Dissolution behavior of 2-ethylanthraquinone in various neat solvents: Solubility, correlation and thermodynamic analysis

Alkylated anthraquinone is widely used as promising redox-active materials for both redox flow batteries technology and hydrogen peroxide production via anthraquinone oxidation (AO) process, yet its inadequate solubility in solvents has been the one of the main limitations resulting to insufficient energy density of working solution. In present study, solubility of 2-ethylanthraquinone was specifically investigated by the synthetic method at the temperature range from 304.15 to 344.15 K under the pressure of 101.325 kPa. In support for decent working solution exploit, various types of solvents were specifically selected as the working solution constituent in this work. Solubility data and activity coefficient of 2-ethylanthraquinone were correlated by modified Apelblat and λ-h models. Furthermore, thermodynamic analysis was subsequently performed based on the thermodynamic fitting results. As a result, dissolution process of 2-ethylanthraquinone is endothermic and entropy-driven in these neat solvents, higher dissolution temperature leads to smaller value of partial molar excess Gibbs free energy and therefore results to a greater solubility.