All-carboxymethyl cellulose sponges for removal of heavy metal ions

In this study, all-carboxymethyl cellulose (CMC) sponges were prepared via acid assisted freeze–thaw method. The sponges were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The results indicate that the carboxylate groups of the resulting CMC sponges were protonated. The formed carboxylic acid groups revealed high capabilities for a stable network crosslinked by hydrogen bonds. Adsorption experiments showed that the sponges with CMC concentration of 1.0% exhibited the highest adsorption capacity for heavy metals, and the adsorption capacity toward Ag+, Cu2+, and Ni2+ was 7.7, 6.8, and 7.2 mg/g, respectively. Moreover, the CMC sponges can be easily regenerated up to 76.5, 99.6, and 92.3% for the above ions, respectively. This work unlocks new possibilities in designing absorbents based on biomass without using petrochemical polymer components, organic solvents, chemical crosslinkers and any high energy beams. All-carboxymethyl cellulose sponges were prepared via acid assisted freeze−thawing method which revealed excellent capability to adsorb and re-adsorb heavy metal ions including silvers, coppers and nickels.