Sorption of malachite green on vinyl-modified mesoporous poly(acrylic acid)/SiO2 composite nanofiber membranes

Vinyl-modified mesoporous poly(acrylic acid)/SiO₂ (PAA/SiO₂) composite nanofiber membranes were prepared through a sol-gel electrospinning process. The sorption behavior of malachite green on the membranes was studied. Fourier transform infrared (FTIR) results demonstrated that vinyl groups were grafted onto the silica skeleton. Transmission electron microscopy (TEM) images confirmed the formation of mesopores on the electrospun nanofibers and the pore size was 3.8 nm based on the Barrett-Joyner-Halenda (BJH) model. According to Brunauer-Emmett-Teller (BET) method, the specific surface area of the membranes was 523.84 m²/g. Three widely used isotherms, the Freundlich, Langmuir, and Redlich-Peterson isotherms, were used to model the experimental data of malachite green adsorption on PAA/SiO₂ nanofiber membranes. The best fit was found to be Redlich-Peterson isotherm and the equilibrium adsorption capacity was 220.49 mg/g. The adsorption kinetics followed a pseudo-second-order model. The removal of malachite green from the aqueous phase reached 98.8% in 240 min. The membranes can be regenerated by treated with alcohol solution and reused for multiple cycles, which is beneficial for practical application.