Phyto-Mechanochemically Extruded Mt-Ag/Sn@CeO₂ Nanocomposites for Crystal Violet Dye Adsorption and CO₂ Capture

The potential of mechanochemistry via extrusion has been investigated for the design of sustainable nanocomposites with dual environmental remediation applications; the removal of organic pollutants from aqueous media and capture of CO2. The Ag/Sn@CeO2 nanocomposite was synthesized using twin screw extruders for the continuous phyto-mechanochemical synthesis utilizing a Melothria scabra leaf extract. To create a stable and high surface area nanocomposite, the Ag/Sn@CeO2 nanocomposite was further combined with montmorillonite (Mt) clay to form the Mt-Ag/Sn@CeO2 composite. The composite was characterized using FTIR, PXRD, SEM, EDS, Zeta Potential, PL, N2 adsorption-desorption isotherm, and BJH pore size analysis. The potential of composites for the adsorption of crystal violet (CV) dye was assessed. The adsorption capacity of Mt-Ag/Sn@CeO2 and Ag/Sn@CeO2 was found to be 48.10mg/g (96.08%) and 31.02mg/g (89.22%) for CV, respectively, at 25℃, reaching equilibrium within 90 min. The adsorption behavior followed both Freundlich and Langmuir isotherms, and the kinetic study followed a pseudo-second order kinetic model, suggesting chemisorption between the adsorbent and the cationic CV dye. Thermodynamic studies indicated that the adsorption was exothermic and spontaneous. The Mt-Ag/Sn@CeO2 composite exhibits the highest K value (0.0039 mmol/g/mmHg) at 298K compared to 313K (0.0033 mmol/g/mmHg), demonstrating greater adsorption at a lower temperature. Based on these results, the Mt-Ag/Sn@CeO2 composite is a valuable candidate for CV dye and CO2 adsorption, with the potential to integrate mitigation of water and air pollution.