Remoção de diclofenaco de sódio por adsorção em carvão ativado: estudo experimental e modelagem matemática

Abstract

The insertion of emerging contaminants into ecosystems represents a significant challenge for the health of living beings. Given this scenario, in the present study, the removal of diclofenac sodium – DCF by adsorption on granular activated carbon – CAG and particulate – CAP was evaluated. The characterization of CAG was based on the determination of the zero charge point - pHPCZ, scanning electron microscopy and absorption spectroscopy in the Infrared region - FTIR. The experimental part was divided into two phases, the first was the study of adsorption in finite bath tests and the second was the adsorption process in continuous flow (column) with mathematical modeling. A complete 24 factorial design was applied to evaluate the removal of DCF in both CAs, with the independent variables adsorbent mass, initial solution concentration, pH and contact time, with the purpose of optimizing the adsorption process, observing the effect on the response variables adsorbed quantity - Qt and reduction - REM, in percentage, of the drug concentration. The planning results show Qt values of approximately 24 mg. g-1 and removal percentages greater than 95% for both CAs. The kinetic and equilibrium tests were carried out with the condition that presented the highest Qt in the experimental design. The kinetic data were adjusted to the pseudo-first-order, pseudo-second-order and Elovich equation models, with the pseudo-second-order model and the Elovich equation obtaining the best fit to the experimental data, presenting higher R2 and Test values. F. For the equilibrium tests with DCF, the data obtained obtained a better fit to the Sips isotherm, presenting a higher value of R2 and Test F. For the study of column adsorption, a complete factorial design was applied with three independent variables, mass of coal, initial concentration and feed flow, with the purpose of evaluating the effects on the response variables saturation time – tSAT and quantity adsorbed at saturation qSAT. The results indicate that for tSAT only the concentration was not relevant from a statistical point of view and for qSAT all variables were statistically significant. Yan's mathematical model was the one that presented the best fit to the rupture curves. CAG proved to be efficient for DCF removal, presenting satisfactory removal percentages for the experimental conditions applied in this study.