Surface-Tailored Nanocellulose Aerogels with Thiol-Functional Moieties for Highly Efficient and Selective Removal of Hg(II) Ions from Water

Developing an easily recyclable and reusable biosorbent for highly efficient removal of very toxic Hg(II) ions from bodies of water is of special significance. Herein, a thiol-functionalized nanocellulose aerogel-type adsorbent for the highly efficient capture of Hg(II) ions was fabricated through a facile freeze-drying of bamboo-derived 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidized nanofibrillated cellulose (TO-NFC) suspension in the presence of hydrolyzed 3-mercaptopropyl-trimethoxysilane (MPTs) sols. Notably, the modified aerogel was able to effectively and selectively remove more than 92% Hg(II) ions even in a wide range of Hg(II) concentrations (0.01–85 mg/L) or coexistence with other heavy metals. Besides, the adsorption capacity of the aerogel was not compromised much by the variation in pH values of Hg(II) solutions over a wide pH range. The fitting results of adsorption models suggested the monolayer adsorption and chemisorptive characteristics with the maximal uptake capacity as high as 718.5 mg/g. The adsorption mechanism of the MPTs-modified TO-NFC aerogel toward Hg(II) was studied in detail. For the simulated chloralkali wastewater containing Hg(II) ions, the novel aerogel-type adsorbent exhibited a removal efficiency of 97.8%. Furthermore, its adsorption capacity for Hg(II) was not apparently deteriorated after four adsorption/desorption cycles while almost maintaining the original structural integrity.