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Separations
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Advanced Oil–Water Separation Technology
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Advanced Oil–Water Separation Technology

A special issue of Separations (ISSN 2297-8739). This special issue belongs to the section "Environmental Separations".

Deadline for manuscript submissions: closed (20 June 2024) | Viewed by 10657

Special Issue Editor

Dr. Chaolang Chen

E-Mail Website
Guest Editor
School of Mechanical Engineering, Sichuan University, Chengdu 610065, China
Interests: separation technology; wettability; surface and interface
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Oil–water mixtures are widely produced in our daily life and industrial production, evident in oil spills, mechanical processing, etc. The direct discharge of untreated oil–water mixtures will cause serious environmental pollution, ecological damage, and even danger to human health. How to achieve efficient separation of oil–water mixtures has become an urgent global issue.

This Special Issue aims to highlight the progress made in the devleopment of oil–water separation technology. We welcome contributions (original research papers and review articles) that report on advanced technology, new materials, new methods, and membranes with special wettability for separating layered oil–water mixtures or emulsified oil–water mixtures (e.g., oil-in-water emulsions, water-in-oil emulsions).

Dr. Chaolang Chen
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Separations is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • oil–water separation
  • oil-in-water emulsion
  • water-in-oil emulsion
  • membrane technology
  • wettability
  • superhydrophobic or superhydrophilic
  • superoleophilic or superoleophobic
  • separation mechanism

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Published Papers (5 papers)

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Research

Jump to: Review

18 pages, 9752 KiB  
Article
Carwash Oily Wastewater Separated by Ultrafiltration
by Piotr Woźniak and Marek Gryta
Separations 2024, 11(6), 164; https://doi.org/10.3390/separations11060164 - 25 May 2024
Cited by 1 | Viewed by 716
Abstract
In the present study, oily wastewater generated during car washing was separated using ultrafiltration (UF). Wastewater was collected from the settling tank of two manual car washes. In addition to pollutants removed from cars, such wastewater contains surfactants, the impact of which on [...] Read more.
In the present study, oily wastewater generated during car washing was separated using ultrafiltration (UF). Wastewater was collected from the settling tank of two manual car washes. In addition to pollutants removed from cars, such wastewater contains surfactants, the impact of which on the process of ultrafiltration has been analyzed. For this purpose, the application of commercial UF polyethersulfone (PES) membranes (10 and 100 kDa) and polyvinylidene fluoride (PVDF) tubular membranes (100 kDa) was comprehensively examined. Almost 100% removal of oil contaminants was achieved; however, intensive fouling was noticed. The membrane morphology and deposit composition were studied using a scanning electron microscope coupled with energy dispersion spectrometry. The fouling phenomenon was reduced by washing the membranes with an alkaline cleaning agent (pH = 11.5), which is used in car washes to remove insects. The filtration/membrane washing cycle was repeated many times to achieve stable operation of the membrane modules. The UF process was carried out for 120–140 h, and the separation efficiency was analyzed based on the rejection of dextrans, COD, BOD, total N and P, turbidity, and anionic surfactants. It has been found that cyclic repeated washing did not deteriorate the membrane’s performance, and a permeate with a turbidity of 0.12–0.35 NTU was obtained. Thus, cleaning agents used for washing cars can also be used for membrane cleaning. Full article
(This article belongs to the Special Issue Advanced Oil–Water Separation Technology)
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15 pages, 4439 KiB  
Article
Enhanced Photocatalytic and Filtration Performance of TiO2-Ag Composite-Coated Membrane Used for the Separation of Oil Emulsions
by Ákos Ferenc Fazekas, Tamás Gyulavári, Áron Ágoston, László Janovák, Judit Kopniczky, Zsuzsanna László and Gábor Veréb
Separations 2024, 11(4), 112; https://doi.org/10.3390/separations11040112 - 5 Apr 2024
Viewed by 1433
Abstract
Polyvinylidene fluoride (PVDF) membranes were coated with TiO2 and TiO2-Ag to enhance their efficiency for oil-in-water emulsion separation. The photocatalytic activities of the two modified membranes and their filtration performances were compared in detail. The significantly enhanced photocatalytic activity of [...] Read more.
Polyvinylidene fluoride (PVDF) membranes were coated with TiO2 and TiO2-Ag to enhance their efficiency for oil-in-water emulsion separation. The photocatalytic activities of the two modified membranes and their filtration performances were compared in detail. The significantly enhanced photocatalytic activity of the TiO2-Ag composite was proved using a methyl orange (MO) solution (c = 10−5 M) and a crude oil emulsion (c = 50 mg·L−1). The TiO2-Ag-coated membrane reduced the MO concentration by 87%, whereas the TiO2-modified membrane reached only a 46% decomposition. The photocatalytic reduction in the chemical oxygen demand of the emulsion was also ~50% higher using the TiO2-Ag-coated membrane compared to that of the TiO2-coated membrane. The photoluminescence measurements demonstrated a reduced electron/hole recombination, achieved by the Ag nanoparticle addition (TiO2-Ag), which also explained the enhanced photocatalytic activity. A significant improvement in the oil separation performance with the TiO2-Ag-coated membrane was also demonstrated: a substantial increase in the flux and flux recovery ratio (up to 92.4%) was achieved, together with a notable reduction in the flux decay ratio and the irreversible filtration resistance. Furthermore, the purification efficiency was also enhanced (achieving 98.5% and 99.9% COD and turbidity reductions, respectively). Contact angle, zeta potential, scanning electron microscopy (SEM), and atomic force microscopy (AFM) measurements were carried out to explain the results. SEM and AFM images revealed that on the TiO2-Ag-coated membrane, a less aggregated, more continuous, homogeneous, and smoother nanolayer was formed due to the ~50% more negative zeta potential of the TiO2-Ag nanocomposite compared to that of the TiO2. In summary, via Ag addition, a sufficiently hydrophilic, beneficially negatively charged, and homogeneous TiO2-Ag-coated PVDF membrane surface was achieved, which resulted in the presented advantageous filtration properties beyond the photocatalytic activity enhancement. Full article
(This article belongs to the Special Issue Advanced Oil–Water Separation Technology)
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14 pages, 4623 KiB  
Article
Design Methodology for a Low-Shear Rotating Swirler
by Zheng Si, Yipeng Ji, Jiaqing Chen, Xiujun Wang, Hong Du, Jian Zhang, Hai Yu, Qiang Ren and Zhao Hua
Separations 2023, 10(11), 550; https://doi.org/10.3390/separations10110550 - 28 Oct 2023
Viewed by 1739
Abstract
The tubular dynamic hydrocyclone (TDH) holds great potential for the pre-deoiling of offshore oil platforms. However, the shear and turbulence in the flow field can cause the oil droplets, the dispersed phase in water, to break up when the swirling flow is produced [...] Read more.
The tubular dynamic hydrocyclone (TDH) holds great potential for the pre-deoiling of offshore oil platforms. However, the shear and turbulence in the flow field can cause the oil droplets, the dispersed phase in water, to break up when the swirling flow is produced by the swirler. A design method is proposed for the low-shear rotary swirler (LSRS) of TDH, the aim of which is to reduce the shear force and local turbulence during the fluid forming swirling flow. The blade setting angle of the LSRS is calculated based on the relative velocity vector between the fluid and the swirler. The distribution characteristics of the tangential velocity and turbulence in the TDH with LSRS are simulated by Computational Fluid Dynamics (CFD). The maximum stable droplet diameter is analyzed. The results show that the shear stress and turbulence energy dissipation rates are reduced by 74.6% and 68.5%, respectively, and that the stable droplet diameter is increased by more than 60%, compared to the conventional rotating swirler. In addition, a TDH prototype with LSRS was tested in an offshore oil field by continuous operation for more than 36 h. The average separation efficiency was 83%, and the average underflow oil concentration was 27 mg/L. The research also found that the drastic changes in the tangential velocity along the axial direction were critical to shear. Moreover, the results make up for the deficiency of the spatial variation of the tangential velocity in the dynamic cyclone separator. Full article
(This article belongs to the Special Issue Advanced Oil–Water Separation Technology)
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Review

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24 pages, 5748 KiB  
Review
Laser Manufacturing of Superwetting Oil–Water Separation Materials: A Review
by Wei Xiong, Linfeng Zhu, Ruisong Jiang and Chaolang Chen
Separations 2024, 11(4), 126; https://doi.org/10.3390/separations11040126 - 19 Apr 2024
Viewed by 1581
Abstract
The frequent occurrence of oil spills and the massive discharge of oily wastewater pose a significant threat to sustainable and healthy human development. Therefore, it is of importance to effectively separate oil–water mixtures. Inspired by nature, many superwetting surfaces/materials for oil–water separation have [...] Read more.
The frequent occurrence of oil spills and the massive discharge of oily wastewater pose a significant threat to sustainable and healthy human development. Therefore, it is of importance to effectively separate oil–water mixtures. Inspired by nature, many superwetting surfaces/materials for oil–water separation have been developed in recent years. However, these surfaces/materials are subject to certain limitations and are unable to fully meet practical needs. With the advancement of laser technology, a novel solution has been provided for fabricating superwetting oil–water separation materials. Based on the design theory and separation mechanism, this paper summarizes the research progress of the laser-fabricated superwetting surfaces/materials for oil–water separation in recent years. First, the basic wetting theory, design strategy, and oil–water separation mechanism of the laser-fabricated materials are introduced in detail. Subsequently, the laser-fabricated oil–water separation materials, including superoleophilic/superhydrophobic materials, superhydrophilic/superoleophobic materials, and materials with reversible or superamphiphilic wettability, are systematically summarized and analyzed. Finally, the challenges and future research directions of laser-fabricated superwetting oil–water separation materials are discussed. Full article
(This article belongs to the Special Issue Advanced Oil–Water Separation Technology)
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18 pages, 7130 KiB  
Review
Nanostructure-Based Oil–Water Separation: Mechanism and Status
by Bao Wang, Shaotong Feng, Caihua Wang, Xiaoyan Liu, Lei Chen and Dayun Yan
Separations 2023, 10(11), 569; https://doi.org/10.3390/separations10110569 - 15 Nov 2023
Cited by 5 | Viewed by 4332
Abstract
Flexible and effective methods for oil–water separation are crucial for reducing pollutant emissions and safeguarding water and fuel resources. In recent years, there has been growing interest in fundamental research and engineering applications related to water and fuel purification, especially oil–water separation. To [...] Read more.
Flexible and effective methods for oil–water separation are crucial for reducing pollutant emissions and safeguarding water and fuel resources. In recent years, there has been growing interest in fundamental research and engineering applications related to water and fuel purification, especially oil–water separation. To date, filter materials with special wetting characteristics have been widely used in oil–water separation. Nanostructured materials are one of the most attractive candidates for next-generation oil–water separation. This review systematically summarizes the mechanisms and current status of oil–water separation using nanostructured materials. Basically, this can be achieved by using nanostructured materials with specific wettability and nanostructures. Here, we provide a detailed discussion of two general approaches and their filtration mechanisms: (1) the selective filtration technique, based on specific surface wettability, which allows only oil or water to penetrate while blocking impurities; (2) the absorption technique, employing porous sponges, fibers, or aerogels, which selectively absorbs impure oil or water droplets. Furthermore, the main failure modes are discussed in this review. The purposes of this article are: (1) to summarize the methods of oil–water separation by nanotechnology; (2) to raise the level of environmental protection consciousness of water pollution by using nanotechnology; (3) to tease out the features of different approaches and provide a pivotal theoretical basis to optimize the performance of filtering materials. Several approaches for oil and water separation are compared. Furthermore, the principle and application scope of each method are introduced. Full article
(This article belongs to the Special Issue Advanced Oil–Water Separation Technology)
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