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  • Removal of sertraline from aqueous matrices through adsorption using green biomass-based activated carbons
    Publication . Schmidt, Guilherme Machado Loureiro; Queiroz, Ana; Ribeiro, António E.; Camargo Filho, Paulo de
    Sertraline, an antidepressant, has been detected in Portuguese wastewater treatment plant influents at ng L⁻¹ level concentrations. This pharmaceutical compound, commonly prescribed for the treatment of depressive disorders, is characterized by its persistence and limited removal efficiency in conventional wastewater treatment nprocesses, constituting a potential environmental hazard as these trace concentrations adversely affect aquatic organisms like organisms such as Dreissena rostriformis. The application of activated carbons is a promising technique for removing sertraline and other emerging pollutants. This study investigates sertraline removal (initial concentration of 3 ppm) using activated carbon derived from olive pits, a lignin-rich and underexploited biomass. The residual sertraline was quantified by HPLC using a mobile phase of 60% acetonitrile and 40% water with 0.01% TFA. A preliminary study compared two carbons produced via chemical activation (ZnCl₂ and H₃PO₄) followed by carbonization at 500°C for 1.5 hours, and a char produced by simple carbonization at 800°C for 1 hour without chemical agents. The material produced by simple carbonization was the most effective, achieving 89% sertraline removal within 3 hours. The influence of pH on adsorption was tested at pH levels from 3 to 11, with removal efficiency increasing from 67% to 95%, respectively. The results suggest that non-electrostatic mechanisms, such as π-π stacking and hydrophobic interactions, are dominant. These interactions are enhanced as sertraline (pKa=9.16) becomes more neutral at higher pH values, proving more significant than the electrostatic attraction present when the carbon surface is anionic (pHPZC≈7). Kinetic assays performed at pH 7 and 11 showed no statistically significant difference, according to an ANOVA test. This is an advantage for wastewater treatment plants, which could apply the process at the pH commonly found in residual waters. The pseudo-second order model best described the adsorption kinetics at pH 7, and the Elovich model at pH 11, these models are usually used as an indicative of chemisorption processes. For the equilibrium models fitting, the best adjustment was obtained with the Freundlich model, indicating that the removal occurs in multiple layers through a heterogeneous surface. This work demonstrates the possibility to valorize an agricultural subproduct to remove sertraline from water matrices.
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