Synthesis of Microporous Cationic Hydrogel of Hydroxypropyl Cellulose (HPC) and its Application on Anionic Dye Removal

Hydroxypropyl cellulose has been crosslinked by epichlorohydrin (EPI) and ammonia in sodium hydroxide aqueous Solution. A temperature induced phase separation (TIPS) process was applied to synthesize a microporous crosslinked HPC hydrogel and was confirmed by SEM studies. The cationic HPC hydrogel showed an excellent ability to adsorb anionic dye AO7, and the maximum adsorption capacity at room temperature was found to be 2478 (g/kg) at pH 3.96. Both Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms, and the Langmuir model agreed well with the experimental data (R-2 > 0.99). Kinetics of the adsorption were tested and the data agreed well with the pseudo-second-order kinetic model. The strong electrostatic interaction between the quaternary ammonium and dye anions could be the main driving force adsorption. The effects of pH and temperature oil the adsorption of the dye have also been investigated and discussed.