Estudo experimental das solubilidades de alguns ácidos em misturas hidro-alcoólicas

Abstract

Solubility data of chemistry compounds in water and in solvent mixtures are fundamental in the project of separation industrial equipments, such as: crystallizers, extractors, evaporators, leachates and absorption units. The accuracy that it is obtained in projects of chemistry industry equipment is closely related with the quality of experimental data used to obtain the parameters of the equations that will be used.In the industrial case of liquid-liquid extraction, The data about solubility of organic and inorganic compounds are fundamental and not always are available in the literature. This research has as objective the experimental study of the solubility of some acids in hidro-alchoolic mixture.The solvents selected for this study were water, etanol and n-propanol, which are of sum importance in extraction process in chemistry, food and pharmaceutical industry. The selected acids were : bórico, dl-málico, succínio, citric e o salicílico. The apparatus selected to do the experiments was developed by OLIVEIRA(2004) in the study of liquid-liquid equilibrium. This apparatus is constituted by equilibrium cells, magnetic shakers, termopares and thermostatic bath. In the beginning it was done a study to determine na approximate value of shaking time and the decantation time of the mixtures (to be used in the experiments). So, it was done a experiment planning not factorial of the central compound(BOX & HUNTER, 1957) with alfa by rotation(1,414). The answers of each experiment were a maximization of solubility in function of shaking and decantation. Defined the conditions of shaking and decantation that maximize the solubility of the referred acids, were done isothermal and isobaric experiments to determine the solubility of the acids that interest, in pure solvents and in solvent mixture in several concentrations and in temperatures of 20, 30, 40, 50 and 60 ºC. With the experimental results obtained for each system, it was used empiric equations, in the polynomial form and in the exponential form and in a quadratic surface to adjust the parameters to known models of experimental data.