Adsorção de ibuprofeno por carvão ativado obtido do resíduo da casca da acácia-negra (Acacia mearsii De Wild.)

Abstract

The improper disposal of medicines in water bodies can be related to several problems that affect from human health to the contamination of the ecosystem. However, traditional methods do not promote a complete removal of these contaminants. An example of this is ibuprofen, an anti-inflammatory used in the treatment of pain and fever, which is often present in effluent treatment plants, and which is not removed by conventional treatment processes, so it is necessary to use more advanced techniques in its removal. Black acacia (Acacia mearnsii De Wild) is commercially planted in Rio Grande do Sul, having its residue produced by the extraction of tannin, which constitute around 35 to 45% of the bark of black acacia, proving to be effective in adsorption, being promising that commercial activated carbon for some adsorbates such as ibuprofen, and diclofenac sodium. Given what has been exposed, this study aims to evaluate the removal of ibuprofen in an aqueous medium by the adsorption process, using activated carbon from the bark of black acacia from the residue generated from the extraction of tannin. The material was ground, dried, impregnated with H3PO4 and followed by pyrolysis in an inert atmosphere of nitrogen for the production of activated carbon. The adsorbent was characterized as its specific mass, porosity, particle diameter, and immediate analysis of moisture, ash, volatiles and fixed carbon. TGA and XRD and SMM analyses were also performed that pointed out that the adsorbent had a reduction in crystallinity and decomposition of hemicellulose after chemical and thermal treatments. Batch adsorption tests (kinetic and isotherm) were carried out using a shaker to remove the contaminant present in the liquid phase and a centrifuge for the separation of activated carbon from the solution, the absorbances of the solutions were read in a spectrophotometer with a wavelength of 221 nm. The particle diameter of the activated carbon produced was 116.4 μm and an actual specific mass of 1.4813 g/cm3. The activated carbon produced was analyzed in different conditions for the removal of ibuprofen, where the kinetic results showed that the model that best adjusted was the pseudo second order, reaching equilibrium in 35 min. For the isotherm, the model that best described was the Freundlich model having a higher correlation coefficient (R2) of 0.94. With this, it was possible to establish the potential for adsorption and the effectiveness of removing ibuprofen from the liquid effluent, and may be a very promising adsorbent in the treatment of this type of emerging contaminant.