Hydrophobic, Superabsorbing Aerogels from Choline Chloride-Based Deep Eutectic Solvent Pretreated and Silylated Cellulose Nanofibrils for Selective Oil Removal

Abstract

Superabsorbents are highly appealing materials for use in cleaning up oil and chemical spills. However, the development of a low-cost, highly efficient superabsorbent remains a major challenge. This paper demonstrates a straightforward method of producing a cellulose nanofibril aerogel that is low-cost, ultralight, highly porous, hydrophobic, and reusable superabsorbing cellulose nanofibril aerogel from recycled waste fibers using a simple, environmentally friendly nanofibrillation treatment involving deep eutectic solvent and freeze-drying. Nanofibrillation and hydrophobic modification (silylation) of waste cellulose fibers resulted in nanofibril sponges with ultralow density (0.0029 g/cm) and high porosity (up to 99.81%) after freeze-drying. These sponges exhibited excellent absorption performances for various oils and organic solvents and were reusable. In particular, the nanofibril aerogels showed selectivity in absorbing marine diesel oil from an oil-water mixture and possessed ultrahigh absorption capacities of up to 142.9 g/g, much higher than those of the commercial absorbent materials (i.e., polypropylene-based material) (8.1-24.6 g/g) that were used as references. The absorbed oil could easily be recovered by means of simple mechanical squeezing. In addition, the nanofibril sponges exhibited excellent reusability, maintaining a high capacity to absorb diesel oil for at least 30 cycles at 71.4-81.0% of capacity compared to a fresh absorbent. The above-mentioned advantages make cellulose nanofibril superabsorbents created from recycled waste cellulose fibers promising material for cleaning oil and chemical spills.

Study on the Dissolution Mechanism of Cellulose by ChCl-Based Deep Eutectic Solvents

“…The O-H vibrational absorption peaks were near 1441.55 cm −1 and 1252.79 cm −1 . A comparison of Figures 5 and 6 revealed that the infrared absorption peak of the C-N stretching vibration of ChCl disappeared, signifying the movement of the C=O vibration absorption peak of oxalic acid toward a higher wave number direction (from 1693.67 cm −1 to 1747.56 cm −1 and 1958.85 cm −1 ) due to the strong electronegativity of Cl − and the induction effect [28]. The peak band narrowed and weakened, and the vibrational absorption peak of O-H disappeared, which implied that the intramolecular hydrogen bonds of ChCl and oxalic acid disappeared.…”

Recent Advances in Hydrophobic Deep Eutectic Solvents for Extraction

“…Recently, a low cost, highly porous, ultralight and hydrophobic HDES was synthesized (combined techniques of nanofibrillation, silylation, and freeze-drying) and the aerosol was capable of squeezing oil (superabsorbing agents) with an absorption capacity of 65-205 (g/g) [66]. The absorbed oil was recovered by mechanical squeezing and the aerosol could be used for about 30 cycles [66]. Since HDES uses low cost renewable raw materials, applying this economical solvent to mitigate environmental pollutants is a promising area for future research.…”

Nanocellulose: Recent advances and its prospects in environmental remediation

“…Chemical treatments are used to isolate cellulose fibres to generate nanocellulose. Existing chemical pretreatment techniques include acid hydrolysis [ 69 ], carboxylation [ 70 ], carboxymethylation [ 71 ], quaternization [ 72 ], sulphonation [ 73 ], ionic liquid [ 74 ], and solvent-assisted pretreatments [ 75 ].…”