Adaptation of the Methylene Blue Adsorption Method for Specific Surface Area Determination of Betulin Particles

Application of the adapted methylene blue (MB) adsorption method in determining specific surface area was investigated on particles containing hydrogels obtained from purified (99 wt%) and unpurified (60 wt%) betulin samples. In order to study the adsorption isotherms of MB on betulin particles in aqueous dispersions, initial concentration of MB was varied. An analysis of the adsorption process with the Langmuir adsorption model was performed. The results indicate that the experimental data fits very well with the Langmuir adsorption model. Straight isotherms are obtained with very good determination coefficients (R 2 =0.99; R 2 =1.00), which means that the surface of purified and unpurified betulin particles is homogeneous energetically and a monomolecular coverage forms during adsorption. The MB adsorption method adapted for betulin particles is simple and requires less complex apparatus and time than other methods. The determined specific surface area can be used to characterize the surface properties of betulin particles.