Study of the Conversion of CaSO4 to CaCO3 within the CaSO4 + Na2CO3 = CaCO3 + Na2SO4 Four-Component Water-Salt System

Abstract

The Pitzer ion-interaction model was employed to predict the conversion in the title quaternary water-salt system. The thermodynamic solubility products (Ks0) were determined and the conversion of CaSO4 to CaCO3 in the CaSO4 + Na2CO3 = CaCO3 + Na2SO4 system was predicted. The standard molar Gibbs free energy ∆rG0 of the conversion reaction was calculated to be -23.62 kJ mol-1. A 98% degree of conversion of CaSO4 was achieved by using calcium sulfate isolated from sea salt production waste brines. Suitable conditions were found for obtaining CaCO3 exhibiting a high dispersity and whiteness.

Thermodynamics of formation of double salts and mixed crystals from aqueous solutions

“…In the presence of a ''neutral'' component (NaOH), system (6) would have a behaviour close to that of system BaSO 4 + K 2 CO 3 = BaCO 3 + K 2 SO 4 , for which a BaSO 4 to BaCO 3 conversion has been established experimentally [52]; 2. In system (7), CaSO 4 should dissolve, and CaCO 3 precipitate, i.e., conversion to CaCO 3 is to be expected [53]. These predictions have been confirmed experimentally.…”

“…In previous studies [52,53], the ion-interaction model has been used to predict the conversion of BaSO 4 and CaSO 4 to BaCO 3 and CaCO 3 , respectively, in the quaternary (water + salt) systems…”

Isodimorphic co-crystallization of isostructural ammonium chloro- and bromo-carnallites

“…(20) The compositions of the thoroughly suction-dried solid phases were calculated by the method of algebraic indirect solid-phase composition identification. (21,15) The double salts were also identified thermogravimetrically with a Paulik-Paulik-Erdey 1500, type 3427 apparatus (22) upon heating to T = 773.15 K. The phase composition of some mixed crystals, obtained from solutions (b 1 NH 4 Cl·MgCl 2 ·6H 2 O + b 2 NH 4 Br·MgBr 2 ·6H 2 O)(aq), were controlled by a DRON-3 powder X-ray diffractrometer (Co Ka radiation) at a recording rate of (p/5400) s −1 .…”

Thermodynamic study of the co-crystallization of 2RbCl·NiCl2·2H2O and 2RbCl·MnCl2·2H2O, at the temperature 298.15 K

“…(18) The compositions of the thoroughly suction-dried solid phases were calculated by the method of algebraic indirect solid phase composition identification. (19,20) The phase composition of some mixed crystals, obtained from solutions (m 1 2RbCl·NiCl 2 ·2H 2 O+m 2 2RbCl·MnCl 2 ·2H 2 O)(aq), were studied by means of a DRON-3 powder X-ray diffractometer (Co Ka radiation) at a recording rate of 5400·p s −1 .…”