A REVIEW ON SOLUBILITY PREDICTION MODELS IN SUBCRITICAL WATER

Subcritical water (SBCW) or hot pressurized water is defined as water with temperature between 100 and 374 and pressure high enough to maintain the liquid state. Under these conditions, because of decreasing the dielectric constant, water acts as a non-polar solvent and various organic compounds can dissolve in it. In some cases, modifiers are added to decrease the dielectric constant of water. Solubility data are important parameters and empirical measurements of solute solubility in SBCW are reported in many publications. Various models are available in the literatures for estimating the aqueous solubility of organic compounds in SBCW. Solubility models are needed to predict the solute solubility in SBCW before the experiments are performed. Also these solubility models are important when the process is scaled-up to a pilot or industrial scale. In this paper, a review of the solubility models for organic compounds in SBCW is presented. The models are empirical and semi-empirical models, regular solution theory (RST), dielectric constant model, cubic-plus-association (CPA) equation of state, and universal functional activity coefficient (UNIFAC) based models. An improved understanding of the interactions between SBCW and solute will lead to more accurate solubility models.

Keywords:

subcritical water , solubility , modeling