Fabrication and characterization of PIB gels as effective adsorbents for methylene blue

The removal of cationic dyes from wastewater remains challenging due to the trade-off between adsorption efficiency and post-treatment solid-liquid separation. In this work, a high-performance thermosensitive polyisobutylene (PIB) gel adsorbent was prepared via the free radical emulsion polymerization of a hypercrosslinked N-isopropylacrylamide-co-butyl methacrylate polymer. Comprehensive characterization including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) analysis, scanning electron microscopy (SEM) and rheological tests confirmed that the gel featured a porous structure, exceptional thermal stability, and a lower critical solution temperature (LCST) of approximately 32°C. The adsorption performance of the PIB gel for methylene blue (MB) was systematically investigated, achieving a removal rate of 88.5% and the adsorption capacity rose to 4.85 mg g^-1. The experimental data were best fitted by the pseudo-second-order kinetic model and the Slips isotherm model, suggesting that the MB adsorption process was predominantly governed by chemisorption accompanied by heterogeneous adsorption behavior. The adsorption of MB by the gel was driven by the synergistic effects of electrostatic attraction, hydrogen bonding, dipole-dipole interactions and physical pore interception. Moreover, the PIB gel exhibited remarkable reusability, maintaining 72.42% of its initial MB removal efficiency after five consecutive adsorption-desorption cycles. Notably, its thermosensitive property enables efficient solid-liquid separation through temperature-induced phase transition, which overcomes the separation difficulty of traditional adsorbents in practical applications. All the above results demonstrate that the PIB gel holds great potential to be a practical and efficient adsorbent for the remediation of MB-contaminated wastewater.