Solubility in the water - oxyethylated nonylphenol - (NH4)2SO4 systems

The paper describes system approach application to optimization of temperature-concentration extraction parameters in water - surfactant - inorganic salting-out agent systems, based on analysis of the polythermic phase diagram of the corresponding ternary system. Solubility in water - Neonol AF-9-12 (or Neonol AF-9-25) - ammonium sulfate systems has been studied in the range 25-80 °C by visual polythermal and isothermal section methods, where Neonol AF-9-12 and Neonol AF-9-25 are oxyethylated nonylphenols with oxyethylation degree of 12 and 25, respectively. It has been established that the delamination region increases when temperature grows, because of increasing salting-out ability of ammonium sulfate and decreasing hydration of surfactant micelles. The maximum differences in delamination region concentration boundaries have been observed at temperatures above 40 °C. In the delaminating mixtures containing Neonol AF-9-25, the water concentration is lower than that for the system with Neonol AF-9-12 at the same temperature, due to greater hydration degree of Neonol AF-9-25. Besides, for the system with Neonol AF-9-12 increase in temperature above 84 °C leads to formation of delamination in water - Neonol AF-9-12 binary system and salting-out of this heterogeneous subsystem. It has been shown that temperature-concentration delamination region boundaries are affected by surfactant oxyethylation degree, the growth of which is accompanied by increase in hydration of surfactant micelles and decrease in their salting-out ability at fixed temperature. On the basis of solubility diagrams, the optimal extraction parameters in the water - Neonol AF-9-12 - ammonium sulfate system at 25 and 60 °C have been established, and it has been shown that temperature increase leads to decreasing extract volume and widening of acidity interval at which separation is observed, due to increasing salting-out ability of the salt and additional number of anions - salting-out agents with an acid. This determines the use of the studied systems for extraction at higher than room temperature.