Synthesis of silver nanoparticles composite mesoporous microspheres for synergistic adsorption-catalytic degradation of methylene blue

This study reports the preparation of polystyrene-divinylbenzene mesoporous microspheres and their composite microspheres with silver nanoparticles using two-step seed-swelling polymerization. Not only the effects of different swelling agents on the morphology and structure of mesoporous microspheres were investigated, but also the difference between sulfonic acid microspheres and silver nanoparticle composite microspheres was discussed during the degradation of methylene blue (MB) dyes. The composite microspheres were characterized using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), specific surface area and pore size analyzer (BET) and Energy-dispersive spectrometer (EDS) techniques. In the dibutyl phthalate system, a small amount of toluene was introduced, which increased the specific surface area of mesoporous microspheres to 68.51 m2/g, while the average pore diameter decreased to 13.62 nm. The degradation experiments showed that the sulfonic acid groups, introduced by the hydrophilic modification, had electrostatic interactions with MB, which promoted the rapid adsorption of MB through microspheres. Meanwhile, the loaded silver nanoparticles (Ag NPs) could also catalyze the reduction of MB, which further improved the rate of degradation of MB using the composite microspheres. Therefore, compared with sulfonated polystyrene mesoporous microspheres (SPPS), the removal efficiency of Ag@SPPS composite microspheres for MB was almost twice. In addition, after five cycles of recycling, the Ag@SPPS composite microspheres maintained a degradation efficiency of 97.12%, indicating excellent reuse value. The results provide a novel pathway to treat dye-containing wastewater.