Amphiphilic Fluoro-Functionalized Cellulosic Materials: Synthesis, Characterization, and Organic Dye Adsorption Properties

The growing interest toward biopolymers application in amphiphilic conditions prompts one to explore the preparation of fluorinated cellulosic materials. Cellulose (CE) and carboxymethylcellulose (CMC) are functionalized with highly fluorinated pendants, through a nucleophilic aromatic substitution on 3-pentadecafluoroheptyl-5-pentafluorophenyl-1,2,4-oxadiazole (FOX) leading to the corresponding fluorinated biopolymers CE-FOX and CMC-FOX. Structural and thermal stability confirm covalent attachment of the fluorinated moiety onto the cellulosic skeleton and highlighted an interesting 2D texture of the CMC-FOX material. Hybrid and amphiphilic features of CE-FOX and CMC-FOX, are confirmed by water and oil contact angle measurements. Applications as adsorbent material for organic contaminants from an aqueous solution are tested by previously incorporating the functional biopolymer into sodium alginate (SA) hydrogel beads. Rhodamine B (RhB) is used as a model wastewater pollutant. Fluoro-functionalization led to a three- to eightfold increase in the dye-removal efficiency of the SA-incorporated biopolymer with respect to the corresponding non-fluorinated material (from 11% to 48% for SA/CE vs SA/CE-FOX beads and from 11% to 94% for SA/CMC vs SA/CMC-FOX beads). Recyclability tests show good residual performance of SA/CMC-FOX beads after seven desorption/reuse cycles opening the way to more sustainable adsorbing processes for the removal of emerging pollutants from contaminated water.