactate (EAL), 1-ethyl-3methyl imidazolium hydrogen sulfate ([C 2 mim]HSO 4 ), and 1-butyl-3-methyl imidazolium hydrogen sulfate ([C 4 mim]HSO 4 ) at 30 °C. The addition of ammonium lactate ILs increased solubility significantly, ∼500%, whereas the addition of imidazolium hydrogen sulfate ILs decreased the solubility by ∼60%. The addition of ILs shifted the solubility maximum of CaSO 4 •2H 2 O toward either higher or lower concentration of NaCl in solution depending on the nature of IL additive. Solution properties such as density (ρ) and speed of sound (u) have been measured for the quaternary systems (CaSO 4 •2H 2 O + NaCl + ILs + H 2 O) at 30 °C. Solution isentropic compressibility (κ S ) has been derived from measurements of u and ρ. Physical and derived properties have been fitted with suitable polynomial equations. Crystal growth formation and surface morphology of CaSO 4 •2H 2 O crystals recrystallized from different aqueous IL solutions have also been examined. IL additives have shown good potential for calcium sulfate scale removal and as calcium sulfate precipitation agent.

Effect of Cu2+ on the nucleation kinetics and crystallization of rod-shaped CaSO4·2H2O in aqueous solution

“…The nucleation and growth rates of the DH crystal are determined by its equilibrium solubility (C*), and according to several previous reports, [44][45][46][47] the value of C* in this system can be measured by a seeded growth equilibration method and the data are displayed in Table 3. The C* value of saturated gypsum solution can be increased effectively by the introduction of Cu 2+ , and as the concentration of Cu 2+ increases, the C* value is increased gradually.…”

Solubility and Physical Properties of α-Calcium Sulfate Hemihydrate in NaCl and Glycerol Aqueous Solutions at 303.15, 323.15, and 343.15 K

“…Most of them are about the effect of adding an electrolyte on the solubility of calcium sulfate in an aqueous solution. − The mechanism of the effect mainly includes three aspects: salt effect, complexation effect, and common-ion effect. For example, Kumar et al. , studied the effects of nitrate salt, chloride, and ionic liquid additives on the solubility, physical properties, and crystal growth of DH. The solubility data of DH and α-HH in a Ca–Mg–K chloride aqueous solution at 348.15–371.0 K were described by Wu et al , The results provide a theoretical basis for the preparation of α-HH from dihydrate gypsum.…”

Management of Solid Waste Marble Powder: Improving Quality of Sodium Chloride Obtained From Sulphate Rich Lake/Subsoil Brines With Simultaneous Recovery of High Purity Gypsum and Light Basic Magnesium Carbonate

“…TGA measurements were performed using a TGA/SDTA851 Mettler Toledo under a nitrogen atmosphere from 0 to 800°C with a heating rate of 10°C min −1 . XRD pattern was recorded using Philips X'pert MPD XRD diffractometer and morphology of precipitated crystals was investigated using FE-SEM (JFM 7100 F; Oxford Inc.) the adopting procedure reported in earlier paper (Shukla et al, 2018).…”