Fabrication and Characterization of Hydrophobic Aerogels Containing Bacterial Cellulose Coated with Copper Species via Mild Reduction

In this study, bacterial cellulose (BC) was coated with copper species via a room-temperature hydrazine-mediated reduction reaction of copper(II) acetate in a suspension phase of nata de coco, which was treated by freeze-drying, yielding hydrophobic lightweight aerogels. Structural and textural characteristics of the prepared aerogels were discovered using several techniques including X-ray diffraction (XRD), thermogravimetry analysis (TGA), water contact angle measurement and isothermal nitrogen physisorption. In detail, XRD results indicated the formation of the metallic copper phase in the aerogel while the high cellulose crystallinity was remained unchanged. No oxidized copper phases were detected in the material. Via the TGA profiles, the Cu loading was determined to be in the range from 3.9 to 13.4 wt.%, depending on the copper(II) acetate amount used for the reduction reaction. These values were generally lower than the theoretical Cu contents probably due to the unexpected Cu losses during the preparation procedure. In addition, increasing the Cu content in the BC aerogel led to a significant decrease in the specific surface area with the presence of Cu in the porous structure. On the other hand, as expected, the hydrophobicity of the BC aerogel was significantly enhanced with the Cu content. Indeed, the Cu-coated BC aerogels with high copper contents (> 6.2 wt.%) were hydrophobic, showing a large water-contact angle of up to 138°. Therefore, the resulting hydrophobic aerogels well interacted with water-immiscible organic solvents including diesel oil and cyclohexane with adsorption capacities varied from 20 to 30 g/g. The successful fabrication of the hydrophobic aerogels upon the simple surface modification of abundant bacterial cellulose with Cu species can introduce novel and efficient biomass-based material for the treatments of oil-based liquids in the aqueous environment.