Preparation of poly(sodium 4-styrene sulfonate) grafted magnetic chitosan microspheres for adsorption of cationic dyes

A novel adsorbent with high adsorption capacity to remove cationic dyes was synthesized. Sodium 4-styrene sulfonate (SSS) was grafted polymerization on the surface of magnetic chitosan microspheres via -NH 2 /S 2 O 8 2− surface initiating system, obtaining MCS-g-PSSS microspheres. The grafted microsphere was characterized by Fourier transforms infrared spectroscopy , X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, vibration sample magnetometer and the Brunauer-Emmett-Teller. Cationic dyes were adsorbed by MCS-g-PSSS and methylene blue(MB) was acted as a typical example. The adsorption performance was explored by varying experimental conditions. The results showed the maximal adsorption capacity was 989 mg/g at pH 1 at 25 °C. The pseudo-second order model was found to be applicable for the adsorption kinetics . The adsorption capacity increased with rising temperature and it decreased owing to adding of ions. The adsorption isotherms were the best fitted by Langmuir. MCS-g-PSSS for MB showed high adsorption capacity due to the strong electrostatic interactions and π-π stacking, which was explained by FTIR and XPS and was verified by DFT calculations. The degree of adsorption spontaneity increased with rising the temperature. The grafted MCS-g-PSSS microspheres had high adsorption capacity for various kinds of cationic dyes and excellent for remove MB in the aqueous solution.