The combination of mussel-inspired chemistry and surface-initiated redox polymerization for surface modification of silica microspheres and their environmental adsorption applications

In this report, a novel strategy that combination of mussel-inspired chemistry and surface-initiated redox polymerization has been developed for preparation of carboxyl groups modified SiO 2 (SiO 2 -PDA-PIA). The potential applications of these SiO 2 -PDA-PIA polymer composites to remove cationic organic dye methylene blue (MB) have also examined. The morphology and structures of SiO 2 -PDA-PIA are systematically characterized using transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) measurements. The SiO 2 -PDA-PIA composites show good surface morphology and abundant functional groups, which can be used as an excellent adsorbent for the removal of cationic dye pollutants. The effects of contact time, initial MB concentration, solution pH and temperature on the MB adsorption have been investigated. The adsorption of MB onto SiO 2 -PDA-PIA is highly dependent on the solution pH, initial MB concentration and temperature. As compared with pure SiO 2 , the SiO 2 -PDA-PIA shows 3-fold increase in adsorption capacity toward MB. The kinetic results show that the adsorption process is well-described by the pseudo-second-order. The equilibrium data are fitted using Langmuir and Freundlich isotherm models. The results show that the better agreement is Langmuir isotherm model with the correlation coefficient of 0.9954. The thermodynamic analyses show that the adsorption of MB onto SiO 2 -PDA-PIA is endothermic and spontaneous. Besides, the maximum adsorption capacity is calculated to be 215.97   mg/g. The high adsorption capacity of SiO 2 -PDA-PIA composites makes them to be promising adsorbents for the practical application in environment.