Hygroscopic Growth and Phase Transitions of Na₂CO₃ and Mixed Na₂CO₃/Li₂CO₃ Particles: Influence of Li₂CO₃ on Phase Transitions of Na₂CO₃ and Formation of LiNaCO₃

Abstract

The hygroscopic behaviors and phase changes of inorganic aerosols have been widely explored, but little is known on the hygroscopicity of soluble carbonates. The hydrated states of solid Na 2 CO 3 particles in an air environment remain largely unclear. In this work, the hygroscopic growth, hydrated form transformations, and influence of internal Li 2 CO 3 on phase transitions of Na 2 CO 3 particles are investigated in linear and pulsed relative humidity (RH) changing modes by the vacuum Fourier transform infrared (FTIR) technique. For pure Na 2 CO 3 , aqueous droplets effloresced to a mixture of anhydrous Na 2 CO 3 and Na 2 CO 3 •H 2 O with the initial efflorescence relative humidity (ERH) of 50.8%, probably concerning the formation of Na 2 CO 3 •10H 2 O in the conversion from aqueous to anhydrous Na 2 CO 3 . A reverse process is presented during the three-stage deliquescence transition beginning at ∼60.1% RH; i.e., anhydrous Na 2 CO 3 transforms into aqueous Na 2 CO 3 and Na 2 CO 3 •10H 2 O in stage I, Na 2 CO 3 •10H 2 O dissolves to aqueous Na 2 CO 3 in stage II, and Na 2 CO 3 •H 2 O dissolves into aqueous Na 2 CO 3 in stage III. For internally mixed Na 2 CO 3 /Li 2 CO 3 particles, a double salt, LiNaCO 3 , is found in mixed crystalline phases for the first time, leading to the eutonic composition with Na 2 CO 3 . The experimental observations point to the excess of LiNaCO 3 and complete consumption of Na 2 CO 3 in eutonic composition formation, which results in the absence of Na 2 CO 3 hydrates during phase transitions. The results provide key data for model simulations of hygroscopic properties and phase transitions of Na 2 CO 3 as well as mixed soluble carbonates.

Advanced Li/Na–CO2 Batteries Enabled by the γ-MnO2 Catalyst with Enhanced Carbonate Decomposition

“…Besides, there is an obvious peak at around 947 cm –1 , which is related to the characteristic peak of Na + ClO 4 – , as the migration of Na + into and out of the electrolyte during the discharge/charge cycle could affect its concentration. , It is noteworthy that the γ-MnO 2 peaks always exist during the whole cycle, indicating its stability. Moreover, the FTIR spectra also demonstrate the reversible formation and decomposition of Na 2 CO 3 , as shown in Figure f . In particular, the remaining peaks at ∼1100 and 1460 cm –1 could be assigned to the residual TEGDME in the cathode. , The XRD pattern is also consistent with the above results (Figure S8b).…”

“…Moreover, the FTIR spectra also demonstrate the reversible formation and decomposition of Na 2 CO 3 , as shown in Figure 5f. 52 In particular, the remaining peaks at ∼1100 and 1460 cm −1 could be assigned to the residual TEGDME in the cathode. 47,53 The XRD pattern is also consistent with the above results (Figure S8b).…”

Unveiling the different physicochemical properties of M-doped β-NaFeO2 (where M = Ni or Cu) materials evaluated as CO2 sorbents: a combined experimental and theoretical analysis

“…On the other hand, the vibrational bands at 1440 and 1411 cm −1 , observed in all samples, are related to the stretching modes ν (CO 3 ) of carbonate species. 51 Due to the low intensity of the bands, these are linked to carbonate species adsorbed on Na + sites, rather than to the Na 2 CO 3 solid phase; this is confirmed below with the Raman characterization. In any case, results indicate that materials can capture some environmental CO 2 at room temperature, regardless of doping.…”