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  • Adsorption of venlafaxine: walnut shell-based activated carbon for antidepressant removal
    Publication . Tsubouchi, Lorena Maihury Santos; Queiroz, A.M.; Ribeiro, António E.; Brito, Paulo; Peron, Ana Paula
    Venlafaxine, a widely prescribed antidepressant, stands out due to its increasing detection in aquatic matrices. This pharmaceutical compound is environmentally classified as an emerging micropollutant, characterized by its persistence across multiple aquatic environments and its ecotoxicological potential. Adsorption is a promising technique for removing micropollutants, particularly when combined with activated carbon as an adsorbent. In this study, the removal of venlafaxine from aqueous media was investigated using an activated carbon produced from agro-industrial residue, walnut shell, chemically activated with zinc chloride. The quantification of venlafaxine was validated by HPLC-DAD using a mobile phase consisting of 60% acetonitrile and 40% water containing 0.05% TFA. The kinetic assays demonstrated a rapid initial removal, with the pseudo-second-order model providing the best fit to the adsorption kinetics, while the activation energy (16.33 kJ.mol-1) indicates a low energy barrier. The equilibrium data were best fitted by the Freundlich isotherm model, indicating energetic heterogeneity of the adsorbent surface. The removal efficiency reached approximately 94% at pH values from 7 to 11, dominated by electrostatic attraction, π-π interactions, hydrophobic interactions, and hydrogen bonding, highlighting the potential for application in Wastewater Treatment Plants (WWTPs) without pH adjustment, given the high efficiency near neutral conditions. Reuse experiments demonstrated that the activated carbon maintained over 80% efficiency through the third thermal regeneration cycle, with a cumulative mass loss of 36% across five cycles. Therefore, the activated carbon produced from walnut shells is a high-performance, economically feasible adsorbent for venlafaxine removal, offering a strategy that aligns with the principles of the circular economy by promoting the valorization of an agro-industrial residue through its conversion into a material capable of mitigating micropollutants in water.
    2026Dissertação de mestrado Acesso embargado Ver mais