Bio-inspired castor oil modified cellulose aerogels for oil recovery and emulsion separation

Recent advances in hydrophobic nanocellulose aerogels for oil spill applications: A review

In a rapidly growing world, petroleum is used extensively in various industries, and the extraction, processing, and transportation of petroleum generates large amounts of petroleum-containing wastewater. Conventional oil/water separation methodologies are often ineffective and costly. Nanocellulose-based aerogels (NA) have emerged as a possible solution to this problem. However, hydrophobic modification is required for effective use in oil/water separation. This review on materials commonly used in these processes and outlines the requirements for adsorbent materials and methods for creating unique lipophilic surfaces. New trends in hydrophobization methods for NA are also discussed. Additionally, it includes the development of composite nanocellulose aerogels (CNAs) and cellulose based membrane specially developed for oil/water (o/w) separation considering different separation requirements. This analysis also examines how CNAs have evolved by introducing special properties that facilitate oil collection or make the adsorbent recyclable. We also discuss the difficulties in creating effective NAs for these important applications in a changing society, as well as the difficulties in creating oil recovery equipment for oil spill cleanup.

Facile construction of multifunctional bio-aerogel for efficient separation of surfactant-stabilized oil-in-water emulsions and co-existing organic pollutant

The deep treatment of robust oily emulsion wastewater has long been an arduous challenge. Herein, a biomass-derived PEI-TiO2@Gelatin aerogel (PEI-TiO2@GA) with honeycomb-like porous structure was fabricated. The interface wetting characteristics of PEI-TiO2@GA could be selectively switched between the superlipophilicity and superoleophobicity through the merely pre-wetting process. Combined with extraordinary structure and superwetting properties, PEI-TiO2@GA was proved to be ideal for oils absorption (17-26 g/g) and MO dye adsorption (73.549 mg/g) with high up-taking rate. Simultaneously, as-prepared PEI-TiO2@GA could realize various surfactant-stabilized oil-in-water emulsions separation simply under gravity with the separation efficiency as high as 99.25%. In addition, PEI-TiO2@GA was highly resistant toward mechanical compression (1.952 MPa), and exhibited acceptable regenerability within 5 cycles by performing solvent replacement approach. Combining with the newly developed separator and dynamic emulsion separation device, the continuous deep separation of the emulsion and the synergistic removal of co-existing pollutants can be achieved with the enhanced separation efficiency and permeation flux. Most importantly, the mechanism results show that the transition of interface wetting properties was a reversible multi-step process, and the demulsification separation of emulsion and the adsorption removal of co-existing pollutants were two independent processes. This work opens up a new avenue to customize advanced bio-aerogels for industrial effluent treatment and environmental remediation.

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.

"Rigid-Flexible" Anisotropic Biomass-Derived Aerogels with Superior Mechanical Properties for Oil Recovery and Thermal Insulation

Aerogels with low density, high mechanical strength, and excellent elasticity have a wide potential for applications in wastewater treatment, thermal management, and sensors. However, the fabrication of such aerogels from biomass materials required complex preparation processes. Herein, a sustainable and facile strategy was reported to construct lignin/cellulose aerogels (LCMA) with three-dimensional interconnected structures by introducing homologous lignin with a polyphenyl propane structure as a structural enhancer through a top-down directional freezing approach, prompting a 2036% enhancement in compressive modulus and an 8-12-fold increase in oil absorption capacity. In addition, the hydrophobic aerogels with superelasticity were achieved by combining the aligned polygon-like structure and flexible silane chains, which exhibited remarkable compressional fatigue resistance and superhydrophobicity (WCA = 168°). Attributed to its unique pore design and surface morphology control, the prepared aerogel exhibited excellent performance in immiscible oil-water separation and water-in-oil emulsion separation. Due to the ultra-low density (8.3 mg·cm-3) as well as high porosity (98.87%), the obtained aerogel showed a low thermal conductivity (0.02565 ± 0.0024 W·m-1·K-1), demonstrating a potential in insulation applications. The synthetic strategy and sustainability concept presented in this work could provide guidance for the preparation of advanced biomass-based aerogels with unique properties for a wide range of applications.

Nanostructured bio-based castor oil organogels for the cleaning of artworks

HYPOTHESIS

Organic solvents are often used for cleaning highly water-sensitive artifacts in modern/contemporary art. Due to the toxicity of most solvents, confining systems must be formulated to use these fluids in a safe and controlled way. We propose here castor oil (CO) organogels, obtained thorough cost-effective sustainable polyurethane crosslinking. This methodology is complementary to previously demonstrated hydrogels, when conservators opt for organic solvents over aqueous formulations.

EXPERIMENTS

The gels were characterized via Small-angle Neutron Scattering and rheology before and after swelling in two organic solvents commonly adopted in cleaning paintings. The removal of a photo-aged acrylic-ketonic varnish was evaluated under visible and ultraviolet light, and with FTIR 2D imaging.

FINDINGS

The new gels are dry systems that can be easily stored and loaded with solvents before use. Their nanoscale organization, viscoelasticity and cleaning action are controlled changing the amount of crosslinking, the polymeric backbone, and the loaded solvents. The fluids are confined in the nanosized polymeric mesh of the gels, which are highly retentive, granting controlled release over delicate paint layers, and transparent, allowing monitoring of the cleaning process. These features, along with their sustainable synthesis, candidate the CO organogels as feasible solutions for cultural heritage preservation, expanding the palette of advanced tools for conservators over traditional thickeners.

Recent Advances in Biomass-Based Materials for Oil Spill Cleanup

Oil spill on sea surfaces, which mainly produced by the oil leakage accident happened on tankers, offshore platforms, drilling rigs and wells, has bring irreversible damage to marine environments and ecosystems. Among various spill oil handling methods, using sorbents to absorb and recover spill oils is a perspective method because they are cost-effective and enable a high recovery and without secondary pollution to the ecosystem. Currently, sorbents based on biomass materials have aroused extensively attention thanks to their features of inexpensive, abundant, biodegradable, and sustainable. Herein, we comprehensively review the state-of-the-art development of biomass-based sorbents for spill oil cleanup in the recent five years. After briefly introducing the background, the basic theory and material characteristics for the separation of oil from water and the adsorption of oils is also presented. Various modification methods for biomass materials are summarized in section three. Section four discusses the recent progress of biomass as oil sorbents for oil spill cleanup, in which the emphasis is placed on the oil sorption capacity and the separation efficiency. Finally, the challenge and future development directions is outlined.

A review on the effectiveness of nanocomposites for the treatment and recovery of oil spill

The introduction of unintended oil spills into the marine ecosystem has a significant impact on aquatic life and raises important environmental concerns. The present review summarizes the recent studies where nanocomposites are applied to treat oil spills. The review deals with the techniques used to fabricate nanocomposites and identify the characteristics of nanocomposites beneficial for efficient recovery and treatment of oil spills. It classifies the nanocomposites into four categories, namely bio-based materials, polymeric materials, inorganic-inorganic nanocomposites, and carbon-based nanocomposites, and provides an insight into understanding the interactions of these nanocomposites with different types of oils. Among nanocomposites, bio-based nanocomposites are the most cost-effective and environmentally friendly. The grafting or modification of magnetic nanoparticles with polymers or other organic materials is preferred to avoid oxidation in wet conditions. The method of synthesizing magnetic nanocomposites and functionalization polymer is essential as it influences saturation magnetization. Notably, the inorganic polymer-based nanocomposite is very less developed and studied for oil spill treatment. Also, the review covers some practical considerations for treating oil spills with nanocomposites. Finally, some aspects of future developments are discussed. The terms "Environmentally friendly," "cost-effective," and "low cost" are often used, but most of the studies lack a critical analysis of the cost and environmental damage caused by chemical alteration techniques. However, the oil and gas industry will considerably benefit from the stimulation of ideas and scientific discoveries in this field.

Mechanically Tough and Regenerable Antibacterial Nanofibrillated Cellulose-Based Aerogels for Oil/Water Separation

Nanofibrillated cellulose (NFC)-based aerogels have been widely used for various applications. However, the disadvantages of poor structural stability, low mechanical toughness, and easy contamination by bacteria hinder their large-scale application. In this work, 3-(3'-acrylicacidpropylester)-5,5-dimethyl hydantoin (APDMH) was grafted on oxidized NFC (ONC) to prepare antibacterial poly(APDMH)-g-ONC (PAC). PAC and poly(ethyleneimine) (PEI) were chemically cross-linked using 3-glycidoxypropyltrimethox (GPTMS), aiming at constructing a PAC-g-PEI aerogel with multiple network structures. The mechanical behaviors of composite aerogel and oil/water separation performances under different conditions were investigated. PAC-g-PEI aerogel exhibits outstanding fatigue resistance (>50 cycles of compression) and superior elasticity (96.76% height recovery after five compression-release cycles at 50% strain). The obtained superhydrophilic and underwater-oleophobic properties endow the aerogel with excellent oil/water separation performances, achieving a satisfactory separation efficiency of over 99% and flux of over 9500 L·m^-2·h^-1. Furthermore, the chlorinated aerogel of PAC-g-PEI-Cl shows highly efficient and rechargeable antibacterial properties, can inactivate 6.72-log Escherichia coli and 6.60-log Staphylococcus aureus within 10 min, and can still kill all inoculated bacteria after 50 cycles. In addition, PAC-g-PEI-Cl aerogel can inhibit biofilm formation, making it a promising candidate for highly efficient oil/water separation applications in diverse harsh conditions.

Biomass poplar catkin fiber-based superhydrophobic aerogel with tubular-lamellar interweaved neurons-like structure

Superhydrophobic aerogels are attractive candidates in controlling oil spills. The major challenges for existing aerogels are the construction of mechanical endurance as well as accessible of building materials. Herein, a newfangled biomass superhydrophobic aerogel (M-PCF/CS) with both superior compressibility and oil caption speed is fabricated by assembling poplar catkin fiber (PCF) hollowed-out shell of 330 nm and chitosan (CS) into tubular-lamellar interweaved neurons-like structure. The resultant aerogels (porosity ~ 96.12%), with flexuous PCF as the elastic buffer and second-pore capillaries, exhibit large longitudinal and transverse compressibility, endurable fatigue tolerance, fast oil sorption rate with a capacity of 28.8-78.1 g/g at 5-25 s. In parallel, the aerogels are tolerant of NaCl, UV radiation, and organic solvents without superhydrophobic variation and a case of oil spill remediation via pump-supported experiment shows that the aerogels facilely achieve continuous oil recycling from seawater by 23052-43956 L·m^-2·h^-1. Furthermore, the resultant M-PCF/CS, with assistance of an oscillator, can be applied to separate oil/water emulsions with efficiency of 98.07-99.11%. The successful fabrication of this material provides a new design strategy for the construction of mechanically robust aerogels for speedy and economical cleanup of oil pollutants from water.

Bio-Based Aerogel Based on Bamboo, Waste Paper, and Reduced Graphene Oxide for Oil/Water Separation

In recent years, the discharge of industrial waste oil has increased and offshore oil leakage has occurred frequently, and thus water pollution has become a worldwide problem that attracts much attention. In this regard, a kind of oil-absorbing material with high oil-absorbing property and good mechanical property is urgently needed. Here, we reported a new type of aerogels with three-dimensional layered voids using natural bamboo powder, waste paper (WP), and graphene oxide (GO) as raw materials. The obtained aerogel had high adsorption capacity (87-121 g/g), compressibility, and high elasticity, which can separate oil from water and selectively absorb oil. This study provides not only a new treatment in agricultural waste treatment but also a facile, green, and low-cost approach to synthesize high-performance graphene-based oil absorbers, which might give us an effective solution for oil pollution of water resources worldwide.

Tannic acid-based functional coating: surface engineering of membranes for oil-in-water emulsion separation

Recent progress in the tannic acid-based functional coating for surface engineering of membranes toward oil-in-water emulsion separation is summarized.