Study on the solid-liquid equilibrium of L-malic acid in binary solvents

In this study, the solubility of L-malic acid in three binary solvents (ethyl acetate + tetrahydrofuran, acetonitrile + tetrahydrofuran, butyl acetate + acetonitrile) at atmospheric pressure from T = (278.15 to 323.15) K was measured via a gravimetric method. The results show that in the temperature range studied, the solubility of L-malic acid in the selected solvent gradually increases with the increase of temperature. The solubility of malic add increases with the increase of the mass fraction of tetrahydrofuran at the binary system (ethyl acetate + tetrahydrofuran, acetonitrile + tetrahydrofuran), the solubility of L-malic acid increases with The mass fraction of butyl acetate increases and decreases at the butyl acetate + acetonitrile system. In addition, the dissolution behavior of L-malic add was explained using Hansen solubility parameter (HSP). Furthermore, the solubility data were correlated with using the modified Apelbiat equation, the NICE model and the newly proposed Apelblat-Sun model, the results have shown that the modified Apelbiat equation has the best fitting effect. After research found, the hydrogen bonding force plays a key role in the solubility oft-malic acid. So solubility of t- resulted malic add from the integrated effect of solute-solvent and solvent-solvent interactions. In addition, the van't Hoff equation was used to calculate and discuss all thermodynamic parameters of dissolution, Including standard Gibbs dissolution (Delta(sol)G degrees), standard dissolution enthalpy(Delta H-sol degrees) and standard dissolution entropy (Delta S-sol degrees), Where Delta H-sol degrees, Delta S-sol degrees, Delta(sol)G degrees were all greater than 0, it have been shown that the dissolution process is driven by heat absorption and entropy. This study can provide basic thermodynamic data for the crystallization and industrial separation of L-malic acid. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study measured the solubility of L-malic acid in three binary solvents and found that the solubility increases with temperature. The dissolution behavior was explained using Hansen solubility parameter, and the data were correlated with different models, with the modified Apelbiat equation showing the best fit. Thermodynamic parameters were calculated using the van't Hoff equation, indicating that the dissolution process is driven by heat absorption and entropy. This study provides important thermodynamic data for the industrial separation of L-malic acid.