Uptake of methylene blue on divinylbenzene cross-linked chitosan/maleic anhydride polymer by adsorption process

In this work, divinylbenzene selected as the cross-linking agent, a two-step one pot method based on the acylation reaction between maleic anhydride and chitosan had been developed to prepare a series of divinylbenzene cross-linked chitosan/maleic anhydride polymers (CS/MAH-DVB), which were used to remove cationic dye methylene blue (MB) from aqueous solutions. The synthesized polymers were characterized by FT-IR, XPS, SEM, TG and pH-drift methods. The adsorption parameters were discussed including pH, contact time, initial concentration of dye and temperature. The maximum adsorption capacities were 448 mg g−1, 482 mg g−1 and 503 mg g−1 respectively for three CS/MAH-DVB polymers with different molar ratios at 298 K, which were superior to other reported bio-based adsorbents. The adsorption process was found well to follow pseudo-second-order model and Sips isotherm. The adsorption mechanism was attributed to electrostatic interaction and π-π stacking interaction between MB and CS/MAH-DVB polymers. Furthermore, the CS/MAH-DVB polymers could easily be recycled by washing with acidic acetone, demonstrating excellent stability and favorable recyclability over five cycles. These results indicated the chitosan grafted maleic anhydride and further cross-linking using divinylbenzene could promote the adsorption performance of chitosan.