Photothermal, Magnetic, and Superhydrophobic PU Sponge Decorated with a Fe₃O₄/MXene/Lignin Composite for Efficient Oil/Water Separation

Abstract

Frequent oil spills and the discharge of industrial oily wastewaters have become a serious threat to the environment, ecosystem, and human beings. Herein, a photothermal, magnetic, and superhydrophobic PU sponge decorated with a Fe 3 O 4 /MXene/lignin composite (labeled as S−Fe 3 O 4 /MXene/lignin@ PU sponge) has been designed and prepared. The obtained superhydrophobic/ superoleophilic PU sponge possesses excellent chemical stability, thermal stability, and mechanical durability in terms of being immersed in corrosive solutions and organic solvents and boiling water and being abrased by sandpapers, respectively. The oil adsorption capacities of the S−Fe 3 O 4 / MXene/lignin@PU sponge for various organic liquids range from 29.1 to 70.3 g/g, and the oil adsorption capacity for CCl 4 can remain 69.6 g/g even after 15 cyclic adsorption tests. The separation efficiencies of the S−Fe 3 O 4 /MXene/ lignin@PU sponge for n-hexane and CCl 4 are higher than 98% in different environments (i.e., water, hot water, 1 mol/L NaOH, 1 mol/L NaCl, and 1 mol/L HCl). More importantly, the introduction of three light absorbers (i.e., Fe 3 O 4 , MXene, and lignin) into the S−Fe 3 O 4 /MXene/lignin@PU sponge shows a synergistic effect in the photothermal heat conversion performance, and the maximum surface temperature reaches 64.4 °C under sunlight irradiation (1.0 kW/m 2 ). The separation flux of the S−Fe 3 O 4 /MXene/lignin@PU sponge for viscous LT147 vacuum pump oil reaches 35,469 L m −2 h −1 under sunlight irradiation, showing an increase of 27.3% compared to that of oil adsorption processes without the photothermal effect. Thus, the rational design of superhydrophobic sponges by introducing proper photothermal heat absorbers provides new insights into facile and cost-effective preparation of sponges for efficient oil/water separation.

Facile Preparation of Photothermal Superhydrophobic Melamine Sponge Decorated with MXene and Lignin Particles for Efficient Oil/Water Separation, Fast Crude Oil Recovery, and Active Deicing

“…The mechanical robustness of MS@PVA-MXene-PDA@LPs was evaluated using the changes of WCAs after cyclic sandpaper abrasion tests. During a sandpaper abrasion test, the MS@PVA-MXene-PDA@LPs was pressed against a sandpaper (800 mesh) with a 100 g stainless-steel weight, and the superhydrophobic sponge was pulled by a pair of tweezers for a distance of 10 cm at a speed of 0.1 cm/s …”

“…The separation efficiency was calculated based on the weight of water, η = ( M b M a ) × 100 % where M a (g) and M b (g) are the weights of water before and after a separation process, and η is the separation efficiency of oil/water mixtures. In addition, the separation flux is calculated as follows, flux = V St where V (L) is the permeate volume of oils (or solvents), S (m 2 ) is the effective contact area of the MS@PVA-MXene-PDA@LPs, and t (h) is the separation time …”

“…Due to the incidents of oil spills and the discharge of oily wastewaters, the pollution of oily wastewaters has become a serious issue for the environment and the health of human beings. − The Deepwater Horizon oil spill in the Gulf of Mexico is regarded as the most severe oil spill event in American history, which significantly influences the marine environment and ecosystem . To mitigate this issue, traditional methods (i.e., chemical dispersion, oil skimming, bioremediation, flotation, and in situ combustion) have been used in the treatment of oily wastewaters, while they suffer from some drawbacks, such as high cost, secondary pollution, complex operations, and poor reusability. , One practical approach to efficiently treat oily wastewaters is the utilization of porous adsorption materials (i.e., aerogels, sponges, foams, membranes, fabrics, and papers).…”

“…Furthermore, MXene possesses an excellent photothermal effect because of the electromagnetic interference (EMI) shielding effect and the local surface plasmon resonance (LSPR) effect . Guo et al fabricated a photothermal, magnetic, and superhydrophobic PU sponge by decorating the Fe 3 O 4 /MXene/lignin composite, and the as-prepared PU sponge showed a synergistic effect of three light absorbers (i.e., Fe 3 O 4 , MXene, and lignin) in the photothermal heat conversion performance. ,, Thus, the introduction of MXene to the construction of photothermal and superhydrophobic sponges facilitates enhancing the separation performance of viscous oil/water mixtures under solar irradiation.…”

“…Sun et al developed a superhydrophobic porous material composed of hexadecyltrimethoxysilane (HDTMS), lignin, and melamine resin sponge via a simple impregnation, and this porous material displayed excellent separation efficiency and recycling separation performances . Meanwhile, lignin exhibits a photothermal conversion performance under solar irradiation due to thermal vibrations of conjugated chemical structures . Therefore, lignin, as a low-cost and reproducible material, can be employed in the preparation of high-value-added, photothermal, and superhydrophobic lignin-based porous materials.…”