Preparation and characterization of nano-TiO2/chitosan/poly(N-isopropylacrylamide) composite hydrogel and its application for removal of ionic dyes

Nano-TiO2/chitosan/poly(N-isopropylacrylamide) (nano-TiO2/CS/PNIPAAm) composite hydrogel was prepared by a two-step polymerization method, and nano-TiO2 can endow the composite hydrogel with photocatalytic activity. The nano-TiO2/CS/PNIPAAm composite hydrogel was characterized by FT-IR and SEM. The properties of dye adsorption and photocatalytic degradation were investigated. The results indicated that dye adsorption was strongly influenced by solution pH and the acid fuchsin (AF) removal rate was maximum at pH = 4. The dye removal rate decreased slightly with increasing temperature, and the composite hydrogel adsorbing AF dyes floated on the solution surface at 40 °C and could be readily removed from the aqueous solution. Kinetics analysis indicated that the dye adsorption by nano-TiO2/CS/PNIPAAm composite hydrogel conformed to pseudo-second order model. Moreover, nano-TiO2/CS/PNIPAAm composite hydrogel exhibited high efficiency of photocatalytic degradation for AF dyes, and AF dye removal rate reached 90.5% under UV irradiation for 160 min.