Investigating Adsorption Behaviors of Herbicide 2, 4, 5-Trichlorophenoxyacetic Acid on Epinephrine Modified Mesoporous Silica Nanoparticles

The study investigates the potential of epinephrine-modified mesoporous silica nanoparticles (Epi-MSNPs) for the removal of 2,4,5-trichlorophenoxyacetic acid (TCA) from aqueous solutions. The characterization of Epi-MSNPs was performed using a scanning electron microscope, transmission electron microscope, FT-IR spectroscopy and dynamic light scattering techniques. Scanning electron microscope and transmission electron microscope images showed the formation of nearly spherical morphology of the nanoparticles with an average particle size of ca. 278 nm. FT-IR spectroscopy confirmed the successful attachment of epinephrine molecules by appearance peaks at around 1460 and 1580 cm⁻¹, attributed to the bending mode of the –CH₂– and the –CH = CH– stretching vibrations of the aromatic ring. The Epi-MSNPs exhibit an average zeta potential of 7.6 mV at pH above 7 and a range of 27.2 to 18.3 mV at pH 2 to 6, demonstrating high stability and electrostatic repulsion between particles. The effect of pH and initial concentration on TCA uptake was investigated, and the highest percentage of TCA uptake was observed at pH 6 and an initial TCA concentration of 90 ppm. Langmuir isotherm was found to be the most suitable model for describing the adsorption of TCA onto Epi-MSNPs, with a maximum monolayer adsorption capacity of 127.4 mg/g. The pseudo-second-order kinetic model was found to be the most accurate in describing the kinetics of TCA adsorption onto Epi-MSNPs. The regeneration of Epi-MSNPs was evaluated, and the adsorbent showed promising results for reuse, with a high removal efficiency after multiple cycles of regeneration. The findings suggest that Epi-MSNPs have the potential to be a reusable and sustainable adsorbent for the removal of TCA from contaminated water sources.