Preparation of highly hydrophilic PVA/SBA-15 composite materials and their adsorption behavior toward cationic dye: effect of PVA content

This work focuses on the preparation of highly hydrophilic polyvinyl alcohol/SBA-15 composites by impregnation method. In order to study the effect of polyvinyl alcohol (PVA) on the structural, textural properties of composites, several percentages of PVA were impregnated into the surface of the mesoporous silica SBA-15. The obtained composites were characterized by different physicochemical techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption-desorption at 77 K adsorption–desorption at 77 K, thermogravimetric analysis (TGA) and scanning electronic microscopy (SEM). The obtained results showed that the structure of SBA-15 was swollen after PVA impregnation, confirming the dispersion of PVA inside the pores. The higher percentages of PVA lead to the decrease in the lattice parameter which results in the formation of PVA aggregates outside the surface. TGA analysis has shown improvement in the hydrophilic character of resulting composite, and this affinity via the water molecules is the result of the increase in number of –OH groups. The obtained composites were used for the adsorption of methylene blue (MB) dye. Effects of contact time, PVA content, adsorbent mass and initial dye concentration were investigated and discussed in terms of adsorption capacity. The experimental data were fitted by pseudo-first-order and pseudo-second-order models and verified by the Langmuir and Freundlich isotherms. The results showed that the adsorption of MB dye on composites followed Langmuir adsorption isotherm models and pseudo-second-order kinetics. The best adsorption capacity of MB dye recorded is ~ 77 mg/g for composite PVA/SBA-15(30%).