Preparation of nanocomposite hydrogel based on Fe3O4-TMSPM/poly(HEMA-PEG6MA-IA) for the removal of methylene blue dye from aqueous solution

In this work, a new hydrogel poly(2-hydroxyethyl methacrylate-co-polyethylene glycol methacrylate-co-itaconic acid) poly(HEMA-PEG₆MA-IA) covalently crosslinked with Fe₃O₄ nanoparticles functionalized with 3-(trimethoxysilyl)propyl methacrylate organosilane (TMSPM) was prepared by free radicals, named Fe₃O₄-TMSPM/HG. FTIR-ATR, TGA, XRD, and TEM experiments were utilized to explore the Fe₃O₄-TMSPM/HG nanocomposite hydrogel. Swelling studies were also carried out in water, in different pH media, and then used in the adsorption of the cationic dye methylene blue (MB) from aqueous media. The factors controlling the adsorption process such as pH, dose, contact time, initial MB concentration, and temperature were investigated. The maximum MB adsorption capacity (270.27 mg/g) using Fe₃O₄-TMSPM/HG was obtained under the best conditions pH 8, dose 0.5 mg/mL, contact time 24 h, and ambient laboratory temperature (≈15 °C). The kinetic and isothermal experiments showed that the adsorption of MB followed the pseudo-second-order and Langmuir models. The effect of temperature on the adsorption capacity is related to the swelling, since the Fe₃O₄-TMSPM/HG nanocomposite hydrogel exhibit temperature-responsive. After 5 adsorption–desorption cycles, the adsorption decreased by 19 mg/g compared to the initial adsorption capacity. All the experimental results show that the prepared Fe₃O₄-TMSPM/HG nanocomposite hydrogel has the potential to be applied as an adsorbent for MB dye.