Adsorptive dye removal using surfactant-exfoliated montmorillonite/crosslinked tetramethacrylate composites

This study introduces the synthesis of a novel nanocomposite adsorbent, comprising a crosslinked tetramethacrylate macromonomer, tetra(2-hydroxy-3-(methacryloyloxy)benzene-1,2,4,5-tetracarboxylate (TM), intercalated into cetyltrimethylammonium bromide (CTAB) modified montmorillonite (CTA-MMT). The goal was to design an efficient adsorbent for dye removal from water. The synthesis process involved intercalating the TM macromonomer into the interlayer spaces of organophilic CTA-MMT, followed by in-situ crosslinking at 50 °C. This resulted in a stable nanocomposite structure with enhanced dye adsorption capabilities. XRD, SEM, and FTIR analysis confirmed successful intercalation and the formation of an amorphous material. The TM-CTA-MMT nanocomposite effectively adsorbed methylene blue (MB) dye, with removal efficiencies of 41.3 %, 82.8 %, and 97.8 % using 40 mg, 80 mg, and 120 mg of adsorbent, respectively, in 24 h at 25 °C. At 318 K (45 °C), the MB removal efficiency reached 94.2 % in 3 h with 120 mg of adsorbent. The adsorption process demonstrated a strong fit with the pseudo-first-order kinetic model and the Langmuir isotherm model, achieving a maximum adsorption capacity of 4.74 mg/g. In contrast, the Freundlich and Temkin models exhibited significantly poorer fits to the data, indicating less applicability to the adsorption mechanism observed. Thermodynamic parameters indicated physisorption with a positive ΔH° value of 24.1 kJ/mol, while negative ΔG° values demonstrated spontaneous and favorable MB dye adsorption, highlighting the nanocomposite's potential for efficient cationic dye removal from aqueous solutions.