Separation Of Oily Wastewater Research Articles

Facile Preparation of Smart Sponge Based on a Zeolitic Imidazolate Framework for the Efficient Separation of Oily Wastewater

The fabrication of durable materials with excellent oil-adsorption capacity and separation performance for the treatment of oily wastewater is meaningful based on the special property of smart responsiveness. Herein, a solvent-responsive melamine sponge (MS) was developed via silanization and the in situ growth of a zeolitic imidazolate framework-8 (ZIF-8). Detailed characterization of the resultant composite MS was conducted using scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and X-ray diffraction (XRD). The multiscale hierarchical MS substrate exhibited highly hydrophobic properties in the pH range of 1–11, along with a satisfactory adsorption capacity in the range of 65.4–134.2 g/g for different oils. The modified surface transformed from superhydrophobic/superlipophilic to superhydrophilic/underwater superoleophobic upon ethanol wetting, reverting to its original superhydrophobic state upon drying. The separation flux of the MS substrate was above 1.5 × 104 L/m2h for both oil and water removal, and the separation efficiency was greater than 98.7%. The absence of obvious changes in separation performance after 50 successive immiscible oil−water separations indicated the excellent durability and robustness of the anchored ZIF-8 nanoparticles on the surface of the modified MS substrate. More importantly, oil-in-water emulsion separation was successfully carried out via the ZIF-8 MS composite, showing high separation efficiency (over 99.1%). The developed smart sponge, which had high oil-adsorption capacity, excellent chemical stability, and fire resistance, has a wide range of potential practical applications in the convenient treatment of oily wastewater.

Synthesis of a demulsifier for treating crude oil-in-water emulsion through a straightforward low-temperature process

The separation of oily wastewater is a significant issue in the petroleum industry. In current work, a highly efficient demulsifier (TCDA) was synthesized through a one-step low-temperature method for the purpose of demulsifying O/W emulsions. The structure was characterized using FT-IR and 1H NMR spectra. The oil–water separation ability was evaluated through light transmittance (T%) and oil removal rate (η%) of separated water. The results showed that T% of 88.6 % and η% of 99.8 % could be obtained with the dosage of 30 mg/L at ambient temperature. In addition, TCDA demonstrated good acid and salt resistance. The relative solubility number (RSN), three-phase contact angle, dynamic interfacial tension, zeta potential and optical micrograph were characterized to explore possible demulsification mechanism. It was found that TCDA effectively reduced interfacial tension and penetrated the interfacial membrane, thereby facilitating the separation of O/W emulsion. Overall, these results indicate that the TCDA demulsifier shows promise for using in the demulsification of oily wastewater.

Modification of PVDF membranes using polyvinyl alcohol-crosslinked functionalized nano-silica sheets: High flux and antifouling properties for efficient oil-water separation

BackgroundsOily wastewater is the leading cause of water and environmental pollution, but conventional treatments suffer from complexity and low efficiency, and explicitly deal with oil-in-water emulsions. Polyvinylidene fluoride (PVDF) membranes have shown immense potential for separation applications; however, these membranes rapidly foul during the separation of oily wastewater. MethodsA simple method is introduced to improve the hydrophilicity of PVDF membranes by decorating their surfaces with acrylic acid-modified nano-silica (NS) nanoparticles, whose surface stability is achieved by crosslinking them with polyvinyl alcohol (PVA). Three distinct oils were employed in this study for oil–water emulsion analysis: vegetable oil, diesel oil, and petroleum ether oil. The antifouling abilities and characterization were elucidated using advanced analytical techniques. Significant findingsThe membrane surface became hydrophilic, and the water contact angle reduced from 64 ± 1.45o to 24.3 ± 1.75o. The NS-PVA-PVDF membrane exhibited the oleophobic behavior underwater, with an underwater oil contact angle of 147.6 ± 2.65o. Under optimized conditions, the NS-PVA-PVDF membranes have shown excellent rejection efficiency for different oil-in-water emulsions, including vegetable oil (99.01± 0.64 %), diesel oil (94.61± 0.26 %), and petroleum ether oil-in-water (84.53 ± 0.85 %) emulsions. For a membrane with a 1:3 ratio of PVA to NS particles, organic foulants like humic acid and dye elucidated better performance with 94.79 ± 1.11 and 92.79 ± 1.41 % removal, respectively, along with the flux recovery ratio of 0.96 and 0.92 for humic acid and dye filtration with irreversible fouling of 0.03 and 0.08, respectively. However, the long-term analysis of the optimum membranes showed an overall stable rejection efficiency of >95 % compared with the pristine membrane. The specific rejection efficiency varied for oil emulsion (44.67–50.14 %), humic acid (59.55–67.75 %), and for dye filtration (61.52–73.5 %). These results verify the potential of the modified NS-PVA-PVDF membrane for oil–water separation for practical applications.

Facile dip-coating of silk fibroin/tannic acid@CaCO3 hybrid film with superhydrophilicity on the surface of polypropylene nonwovens for oil–water separation

Superhydrophilic membrane materials are widely used for oil/water separation due to their excellent resistance to anti-fouling underwater. The key factors for realizing superhydrophilicity of membranes are the introduction of hydrophilic groups and the construction of surface micro/nano roughness structures. Herein, we propose a simple, mild, and green dip-coating method to prepare silk fibroin (SF)-tannic acid (TA)@CaCO3 hybrid film to achieve superhydrophilicity of polypropylene nonwovens (PP). Specifically, the hydrophobic interactions between SF and hydrophobic materials were used to create the pre-coatings. TA molecules were deposited onto the surface of SF via hydrogen bonding to provide phenolic hydroxyl groups for achieving the hydrophilicity of PP membranes. Then, the CaCO3 was synthesized in situ by introducing Ca2+ into the pre-coating while depositing TA to construct micro/nano-roughness structures on the PP membrane surface for obtaining superhydrophilicity. PP-SF-TA@CaCO3 membranes exhibit outstanding superhydrophilicity and underwater superoleophobicity, with separation efficiencies exceeding 99 % for a variety of oil–water mixtures and oil-in-water emulsions, and water fluxes ranging from 4000 L m-2h−1 to 5500 L m-2h−1. The separation efficiencies remained above 99 % throughout 50 separation cycles, indicating the excellent separation stability of the modified membranes. Moreover, no significant loss of separation efficiency was observed when separating oil mixtures from harsh water sources, including acidic, alkaline, cold, and hot water. Therefore, the membranes modified by the above process have a promising application in the practical separation of oily wastewater.

UiO-66-NH2/hydrothermal carbon nanocomposite assembled mesh membrane with photocatalytic self-cleaning and antibacterial properties for on-demand oily wastewater separation

The poor wettability, limited permeation flux and unsatisfactory anti-fouling property of oil/water separation membranes significantly hinder their practical application. This study developed a novel UiO-66-NH2/hydrothermal carbon@stainless steel mesh (UiO/HC@SSM) membrane, fabricated through a straightforward dip-coating strategy that offers membrane thickness control. The resulting membrane exhibited superhydrophilic/underwater superoleophobic property and high porosity, enabling gravity-driven separation of emulsified and stratified oil/water mixtures on-demand with high separation efficiency and superior flux. Specifically, UiO/HC@SSM-5 (dip-coating five times) showed ultrahigh permeate fluxes of 51428–56425 L m−2 h−1 for stratified oil/water mixtures separation, and UiO/HC@SSM-10 exhibited interface demulsification and gravity separation ability for emulsified oil/water mixtures with high fluxes of 4050–4504 L m−2 h−1. Notably, UiO/HC nanocomposite endowed the membrane with exceptional photocatalytic self-cleaning and antibacterial activities, effectively addressing both oil and microbial fouling. High-viscosity crude oil fouling can be light-induced decontaminated from the composite membrane surface with superior flux recovery ratio (FRR) up to 97 %. The as-prepared UiO/HC@SSM also exhibited near-complete bacterial inactivation activity after 10 min of visible light irradiation. Encouragingly, UiO/HC@SSM demonstrated superior separation and photocatalytic capabilities compared to UiO@SSM, attributed to the dual promoting role of cost-effective hydrothermal carbon in hydrophilicity and photoelectric properties. Moreover, UiO/HC modified SSM membrane displayed robust chemical and mechanical stability, coupled with superior harsh environments and oil pressure resistances. This membrane, boasting desirable wettability, high permeability, exceptional photocatalytic activity, and excellent stability, offers a reliable solution for treating complex oily wastewater. Additionally, the demulsification and photocatalysis mechanisms of UiO/HC@SSM membrane were examined in depth. This study holds significant potential in advancing the development of novel SSM membranes functionalized with MOF/carbon material, thereby enhancing their practical applications in purifying oily wastewater.

In-situ construction of stable and efficient superhydrophobic MOFs-based cellulose paper for oil–water separation

In recent years, separating oil-water mixed pollutants has emerged as an increasingly significant part of sustainable development due to oil-containing wastewater discharged and offshore oil spills. Therefore, developing stable and efficient materials for the separation of oily wastewater has garnered significant attention in current research. Herein, a novel superhydrophobic functionalized MOFs-based cellulose paper (PDMS/UiO-66-NH2@CP) was successfully synthesized by integrating cellulose paper (CP) with UiO-66-NH2 via solvothermal method and further modifying with polydimethylsiloxane (PDMS), which was used as an oil-water separation material to purify oily wastewater. The reaction procedure is facile and simple, and the preparation method is efficient. Notably, the as-synthesized PDMS/UiO-66-NH2@CP showed excellent superhydrophobicity/superlipophilicity, with a water contact angle up to 162° and an oil contact angle (OCA) of approximately 0º, and it can still maintain superhydrophobic stability under strong acid or alkali conditions. Furthermore, the surface of superhydrophobic paper cannot been adhered by dye solution and powder, indicating its good self-cleaning and anti-fouling ability. Moreover, the composite paper displayed exceptional UV blocking property with the ability to block 99% ultraviolet. Attributed to these characteristics, PDMS/UiO-66-NH2@CP as an oil-water separator demonstrated exceptional performance in separating oil-water mixtures and emulsions, achieving efficiencies exceeding 98% and fluxes in the range of 105.26−412.14 L·m-2·h-1. More importantly, it displayed remarkable recyclability and its separation efficiency was still above 98% after 50 cycles. This study not only develops a facile and effective strategy for preparing superhydrophobic papers, but also provides innovative and instructive guidance for developing efficient oil-water separation materials.

Anti-fouling ampholytic polymer membrane with super-wetting surfaces for efficient oil-water emulsion separation

The development of highly efficient polymeric membranes with super-wetting surfaces (superhydrophilic/submerged superoleophobic) is one of the ideal options to achieve emulsified oily wastewater separation. However, this remains a challenging due to low fluxes and severe membrane contamination limitations. Here, we have demonstrated an ultra-hydrophilic, underwater super-oleophobic, highly anti-fouling and antibacterial (polydopamine/poly [2-(methacryloyloxy) ethyl] dimethyl- (3-sulfopropyl) ammonium hydroxide) PDA/PSBMA modified membrane by grafting amphoteric polymers via atom transfer radical polymerization (ATRP). Benefiting from PSBMA's superhydrophilicity and the unique adhesion of dopamine (DA), the PDA/PSBMA modified membrane shows superhydrophilic properties, superoleophobicity underwater, oil resistance, and fouling resistance. Meanwhile, PDA/PSBMA modified membrane reached a superb permeability to water as high as 5620 L·m−2·h−1·bar−1 and remarkable oil rejection rate of 98 % in separating diesel-in-water emulsions. Furthermore, the separating performance remained fairly constant over 10 emulsion filtration cycles. Besides, the PDA/PSBMA modified membranes have excellent acid and alkali resistance and antibacterial properties, showing its potential for oily wastewater purification. This work offers a simple and versatile strategy to fabricate superwetting efficient polymeric membranes to separate emulsified oily wastewater.

Antifouling macrocyclic-engineered PVDF membrane for the low-pressure separation of surfactant-stabilized oily wastewater

Fouling is a common phenomenon which affects the long-term efficacy of membranes in the practical treatment of oily wastewater. It often results in a dramatic decline in flux, and a consequent increase in maintenance and operational cost. To address this, various substrates have been incorporated during membrane fabrication to enhance the fouling resistance, and improve the separation efficiency. Herein, we report the fabrication of a novel symmetrical ball-copper phthalocyanine incorporated PVDF membrane (CuPc@PVDF) for the effective separation of surfactant-stabilized oil-in-water emulsions. The symmetrical ball-Cu phthalocyanine with four non-peripheral substituents synthesized ab-initio and characterized using UV–vis, FT-IR, 1H NMR, and MALDI-TOF spectroscopies was added to the casting solution during membrane fabrication resulting in the formation of highly hydrophilic and anti-fouling CuPc@PVDF membrane. In contrast to the PVDF membrane, having a water contact angle of 82.3° ± 0.7°, the CuPc@PVDF membrane demonstrated high hydrophilicity with a contact angle of 55.5° ± 0.5°, and pure water permeance up to 768 LMH at 3 bar. It further achieved 99.9 % rejection of oil with size in the range of 50–450 nm at 1 bar, and demonstrated high stability and excellent anti-fouling property during 10 cycles of continuous demulsification, with a flux recovery ratio (FRR) of 98.5 %, and extremely low irreversible flux of 1.5 %. Similarly, the CuPc@PVDF membrane exhibited high resistance to accelerated organic fouling, maintaining a steady flux and an FRR of 93.0 % during 1 hour of continuous operation with 10 ppm sodium alginate and Ca2+ ions. This study reports a novel strategy to enhance the fouling resistance of demulsification membranes, and could be further explored in the design of next generation of advanced membranes for the purification of oily wastewater.

Synthesis of cyclodextrin-based demulsifier for treatment of oily wastewater through hydrophobic modification strategy

The discharge of oily wastewater not only has an impact on the environment, but also poses a threat to human health. Therefore, the treatment of oily wastewater is crucial. In current work, a novel demulsifier (CD-LA) was prepared using β-cyclodextrin (β-CD) as raw material by the acylation of –OH and subsequent grafting of dodecylamine. The demulsifier was intended for the treatment of oily wastewater. Detailed examinations were conducted on the surface morphology, chemical composition, interfacial activity, and the capacity of CD-LA to engage competitively at the interface. This substance demonstrated a pronounced ability to lower interfacial tension, indicating its utility in supplanting asphaltenes at the oil–water boundary. This action facilitates the weakening or disruption of the interfacial film, which is critical for the successful separation of oily wastewater. The findings revealed that CD-LA excelled in clarifying oily wastewater, proving effective under near-neutral conditions and in environments with elevated salinity. Separated water phase could obtain light transmittance (WT) of 89.75 % and oil removal rate (WR) of 99.83 % after the oily wastewater was demulsified with a concentration of 50 mg/L at room temperature.

Insight into soft chemometric computational learning for modelling oily-wastewater separation efficiency and permeate flux of polypyrrole-decorated ceramic-polymeric membranes

Reliable modeling of oily wastewater emphasizes the paramount importance of sustainable and health-conscious wastewater management practices, which directly aligns with the Sustainable Development Goals (SDG) while also meeting the guidelines of the World Health Organization (WHO). This research explores the efficiency of utilizing polypyrrole-coated ceramic-polymeric membranes to model oily wastewater separation efficiency (SE) and permeate flux (PF) based on established experimental procedures. In this area, computational simulation still needs to be explored. The study developed predictive regression models, including robust linear regression (RLR), stepwise linear regression (SWR) and linear regression (LR) for the ceramic-polymeric porous membrane, aiming to interpret its complex performance across diverse conditions and, thus, develop its utility in oily wastewater treatment applications. Subsequently, a novel, simple average ensemble paradigm was explored to reduce errors and improve prediction skills. Prior to the development of the model, stability and reliability analysis of the data was conducted based on Philip Perron tests with the Bartlett kernel estimation method. The accuracy of the SE exhibited a high consistency, averaging 99.92% with minimal variability (standard deviation of 0.026%), potentially simplifying its prediction compared to PF. The modes were validated and evaluated using metrics like MAE, RMSE, Speed, and MSE, in addition to 2D graphical and cumulative distribution function graphs. The LR model emerged as the best with the lowest RMSE =0.21951, indicating superior prediction accuracy, followed closely by RLR with an RMSE = 0.22359. SWLR, while having the highest RMSE = 0.34573, marked its dominance in prediction speed with 110 observations per second. Notably, the RLR model justified a reduction in error by approximately 35.29% compared to SWLR. Moreover, the training efficiency of the LR model exceeded, demanding a mere 2.9252 s, marking a reduction of about 32.54% compared to SWLR. The improved simple ensemble learning proved merit over the three models regarding error accuracy. This study emphasizes the essential role of soft-computing learning in optimizing the design and performance of ceramic-polymeric membranes.

High performance and antifouling zeolite@polyethersulfone/cellulose acetate asymmetric membrane for efficient separation of oily wastewater

Microfiltration membranes have emerged as a promising alternative for oily wastewater treatment due to their high efficiency, low cost, and ease of operation. In this study, polyethersulfone (PES), cellulose acetate (CA), and 4A zeolite were blended to fabricate asymmetric membranes by the phase inversion technique and examined in oily wastewater treatment. Kerosene was chosen as a model polluting oil. The fabricated pure PES membrane (P), PES membranes incorporating 4A zeolite (ZP), PES membrane blended with CA (PC), and PES/CA blended membranes with 4A zeolite (ZPC) were characterized using field emission scanning electron microscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, porosity, and contact angle to study the structure properties of these membranes. The performance of membranes was examined by water permeation, oil permeation flux, oil rejection, flux recovery ratio, and relative flux reduction. The ZPC membranes showed the highest performance in comparison with other prepared membranes. Incorporating 4A zeolite nanoparticles with 0.5 wt% into the PES/CA blended membrane significantly enhanced the microfiltration performance and decreased the contact angle of the P membrane from 70° to 29.8°. The effect of operation parameters such as transmembrane pressure (1–4 bar), feed temperature (25–50 ºC), and concentration of oil feed solution (250–1000 mg/L) on the permeation flux and oil rejection was studied on the PES/CA blended membrane containing 0.5 wt% 4A zeolite (0.5%ZPC). The 0.5%ZPC membrane showed improved porosity of 87.7% and it gave the highest value of pure water flux of 91.1 L/m2.h, oil permeation flux of 75.55 L/m2.h, maximum oil rejection of 98.8%, flux recovery ratio of 97.7%, and relative flux reduction of 21.8%. The permeation flux given by the 0.5%ZPC membrane was improved by about 8 times that of the P membrane. Re-usability studies verified the durability of the blended membranes and their performance in oily wastewater treatment.

Fast fabricating superhydrophilic PVDF membrane via proanthocyanidins crosslinking at room temperature

Mussels in nature can adhere to the surface of hydrophobic substances by secreting adhesive substances, which has attracted wide attention by coating method for membrane modification. However, complicated processing procedures remain major problems. Here, we proposed a simple, mild and fast surface coating method. Proanthocyanidins (PC) react with 3-aminopropyl triethoxysilane (KH550) under the accelerated action of the oxidant ammonium persulfate (APS) at room temperature to form a polyphenol network. The hydrophilic network coating was constructed on PVDF membrane by surface co-deposition method for 1 h, which could effectively separate different emulsions. The water permeability of modified membrane was 18,271 L∙m−2∙h−1∙bar−1. The permeability for separating isooctane-in-water emulsion arrived at 14,223 L∙m−2∙h−1∙bar−1 and the oil rejection rate was 99.6 %. After ten cycles, the separation flux was 10,836 L∙m−2∙h−1∙bar−1 with the rejection rate of 98.8 %. Modified membranes were soaked in acid and alkali salt solutions of different pH values for 30 days, and maintained good underwater oleophobic performance (>156°). The developed membrane showed excellent separation performance, oleophobic property and acid-base stability. The proposed membrane modification strategy was prospective for efficient separation of oily wastewater.

MXene sheets surface constructed a strong hydrogel coating for sustainable oily wastewater separation

Membrane separation technology can effectively address the issues of high energy consumption and low efficiency encountered in traditional separation processes. However, oil fouling hinders the widespread adoption of membrane technology in the field of oil-water separation. Therefore, preventing membrane fouling is crucial for overcoming this bottleneck. Titanium carbide (Ti3C2Tx, MXene), a recent addition to the two-dimensional material family, has garnered significant interest in the domain of water treatment owing to its controllable surface groups, hydrophilic nature, antimicrobial properties, and high electrical conductivity. Hence, we proposed a strategy to construct hydrogel coatings on carboxylated MXene surfaces. Moreover, the rigidity of the hydrogel framework was further improved by introducing CaCO3 nanoparticles. A stronger hydrogel layer ensured that the hydration layer is difficult to contaminate with oil and the fastness of the membrane material. Naturally, the as-prepared membrane showed excellent separation performance for a wide range of emulsions, maintaining high levels (3979.5 L m–2 h−1 bar−1 and 99.96 %) after 5 consecutive separation cycles of 200 min. Additionally, the membrane separated emulsions containing acids, salts, or alkali with a permeability of 2982.8 L m–2 h−1 bar−1 after 40 min; it also treated actual oily wastewater achieving a permeability of 238.9 L m–2 h−1 bar−1 and showed high removal efficiency (>99.9 %) for several heavy metals (Cu, Li, Pb, Se, and V), as well as antimicrobial (92.5 %) properties that enhance its potential for industrial applications. This study offers a new idea for designing anti-oil-fouling MXene oil-water separation membranes.

A synergistically enhanced photocatalytic 2D MXene nanofibrous composite membrane for wastewater treatment

Despite notable advancements in membrane technology, the efficacious separation of intricate oily wastewater via membrane filtration continues to pose formidable barriers for the industry. Recent methods, encompassing the integration of two-dimensional (2D) nanosheets to improve membrane properties, have demonstrated a propensity for encountering challenges like swelling, fouling, and operational instability during the filtration process. Herein, we meticulously designed a polyvinylidene fluoride (PVDF) nanofibrous membrane (NFM) tailored with a 2D nanostructured composite of MXene nanosheets and TiO2 nanofrost for the pioneering treatment of intricate oily wastewater. The resultant membrane exhibited remarkable separation performance concerning surfactant-stabilized emulsions while maintaining excellent water permeability. Additionally, the membrane demonstrated outstanding antifouling and self-cleaning capabilities while also showing high efficiency in removing metal cations from oily wastewater, which may be related to the intercalation of TiO2 nanofrost. Furthermore, in response to the synergistic impact of MXene nanosheets and TiO2 nanofrost, the TiO2@MX-PVDF NFM presented exceptional photocatalytic degradation ability for the breakdown of organic pollutants under visible irradiation. Consequently, present work unveils an advanced, reliable and remarkably efficient approach for developing a 2D multifunctional MXene composite membrane designed specifically for treating complex oily wastewater.

F-free etching and ingenious construction of hydrogel layer-prepared MXene membranes for oily wastewater separation.

A strategy for the preparation of hydrogel layer MXene membranes by an F-free method was proposed. It maintained high permeance (2686.1 L m-2 h-1 bar-1) and separation efficiency (99.99%) even after 300 min of emulsion separation. The membrane resisted harsh chemical and microbiological environments and efficiently treated actual oily wastewater.

Investigation of the Aging Effect of Bio-Coagulant for Oily Wastewater Treatment

The separation of oily wastewater is one of the main processes in the water treatment field. A biological approach that can replace the use of chemical coagulants hazardous to human health is an efficient solution in treating oily wastewater. However, bio- coagulants have a time limit that can affect their effectiveness in treating oily wastewater. Thus, this paper presents research for the aging effect of bio-coagulant for treating oily wastewater. In this study, G-Treat was used as the bio-coagulant, which was produced from chitosan powder, acetic acid, and deionized water. The experimental procedure started by filling 500 mL of oily wastewater into a beaker. Next, 10 wt. % of G- Treat was added into the beaker for the jar test, which was mixed for 30 min at 150 rpm, followed by 2 h settling time. Then, the mixture was separated using filter paper. The analysis of oily wastewater characteristics was conducted using five types of analyses, which are pH, chemical oxygen demand (COD), biological oxygen demand (BOD), total sus- pended solids (TSS), and oil and grease (O&G) under the parameters of days (0–7 days), weeks (0–6 weeks), and months (0–3 months). From the result, the best performance of G-Treat was achieved at the optimum parameters during week 2, with 33.16%, 65.75%, 35.73%, 28.58%, and 0% removal of pH, COD, BOD, TSS, and O&G, respectively. In conclusion, the studied bio-coagulant demonstrated higher removal of pH, COD, BOD, TSS, and O&G at optimum parameters, and eventually, the level of effectiveness will drop.

Enhanced management and antifouling performance of a novel NiFe-LDH@MnO2/PVDF hybrid membrane for efficient oily wastewater treatment

Layered double hydroxides (LDHs) have gained significant recognition for their facile synthesis and super-hydrophilic two-dimensional (2D) structure to fabricate antifouling membranes for oily wastewater separation. However, conventional PVDF membranes, due to their hydrophobic nature and inert matrix, often exhibit insufficient permeance and compatibility. In this study, a novel NiFe-LDH@MnO2/PVDF membrane was synthesized using ultrasonic, redox, and microwave-hydrothermal processes. This innovative approach cultivated grass-like NiFe-LDH@MnO2 nanoparticles within an inert PVDF matrix, promoting the growth of highly hydrophilic composites. The presence of NiFe-LDH@MnO2 resulted in pronounced enhancements in surface morphology, interfacial wettability, and oil rejection for the fabricated membrane. The optimal NiFe-LDH@MnO2/PVDF-2 membrane exhibited an extremely high pure water flux (1364 L m−2•h−1), and increased oil rejection (from 81.2% to 93.5%) without sacrificing water permeation compared to the original PVDF membrane. Additionally, the NiFe-LDH@MnO2/PVDF membrane demonstrated remarkable antifouling properties, evident by an exceptional fouling resistance ratio of 96.8% following slight water rinsing. Mechanistic insights into the enhanced antifouling performance were elucidated through a comparative “semi-immersion” investigation. The facile synthesis method, coupled with the improved membrane performance, highlights the potential application prospects of this hybrid membrane in emulsified oily wastewater treatment and environmental remediation.

2D Ti3C2Tx modified with nano-AgPNPs antioxidant constructed hierarchical interface for high-throughput oily wastewater separation

Over-exploitation of fossil energy has led to the formation of enormous amounts of oily wastewater, which is increasingly polluting the environment of water bodies. The Ti3C2Tx-modified separation material is limited by surface roughness and surface chemical composition, and the permeation flux decreases significantly during continuous testing. In this study, silver-loaded polydopamine nanospheres (nano-AgPNPs) as antioxidants were prepared by in-situ reduction from Ag+ ions and polydopamine nanospheres, and then they self-assembled with Ti3C2Tx nanosheets to obtain hierarchical micro-nano structural nano-AgPNPs modified Ti3C2Tx [(AgPNPs)xT (x = 0.25, 0.5, 0.75, and 1)]. Because of their strong reduction properties, nano-AgPNPs antioxidants can effectively protect the active edges of Ti3C2Tx from dissolved oxygen, and greatly improve the oxidation resistance of Ti3C2Tx nanosheets, with no significant changes in morphology and physical phase after long-term placement. (AgPNPs)xT formed underwater oleophobic interfaces with the hierarchical structure on polyurethane (PU) sponge to prepare (AgPNPs)xT@PU separation sponges. Among them, (AgPNPs)0.5T@PU sponge showed the highest comprehensive performance with separation efficiency higher than 99.6% for various oil-water mixtures, especially high-throughput and permeation flux up to 247,787 L m–2 h–1 for cyclohexane-water mixtures. In addition, nano-AgPNPs greatly broadened the layer spacing of Ti3C2Tx and can form a functionalized interface of modified Ti3C2Tx on polyamide (PA) membrane and provide additional permeation channels, which enabled the (AgPNPs)0.5T@PA membrane to have excellent toluene-water emulsion separation efficiency up to 99.6%.

High efficiency and selective separation of oily wastewater based on superamphiphilic biomass aerogel: Characteristics, mechanisms and application

The design and development of multifunctional materials to meet the sophisticated requirements of oily wastewater treatment is an urgent need and remains a great challenge. Herein, a superamphiphilic bio-aerogel (PTGA) with honeycomb-like porous structure was synthesized. The directional and reversible control of interfacial wettability can be achieved by simple pre-wetting process and solvent replacement method. Combined with the advantages of structure and wettability, PTGA was proved to be ideal for high-efficient oil-water mixture separation (J> 1500 L/m2·h, η > 99.8%), oils absorption (Cabs = 17–26 g/g) and dye selective removal (MO: 73.552 mg/g, MB: 45.876 mg/g). Furthermore, based on the newly developed dynamic separation device and excellent mechanical property of PTGA, enhanced separation of oil-water mixture (J = 3007 L/m2·h) and synergistic removal of co-existing pollutants (MB: 51.274 mg/g) were realized. Mechanism results indicated that the transition of interfacial wetting properties of PTGA was a multi-stage process, while oil/water separation and dye adsorption were two independent processes. Benefit from facile synthesis and unparalleled characteristics, the designed PTGA promise to be reliable and competitive candidates in wastewater remediation.

Preparation of a Magnetic Core-Shell Bioreactor for Oil/Water Separation and Biodegradation.

With the frequent occurrence of offshore oil spills, the effective separation and treatment of oily wastewater are essential to the environment. In this work, the core-shell bioreactor (abbreviated as Fe3O4/MHNTs-CNF@aerogel) was prepared with a core composed of camphor leaf cellulose-based aerogels for loading microorganisms and a shell derived from hydrophobic silane-modified halloysite doping with Fe3O4 for selective absorption of oil and maganetic recycling. The core-shell-structured bioreactor Fe3O4/MHNTs-CNF@aerogel has excellent self-floating properties and can float on water for up to 100 days. The whole core-shell structure not only has excellent oil/water separation performance but also has good microbial degradation performance. By applying it in water containing 5% diesel for the biodegradation test, the biodegradation efficiency of Fe3O4/MHNTs-CNF@aerogel for diesel can reach 82.4% in 10 days. The efficiency was 20% higher than for free microorganisms, and it still had excellent degradation ability after three degradation cycles, with a degradation rate of over 75%. In addition, the result obtained from the study on environmental tolerance shows that Fe3O4/MHNTs-CNF@aerogel possessed a strong tolerance ability under different pH and salinity conditions. The Fe3O4/MHNTs-CNF@aerogel also has superior mechanical properties; i.e., nearly no deformation occurs at 30 kPa. Compared with those conventional oil/water separation materials which can only absorb or separate the oils for water with limited capacity and taking the risk of secondary contamination, our core-shell-structured bioreactor is capable of not only selectively absorbing oil from water through its hydrophobic shell but also degrading it into a nontoxic substance by its microorganism-loaded core, thus showing great potential for practical application in oily wastewater treatment.