Superhydrophobic and superelastic thermoplastic polyurethane/multiwalled carbon nanotubes porous monolith for durable oil/water separation
Introduction
Oil spill and chemical leakage events are causing catastrophic damages to our environment nowadays [[1], [2], [3], [4]]. The leaked toxic substances also threaten various species through the food chain, from low-grade algae to high-level animals and even humans. During past decades, a great deal of attempts including oil skimmers [5], direct burning [6], physical diffusion [7], absorbent [8], and biodegradation [9], have been used to overcome this challenge. Among them, absorption is one of the most popular approaches in view of its advantages of no secondary pollution, simplicity of operator and low cost [10,11]. A desired absorbent material should be highly porous with super-hydrophobicity and super-oleophilicity in order to selectively absorb oils and hydrophobic organic solvents from water to the maximum extent [12,13]. High reliability and reusability are also hoped in practical application [14]. Recently, various kinds of materials including carbon-based aerogels, inorganic or organic silicon sponges have been proposed for oil/water separation [[15], [16], [17]]. However, although the outstanding absorption capacity, these aerogels or sponges are usually limited by low mechanical properties and high-cost of raw materials and complex synthesis [18].
Hydrophobic porous polymer-based monoliths are believed to be one of the most promising candidates used in oil/water separation because of their ultralow material/preparation costs and satisfying mechanical strength [19]. The adjustable pore structure and thermal/chemical resistance endow them high selectivity and efficiency for oil absorption, showing good application prospect in oil/water separation [20]. Benefiting from the versatile processing of polymers, electrospinning, sol-gel process, chemical/physical foaming, phase separation, self-assembly process, template methods etc., have been developed to prepare porous polymer monoliths [[21], [22], [23]]. Among them, the simple solution phase separation process without complex equipment requirement is believed to be an ideal mass-produce way. On the other hand, porous polymer monoliths with high mechanical resilience are desired when taking the high-efficient reusability into consideration [24]. The mechanical resilience allows the absorbed oils to be removed by the convenient and high-efficient squeezing process rather than the time-consuming centrifugation or evaporation treatment. Up to now, it is still a challenge to develop the high-performance porous monoliths produced by commercial polymers with desired absorption capacity and mechanical resilience, simultaneously.
Generally, the mechanical characters of polymer monoliths are decided by their raw materials. Commercial thermoplastic elastomers are thus thought to be the promising alternatives to prepare high-elastic monoliths [25]. Thermoplastic polyurethane (TPU) comprising of adjusting soft and hard segments shows a controllable mechanical elasticity and resilience [26,27]. Our group has recently reported a porous TPU monolith with well oil/water separation ability showing an excellent mechanical elasticity [28]. However, the oversize pore structure with loose skeleton results in the relatively low mechanical strength which is not conducive to the reusability performance of TPU monoliths during the long-term reuse. Besides, the hydrophobicity of pure TPU monolith is also not ideal (<150°) due to the undesired pore structure and surface morphology. To solve these questions, a feasible approach of introducing carbon-based nanomaterials into polymer monolith has been proposed based on our previous reports [[29], [30], [31]]. On the one hand, the strength and rigidity of monolith's skeleton can be effectively improved by combing the rigid nanoparticles [32]. On the other hand, the introducing nanoparticles can significantly affect the phase separation process by changing the viscosity and compatibility, further adjust the pore structure of polymer monolith [33].
For this reason, carboxyl multiwalled carbon nanotubes (cMWNTs), with high specific surface area, excellent oil affinity and outstanding mechanical property were introduced to tailor pore structure of TPU monolith in this work. Typically, TPU/cMWNTs monolith with hierarchical porous structure was first produced by thermally induced phase separation (TIPS) method assisted by non-solvent. Comparing to pure TPU monolith, the pore structure of composite monolith was significantly improved in terms of the pore size and skeleton. As a result, TPU/cMWNTs monolith with super-hydrophobicity (151°) and super-oleophilicity (0°) exhibited high separation efficiency for oils/organic solvents in different thermal/corrosive environments. It is worth noting that the mechanical elasticity and resilience of monolith were obviously increased, which ensured its durability and reusability. Moreover, the high-performance TPU/cMWNTs monolith showed ability to achieve continuous absorption and removal of a large amount of oil on water surface through the pump-assisted system, which meant the high potential in practical application.
Section snippets
Materials
Commercial used TPU (Elastollan 1185A with a density of 1.12 g/cm3) was obtained from BASF Co. Ltd., Germany. cMWNTs with the length between 10 and 30 μm, outer diameter of 10–20 nm, and purity greater than 98 wt% were supplied by Chengdu Organic Chemicals Co., Ltd., China. 1,4-Dioxane, chloroform, phenixin, ethyl acetate were bought from Tianjin Fuyu Fine Chemical Co., Ltd., China. Deionized water, oils (soybean oil, pump oil, and olive oil), coloring agents (oil red and methylene blue),
Preparation process of porous TPU/cMWNTs monolith
The preparation schematic of porous TPU/cMWNTs monolith is shown in Fig. 1a–c. Commercial TPU pellets can be completely dissolved in cMWNTs/dioxane/water mixed system at 60 °C (Fig. 1a). The existence of deionized water (non-solvent) is conducive to the phase separation during cooling processes. During the first cooling process (ice bath at 0 °C), the reduced solubility of mixed solvent caused TPU chains linking with cMWNTs to aggregate together and form embryonic skeletons (Fig. 1b). The
Conclusion
In conclusion, TPU/cMWNTs monolith with hierarchical porous structure, super-hydrophobicity, high mechanical strength, corrosion resistance was prepared for durable oil/water separation. The addition of 2 wt% cMWNTs into the skeleton of TPU monolith is able to improve the hydrophobicity and compression strength and water/oil separation ability. Typically, the water CA, compression strength are improved to 151° and 261 kPa from 143° and 160 kPa, respectively. The as-prepared TPU/cMWNTs monolith
CRediT authorship contribution statement
Shihang Ye: Investigation, Methodology, Writing - original draft. Yutao Shi: Conceptualization, Project administration. Bingzhong Wang: Conceptualization, Project administration, Investigation. Yiru Zhang: Validation. Yuezhan Feng: Data curation, Writing - review & editing. Wenjuan Han: Methodology, Software. Chuntai Liu: Conceptualization, Funding acquisition. Changyu Shen: Resources.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
The authors gratefully acknowledge the financial support of this work by National Natural Science Foundation of China (Contract Number: 51603190, 51903223), National Natural Science Foundation of China-Henan Province Joint Funds (Contract Number: U1604253), Key Technologies R&D Program of Henan Province (Contract Number: 202102210231).
References (44)
- et al.
A major leak in a crude oil tank: predictable and unexpected root causes
Eng. Fail. Anal.
(2019) - et al.
Superhydrophobic and superoleophilic porous reduced graphene oxide/polycarbonate monoliths for high-efficiency oil/water separation
J. Hazard Mater.
(2018) - et al.
Cobalt-containing nanoparticles embedded in flexible carbon aerogel for spilled oil cleanup and oxygen reduction reaction
Compos. B Eng.
(2019) - et al.
Hydrogel-coated basalt fibre with superhydrophilic and underwater superoleophobic performance for oil-water separation
Compos Commun
(2019) - et al.
Assessing response capabilities for responding to ship-related oil spills in the Chinese Bohai Sea
Int J Disast Risk Re
(2018) - et al.
The poly(vinyl alcohol-co-ethylene) nanofiber/silica coated composite membranes for oil/water and oil-in-water emulsion separation
Compos Commun
(2018) - et al.
Ultrastrong, flexible and lightweight anisotropic polypropylene foams with superior flame retardancy
Compos. Appl. Sci. Manuf.
(2019) - et al.
Magnetically driven superhydrophobic silica sponge decorated with hierarchical cobalt nanoparticles for selective oil absorption and oil/water separation
Chem. Eng. J.
(2018) - et al.
Cellulose acetate monolith with hierarchical micro/nano-porous structure showing superior hydrophobicity for oil/water separation
Carbohydr. Polym.
(2020) - et al.
Design and preparation of efficient, stable and superhydrophobic copper foam membrane for selective oil absorption and consecutive oil–water separation
Mater. Des.
(2018)
Nanosized bimetal-organic frameworks as robust coating for multi-functional flexible polyurethane foam: rapid oil-absorption and excellent fire safety
Compos. Sci. Technol.
Graphene/nanofiber aerogels: performance regulation towards multiple applications in dye adsorption and oil/water separation
Chem. Eng. J.
Lightweight, mechanical robust foam with a herringbone-like porous structure for oil/water separation and filtering
Polym. Test.
Superhydrophobic sponge containing silicone oil-modified layered double hydroxide sheets for rapid oil-water separations
Colloid. Surface.
Versatile fabrication of the magnetic polymer-based graphene foam and applications for oil–water separation
Colloid. Surface.
Porous polymer monoliths: amazingly wide variety of techniques enabling their preparation
J. Chromatogr. A
Novel hydrophobic macroporous polypropylene monoliths for efficient separation of hydrocarbons
Compos. B Eng.
Preparation of compressible polymer monoliths that contain mesopores capable of rapid oil–water separation
Polym. Chem.
A novel monolith ZnS-ZIF-8 adsorption material for ultraeffective Hg (II) capture from wastewater
J. Hazard Mater.
Characterization of thermoplastic polyurethane/polylactic acid (TPU/PLA) tissue engineering scaffolds fabricated by microcellular injection molding
Mater. Sci. Eng. C
Hydrophobic polycarbonate monolith with mesoporous nest-like structure: an effective oil sorbent
Mater. Lett.
Utilization of Ag nanoparticles anchored in covalent organic frameworks for mercury removal from acidic waste water
J. Hazard Mater.
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