HIPE-derived polysiloxane-halloysite nanocomposites as dual adsorbents for pharmaceutical and dye pollutants: Structural characterization, adsorption performance, and thermal regeneration challenges

A novel class of polysiloxane–halloysite hybrid nanocomposites derived from high internal phase emulsion (HIPE) templating was developed and evaluated as multifunctional adsorbents for pharmaceutical (ibuprofen, IB) and dye (methylene blue, MB) pollutants in water. Pure polyHIPE (HPD) and nanocomposites containing 20 wt% (HPD20) and 40 wt% (HPD40) halloysite nanotubes were synthesized and characterized by XRD, FTIR, SEM, helium pycnometry, and N2 adsorption–desorption analysis. HPD20 retained the characteristic HIPE-derived porous structure, whereas HPD40 showed clear structural disruption at excessive filler loading. In adsorption experiments, HPD showed the highest IB removal, reaching 90% at 20 g/L, while HNTs exhibited negligible affinity toward IB. In contrast, MB adsorption was governed by HNTs, and their incorporation significantly improved dye removal, with HPD20 achieving 49.5% removal at 2 g/L and 80.7% at 5 g/L. In the binary IB–MB system, both contaminants were removed simultaneously without significant mutual interference. The corresponding physical mixtures showed adsorption performance comparable to the nanocomposites for IB and only slightly higher for MB, confirming that immobilization of HNTs within the polymer matrix largely preserves their adsorption functionality. Nonlinear isotherm analysis indicated fitted maximum IB adsorption capacities in the range 16.0–24.5 mg/g. Thermal regeneration at 250 °C proved ineffective, as matrix densification and incomplete decomposition of adsorbed species reduced subsequent adsorption capacity. HIPE-derived polysiloxane–halloysite nanocomposites are promising multifunctional adsorbents for complex aqueous systems. The absence of detectable HNT leaching and the possibility of converting the monolithic materials into particulate form make them attractive candidates for future packed-bed and flow-through column applications.