A highly efficient and simple composite process is developed to prepare a sand core funnel with superhydrophobic properties, providing a simple and effective method for the separation of stratified oil-water mixtures and oil-in-water emulsions. The method involves treating the sand core funnel with a 5% NaOH solution to negatively charge the hydroxyl groups (—OH) on the surface of the sand core. Through electrostatic attraction, the reducing Sn2+ ions are self-assembled onto the surface of the sand core to obtain a Sn2+functionalized sand core funnel. The Sn2+ functionalized sand core funnel is immersed in a silver ammonia solution, where the Sn2+ ions are oxidized to Sn4+ ions, and the silver (Ag+) in the [Ag(NH2)2]+ is reduced to elemental silver (Ag0) in situ and attached to the surface of the sand core as "seeds". The sand core funnel with "silver seeds" is placed in a seed growth solution containing glucose, tartaric acid, and silver ammonia solution. The elemental silver (Ag0) produced by the reduction of [Ag(NH2)2]+ by glucose continuously wrap around the "silver seeds" on the surface of the sand core, causing the "silver seeds" to grow and eventually form a micro-nano hierarchical structure, thereby increasing the roughness of the sand core surface. Finally, the surface of the sand core funnel is modified with octadecyltrimethoxysilane (OTMS) to achieve superhydrophobic properties. The microstructure and wettability of the modified and unmodified sand core funnels are characterized by scanning electron microscopy (SEM) and optical contact angle meter (CA). The separation efficiency of the modified sand core funnel for stratified oil-water mixtures and water-in-oil emulsions, its recyclability and chemical stability are systematically studied. The microscopic separation mechanism of the superhydrophobic sand core funnel for stratified oil-water mixtures and water-in-oil emulsions is scientifically explored. The results show that the modified sand core funnel is loaded with "mushroom" shaped micro-nano-sized Ag0, with contact angles of 162° and 0° for water and oil droplets, respectively. The separation efficiency for various types of stratified oil-water mixtures and oil-in-water emulsions is greater than 95.6%. After 20 consecutive separations, there is no significant change in the separation efficiency for stratified oil-water mixtures and oil-in-water emulsions, indicating that the prepared superhydrophobic sand core funnel has good recyclability. Even in harsh environments such as various organic solvents (methyl chloride, carbon tetrachloride, chloroform, n-butane, toluene), cold water, hot water, strong acids, and high salt concentrations, the modified sand core funnel still maintains superhydrophobic properties and exhibits excellent chemical stability. Due to the superhydrophobic and superoleophilic properties of the modified sand core funnel, water presents a convex liquid surface in the pores of the sand core, experiencing an additional pressure pointing towards the interior of the water, while oil presents a concave liquid surface in the pores of the sand core, experiencing an additional pressure pointing towards the exterior of the oil. Therefore, the pressure required for water and oil to pass through the sand core pores is different. The operating pressure must be lower than the through pressure of water and higher than that of oil to achieve the separation of stratified oil-water mixtures. For the separation of oil-in-water emulsions, under the action of additional pressure, the Vanderwals force connecting the oil droplets and water droplets is disrupted, causing the oil-in-water emulsion to break up. The oil droplets aggregate through friction, compression and collision into larger droplets and pass through the sand core funnel, while the water droplets are retained under the additional pressure of the channel, thereby achieving the separation of oil-in-water emulsions. The experimental preparation of superhydrophobic-superhydrophilic sand core funnels not only can separate stratified oil-water mixtures but also can separate oil-in-water emulsions. It is a material that can be applied in the treatment of oily wastewater in production and life.
Key words
sand core funnel /
nano silver /
oil water separation /
superhydrophobic /
superlipophilic
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References
[1] LUO Y F, SUN Y H, et al.Janus Composite Porous Structure with Asymmetric Selective-Wettability for Unidirectional Liquid Transportation and High-Efficiency Oil-Water Separation[J]. ACS Applied Materials & Interfaces, 2025, 17(21): 31654-31666.
[2] YU Y, ZHANG S Y, WU J F, et al.An Amphiphilic Ionic Polymer-Modified Wood-Based Membrane for Efficient Oil-Water Separation[J]. Langmuir, 2025, 41(32): 21757-21767.
[3] DONG J H, UNIVERSITY F, DONG S F, et al.Superhydrophobic Nanoporous Covalent Organic Frameworks Decorated on Stainless Steel Nets for Oil/Water Separation[J]. ACS Applied Nano Materials, 2025, 8(5): 2299-2309.
[4] LICHADE K M, et al.3D Printing of Hierarchical Porous Structures for Oil/Water Separation and Absorption[J]. ACS Applied Polymer Materials, 2025, 7(17): 11425-11434.
[5] KONG W T, JIA H, et al.Durable Superhydrophobic Coating with Adjustable Superwettability for Oil-Water Separation[J]. ACS Applied Nano Materials, 2025, 8(39): 18817-18828.
[6] HOU J J, YU Z X, CHEN Z Q, et al.Fabrication of Photothermal Membranes with High-Efficiency Oil-Water Separation Capabilities: Applicable for Oil-in-Water Emulsions, Dyes, and Metal Salt Ions[J]. Langmuir, 2025, 41(34): 23050-23063.
[7] WU W Z, BAO L, et al.Facile Fabrication of Photothermal Superhydrophobic Copper Foam Using the Ultrafast Electroplating Approach[J]. ACS Applied Materials & Interfaces, 2025, 17(8): 12973-12983.
[8] LUO W J, SUN D W, CHEN S S, et al.Robust Microcapsules with Durable Superhydrophobicity and Superoleophilicity for Efficient Oil-Water Separation[J]. ACS Applied Materials & Interfaces, 2020, 12(51): 57547-57559.
[9] AHMAD W, AHMAD N, RASHEED S, et al.Silica- Based Superhydrophobic and Superoleophilic Cotton Fabric with Enhanced Self-Cleaning Properties for Oil-Water Separation and Methylene Blue Degradation[J]. Langmuir, 2024, 40(11): 5639-5650.
[10] LIAN Z X, XU J K, WANG Z B, et al.Nanosecond Laser-Induced Underwater Superoleophobic and Underoil Superhydrophobic Mesh for Oil/Water Separation[J]. Langmuir, 2018, 34(9): 2981-2988.
[11] WANG C, HE G H, CAO J L, et al.Underwater Superoleophobic and Salt-Tolerant Sodium Alginate/ N-Succinyl Chitosan Composite Aerogel for Highly Efficient Oil-Water Separation[J]. ACS Applied Polymer Materials, 2020, 2(3): 1124-1133.
[12] HASAN M, MOZUMDER D, SAMS S U, et al.Ultralow-Density Mesoporous PDMS-Doped Graphene Oxide Foam for Cyclic Oil Absorption and FOG Deposition Mitigation[J]. ACS Applied Engineering Materials, 2025, 3(4): 998-1011.
[13] BELAY H, GUO Y S, LIU M Y, et al.Large-Scale Roll-to-Roll Manufacturing of Flexible, Hydrophobic, and Fire-Resistant Mica/SiO2 Nanofiber Aerogel Paper[J]. Nano Letters, 2025, 25(33): 12562-12569.
[14] ZHU J F, LI L Y, HAN L X, et al.Mask Waste: A Sustainable Mask-Based Epoxy Resin/SiO2 Composite for Efficient Purification of Water-in-Oil Emulsions[J]. ACS Applied Polymer Materials, 2022, 4(7): 5180-5188.
[15] 杨福生, 任永忠, 张振宇, 等. 用于油水分离的超疏水-超亲油沙子的制备及其性能[J]. 表面技术, 2021, 50(11): 165-171.
YANG F S, REN Y Z, ZHANG Z Y, et al.Preparation and Properties of Superhydrophobic-Superoleophilic Sand for Oil-Water Separation[J]. Surface Technology, 2021, 50(11): 165-171.
[16] QU M N, MA L L, WANG J X, et al.Smart Materials with Special Wettability Toward Oil/Water Separation and Recovery[M]//Oil-Water Mixtures and Emulsions, Volume 2: Advanced Materials for Separation and Treatment. Washington, DC: American Chemical Society, 2022: 77-106.
[17] PENG Y, TAN Z Q, XIE Y S, et al.Strong Flexible Ceramic Nanofiber Membranes for Ultrafast Separation of Oil Pollutants[J]. ACS Applied Nano Materials, 2022, 5(7): 9389-9400.
[18] CORTI G, SCHMIESING N C, BARRINGTON G T, et al.Characterization of Methyl-Functionalized Silica Nanosprings for Superhydrophobic and Defrosting Coatings[J]. ACS Applied Materials & Interfaces, 2019, 11(4): 4607-4615.
[19] NEMATPOUR M, UNIVERSITY F, RASHIDI M, et al.Synthesis of Stable Castor/Polysulfide for Fabrication of Recyclable Super-Hydrophobic Filters for Oil-Water Separation via Green Chemistry[J]. Journal of Chemical Education, 2025, 102(4): 1619-1625.
[20] YU L S, KANG Y H, TANG H D, et al.Functionalization of Commercial Sand Core Funnels as Hydrophobic Materials with Novel Physicochemical Properties[J]. ACS Applied Materials & Interfaces, 2019, 11(7): 7510-7521.
[21] WANG Z L, QU G F, REN Y C, et al.Study on the Mechanism of Rapid Oil-Water Separation by a Fe3O4@PMMA@PDMS Intelligent Superhydrophobic Micro/Nanorobot[J]. Chemistry - An Asian Journal, 2024, 19: e202300863.
[22] YANG Y Q, ZHOU J, LIU R Z, et al.A Review of Superwetting Surface Preparation and Its Application in Oil-Water Separation[J]. ACS ES&T Water, 2025, 5(6): 2738-2759.
[23] VAITHILINGAM S, THIRVIYAM S K, MUTHUKARUPPAN A, et al.CdO-Nanografted Superhydrophobic Hybrid Polymer Composite-Coated Cotton Fabrics for Self-Cleaning and Oil/Water Separation Applications[J]. ACS Omega, 2023, 8(45): 43163-43177.
[24] DAS S, KUMAR S, SAMAL S K, et al.A Review on Superhydrophobic Polymer Nanocoatings: Recent Development and Applications[J]. Industrial & Engineering Chemistry Research, 2018, 57(8): 2727-2745.
[25] 李群, 丁秋夫, 刘鑫磊, 等. 超疏水膜油水分离特性实验研究[J]. 工程热物理学报, 2018, 39(2): 341-347.
LI Q, DING Q F, LIU X L, et al.Experimental Research on Oil-Water Separation Characteristic with Super- Hydrophobic Membrane[J]. Journal of Engineering Thermophysics, 2018, 39(2): 341-347.
[26] GONG J L, XIANG B, SUN Y Q, et al.Janus Smart Materials with Asymmetrical Wettability for On-Demand Oil/Water Separation: A Comprehensive Review[J]. Journal of Materials Chemistry A, 2023, 11(46): 25093-25114.
[27] DA SILVA F P, BORGES C P, DA FONSECA F V. Trends in Fouling Resistant Membranes Containing Metals or Metallic Nanoparticles for the Separation of Oil-in-Water Emulsions[J]. ACS Omega, 2025, 10(8): 7510-7529.
[28] GONG J L, XIANG B, JIN R R, et al.Robust Peony-Like Cu3(PO4)2/UiO-66-NH2/PVA Membranes with Exceptional Anti-Fouling Performance for High Flux Emulsion Separation[J]. Separation and Purification Technology, 2025, 379: 134915.
Funding
Gansu Province University Teachers' Innovation Fund (2025B-250); Provincial Innovation and Entrepreneurship Training Program for College Students (DC202501-210, DC202502-130); The Youth Science and Technology Innovation Foundation of Lanzhou Institute of Technology (2025KJ-23, 2025KJ-25)
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