Hydrophobic Absorbent Research Articles

Entropy‐Driven Carbon Dioxide Capture: The Role of High Salinity and Hydrophobic Monoethanolamine

Addressing atmospheric CO2 levels during the transition to carbon neutrality requires efficient CO2 capture methods. Aqueous amine scrubbing dominates large‐scale flue gas capture but is hampered by the energy‐intensive regeneration step, sorbent loss, and consequent environmental concerns with volatile amines. Herein, hydrophobic non‐volatile alkylated monoethanolamine (MEA) is introduced as a water‐lean CO2 absorbent in brine. The effects of alkylation of MEA, salinity, and aggregation of absorbents on the improved CO2 capture process are systematically investigated. The CO2 absorption facilitates spontaneous self‐aggregation of hydrophobic absorbents, which increases the entropy of water in high‐ion strength solutions. This effect is controlled by the salinity of aqueous solutions, affording comparative gravimetric CO2 uptake performance to benchmark MEA. It is experimentally verified that the hydrophobicity of alkylated MEAs in saline water is responsible for facile absorption, and also for mild regeneration conditions. Therefore, the entropy‐driven approach minimizes absorbent evaporation, corrosion, and decomposition, thus paving the way to realize energy‐efficient carbon capture.

Mechanically robust, compressible, and photothermal silane/reduced graphene oxide modified plant fiber sponge for highly efficient cleanup of crude oil spill

Developing solar-assisted self-heating hydrophobic absorbents for efficient cleanup of viscous crude oil spills is attracting attention. However, using a simple, environment-friendly, and scalable fabrication approach to prepare solar-heating absorbent remains a big challenge. Due to the viscosity of crude oil can enormously decrease with increasing temperature, the self-heating absorbent which can in-situ raise the temperature to decrease the viscosity of crude oil shows potential application in accelerating the absorption and recovery of crude oil. Here, a hydrophobic and photothermal reduced graphene oxide and hexamethyldisilane synergistically modified plant fiber sponge (PFS@rGO@HMDS) is developed by an easy and efficient mechanical foaming strategy combined with in-situ vapor and thermal reduction treatment. The obtained PFS@rGO@HMDS exhibits good hydrophobicity (135° in water contact angle), excellent mechanical compressibility and durability, high solar absorption (>97.84 %), and oil absorptive capacity (27.3–52.0 g/g). Benefiting from the excellent photothermal conversion capacity, the surface temperature at the equilibrium of PFS@rGO@HMDS can reach 71.2 °C under 1 sun irradiation to reduce the viscosity of crude oil and realize the rapid crude oil spill remediation. The PFS@rGO@HMDS also can be used in a continual absorbent system to accomplish the ongoing and quick repair of viscous oil spills from the seawater surface, showcasing its enormous potential for use in huge-scale oil spill clean-up and recovery.

A sustainable layered nanofiber/sheet aerogels enabling repeated life cycles for effective oil/water separation

Discarded oil-containing absorbents, which has been used in handling oil spills, are tricky to deal with and have rose global environmental concerns regarding release of microplastics. Herein, we developed a facile strategy to fabricate sustainable absorbents by a gas-inflating method, through which 2D electrospinning polycaprolactone nanofiber membranes were directly inflated into highly porous 3D nanofiber/sheet aerogels with layered long fiber structure. The membranes were inflated rapidly from a baseline porosity of 81.98% into 97.36–99.42% in 10–60 min. The obtained aerogels were further wrapped with -CH3 ended siloxane structures using CH3SiCl3. This hydrophobic absorbent (CA ≈ 145°) could rapidly trap oils from water with sorption range of 25.60–42.13 g/g and be recycled by simple squeeze due to its mechanical robustness. As-prepared aerogels also showed high separation efficiency to separate oils from both oil/water mixtures and oil-in-water emulsions (>96.4%). Interestingly, the oil-loaded absorbent after cleaning with absolute ethanol could be re-dissolved in selected solvents and promptly reconstituted by re-electrospinning and gas-inflation. The reconstituted aerogels were used as fire-new oil absorbents for repeated life cycles. The novel design, low cost and sustainability of the absorbent provides an efficient and environmentally-friendly solution for handling oil spills.

Preparation of porous poly(4‐tert‐butylstyrene) based monoliths with high efficiency for oil‐water separation via high internal phase emulsion template

AbstractDeveloping low‐cost and highly efficient hydrophobic absorbents via simple and environmentally friendly method is demanded for oil‐water separation. This paper reports the preparation of hydrophobic absorbents of porous poly(4‐tert‐butylstyrene‐co‐divinylbenzene) (poly(tBS‐co‐DVB)) via high internal phase emulsion (HIPE) template method. The effects of crosslinking degree and internal phase volume fraction on the porous structure and adsorption performance of the absorbents are investigated. As the tBS/DVB molar ratio increases from 1:1 to 4:1, the adsorption performance of poly(tBS‐co‐DVB) toward hexane first increases to a maximum at a molar ratio of 3:1 and then decreases. As the internal phase volume fraction increases, the specific surface area (SSA) and porosity of the poly(tBS‐co‐DVB)s notably increase from 33.06 m2/g and 84.07% to 102.89 m2/g and 92.94%, respectively. When the internal phase fraction is 95 vol%, the obtained poly(tBS‐co‐DVB) foam with a water contact angle of 140° shows an absorbing capacity as high as 70.21 g/g for dichloromethane. After 10 consecutive adsorption‐desorption cycles, the adsorption performance of the poly(tBS‐co‐DVB) foam shows only a slight decrease, indicating an excellent recycling ability. The obtained poly(tBS‐co‐DVB) foams exhibit the advantages of facile preparation, high oil absorption capacity and satisfactory recoverability, which enable them potential as sustainable oil adsorbents.

Investigation of the elution behavior of dissociating itaconic acid on a hydrophobic polymeric adsorbent using in-line Raman spectroscopy

The use of adsorption for the purification of dicarboxylic acids is rather limited and currently predominantly confined to ion-exchange chromatography. A promising, but less regarded alternative is the use of hydrophobic adsorbents. Regarding hydrophobic absorbents, the literature focuses on screenings of adsorbents for purification of (di)carboxylic acids with regard to adsorption equilibria. The investigation of dynamic phenomena in the column received only minor attention. In this contribution, this knowledge gap is addressed. First, the adsorption behavior of itaconic acid species on the hydrophobic, highly-crosslinked polymeric adsorbent Chromalite™ PCG1200C is investigated. For this purpose, adsorption isotherms are determined via frontal analysis at pH values of 2, 3, 4.5, 6.5, and 8 to evaluate the dependency of the adsorption capacity on the dissociation state. Capacities above 150 g Lads−1 at liquid phase concentrations of 70 g L−1 are observed at a pH of 2. A strong decrease of capacity with increasing pH value, i.e., with increasing fraction of dissociated negatively charged acid species, is observed. Second, pulse experiments at aforementioned pH values are performed. Thereby, in-line Raman spectra are recorded at the column outlet, which allows the direct differentiation of the acid species state of dissociation. The spectral information is evaluated for quantitative concentration profiles of itaconic acid species using Indirect Hard Modeling with mixture hard models that are calibrated subject to ideal as well as non-ideal thermodynamics. In-line measurement errors of ≤ 3.5 g L−1 are achieved for the itaconic acid species. In dependency of the pH of the feed solution, a separation of the individual acid species within the pulse experiments is observed. It is conjectured that the process is dominated by a superposition of species-dependent adsorption characteristics and dissociation reactions.

Preparation of highly hydrophobic sepiolite for efficient oil removal

Oil spill cleanup has aroused increasing concern in environmental protection, which makes the development of a low-cost absorbent with good hydrophobicity to be a task of high practical significance. In this work, a novel and highly hydrophobic absorbent based on natural clay minerals was prepared and used for oil removal from water. The originally hydrophilic sepiolite was modified by tetraethyl orthosilicate (TEOS) and hexadecyltrimethoxysilane (HDTMS) through a one-pot direct modification. The pristine and modified sepiolite (MS) were characterized for hydrophobicity, morphology, and composition. The results showed that the modify agent was successfully grafted onto the sepiolite surface, improved the roughness and disaggregation of fibers. And MS exhibited higher contact angle compared to the pristine sample. The diesel oil removal efficiency of MS was significantly higher compared to pristine sepiolite. The surface roughness and high hydrophobic properties played important role in the retention of oil from water. This study presented a facile method to produce promising absorbent based on clay minerals with excellent properties for oil spill cleanup.

A Strategy of Liquid‐Grafted Slippery Sponges with Simultaneously Enhanced Absorption and Desorption Performances for Crude Oil Spill Remediation

AbstractCrude oil spill accidents pose a worldwide environmental threat. Oleophilic and hydrophobic absorbents that can selectively absorb oil from water have shown promising application potential in oil spill remediation. Simultaneous optimization of the absorption and desorption speed of absorbents towards oil is highly desirable for their recyclable usage, but remains a great challenge, because these two properties are generally conflicting. Here, a facile and ingenious strategy is proposed to tackle the above challenge via surface modification of porous sponges with highly flexible linear polydimethylsiloxane (LPDMS) brushes. The LPDMS brushes feature liquid‐like properties at room temperature owing to its extremely low glass transition temperature, and act as a covalently‐grafted lubrication layer throughout the 3D network channels of the sponge, which can minimize contact angle hysteresis and reduce friction between oil and sponge channel. Compared to the prevalent cross‐linked polydimethylsiloxane (CPDMS) modification strategy, sponges modified with LPDMS brushes not only shows significantly enhanced absorption speed, but also exhibits superior desorption dynamics towards viscous crude oils. The design strategy of slippery sponges with liquid‐like molecules may open a new avenue for developing advanced absorbents with simultaneously enhanced absorption and desorption performances for liquid separation and purification applications.

Superhydrophobic magnetic cotton fabricated under low carbonization temperature for effective oil/water separation

Carbonization of bio-based porous substrates is a facile, environmentally friendly and cost-effective way to create hydrophobic absorbents for oil/water separation applications. However, the processes usually take place under high temperature, which can cause large consumption of energy. Therefore, it is still a challenge to fabricate such absorbent under low temperature. Herein, a kind of superhydrophobic magnetic cotton was successfully fabricated by dip-coating of cotton with Fe3O4 nanoparticles, adsorption of oleic acid and carbonization at 400 °C. The prepared absorbent was integrated with various excellent properties after modifications, including low apparent density (0.0436 g/cm3), high porosity (92.2%), remote controllability, excellent thermal stability and outstanding hydrophobicity (water contact angle, 157.0 ± 1.8°). It could selectively collect oil from different types of oil/water mixtures with large absorption capacity (13.63–37.39 g/g for the testing oils) and high separation efficiency (higher than 99%). After removed the absorbed oil by distillation or direct combustion, the absorbent could be used again with no obvious performance deterioration. The proposed method offers an energy-saving way to fabricate oil absorbent via carbonization.

Cost-Effective, Highly Selective and Environmentally Friendly Superhydrophobic Absorbent from Cigarette Filters for Oil Spillage Clean up.

Ecological and environmental damage caused by oil spillage has attracted great attention. Used cigarette filters (CF) have also caused negative environmental consequences. Converting CF to economical materials is a feasible way to address these problems. In this study, we demonstrate a simple method for production of a highly hydrophobic absorbent from CF. CF was modified by using different volume ratios of octadecyltrichlorosilane and methyltrimethoxysilane. When the volume ratio was 3:2, the modified CF had the high water contact angle of 155°. It could selectively and completely absorb silicone oil from an oil-water mixture and showed a good absorption capacity of 38.3 g/g. The absorbed oil was readily and rapidly recovered by simple mechanical squeezing, and it could be reused immediately without any additional treatments. The as-obtained superhydrophobic modified CF retained an absorption capacity of 80% for pump oil and 82% for silicone oil after 10 cycles. The modified CF showed good elasticity in the test of repeated use. The present study provides novel design of a functional material for development of hydrophobic absorbents from used CF via a facile method toward oil spillage cleanup, as well as a new recycling method of CF to alleviate environmental impacts.

CHITIN LIQUID CRYSTAL- DERIVED SPONGE- LIKE AEROGEL

<p class="RSCB01COMAbstract"><span class="06CHeading"><span lang="EN-GB">Abstract: </span></span><span lang="EN-GB">Chitin nanocrystals in anisotropic liquid crystals have been used as a colloidal precursor to fabricate hydrogels and aerogels. Native chitin nanofibrils are deacetylated and hydrolyzed to generate rod-shaped chitin nanocrystals that are dispersible in water to form colloidal aqueous suspensions. Chitin nanocolloids self-organize into anisotropic liquid crystals that can solidify into layered nematic films. Chitin liquid crystals are hydrothermally gelatinized with formaldehyde crosslinkers to form homogeneous chitin hydrogels. The removal of water in the hydrogels by freeze-drying recovers ultralight chitin sponge-like aerogels with morphological retention of layered nematic chitin structure. These biocompatible chitin aerogels hold promise for developing advanced functional materials such as fabrics for antibacterial bandages and tissue engineering and hydrophobic absorbents for oil/water separation. Potentially, chitin nanocrystals assembled in the aerogels may be functionalized into hydrophobic sponges for oil/water separation or carbonized into nitrogen-doped carbon foams for supercapacitors.</span></p>

The Combination Process for Preparative Separation and Purification of Paclitaxel and 10-Deacetylbaccatin III Using Diaion® Hp-20 Followed by Hydrophilic Interaction Based Solid Phase Extraction.

There is no other naturally occurring defense agent against cancer that has a stronger effect than paclitaxel, commonly known under the brand name of Taxol®. The major drawback for the more widespread use of paclitaxel and its precious precursor, 10-deacetylbaccatin III (10-DAB III), is that they require large-scale extraction from different parts of yew trees (Taxus species), cell cultures, taxane-producing endophytic fungi, and Corylus species. In our previous work, a novel online two-dimensional heart-cut liquid chromatography process using hydrophilic interaction/ reversed-phase chromatography was used to introduce a semi-preparative treatment for the separation of polar (10-deacetylbaccatin III) and non-polar (paclitaxel) taxanes from Taxus baccata L. In this work, a combination of the absorbent (Diaion®HP-20) and a silica based solid phase extraction is utilized as a new, efficient, and cost effective method for large-scale production of taxanes. This process avoids the technical problem of two-dimensional preparative liquid chromatography. The first stage of the process involves discarding co-extractive polar compounds including chlorophylls and pigments using a non-polar synthetic hydrophobic absorbent, Diaion®HP-20. Extract was then loaded on to a silica based hydrophilic interaction solid phase extraction (silica 40-60 micron). Taxanes was eluted using a mixture of water and methanol at the optimized ratio of 70:30. Finally, the fraction containing taxanes was applied to semi-preparative reversed phase HPLC. The results revealed that using this procedure, paclitaxel and 10-DAB III could be obtained at 8 and 3 times more, respectively than by the traditional method of extraction.

Petrogel: New Hydrocarbon (Oil) Absorbent Based on Polyolefin Polymers

We discuss a new class of polymer absorbents called “petrogels”, polyolefin-based hydrophobic absorbents that demonstrate selective absorption of hydrocarbon (oil) molecules in water, counterpart to “hydrogels” that are known for absorbing aqueous solutions. To understand the effects of the molecular structure (i.e., polymer composition, cross-linking density, and morphology) to the absorption capacity with various hydrocarbons and mixtures, a systematical study was conducted involving polyolefin copolymers that exhibit a highly swellable network but no dissolution in hydrocarbons at ambient temperature. They include a set of semicrystalline poly(ethylene-co-1-octene) thermoplastics (metallocene-LLDPEs) with low crystallinity, melting temperature, and various morphologies (i.e., pellets, films, and foams) and a set of cross-linked amorphous poly(1-decene-co-divinylbenzene) (x-D-DVB) elastomers with low cross-linking densities. The absorption study involves pure hydrocarbons (toluene and heptane), refined ...

Absorption of a linear (L2) and a cyclic (D4) siloxane using different oils: application to biogas treatment

Hydrophobic volatile methyl siloxanes (VMS), such as hexamethyldisiloxane (L2) and octamethylcyclotetrasiloxane (D4), present a low solubility in water. An alternative treatment by absorption into hydrophobic absorbents was therefore studied. For this purpose, three different absorbents, motor oil, cutting oil and a water-cutting oil mixture, were selected with the aim of re-using a waste product. The set of experiments was carried out in a bubble column, where parameters such as inlet concentration, residence time and temperature were studied. The best performance for the removal of both siloxanes, in terms of absorption capacity, was observed for motor oil, particularly for D4. In fact, motor oil removal efficiency for D4 was 80%, whereas for L2 it was 60%, indicating that D4 is more easily absorbed than L2. In the case of water-cutting oil, this showed a mass transfer enhancement from the gas phase to the liquid phase compared with water alone. Furthermore, a removal efficiency of 70% was observed for D4, showing that the addition of an oil fraction to a water system improves the absorption of VMS. These results show that VMS absorption into oils could be a promising way to achieve their abatement.

ChemInform Abstract: Solid‐Phase Glycan Isolation for Glycomics Analysis

AbstractReview: 108 refs.

Solid-phase glycan isolation for glycomics analysis.

Glycosylation is one of the most significant protein PTMs. The biological activities of proteins are dramatically changed by the glycans associated with them. Thus, structural analysis of the glycans of glycoproteins in complex biological or clinical samples is critical in correlation with the functions of glycans with diseases. Profiling of glycans by HPLC-MS is a commonly used technique in analyzing glycan structures and quantifying their relative abundance in different biological systems. Methods relied on MS require isolation of glycans from negligible salts and other contaminant ions since salts and ions may interfere with the glycans, resulting in poor glycan ionization. To accomplish those objectives, glycan isolation and clean-up methods including SPE, liquid-phase extraction, chromatography, and electrophoresis have been developed. Traditionally, glycans are isolated from proteins or peptides using a combination of hydrophobic and hydrophilic columns: proteins and peptides remain on hydrophobic absorbent while glycans, salts, and other hydrophilic reagents are collected as flowthrough. The glycans in the flowthrough are then purified through graphite-activated carbon column by hydrophilic interaction LC. Yet, the drawback in these affinity-based approaches is nonspecific binding. As a result, chemical methods by hydrazide or oxime have been developed for solid-phase isolation of glycans with high specificity and yield. Combined with high-resolution MS, specific glycan isolation techniques provide tremendous potentials as useful tools for glycomics analysis.

Absorption of Hydrophobic Volatile Organic Compounds by a Rotating Packed Bed

The high development of industries leads to significant amount of waste hydrophobic volatile organic compounds (VOCs), and these have caused serious environmental concerns. Because of the physical properties of the hydrophobic VOCs, a hydrophobic absorbent is needed in order to make the process more efficient if absorption is considered. However, most of these absorbents have high viscosities which leads to a low mass transfer coefficient. Thus, a cross-flow rotating packed bed (RPB) was evaluated for the feasibility of absorbing the hydrophobic VOCs, xylene, and toluene, by silicon oil, a model hydrophobic absorbent. The result shows that the absorption percentage could be up to 98% within a second contact of liquid and gas.

Absorptive removal of biomass tar using water and oily materials

Water is the most common choice of absorption medium selected in many gasification systems. Because of poor solubility of tar in water, hydrophobic absorbents (diesel fuel, biodiesel fuel, vegetable oil, and engine oil) were studied on their absorption efficiency of biomass tar and compared with water. The results showed that only 31.8% of gravimetric tar was removed by the water scrubber, whereas the highest removal of gravimetric tar was obtained by a vegetable oil scrubber with a removal efficiency of 60.4%. When focusing on light PAH tar removal, the absorption efficiency can be ranked in the following order; diesel fuel>vegetable oil>biodiesel fuel>engine oil>water. On the other hand, an increase in gravimetric tar was observed for diesel fuel and biodiesel fuel scrubbers because of their easy evaporation. Therefore, the vegetable oil is recommended as the best absorbent to be used in gasification systems.

High-speed chromatographic purification of plasmid DNA with a customized biporous hydrophobic adsorbent

Interest in producing large quantities of plasmid DNA has recently increased as a result of the rapid evolution of gene therapy and DNA vaccines. Hydrophobic chromatography is a popular technique in the downstream processing of plasmid DNA. However, the low capacity and the high mass transfer resistance of most commercially available packings for bio-macromolecules limit their application in a large-scale process. In this work, a hydrophobic absorbent with wide pores was synthesized by the solid porogenic method. Analyses by scanning electron microscopy and mercury intrusion porosimetry revealed that the matrix contained two families of pores, i.e., micropores smaller than 100 nm and superpores of 500–7300 nm. The superpores provided not only convective flow channels for the mobile phase, but also a large surface for biomolecules binding. So the chromatographic process can be operated at high flow rate with high column efficiency and low backpressure as identified on a 2-mL column (5 mm i.d., 2 cm length). With a loading up to 2.6 mg of 5.4 kb plasmid (pcDNA3) in 8 mL feedstock and operated at a flow rate as high as 20 cm/min, nearly 100% of plasmid was recovered with a purity of 100%. The results indicate that the hydrophobic medium is promising for high-speed purification of plasmid DNA.

Detection of iron(III)-binding ligands originating from marine phytoplankton using cathodic stripping voltammetry.

The sample preparation and analytical methodology are described for detecting biologically produced iron(III)-binding ligands in laboratory cultures of coastal marine phytoplankton. The iron(III)-binding ligands from the culture media were purified by passage through a column packing with a hydrophobic absorbent. The concentrations and stability constants of the ligands were determined by adsorptive cathodic stripping voltammetry with competitive ligand equilibration. The analytical results of the cultivated cultures suggest that eukaryotic phytoplankton would produce iron(III)-binding ligands in analogy with other microorganisms.

An improved procedure for the isolation of rat brown adipose tissue cells.

A method for the isolation of brown adipocytes free of fat interferences and sensitive to noradrenalin is presented. The cells were isolated from pieces of brown adipose tissue with a collagenase treatment. The cells were obtained in the presence of heparin, in order to free the lipoprotein lipase attached to the cell surface. The cells were isolated in the presence of Amberlite XAD-2 [polymeric hydrophobic absorbent beads], which retained most of the fat droplets, formed from broken cells, during the process of disaggregation. The combined use of heparin and Amberlite XAD-2 during the isolation procedure resulted in a lowered cell basal oxygen consumption rate when compared with that of cells isolated with standard methods. The treatment presented lowered the availability of extracellular fatty acids for the isolated brown fat cells, resulting in lower operation of the thermogenin shunt, and thence in decreased basal oxygen consumption and higher sensitivity to glucose and noradrenalin stimulation.