Determinação da solubilidade do fertilizante ureia em solventes puros e em misturas hidroalcoólicas

Abstract

Urea is the most used nitrogen fertilizer in the world and little has been done in order to characterize their behavior in solution. In this work we experimentally determined the solubility of urea in water, ethanol, isopropanol, methanol and mixtures of these solvents, at temperatures from 274.9 to 336.5 K at constant atmospheric pressure. The gravimetric method was used to obtain experimental data. The experimental equipment used consisted of two solid-liquid equilibrium cells connected in series, joined by a latex hose and connected to a thermostatic bath. The experiment was conducted with two hours of stirring followed by two hours of decanting. Samples were withdrawn only from the supernatant liquid mixture by glass syringe and analyzed by gravimetric. Central planning compounds were performed with varying temperatures and concentration of solvents to determine the effect of each response in solubility. In experimental studies, it was also possible to correlate the experimental data estimating parameters of rational equations available in the literature. The results of the adjustments were compared with the data obtained in the experiments. The obtained results are in agreement with literature. This work also contribute sought in order to determine the solubility curves and parameters of thermodynamic equilibrium models Margules, Van Laar, Wilson and NRTL for urea solutions in water, ethanol , isopropanol, and methanol. With the thermodynamic adjustments, it can be concluded that the model proposed by Wilson was best represented the experimental data of solubility of urea, with low average percentage deviations and quadratic correlation coefficient close to one.