measurement and modeling of acridine solubility in supercritical carbon dioxide

supercritical carbon dioxide has gained increasing attention in food and pharmaceutical processing owing to the fact that it is environmentally inexpensive, not flammable, essentially non-toxic, and it has a convenient critical point. also, it has been attracting much attention in many fields, such as extraction of sensitive materials and pharmaceutical processing and polymerization processes. for designing these processes, solubility data of solute in scco2 are needed as the fundamental knowledge. and the correlation and extension of existing equilibrium data is an important step in the application and development of such processes.  acridine is a raw material used for the production of dyes and some valuable drugs and its derivatives have antiseptic properties like proflavine. in this research, the solubility of acridine in supercritical carbon dioxide was measured at temperatures of 313, 323 and 333 k and in the pressure range of 120 to 350 bar using static method. the crossover pressure of acridine was observed at about 150 bar. the experimental data were correlated using peng- robinson (pr) and soave- redlich- kwong (srk) equations of state (eos) and van der waals mixing rule with one (vdw 1) and two adjustable parameters (vdw 2) and huron-vidal mixing rules. for applying the huron-vidal mixing rule, nrtl activity coefficient model was used.  the binary interaction parameters of the studied models were reported. the results of average absolute relative deviations (aard) illustrated good accuracy of the studied models. furtheremore, the modeling has been done with and without considering the sublimation pressure of the solid (acridine) as an additional adjustable parameter.  it can be concluded when sublimation pressure is considered as adjustable parameter, the aard results of the studied models significantly decrease. also, the estimated values of sublimation pressure of acridine were reported at different temperatures. the results also showed that, among the studied models, pr- hv model with adjusted psub has the minimum aard (2.47 %).