Aplicação de tensoativo não iônico na remoção de fenol de meio aquoso: equilíbrio e modelagem

Abstract

Environmental sustainability has been the subject of interest and concern in the industry, mainly due to the generation of waste. As the phenolic compounds are toxic to aquatic organisms, the maximum level of 0.5 ppm is considered as concentration limit for releases in freshwater bodies by the Federal CONAMA Resolution no. 430 2011. In the process of treatment of these effluents, liquid-liquid extraction is the most economical process for the recovery of phenol, because it consumes little energy, but most often implements an organic solvent that can cause serious environmental problems. Some studies demonstrate the feasibility of using non-ionic surfactants to replace organic solvents. The main objective of this work was to study the process of wastewater phenol extraction using as extracting agent non-ionic surfactants nonylphenol ethoxylat. It was evaluated several properties such as the cloud point remove and, critical micelle concentration (c.m.c.) of surfactants micellization thermodynamic, effect of salt concentration (Xsal), surfactant concentration (Xt), phenol concentration (Xf) and ethoxylation degree of surfactant (EO) as well as the parameters of the extraction process. The results shows that the cloud point (PN) of the surfactants is directly affected by the amount of phenol and salts present in the effluent. The experimental design technique was efficient in the development of mathematical models capable of predicting the PN of surfactants and optimization of variables aimed a low energy cost (reduction of PN). The conditions to obtain the lowest value PN is Xsal = 0.2%, Xt = 0.5 and EO = 10. Assays for determining the c.m.c. and micellization thermodynamic analysis allowed to verify that the increase in temperature tends to decrease c.m.c. of surfactants, the micellization is a spontaneous and exothermic process for all temperatures studied and surfactants. The phenol removal efficiency of the systems was satisfactory and in some cases greater than 95%, despite the high percentage of the volume of coacervate phase. The modeling and statistical analysis of experimental data generated models capable of describing and predicting the removal efficiency and the process parameters depending on the composition of the system. Therefore, the remover use of non-ionic surfactants nonylphenol ethoxylate represent a practical alternative for phenol removal from wastewater, resulting in less environmental risks than conventional systems used in industry.