Remoção de compostos persistentes com biorreator de membrana e adsorção em carvão ativado

Abstract

One of the biggest environmental concerns nowadays is the contamination of water bodies, caused by drugs, pesticides, hormones, among others. One of the routes of these contaminants are the sanitary sewers. Then, this study aimed to evaluate the removal of pesticides in an industrial wastewater using an ultrafiltration bioreactor membrane (MBR) and applying an activated carbon adsorption process. The tests were performed adding 2 mL of standard solution (10 g/L) of 2.4-D and metribuzin and 5 mL of glyphosate. Moreover, 10 g of NaCl was previously added to the MBR as a marker aiming to predict MBR behavior in relation to the removal of this compound. The aliquots of permeated were taken at pre-determined intervals of time and the results were collected analyzing the samples in both conductivity meter and spectrophotometer. The adsorption tests of 2.4-D and metribuzin were performed in batches at 25 ± 2°C and pH=6.0, with dried samples of activated carbon (0.5; 1.0; 1.5; 2.0 g) reserved in flasks. First, 100 mL of 2.4-D and metribuzin, respectively, were added to each flask. Next, the flasks were placed in an incubator under agitation (250 rpm). Finally, at pre-determined intervals of time, 3 mL of each sample were collected and these samples were quantified using the spectrophotometer. The results showed that the MBR was not effective in what concerns to the removal of 2.4-D, glyphosate and metribuzin, as high concentrations of these compounds were detected in the permeate after the analysis. However, the activated carbons applied in the adsorption tests showed high efficiency in the removal of these pesticides. The kinetic models were also studied and the kinetics of pseudo-first order was the best fit on the adsorption of the 2.4-D. On the adsorption of metribuzin, the pseudo-first order model can be applied for the samples containing 0.5 g and 2.0 g of activated carbon. For the samples with 1.0 g and 1.5 g of activated carbon, the data obtained for the adsorption process resulted in a model of pseudo- second order. It can be affirmed that chemical adsorption of the metribuzin occurred.