Solubility of disodium 4,4′-dinitrostilbene-2,2′-disulfonate and sodium 4-nitrotoluene-2-sulfonate in aqueous organic solutions and its application feasibility in oxidation stage of DSD acid synthesis

• Solubility of sodium 4-nitrotoluene-2-sulfonate in two aqueous organic solution were measured using dynamic method.
• Solubility of disodium 4,4′-dinitrostilbene-2,2′-disulfonate in corresponding solution were measured using dynamic method.
• The experimental data were correlated with electrolyte non-random two-liquid (E-NRTL) model.
• A synergistic effect on disodium 4,4′-dinitrostilbene-2,2′-disulfonate solubility was observed.
• A suitable solvent for oxidation of 4-nitrotoluene-2-sulfonic to 4,4′-dinitrostilbene-2,2′-disulfonic has been suggested.

Solid–liquid equilibrium (SLE) measurements for disodium 4,4′-dinitrostilbene-2,2′-disulfonate (DNSNa) and sodium 4-nitrotoluene-2-sulfonate (NTSNa) in aqueous ethylene glycol monoethyl ether solution and aqueous ethylene glycol monobutyl ether solution were conducted using a dynamic method over the temperature range from (280 to 335) K. A synergistic effect on DNSNa solubility was observed with the maximum solubility at solute-free mass fraction of ethylene glycol monoethyl ether w30=0.4000 and solute-free mass fraction of ethylene glycol monobutyl ether w40=0.5999, respectively. The solubility data were correlated using the thermodynamic electrolyte non-random two-liquid (E-NRTL) model and model parameters were determined simultaneously. Aqueous ethylene glycol monobutyl ether solution at solute-free mass fraction of ethylene glycol monobutyl ether w40=0.2000 was found to be suitable solvent medium for the oxidation of 4-nitrotoluene-2-sulfonic acid (NTS) to 4,4′-dinitrostilbene-2,2′-disulfonic acid (DNS) and the conclusion was confirmed using the static analytical method combined with UV–VIS spectrophotometer.