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