Pre-oxidized PAN/PVP nanofibrous membranes with enhanced mechanical robustness and chemical stability for high-flux separation of oily wastewater from petroleum production

Abstract

Discharge of oily wastewater, generated from oil and gas production can lead to severe marine and soil contamination, posing long-term threats to ecosystems and water security. Therefore, developing environmentally sustainable, high-flux, and chemically robust separation membranes is crucial for green petroleum production and water reuse. In this work, pre-oxidized polyacrylonitrile/polyvinylpyrrolidone (p-PAN/PVP) nanofibrous membrane has been fabricated to address this challenge aforementioned. The PVP, during pre-oxidation, formed cross-linked junctions, reinforcing the mechanical stability and the resistance to harsh chemical conditions. Additionally, our membrane also exhibited superhydrophilicity in air, underwater super-oleophobicity, low oil adhesion, ultrahigh flux (>8500 L·m⁻²·h⁻¹·bar⁻¹), and >99.8% separation efficiency for both crude-oil-in-water and surfactant-stabilized emulsions. More importantly, the p-PAN/PVP membrane could maintain integrity and wettability under acidic, alkaline, and high-salinity environments (1 M HCl, 1 M NaOH, 10 wt% NaCl) as well as in organic solvents (N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, etc). Our study provides a sustainable strategy to protect vulnerable ecosystems and promote cleaner energy development.

Keywords

Pre-oxidized PAN/PVP nanofibrous membrane / Superhydrophilicity/underwater superoleophobicity / Oil–water emulsion separation / Antifouling / Reusability

CRediT authorship contribution statement

Zhuo Huang: Writing – review & editing, Writing – original draft, Investigation. Zhenyu Li: Conceptualization.

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.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (No. 52073238) and Open Funds of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (PLN2022_38, SWPU).

References

[1] H. Li, et al., Construction of MXene-MOF membranes with photocatalytic self-cleaning for enhanced oil-water emulsion separation, J. Membr. Sci. 718 (2025) 123685.

[2] P. Pi, et al., Composite dimensional structure superhydrophilic-underwater superoleophobic material for efficient separation of oil-in-water emulsions, Separ. Purif. Technol. 362 (2025) 131623.

[3] L. Qiao, et al., Non-fluorinated and photothermal lignin microspheres/candle soots-based superhydrophobic sponge for crude oil recovery and separation of oil/water mixtures and emulsions, J. Hazard Mater. 495 (2025) 138909.

[4] R. Wang, et al., Highly efficient multifunctional 3D polyurethane sponge with photothermal responsiveness for efficient oil-water separation and microplastic extraction, Desalination 601 (2025) 118604.

[5] J. Liu, et al., Fluid and electric field simulation and optimization of the multi-vane and multi-slit electrospinning nozzle, Nanomaterials 15 (6) (2025) 461.

[6] F.A. Jabri , L. Muruganandam , N. Rajamohan , Sustainable treatment of oil produced water using novel methods - a review, J. Hazard. Mater. Adv. 18 (2025) 100658.

[7] N.Y. Abu-Thabit , et al. , Superwetting metal mesh membranes for oil/water separation: a comprehensive review, Separ. Purif. Technol. 363 (2025) 132016.

[8] G. Dong, et al., Preparation of superhydrophilic/underwater superoleophobic PA56/BNNS-OH composite nanofiber membranes and their efficient separation of oil-in-water emulsions, Separ. Purif. Technol. 375 (2025) 133818.

[9] Y. He, et al., Hydrogels: a review on their versatile applications for efficient and stable oil-water separation, J. Mater. Chem. A 13 (10) (2025) 6919-6953.

[10] J. Jiang, et al., Frontiers in innovative materials and technologies for oil-water separation, Polymers 17 (12) (2025) 1635.

[11] Z. Li, et al., Recent advances in anti-fouling oil-water separation membranes: a review focusing on active and passive anti-fouling strategies, J. Mater. Chem. A 13 (29) (2025) 23418-23438.

[12] A. Rehman, et al., Next-generation stimuli-responsive smart membranes: developments in oil/water separation, Adv. Colloid Interface Sci. 341 (2025) 103487.

[13] N.E.B. Surat'man , et al. , Sustainable nanofibrous membranes for air filtration, water purification and oil removal, Nanoscale 17 (11) (2025) 6427-6447.

[14] M.M. Basuliman , et al. , A mini-review on lignin isolation and modification based on sorbent materials with porous nature as demulsifier for oil/water separations, Int. J. Biol. Macromol. 318 (2025) 145064.

[15] Q. Li, et al., High-strength, super-hydrophilic alginate electrospun nanofibrous membranes for rapid oil-water emulsion separation, Colloids Surf. A Physicochem. Eng. Asp. 705 (2025) 135637.

[16] H.K. Meresht , S.S.A. Talesh , R. Mahdavi , Superhydrophobic/superoleophilic porous adsorbents for oil-water separation: a comprehensive review of materials, fabrication techniques, and performance assessments, Environ. Sci. Pollut. Res. Int. 32 (24) (2025) 14281-14315.

[17] J. Sharma, et al., A comprehensive review on photocatalytic sponges for dual wastewater treatment: pollutant degradation and oil-water separation, J. Environ. Chem. Eng. 13 (5) (2025) 119082.

[18] A.K. Kota , et al. , Hygro-responsive membranes for effective oil-water separation, Nat. Commun. 3 (2012) 1025.

[19] M. Padaki, et al., Membrane technology enhancement in oil-water separation. A review, Desalination 357 (2015) 197-207.

[20] W. Zhang, et al., Superhydrophobic and superoleophilic PVDF membranes for effective separation of water-in-oil emulsions with high flux, Adv. Mater. 25 (14) (2013) 2071-2076.

[21] M.P. Aulia , et al. , Tuning membrane structure and fouling resistance via fluorine-free hydrophobic modification: chitin propionate-polyketone membrane for efficient water-oil separation, J. Membr. Sci. 739 (2026) 124891.

[22] F. Xiao, et al., Efficient purification of emulsified oil-containing wastewater via groove-structure PAN nanofiber membranes loading superhydrophilic amidoxime functionalized UiO-66 fabricated using coaxial sacrificial-template method, Separ. Purif. Technol. 380 (2026) 135462.

[23] C. Zhao, Y. Dai, The application of functional modified membrane for the demulsification and separation of oil/water emulsion-a review, Separ. Purif. Technol. 380 (2026) 135538.

[24] T. Ahmad, C. Guria, A. Mandal, Optimal synthesis, characterization and antifouling performance of Pluronic F127/bentonite-based super-hydrophilic polyvinyl chloride ultrafiltration membrane for enhanced oilfield produced water treatment, J. Ind. Eng. Chem. 90 (2020) 58-75.

[25] T. Ahmad, C. Guria, A. Mandal, Enhanced performance of salt-induced Pluronic F127 and bentonite blended polyvinyl chloride ultrafiltration membrane for the processing of oilfield produced water, J. Water Proc. Eng. 34 (2020) 101144.

[26] X. Chai, et al., Efficient crude oil emulsion separation via a micro-nano structured superhydrophilic and underwater superoleophobic membrane, Colloids Surf. A Physicochem. Eng. Asp. 733 (2026) 139318.

[27] C. Chen, et al., Self-assembly superwetting supramolecular nanofiber membrane via metal-coordination reinforced hydrogen-bonding for high-efficiency oil/water separation, Separ. Purif. Technol. 387 (2026) 136701.

[28] J. Shen, et al., A dual defense anti-oil-fouling superhydrophilic mesh for efficient and sustainable oil-in-water emulsions separation, Colloids Surf. A Physicochem. Eng. Asp. 734 (2026) 139405.

[29] L.L. Zhao, et al., Zinc oxide-oleic acid modified coal-based fiber membrane with switchable wettability for intelligent oil/water separation, J. Water Proc. Eng. 82 (2026) 109426.

[30] Q.H. Yu , et al. , Efficient preparation of ultrathin ceramic wafer membranes for the high-effective treatment of the oilfield produced water, Separ. Purif. Technol. 308 (2023) 122720.

[31] H. He, et al., Asymmetric superwetting Janus copper mesh membrane for directional and switchable oil-water emulsion separation, Separ. Purif. Technol. 378 (2025) 134711.

[32] L. Hou, et al., High-efficiency oil/water separation by electrospun PVDF-HFP critical superwetting interfacial membranes, Colloids Surf. A Physicochem. Eng. Asp. 726 (2025) 137986.

[33] Y.-H. Jin , et al. , Super-Wettable macrocycle polymer membranes for effective oil-water separation, ACS Appl. Mater. Interfaces 17 (46) (2025) 64015-64025.

[34] H. Su , et al. , Pre-oxidized PAN nanofibrous membrane to efficiently and continuously separate large-scale viscous oil-in-water emulsions under harsh conditions with ultra-long-term oil-fouling recovery, Adv. Fiber Mater. 6 (3) (2024) 852-864.

[35] H.P. Karki , et al. , Three-dimensional nanoporous polyacrylonitrile-based carbon scaffold for effective separation of oil from oil/water emulsion, Polymer 153 (2018) 597-606.

[36] S.R. Al-Mhyawi , et al. , Synthesis, characterization, and multifunctional properties of polyvinylpyrrolidone/chitosan/iron molybdate nanocomposites for electrochemical devices, J. Sci. Adv. Mater. Devices 10 (3) (2025) 100920.

[37] H. Pan, et al., Facile fabrication of porous carbon nanofibers by electrospun PAN/dimethyl sulfone for capacitive deionization, J. Mater. Chem. A 3 (26) (2015) 13827-13834.

[38] Y. Ma, et al., Scalable, ultrathin, and high-temperature-resistant solid polymer electrolytes for energy-dense lithium metal batteries, Adv. Energy Mater. 12 (15) (2022) 2103720.

[39] X.-L. Sun , Z. Liu , Z.-L. Cheng , Design and fabrication of in-situ N-doped paper-like carbon nanofiber film for thiophene removal from a liquid model fuel, J. Hazard Mater. 389 (2020) 121879.

[40] G. Dong, et al., Preparation of superhydrophilic/underwater superoleophobic PA56/BNNS-OH composite nanofiber membranes and their efficient separation of oil-in-water emulsions, Separ. Purif. Technol. 375 (2025).