Adsorption of Fluoxetine and Venlafaxine onto the Marine Seaweed Bifurcaria bifurcata

Abstract

Marine macroalga Bifurcaria bifurcata was investigated as sorbent for two environmental emerging pollutants, the pharmaceuticals venlafaxine (VLF) and fluoxetine (FLX), from aqueous solutions, both in mono and bicomponent batch systems. The alga was characterized by means of IR spectroscopy, allowing to identify the most important groups for biosorption, carboxylic, sulfonic and hidroxile. The point of zero charge was determined, being 6.4. Adsorption of FLX follows a pseudo first order kinetics and kinetic constants are higher for FLX than for VLF. Its adsorption better represented by the pseudo second order model. For both pharmaceuticals, the equilibrium was reached within *100 min. Adsorption studies reveal that the process was more efficient at lower pH range and followed the Langmuir-Freundlich's model for VLF and Langmuir's model for FLX. Maximum adsorption capacities reached a level of 12-3 and 22-4 lmol/g for VLF and FLX, respectively, in the mono-component system. The difference was attributed to the presence of various functional groups of varying polarity within the adsorbates' molecules that affected their interactions with the adsorbent surface. The Langmuir-Freundlich's extended model was applied to the adsorption data of the bicomponent system and no changes in the maximum adsorption capacities were found (14-2 and 20-3 lmol/g for VLF and FLX, respectively), there is no evidence of competition between the adsorbates.

Evaluation of the adsorption potential of biochars prepared from forest and agri-food wastes for the removal of fluoxetine

“…Regarding the biochars tested, all the pH pzc values were above 9.59 (Table 2), which means that in the pH range of the experiments (5.5-9.5) the biochars should be positively charged (pH < pH pzc ) contributing to the electrostatic repulsion between the adsorbent and the adsorbate. This repulsion increases as the pH decreases, since 2 units below the pKa FLX should be positively charged and the same occurs for biochars 2 units below the pH pzc (Silva et al, 2019). The maximum electrostatic repulsion should occur below pH 7, but this was not the main factor that influenced the adsorption, since the best results were obtained for eucalyptus biochar near this pH value.…”

“…The differences observed between FLX adsorption at different pH values could be related with the electrostatic interaction between the net surface charge of the adsorbent and the electric charge of FLX molecules. Once the pKa of FLX is 9.8, for all pH values studied (pH < pKa), the molecules were mainly protonated, increasing the net positive charge with the decrease of pH (Silva et al, 2019). Regarding the biochars tested, all the pH pzc values were above 9.59 (Table 2), which means that in the pH range of the experiments (5.5-9.5) the biochars should be positively charged (pH < pH pzc ) contributing to the electrostatic repulsion between the adsorbent and the adsorbate.…”

“…The control of the chromatographic system and the acquisition and processing of chromatographic data were made using LC solution version 1.25 SP2 software. The separation was achieved with a Luna C 18 column (150 mm × 4.6 mm, 5 μm) from Phenomenex, using the method described by Silva et al (2019). FLX quantification was carried out using external calibration.…”

“…From the functional groups identified in the FTIR of this biochar, there are no groups with marked acidic or alkaline characteristics that could be involved in the adsorption process. However, some functional groups on the biochar surface become deprotonated when pH increases and therefore negatively charged, thus favoring adsorption of the pharmaceutical compound (Silva et al, 2019).…”

Green Microalgae Scenedesmus Obliquus Utilization for the Adsorptive Removal of Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) from Water Samples

“…The infrared spectra of the samples diluted with KBr and pressed (press PanReac, PAI for IR spectroscopy) (0.5 mg of ground sample with 200 mg of KBr) were recorded in the range of 4000-500 cm −1 with resolution of 2 cm −1 (200 scans) (Nicolet 6700 FT-IR, Thermo Scientific, MCT/A detector). Spectra were acquired and processed with the OMNIC Software Version 8.3.103 [57].…”