Abstract
In this study, we developed a new procedure to prepare monodispersed functionalized SiO2 (SiO2-PDA-PDMC) composites via mussel inspired chemistry and surface initiated atom transfer radical polymerization (SI-ATRP). Samples were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis (TGA) measurements. TEM results showed that spherical morphology was unchanged after the functionalization. FT-IR results confirmed the successful modification with polydopamine (PDA) and the presence of poly-([2-(Methacryloyloxy) ethyl] trimethylammonium chloride) (PDMC) layer on the surface of SiO2 spheres. TGA data showed that the PDMC account for about 12.12 wt% in the sample of SiO2-PDA-PDMC composites. The XPS analysis further confirmed the existence of PDMC on the surface of SiO2-PDA-PDMC composites. The obtained SiO2-PDA-PDMC composites were used as adsorbent for the removal of Congo red (CR) from aqueous solution to evaluate the performance in environment application. The effect of contact time, solution pH, initial CR concentration and temperature on the adsorption of CR onto SiO2-PDA-PDMC composites was investigated. Adsorption results demonstrated that adsorption of CR onto SiO2-PDA-PDMC composites was a fast and efficient process. The adsorption equilibrium reached within 60 min, and the adsorption process followed the pseudo-second-order model. The experimental data of isotherms were better described by the Freundlich model. Thermodynamic study depicted the endothermic nature of adsorption and the process was spontaneous. Results from the effect of solution pH on the CR adsorption showed that the acidic condition favors the adsorption and provided evidence for the contribution of PDMC on the SiO2-PDA-PDMC composites in the removal of CR. This study suggests SiO2-PDA-PDMC composites can be developed as a new adsorbent for the removal of anionic dyes from aqueous solution.
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