Solubility of 2-nitro-p-phenylenediamine in nine pure solvents and mixture of (methanol plus N-methyl-2-pyrrolidone) from T = (283.15 to 318.15) K: Determination and modelling

By using the isothermal saturation method, the solid-liquid equilibrium of 2-nitro-p-phenylenediamine in pure organic solvents of methanol, ethanol, n-propanol, isopropanol, N-methyl-2-pyrrolidone, acetonitrile, ethyl acetate, toluene and 1,4-dioxane and liquid mixture of (N-methyl-2-pyrrolidone + methanol) was obtained experimentally at the temperatures ranging from (283.15 to 318.15) K under atmospheric pressure, and the solubility of 2-nitro-p-phenylenediamine in the selected solvents was determined by a high-performance liquid chromatography (HPLC). Within the studied temperature range, the 2-nitro-p-phenylenediamine solubility in mole fraction in these solvents increased with increasing temperature. The descending order of the mole fraction solubility in pure solvents was as follow: (N-methyl-2-pyrrolidone, 1,4-dioxane) > ethyl acetate > acetonitrile > methanol > ethanol > n-propanol > isopropanol > toluene, and for the (N-methyl-2-pyrrolidone + methanol) mixture with given initial composition, the mole fraction solubility of 2-nitro-p-phenylenediamine increased with increasing temperature and mass fraction of N-methyl-2-pyrrolidone. The values of solubility for 2-nitro-p-phenylenediamine in pure solvent were correlated and calculated with the modified Apelblat equation, lambda h equation, Wilson model and NRTL model; and in the binary solvent mixture of (N-methyl-2-pyrrolidone + methanol), the Jouyban-Acree model, modified Apelblat-Jouyban-Acree model and Sun model. For the pure solvents, the largest values of the relative average deviation (RAD) and root-mean square deviation (RMSD) obtained by the four models were 1.17% and 6.80 x 10(-4), respectively; and for (N-methyl-2-pyrrolidone + methanol) mixture, they were a lirger, which were 3.59% and 19.12 x 10-4(-1) ln general, the selected thermodynamic models were all acceptable for describing the solubility behaviour of 2-nitro-p-phenylenediamine in the solvents. In addition, the mixing properties including the mixing Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient at infinitesimal concentration (gamma(infinity)(1)) and reduced excess enthalpy (H-1(E,infinity)) were calculated for 2-nitro-p-phenylenediamine in pure solvents. Knowledge of the solubility and thermodynamic studies is essential in optimizing the purification process of 2-nitro-p-phenylenediamine. (C) 2017 Elsevier Ltd.