Hydrophobic poly(alkoxysilane) organogels as sorbent material for oil spill cleanup

Facile fabrication and application of highly efficient reduced graphene oxide (rGO)-wrapped 3D foam for the removal of organic and inorganic water pollutants

The pace of water contamination is increasing daily due to expanding industrialisation. Finding a feasible solution for effectively remediating various organic and inorganic pollutants from large water bodies remains challenging. However, a nano-engineered advanced hybrid material could provide a practical solution for the efficient removal of such pollutants. This work has reported the development of a highly efficient and reusable absorbent comprising a porous polyurethane (PU) and reduced graphene oxide (rGO) nanosheets (rGOPU) for the removal of different organic oils (industrial oil, engine oil and mustard oil), dyes (MB, MO, RB, EY and MV) and heavy metals (Pb(II), Cr(VI), Cd(II), Co(II) and As(V)). The structure, morphology and properties of the rGOPU hybrid absorbents were analysed by using Raman spectroscopy, field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Brunner-Emitte-Teller (BET) analysis. The rGOPU possessed both superhydrophobicity and superoleophilicity with water and oil contact angles of about 164° and 0°, respectively. The prepared rGOPU has demonstrated an excellent oil-water separation ability (up to 99%), heavy metals removal efficiency (more than 75%), toxic dye adsorption (more than 55%), excellent recyclability (> 500 times for oils), extraordinary mechanical stability (90% compressible for > 1000 cycles) and high recoverability. This work presents the first demonstration of rGOPU's multifunctional absorbent capacity in large-scale wastewater treatment for effectively removing a wide variety of organic and inorganic contaminants.

The preparation of CaCO3-polyalkoxysilane porous nanocomposites as effective sorbent for oil spill removal

The novel porous nanocomposite sorbent was synthesized by the condensation of the diol monomer with the alkoxysilane cross-linker at moderately high temperatures in the presence of nano-CaCO₃ particles. The structural, thermal, and morphological properties of the nanocomposite sorbents were determined by using Fourier transform infrared spectroscopy (FTIR), solid-state CPMAS ¹³C and ²⁹Si NMR, scanning electron microscope (SEM), and thermal gravimetric analysis (TGA). Adding nano-CaCO₃ to the network structure of the polymer not only provided pores to the sorbent but also enhanced its sorption capacity towards various oils and toxic organic solvents. The nanocomposite sorbent exhibited excellent absorption capacity for different toxic organic solvents and oils and great reusability for ten cycles. Moreover, the obtained sorbent material selectively absorbed organic liquids from the surface and bottom of the water without any capacity change owing to their hydrophobicity and oleophilicity. These features of the nanocomposite make it a potential sorbent for the cleaning of oils and oil derivative organic contaminants from the environment.

Detection of 2,4-dichlorophenoxyacetic acid in water sample by organosilane based silica nanocomposites

The present study aims to produce nanocomposites of silica based organosilane as sensitive and selective fluorescent sensor for the recognition of 2,4 dichlorophenoxyacetic acid (2,4-D). Hydrazone tethered triazole functionalized organosilane has been synthesized by the condensation reaction of 4-hydroxybenzaldehyde and phenyl hydrazine followed by Cu(I) catalysed cycloaddition of azide with alkyne. The prepared compound has been further grafted over silica surface and the synthesized materials were characterized by FT-IR, NMR (¹H and ¹³C), XRD, mass spectrometry and FE-SEM spectral analyses. The prepared organosilane and its HSNPs have been utilized as an effective emission probe for the selective detection of 2,4 D with good linear relationship in the range of 0-160 μM and 0-115 μM and LOD value of 46 nM and 13.5 nM respectively. In the presence of other active species, the sensor shows minimal interference while the comparison with the previously reported techniques suggests it to be more desirable for the sensitive and selective detection of 2,4 D. Further, the real sample application for detection of 2,4 D was analyzed in field water and the HSNPs based sensing system gave recovery percentage of above 98 %.

Removal of oils and organic solvents from wastewater through swelling of porous crosslinked poly(ethylene-co-vinyl acetate): Preparation of adsorbent and their oil removal efficiency

In this novel study, an attempt has been made to prepare porous crosslinked poly(ethylene-co-vinyl acetate) polymer (C-EVA). The porous C-EVA was prepared by grafting of maleic anhydride and cetyl alcohol onto the polymer backbone with addition of NaCl as porogen in the brabender mixture at 120 °C and 80 rpm. This was followed by leaching of NaCl with water extraction to generate a highly porous polymer structure which was evident from its SEM micrographs. The polymer was found to have excellent swelling capacity in various oils and organic solvents and showed good selective absorption capacity. The reusability of the synthesized polymer was studied and it was found that it could be reused for more than 30 absorption desorption cycles without undergoing much change in its absorption capacity. The cross-linked polymeric composite was further characterized by FTIR, TGA, XRD, and SEM.

Dispersants as an oil spill clean-up technique in the marine environment: A review

Oil is a major source of energy in the industrial world. Exploitation of oil and rigging activities, transportation via sea, and many other mechanical failures lead to oil spills into the marine environment. In view of these, the suitability and effectiveness of oil spill response methods have always been a topical discussion worldwide. It has become necessary, now than ever, for existing spill response methods used to remove oil from the environment to be improved upon and more importantly, develop new response materials that are sustainable and environmentally friendly. There exist surfactants in nature that are non-toxic and biodegradable, which can be explored to produce potential dispersants to help remove oil safely from the surface of marine water. This review comprises of the works and resourceful materials produced by various researchers and agencies in the field of oil spill response, placing emphasis on the use of dispersants in the marine environment.

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Smart dispersants have the potential to minimize dispersant wastage.

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Biodegradable dispersants may bring a closure to discussions on toxicity.

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Bio-based formulations have the potential to replace chemical based dispersants.

Evaluation of Polyurea-Crosslinked Alginate Aerogels for Seawater Decontamination

Polyurea-crosslinked Ca-alginate (X-Ca-alginate) aerogel beads (diameter: 3.3 mm) were evaluated as adsorbents of metal ions, organic solvents, and oils. They were prepared via reaction of an aromatic triisocyanate (Desmodur RE) with pre-formed Ca-alginate wet gels and consisted of 54% polyurea and 2% calcium. X-Ca-alginate aerogels are hydrophobic nanoporous materials (90% v/v porosity), with a high BET surface area (459 m²/g⁻¹), and adsorb Pb^II not only from ultrapure water (29 mg/g⁻¹) but also from seawater (13 mg/g⁻¹) with high selectivity. The adsorption mechanism involves replacement of Ca^II by Pb^II ions coordinated to the carboxylate groups of the alginate backbone. After treatment with a Na₂EDTA solution, the beads can be reused, without significant loss of activity for at least two times. X-Ca-alginate aerogels can also uptake organic solvents and oil from seawater; the volume of the adsorbate can be as high as the total pore volume of the aerogel (6.0 mL/g⁻¹), and the absorption is complete within seconds. X-Ca alginate aerogels are suitable for the decontamination of aquatic environments from a broader range of inorganic and organic pollutants.

One-pot fabrication of reusable hybrid sorbents for quick removal of oils from wastewater

The leaking of harmful organic liquids into water resources has had hazardous impacts on living organisms. Herein, we demonstrated the fabrication of hybrid sorbents using s-PPG and organosilane cross-linker. The final product exhibited high, quick absorption capacity, great reusability and excellent oil separation performance from wastewater. They also selectively absorb different oils from the bottom and surface of water without any capacity change, even in harsh conditions like wavy and sub-zero water environment. Experimental results demonstrated that the obtained sorbents are efficient to successfully remove oil from water surface, even at harsh conditions, and float on the water surface before and after oil sorption without any capacity loss and structural change. Simple preparation by avoiding time consuming multistep process, initiator, solvent, activator free reaction medium, high and selective sorption characteristics and great reusability could make these sorbents a promising candidate for the cleaning of water from harmful organic liquids, by absorbing them.

Use of cork granules as an effective sustainable material to clean-up spills of crude oil and derivatives

The use of cork granules for cleaning up crude oil or oil derivative spills and further oil recovery appears as a promising option due to their unique properties, which allow a high oil sorption capacity, low water pickup and excellent reuse. The present work reports the effect of oil viscosity on cork sorption capacity by using five types of oils (lubricating oil, 5.7 g_oil g_cork^-1; heavy oil, 4.2 g_oil g_cork^-1; light oil, 3.0 g_oil g_cork^-1; biodiesel, 2.6 g_oil g_cork^-1; and diesel, 2.0 g_oil g_cork^-1). The cork sorption capacity for light petroleum was also evaluated as a function of temperature and sorbent particle size. Additionally, improvements on oil recovery from cork sorbents by a mechanical compression process have been achieved as a result of a design of experiments (DOE) using the response surface methodology. Such statistical technique provided remarkable results in terms of cork sorbent reusability, as the oil sorption capacity was preserved after 30 cycles of sorption-squeezing steps. The sorbed oils could be removed from the sorbent surface, collected simply by squeezing the cork granules and further reused. The best operational region yielded near 80% oil recovery, using a cork mass of 8.85 g (particle size of 2.0-4.0 mm) loaded with 43.5 mL of lubricating oil, at 5.4 bar, utilising two compressions with a duration of 2 min each. Graphical abstract.

Sorption and removal of crude oil spills from seawater using peat-derived biochar: An optimization study

Bio-based sorbents are preferred over chemical-based methods for the clean-up of crude oil spills in marine environments because bio-based sorbents are more environmentally friendly. This study evaluates the use of peat-derived biochar (PB) as a bio-sorbent for the sorption and removal of crude oil spills from synthetic seawater. Experiments were designed to determine the effect of four operating factors (PB/crude oil contact time, PB dosage, oil dosage, and temperature) on two performance indicators (crude oil sorption capacity of PB, S, and oil removal efficiency, R%). Regression models containing linear, quadratic, and two-way interaction terms were developed to predict S and R% from the four factors. Response surface methodology (RSM) was employed to identify the optimum conditions for the sorption and removal of crude oil from seawater. The performance indicators were predicted with a high degree of accuracy, i.e. with coefficient of determination (R²) values exceeding 90%. The optimum values of S and R% were estimated to be 32.5 g of crude oil/g of sorbent and 91.2% respectively. These optimum values were attained after 70 min of PB/crude oil contact time and at a temperature of 45 °C. The spent sorbent maintained its performance after three cycles of regeneration and reuse, suggesting that the material is reusable.

A review on sorbent devices for oil-spill control

Multiple research areas have emerged in view of the deleterious impacts of oil-spills on the environment and the relative intractability of the problem per se. The dimensions mostly explored thus far, relate to the prediction of the fate of oil-spill and development of effective counter-measures. Among the counter measures, development of effective sorbents for oil-spill remediation has sustained interest for quite long, in spite of the numerous challenges associated with it. Most importantly, the sorbent materials need to be assembled in such a structure or form that they can survive the oceanic currents and other prevailing environmental conditions without themselves becoming a source of secondary pollution. This review paper focuses on the chronological development of such assemblies or devices over the past century and a critical appraisal of the same. Relevant major factors affecting the performance of sorbent assemblies can be identified as: structural features and modes of sorption, effect of weathering on oil-sorption capacity, mode of distribution and harvesting of such absorbent units, and the final disposal after feasible cycles of sorption and release. This review paper incorporates a detailed discussion on the major inventions and the extant open literature in this field.

Polyolefin-based interpenetrating polymer network absorbent for crude oil entrapment and recovery in aqueous system

In this research, a series of different two polyolefin-based interlaced polymer network material was prepared with a semi-crystalline linear low density polyethylene (LLDPE, thermoplastic) and a crosslinked 1-decene/divinylbenzene (1-D/DVB, elastomer) having high crude oil absorption capacity. The prepared absorbents, LLDPE/D/DVB, were characterized by NMR, TEM, contact angle measurement and TGA analysis. It was observed that the mixing ratio of two interlaced polymer network played a crucial role in determining its crude oil absorption capacity. The swelling capacity of absorbent prepared from a 1:1 mixing of LLDPE and D/DVB (0.2 ml) exhibit high removal efficiency in crude oil absorption over 40 g/g at both 25 °C and 0 °C. The removal of the absorbed crude oil from the water surface is effective. As the absorbent made of polyolefin materials have pure hydrocarbon content, offer significant advantages such as high absorption capacity, simple recovery, and recyclability.

Lipophilic polyelectrolyte gel derived from phosphonium borate can absorb a wide range of organic solvents

Herein, we demonstrate a polyelectrolyte gel which can absorb a wide range of organic solvents from dimethylsulfoxide (DMSO, permittivity: ε = 47.0) to tetrahydrofuran (ε = 5.6). The gel consists of polystyrene chains with small amounts (∼5 mol%) of lipophilic electrolytes derived from triphenylphosphonium tetraaryl borate. The swelling ability of the polyelectrolyte gel was higher than that of the alkyl ammonium tetraaryl borate previously reported by us, and this is attributed to the higher compatibility with organic solvents, as well as the higher dissociating ability, of the triphenyl phosphonium salt. The role of the ionic moieties was additionally confirmed by post modification of the polyelectrolyte gel via a conventional Wittig reaction, resulting in a nonionic gel. Our findings introduced here will lead to a clear-cut molecular design for polyelectrolyte gels which absorb all solvents.

Oil loving hydrophobic gels made from glycerol propoxylate: Efficient and reusable sorbents for oil spill clean-up

Glycerol propoxylate based oil loving sorbents were prepared through bulk polymerization, without using of an activator, initiator, or catalyst. Fourier transform infrared spectroscopy (FTIR), ¹³C and ²⁹Si CPMAS nuclear magnetic resonance (NMR), as well as elemental analysis and thermal gravimetric analysis (TGA) were operated in order to identify the structural and thermal features of sorbents. The synthesized gels were employed as absorbents for various organic solvents and oils. The swelling capacity, absorption-desorption kinetics, reusability, and selective removal from an oil/water mixture were also examined. To explore the effects of a crosslinker's concentration on oil absorption capacity, star type propoxylate monomers were reacted at different concentration of tris[3-(trimethoxysilyl)propyl]isocyanurate (ICS) crosslinker; swelling capacity was calculated using dichloromethane as an organic solvent. Oil removal ability from the water surface is another important section contained within this article.

Resource recovery of Eichhornia crassipes as oil superabsorbent

The elastic cellulose-based aerogels (CBAs) with highly porous (99.56%) and low-density (0.0065gcm^-1) were prepared using Eichhornia crassipes as cellulose source and polyvinyl alcohol directly as cross-linker via a facile and environment-friendly process. The prepared CBAs exhibited excellent oil/solvent sorption capacities (60.33-152.21gg^-1), super-hydrophobicity (water contact angle of 156.7°) as well as remarkable reusability. More importantly, the absorbed oil could be quickly recovered by simple squeezing without significantly structure damage (at least 16 times). All these merits make CBAs very promising materials for oil spillage cleaning.

Effective clean-up of organic liquid contaminants including BTEX, fuels, and organic solvents from the environment by poly(alkoxysilane) sorbents

Novel cross-linked poly(alkoxysilane)s, which can be used for the removal of organic liquid contaminants from water, were synthesized in one step, in a solvent free reaction medium, at moderately high temperature without using a catalyst. The synthesized polymers were characterized by Fourier transform infrared spectroscopy (FTIR), solid-state (13)C and (29)Si cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) methods and elemental analysis. The swelling features of the poly(alkoxysilane)s were investigated in organic solvents and oils, such as dichloromethane, benzene, toluene, xylene, methyl tertiary butyl ether, and also some fuel derivatives, such as gasoline and euro diesel. All polymers have high-fast solvent uptake abilities, good reusability and thermal stability. The swelling features of the synthesized cross-linked polymers were evaluated by the swelling test, absorption-desorption kinetics. Thus, the results propose that cross-linked poly(alkoxysilane)s are suitable for the absorption of oil-organic pollutants from the water surface.

Organic-inorganic hybrid gels for the selective absorption of oils from water

Organic-inorganic hybrid gels were synthesized by the condensation of a linear aliphatic diol (1,8-octanediol) and altering the chain length of the alkyltriethoxysilanes (from ethyltriethoxysilane to hexadecyltrimethoxysilane) through a bulk polymerization process without using any initiator, activator, catalyst, or solvent for the selective removal of oils from water. Fourier transform infrared spectroscopy (FTIR) and solid-state (13)C and (29)Si cross-polarization magic-angle spinning nuclear magnetic resonance (CPMAS NMR) were used for the structural analysis of hybrid gels. Thermal properties of the hybrid gels were determined by thermogravimetric analysis (TGA). Oil absorbency of organic-inorganic hybrid gels was determined by oil absorption tests. The results showed that hybrid gels have high and fast absorption capacities and excellent reusability. Good selectivity, high thermal stability, low density, and excellent recyclability for the oil removal give the material potential applications.

Cross-linked poly(tetrahydrofuran) as promising sorbent for organic solvent/oil spill

In this study, a series of different molecular weights of poly(tetrahydrofuran) (PTHF), which is one of the most important commercial polymers around the world, was condensed with tris[3-(trimethoxysilyl)propyl]isocyanurate (ICS) to generate a cross-linked 3-dimensional network in order to obtain organic solvent/oil sorbents having high swelling capacity. The prepared sorbents show high and fast swelling capacity in oils such as dichloromethane (DCM), tetrahydrofuran (THF), acetone, t-butyl methyl ether (MTBE), gasoline, euro diesel, and crude oil. The recovery of the absorbed oils from contaminated surfaces, especially from water, and the regeneration of the sorbents after several applications are effective. The characterization and thermal properties of the sorbents are identified by Fourier transform infrared spectroscopy (FTIR), solid-state (13)C and (29)Si cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and thermal gravimetric analyses (TGA), respectively. The new usage area of PTHF is emerged by the preparation of PTHF-based network structure with high oil absorption capacity and having excellent reusability as an oil absorbent for the removal of organic liquids from the spill site.

Recent Development of Advanced Materials with Special Wettability for Selective Oil/Water Separation

The increasing number of oil spill accidents have a catastrophic impact on our aquatic environment. Recently, special wettable materials used for the oil/water separation have received significant research attention. Due to their opposing affinities towards water and oil, i.e., hydrophobic and oleophilic, or hydrophilic and oleophobic, such materials can be used to remove only one phase from the oil/water mixture, and simultaneously repel the other phase, thus achieving selective oil/water separation. Moreover, the synergistic effect between the surface chemistry and surface architecture can further promote the superwetting behavior, resulting in the improved separation efficiency. Here, recently developed materials with special wettability for selective oil/water separation are summarized and discussed. These materials can be categorized based on their oil/water separating mechanisms, i.e., filtration and absorption. In each section, representative studies will be highlighted, with emphasis on the materials wetting properties and innovative aspects. Finally, challenges and future research directions in this emerging and promising research field will be briefly described.

Flexible and durable cellulose aerogels for highly effective oil/water separation

A facile and green method was presented to prepare flexible, ultralight, and hydrophobic CA on the chemical cross-linking of cellulose solution, lyophilization and subsequent hydrophobic modification with methyltrichlorosilane by a CVD process.