A Novel Green Lithium Oxide Nanoparticle for Adsorption of the Escitalopram Oxalate and <i>In Vitro</i> Safety Profile

One of the major environmental and socioeconomic challenges today is the improper disposal of stable pharmaceutical compounds. In this context, this study focuses on the biosynthesis and characterization of lithium oxide nanoparticles (Li₂O-NPs) using <i>Mentha arvensis</i> extract for the adsorption-based removal of the escitalopram oxalate (OxE) drug from aqueous solutions. The nanoparticles were characterized by Fourier transform infrared (FTIR) spectroscopy, field emission gun scanning electron microscopy (FEG-SEM), N₂ porosimetry, ζ-potential (ZP), thermogravimetric analysis (TGA/DTG), and X-ray diffraction (XRD) to assess their textural, structural, morphological, and thermal properties. Moreover, their <i>in vitro</i> biocompatibility was evaluated using SH-SY5Y cells. Li₂O-NPs exhibited mesoporous morphology with small particle clusters, characteristic peaks of the antifluorite crystalline phase, a negative surface charge, and functional groups consistent with Li₂O. Cytotoxicity assays confirmed that the nanoparticles provided a biocompatible environment, causing no oxidative stress or inflammation with the tested concentration range (1-150 μg mL^-1). Regarding the adsorption equilibrium, analysis showed that OxE adsorption onto Li₂O-NPs followed the Hill model (<i>q_H</i> = 38.96 mg g^-1, <i>K_H</i> = 0.0384 mg L^-1, <i>n</i> _<i>H</i> = 0.5582, <i>R</i> ² = 0.9975), indicating moderate affinity between the adsorbate and nanoadsorbent. Kinetics studies revealed that the pseudo-first-order (PPO) model provided the best fit, with <i>q</i> ₁ = 130.7 mg g^-1 and <i>k</i> ₁ = 0.0061 min^-1, indicating physical adsorption as the predominant mechanism for the OxE removal. Therefore, Li₂O-NPs demonstrated strong potential as a nanoadsorbent for the treatment of water contaminated with stable pharmaceutical compounds.