Removal of methyl orange from aqueous solutions by adsorption on cellulose hydrogel assisted with Fe2O3 nanoparticles

Cellulose hydrogel, fabricated from cellulose solution in an LiOH/urea aqueous system at low temperature, was successfully applied for in situ synthesis of Fe2O3 nanoparticles to obtain hybrid magnetic nanomaterials. The microporous structure of cellulose hydrogel at wet state provided reaction chambers to synthesize the Fe2O3 nanoparticles. The structure and properties of the magnetic cellulose/Fe2O3 hydrogels were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, magnetic detection, thermal analysis, etc. The results revealed that the magnetic cellulose/Fe2O3 hydrogels exhibited efficient adsorption of methyl orange in the aqueous solution as a result of the microporous structure, large surface area, and affinity for organic dyes. The equilibrium process was described well by the Langmuir isotherm model, showing a monolayer adsorption. From kinetic experiments, the adsorption process followed the pseudo-second-order kinetic model, indicating that the overall rate of dye uptake could be controlled by external mass transfer at the beginning of adsorption, while intra-particle diffusion controlled the overall rate of adsorption at a later stage. This work provided an attractive adsorbent for removing hazardous materials from wastewater.