Oily Contaminants Research Articles

Treatment of Oily Effluents Using a Bacterial Cellulose Membrane as the Filter Bed

One of the main challenges in the treatment of industrial wastewater is the removal of oil-in-water emulsions, which are stable and therefore difficult to treat. Bacterial cellulose (BC) has structural characteristics that make it an ideal filtration membrane. Several research projects are underway to develop new materials, both biotechnological and traditional, for use in filter beds. The study examined the potential of a BC membrane filtration system for treating oily industrial wastewaters, an underexplored biomaterial in wastewater treatment. The results demonstrated that BC is highly effective at removing oily contaminants (~99%), reducing the colour and particulate matter of wastewater, as well as eliminating nearly the entire microbiological load (~99%). SEM, MEV, FTIR, XRD, and TGA confirmed the presence of oil in the interior of the membrane after filtration, characteristic peaks of its chemical composition, and a 40% reduction in crystallinity. TGA revealed an increase from three (pre-filtration) to five (post-filtration) stages of thermal degradation, indicating the retention of the contaminant in the BC. The mechanical tests demonstrated that the membrane has a tensile strength of 72.13 ± 8.22 MPa and tolerated elongation of up to 21.11 ± 4.81% prior to tearing. The BC membrane also exhibited excellent flexibility, as it could be folded >100 times at the same point without exhibiting signs of tearing. The BC surpasses traditional methods, such as activated charcoal and effluent treatment stations, in the removal of emulsified oils. The findings demonstrate that BC is promising for the treatment of industrial wastewaters, which is a field that requires continual technological innovations to mitigate the environmental impacts of the oil industry.

Modifications and applications of aerogel prepared with waste palm leaf cellulose in adsorptions for oily contaminations

Abstract Aerogels are essential and effective materials for oily pollution adsorption and recovery. This work described a hydrophobic modified cellulose aerogel using waste palm leaf and its oil adsorption mechanism. By chemical vapor deposition, Methyltrimethoxysilane (MTMS) was employed as a hydrophobic modifier for aerogel of waste palm leaf cellulose at 80 °C for 5 h, and the modified aerogel demonstrated exceptional and stable hydrophobicity with a water contact angle of 132.4° that can still be maintained above 120° after two months of air exposure. After 10 adsorption and extrusion cycles, kerosene adsorption capacity can still reach over 18 times its weight with good regeneration and reuse performance. The kinetic analysis found that the pseudo-second order model was more appropriate for the aerogel’s oil absorption process, including mainly physical adsorption at the beginning and the following chemical adsorption. Owing to its low cost, hydrophobicity, high absorption capacity, and favorable reusability, this aerogel is expected to be used in oils, organic solvent spill cleanup, and oil/water separation fields.

ADSORPTION PROCESSES FOR RESTORING TECHNICAL CHARACTERISTICS AND PROPERTIES OF USED OIL

The work carried out systematic research to create a technology for restoring the original properties of used oils. Adsorption purification of waste oils using the bentonite-vermiculite method was carried out. based on the use of the ability to retain oily contaminants penetrating through the outer surface and internal capillaries -the pores of the sorbent granules.

Robustly Adherable Hierarchical Nanostructures via Self-Bonding and Self-Texturing of Aluminum Nitride for Applications in Highly Efficient Oil/Water Separation.

The release of wastewater containing oily contaminants into water bodies and soils severely threatens the environment and human health. Although several conventional techniques are used in treating oil/water mixtures and emulsions, these methods are often expensive, time-consuming, and inefficient. Porous membranes or sponges are widely used in filtration or absorption, but their use is limited by their low separation efficiencies and secondary contamination. Recently, a novel technology that is designed to selectively separate oil from oil/water mixtures or emulsions by using materials with special wetting surfaces was developed. Superwetting surfaces may be used to selectively separate oils from emulsions. This approach enables the use of materials with relatively large pores, resulting in high throughput properties and efficiencies. In this study, a facile method is proposed for use in preparing a superhydrophobic-superoleophilic felt fabric for utilization in separating oil/water mixtures and emulsions. By hydrolyzing aluminum nitride nanopowders, the desired micro-/nanostructures may be successfully fabricated and firmly attached to a fabric surface without using a binder resin. This results in various materials with special wetting properties, regardless of their sizes and shapes and the successful separation of oil and water from oil/water mixtures and emulsions in harsh environments. This approach exhibits promise as a low-cost, scalable, and efficient method of separating oily wastewater, with the potential for use in wider industrial applications.

Superhydrophobic, Magnetic Aerogels Based on Nanocellulose Fibers Derived from Harakeke for Oily Wastewater Remediation.

Cellulose-based aerogels have been seen as a promising sorbent for oil and organic pollutant cleaning; however, their intrinsic hydrophilicity and difficulty of recycling has hindered their practical application. In this work, a superhydrophobic, magnetic cellulose-based aerogel was fabricated as a highly efficient sorbent for the adsorption of oils and organic solvents. The aerogel was prepared via a simple freeze-drying method, followed by chemical vapor deposition (CVD). The incorporation of Fe3O4 nanoparticles into the aerogel not only makes it responsive to external magnetic field, but also contributes to the better hydrophobicity of the aerogel, in which the water contact angle (WCA) was about 20° higher than the aerogel without loading with Fe3O4 nanoparticles. The adsorption test showed that the resultant aerogel can selectively adsorb a wide range of oils and organic solvents from oil/water mixtures with a high adsorption capacity (up to 113.49 g/g for silicone oil). It can retain about 50% of its adsorption capacity even after 10 adsorption-squeezing cycles, which indicates its outstanding reusability. Moreover, the aerogels can be easily controlled by an external magnet, which is preferred for the adsorption of oily contaminants in harsh environments and enhanced the recyclability of the aerogel. We believe that this study provides a green and convenient approach for the practical fabrication of cellulose-based oil sorbents.

Bacterial cellulose based three-dimensional porous composites with remarkable amphiphobic monolith properties for passive daytime radiative cooling

To tackle the daytime radiative cooling performance (DRCP) degradation of passive daytime radiative cooling materials (PDRCMs) due to contamination from aqueous or oily contaminants, modified three-dimensional porous composites of bacterial cellulose (BC) and barium sulfate (BaSO4) were fabricated by a unidirectional freeze-casting process and silanization modification. The modified BC/BaSO4 (M−BC/BaSO4) composites exhibited average reflectivity of 97.75%, average emissivity of 95.74%, and remarkable amphiphobic monolith properties with a water contact angle (WCA) and oily contact angle (OCA) of 154° and 145.5° for the surface and those of 153.5° and 143.5° for the internal section, respectively. They also exhibited insignificant changes in the DRCP before and after self-cleaning, achieving an average and maximum temperature drop of 10.40°C and 16.38°C before self-cleaning and those of 9.92°C and 16.40°C after self-cleaning, respectively. This work provides a new strategy for sustainable PDRCMs in practical applications.

Treatment of oily wastewater by electrocoagulation: Simultaneous optimization of oil removal efficiency and specific energy consumption

Electrocoagulation (EC) is an effective process to treat oily wastewater. However, the optimal conditions required to design a continuous EC reactor are still unclear. In this study, an experimental and statistical investigation was performed on the factors affecting the design of a continuous EC reactor used for the removal of oily contaminants. By employing the response surface methodology (RSM), the oil removal efficiency and specific energy consumption (energy consumption per unit volume of treated wastewater) were modeled as a function of three factors, i.e. the current density (30–80 A/m2), the reactor residence time (10–30 min), and the ratio of the anode surface to the reactor volume (S/V ratio, 15–45 m2/m3). The statistical analysis of the experimental results unveiled the considerable impact of the effluent flow rate on the oil removal efficiency. Maximizing the oil removal efficiency and minimizing specific energy consumption were done simultaneously by combining them into an overall desirability function. The optimization results demonstrated that the energy required to treat a unit volume of the tested wastewater in an EC reactor is halved and the operating costs are reduced by 37 % at the cost of <2 % of the oil removal efficiency (from >99 % to 98 %) only by extending the residence time from about 16 to 28 min. The results of this research can pave the path to the development of an efficient and economical industrial EC unit used for the treatment of oily wastewater.

Amphiphilic micromotors as active demulsifiers for rapid oil–water separation

The disposal of oil-in-water emulsion wastewater produced by many industries needs to undergo demulsification treatment before release. Herein, self-propelled amphiphilic micromotors were developed as active heterogeneous demulsifiers for efficient oil/water separation. The amphiphilic structures of micromotors were constructed by asymmetrically coating hydrophobic carbon soot on the surface of the hydrophilic Fe3O4@FeS@MnO2 composites. Benefiting from autonomous propulsion and considerable bubble generation, amphiphilic micromotors can push the oil droplets away from the aqueous phase and aggregate them to form an oil layer, achieving rapid oil–water separation. The demulsification process by the amphiphilic micromotors was investigated, in which both the interaction of micromotors with oil droplets and the collision by bubbles played important roles. After demulsification, oily contaminants with amphiphilic micromotors embedded inside can be separated from the aqueous phase and collected by external magnetic fields. The proposed amphiphilic micromotors blaze new trails for the treatment of emulsified oily wastewater.

Asymmetric wettable three-dimensional Janus all-cellulose aerogel: Controllable construction with a similar phase self-assembling strategy and oil-water separation performance

Aqueous ecological environment is exacerbated by indiscriminate discharge of industrial and municipal wastewater, particularly oily contaminants. Janus materials with unique asymmetric wettability have been considered potential candidates for oil-water separation. Herein, we developed a novel approach to accomplish controllable construction of three-dimensional Janus all-cellulose aerogel with asymmetric wettability based on a similar phase self-assembling strategy. Significantly, the ratio of asymmetric structures could be controlled by tailoring thickness of hydrophobic/hydrophilic layers. Three-dimensional Janus all-cellulose aerogel had both super-hydrophilic/oleophilic and super-hydrophobic/oleophilic cellulose skeleton structures simultaneously. The adsorption capacity of the aerogel for oil reached up to 34.38 g/g. It could effectively separate a variety of oil-water mixtures and water-in-oil emulsions only driven by gravity, even surfactant-stabilized emulsions. The separation efficiency was more than 99% with the high separation flux. The ‘Trade-off’ effect in the field of membrane separation was avoided effectively. Three-dimensional Janus all-cellulose aerogel exhibited good stability and recyclability. Moreover, the demulsification and separation mechanism was analyzed in details. This work provided not only an environmental-friendly, facile and flexible approach to construct controllable three-dimensional asymmetric wettable Janus materials, but also a scientific understanding and development of the separation mechanism of three-dimensional Janus materials.

Fourier Transform Mid-Infrared Spectroscopy (FT-MIR) as a Method of Identifying Contaminants in Sugar Beet Production Process-Case Studies.

Food safety has received considerable attention in recent years. Methods for rapid identification of a variety contaminants in both the final product and the manufacturing process are constantly developing. This study used Fourier Transform Mid-Infrared Spectroscopy (FT-MIR) spectroscopy to identify various contaminants endangering white sugar production. It was demonstrated that inorganic compounds (calcium carbonate-CaCO3), plastic contaminants (polypropylene), and oily contaminants (compressor sealing and lubrication lubricant) can be identified with a high degree of precision. FT-MIR spectroscopy was proved to be a useful technique for detecting sugar contaminants rapidly and precisely even without the application of a sophisticated spectra analysis. Commercial databases of reference spectra usage significantly simplify and facilitate the application of this method.

Photo-responsive Zinc Oxide-coated alumina ceramic membrane with super-wettable and self-cleaning features fabricated by single step RF magnetron sputtering for oily water treatment

Zinc Oxide (ZnO) coated alumina ceramic membrane with super-wettable and photo-responsive self-cleaning features was fabricated by radio frequency (RF) magnetic sputtering, and used as a filtering medium in the dead-end filtration system for oily water treatment. The chemistry of the material in conjunction with the optimum surface roughness accomplish by RF magnetic sputtering rendered a unique surface wettability, favorable for water passing oil-in-water emulsion separation. The second desirable functionality of the membrane is its self-cleaning potential under light irradiation, owing to the efficient photo-catalytic property of ZnO. Oil-surface-air and water-surface-air interfacial contact angles for the membrane surface were measured using goniometer and they are close to 0° (superhydrophilic / superoleophillic in air), whereas under the water oil-surface-water interfacial contact angle switched to 158.70° (underwater superoleophobic). The oil-in-water emulsion separation efficiency, the water permeate flux were measured at different trans-membrane pressures, and oil concentrations in oily water emulsion, and the results showed that 99.9% oil-in-water emulsion separation efficiency was maintained for a range of trans-membrane pressure, and oil concentration for a long duration of use. The highest permeate flux rate and separation efficiency (%) of the fabricated Zinc oxide-coated alumina ceramic membrane were found to be ∼325 L/m2.h and 99.9%, respectively at 2 bar using surfactant stabilized oil-in-water emulsions as feed. However, the water flux declined with reduced trans-membrane pressure, increased oil concentration and with the long use of the membrane. The advantage of ZnO-coated alumina ceramic membrane is that it is water passing, and hence the oil clogging of the membrane is quite minimal. However, with the long use the membrane is prone to the deposition of oily contaminant on the membrane surface, which resulted in low water permeate flux, and this problem was resolved, and the original permeate flux was restored by routine self-cleaning of the membrane surface by illuminating light on the photo-catalytic ZnO film on the membrane surface. In addition to the wettability studies of the membrane, the structural, chemical and morphological characterizations of the material, and the coated membrane were carried out.

Adsorption-Controlled Wettability and Self-Cleaning of TiO2.

Molecular adsorption on solids is inevitable and has significant influences on the wettability of materials, while the tuning mechanism of the wettability from molecular adsorption is yet to be understood. Using molecular dynamics (MD) simulations, we comprehensively studied the relation between the wettability of the TiO2 surface and the adsorption of water and carboxylic acid molecules. Our results reveal that the increasing amount of surface hydroxyl groups from the decomposition adsorption of H2O increases the hydrophilicity of TiO2, providing molecular-level evidence for the previously proposed mechanism of photo-induced hydrophilicity. By contrast, the surface wettability becomes tunable with water contact angles changing from 0 to ∼130° through length adjustment of the adsorbed carboxylic acids. The TiO2 surface is hydrophilic with the adsorption of short-alkyl-chain carboxylic acids (e.g., HCOOH) and becomes hydrophobic when longer-alkyl-chain carboxylic acids (H(CH2)nCOOH, n > 2) are present. Furthermore, long-alkyl-chain acids also increase surface oleophilicity, while the adsorption of HCOOH and CH3COOH significantly enhances the oleophobicity of TiO2. Water molecules can also more easily penetrate the space between oily contaminants and adsorbed short acid molecules, thereby further increasing its self-cleaning capacity. The present simulations not only reveal the mechanism of wettability caused by molecular adsorption but also provide a promising method to create materials with controllable wettability and high self-cleaning efficiency.

Multifunctional antifogging, self-cleaning, antibacterial, and self-healing coatings based on polyelectrolyte complexes

In this study, a multifunctional coating with antifogging, self-cleaning, antibacterial, and self-healing capabilities is developed based on polyelectrolyte complexes of polyethylenimine (PEI), phytic acid (PA), and Cu2+ (denoted as PEI-PA-Cu). The multifunctional PEI-PA-Cu coating with high transparency can be prepared by spraying, brushing, or other one-step deposition onto various substrates (e.g., polymeric substrates and glass slides). Such a coating shows an excellent antifogging effect in both high temperature (85 ℃) and cold environments (−20 ℃) and maintains stable antifogging performance after placing in ∼65 ℃ vapor for 9 h. In addition, the coating is superhydrophilic and allows for easy spreading of water to isolate the oily contaminants, realizing self-cleaning. Meanwhile, the coating possesses superior antibacterial capability against Escherichia coli and Staphylococcus aureus thanks to PEI with amino groups and Cu2+. Importantly, the PEI-PA-Cu coating can heal damages rapidly and repeatedly due to the presence of hydrogen bonds and electrostatic interactions, effectively prolonging the service life. This study provides a facile route to construct multifunctional superhydrophilic coatings with promising prospects in the field of personal protective, medical, and optical devices.

Simulation on oily contamination removal by ozone using molecular dynamics

Ozone (O3) is characteristic of high oxidative activity. It displays a high potential value in sterilization and decontamination. Although O3 has been widely investigated for its efficiency and environmentally friendly effectiveness, the fundamental issue regarding the complicated microscopic interaction mechanism between O3 and contaminant molecules remains largely unaddressed. We addressed this knowledge gap through molecular dynamics (MD) simulation at the molecular scale. Results indicated that five representative hydrocarbon molecules (n-hexadecane, phytane, terpane, naphthalin and acenaphthylene) on a rough silica (SiO2) surface were almost removed after about 300 ps simulation. And the aromatic molecules were easier to be removed than aliphatic ones. The hydroxyl oxidation reaction was demonstrated as a predominant mechanism. As the large dose of O3 was supplied by atmospheric air dielectric barrier discharge (DBD) plasma, this work provided an important theoretical reference for better using plasma technology for oily contaminant removal.

“Liquid‐Like” Surface Topography Waterborne Polyurethane Coatings with Bio‐Based and Easy‐Sliding Oil Repellency

AbstractHerein, a “liquid‐like” surface topography and sustainable approach is reported to fabricate transparent oil‐repellent coatings, which involves fabricating new crosslinking polyols by siloxane oligomer modified castor oil fatty chain, followed to obtain waterborne polyurethane coatings. This surface morphology is formed by the grafted polydimethylsiloxane (PDMS) molecular chains in the coating molecules. This low surface tension and liquid‐like topography reduces the coefficient of friction with oily contaminants. Various low‐surface‐tension liquids can easily slide down the coating surfaces on substrates with lower tilting angle. The coatings are applicable to different substrates including glass, plastic, steel, and wood, and those with complex shapes and large surface areas. Thanks to the as‐described crosslinking structure of the coatings, their easy‐sliding oil repellency can be well maintained to avoid sand abrasion damages. Therefore, the advantageous characteristics of the as‐developed high transparency oil‐repellent and eco‐friendly coatings have the potential to replace traditional coatings and are highly practical for shielding against oily contaminants, chemical‐shield that protect coated plastics from dissolution by organic solvents, and nonstick coatings.

Fabrication of amphiphobic concrete coating with good abrasion resistance and anti-oil adhesion properties by using waste clam powder

The hydrophobic coating protection of concrete plays a critical role in mitigating the corrosion damage caused by water-based liquids. But the hydrophobicity of the coating can be easily damaged when used in water with oil-spill containment, because of the low adhesion of the oily contaminants. In this paper, a method for preparing an amphiphobic (i.e. superhydrophobic and oleophobic) clam powder coating (ACP-coating) on concrete surface was proposed. The results demonstrate that the prepared ACP-coating presents good oil stain resistance, which can effectively protect the concrete from damage by oil-based liquids. In addition, even after mechanical polishing, ACP-coating still kept good amphiphobicity. Electrochemical experiments show that ACP-coating can improve the corrosion resistance property of concrete. It is expected that the ACP-coating prepared in this paper may provide a method for improving the corrosion resistance of concrete used in coastal environment.

Comprehensive treatment of oil-contaminated soils using CO2-Responsive O/W microemulsions

In exploration of petroleum resources, a considerable amount of soils are inevitably contaminated, leading to many long-term environmental impacts. However, the treatment of oil-contaminated soils to reduce the residual oil for safe disposal at low energy intensity is a challenging task. In this study, a CO2-responsive microemulsion was formulated to treat oil-contaminated soils effectively at ambient temperatures of low energy consumption. Such effective treatment reduced the oil level of the contaminated soils from ∼15 wt% to below the discharge limit of 1 wt%. Purging of CO2 through the spent microemulsions for 30 s caused a rapid dissociation of the superamphiphile in the microemulsions, leading to a complete phase separation with the cleaned soils settled to the bottom for safe disposal, followed by an aqueous phase in the middle for recycling and a value-added oil product on top. The rapid and deep cleaning of oil-contaminated soils was attributed to an ultra-low interfacial tension and high level solubilization of oily contaminants in the O/W microemulsions. Such approach leads to a zero-waste discharge operation of remediating oil-contaminated soils while recovering value-added oil. Compared with other treatment methods operated at high temperature and/or pressure conditions, treatment of oil-contaminated soils using CO2-responsive microemulsions is easier to reach the discharge limit of residual oil while operating at ambient temperatures without any expensive equipment or extreme working conditions, making this microemulsion method a promising candidate for commercial applications of treating oil-contaminated soils in the oil field.

Simulation on Oily Contamination Removal by Ozone Using Molecular Dynamics

Simulation on Oily Contamination Removal by Ozone Using Molecular Dynamics

A self-cleaning hierarchical carbon nitride-based membrane for highly efficient oily wastewater purification

Nowadays, membrane fouling critically limits the further application in high-efficient oily emulsions separation. Herein, we constructed a hierarchical visible-light driven self-cleaning membrane by metal-tannin complex synergistically manipulating self-assembly g-C3N4 nanosheets and followed in-situ mineralization of β-FeOOH on g-C3N4/TA membrane. The TA-metal complex manipulated the stability of g-C3N4-based membrane, and the uniform distribution of mineralized layer onto membranes endued g-C3N4/TA@FeOOH-x with outstanding wettability. Herein, g-C3N4/TA@FeOOH-x membranes exhibited highly oil/water emulsion separation efficiency (above 99.1%) with relatively high water permeance (639.9–1349.4 L m−2 h−1 bar−1), simultaneously possessed exceeding anti-fouling properties. In addition, the synergistic effect between photo-Fenton reaction of β-FeOOH and photocatalytic ability of g-C3N4 nanosheets improved the visible-light driven photodegradation performance of composite membranes, which could completely separate MB/oil mixture emulsions. Our work showed integration of membrane separation and photodegradation technology effectively separated oily contaminations from polluted water and alleviated the membrane fouling problems, further pushing forward to practical application of oil-water separation membranes.

Zwitterionic hydrogel-coated cotton fabrics with underwater superoleophobic, self-healing and anti-fouling performances for oil-water separation

• Zwitterionic hydrogel with self-healing property was coated on the cotton fabric. • The coated fabric exhibited anti-fouling and underwater superoleophobic properties. • The coated fabric had superior oil/water separation property under gravity drive. • The coated fabric displayed the outstanding cyclic stability and reusability. Oil-water separation technology has attracted widespread attention, due to the increasingly serious oil pollution. In this work, novel poly(sulfobetaine methacrylate- co -2-hydroxyethyl acrylate)/poly(vinyl alcohol)/borax (PSBMA/PVA/Borax) hydrogels were prepared. Then, the related gel-coated cotton fabrics for oil-water separation were successfully developed in a facile route. The results presented the as-prepared zwitterionic hydrogels had outstanding self-healing ability, low swelling ratio, and satisfactory mechanical properties because of multiple interactions in the hydrogel’s network. As expected, the zwitterionic hydrogel-coated cotton fabric was imparted with excellent underwater superoleophobicity and outstanding anti-fouling ability due to the existence of zwitterionic groups on the surface. The underwater oil contact angle of the as-prepared fabric was approximately 160° towards a series of oils. Meanwhile, oily contaminations on the zwitterionic hydrogel-coated fabric surface can be rapidly removed just by water immersion. Most importantly, the zwitterionic hydrogel-coated fabric exhibited excellent oil-water separation efficiency (approximately 99%) and water flux (about 15, 181 L -1 ·m −2 ·h −1 ) even after 50 successive cycles. Additionally, the zwitterionic hydrogel-coated fabric also presented remarkable chemical and mechanical stabilities in harsh conditions. The as-prepared cotton fabric presents a great application prospect in oily wastewater treatment.