Hydrophobic modification of cellulose nanocrystal via covalently grafting of castor oil

Hydrophobic cellulose nanocrystals (CNs) have been prepared by grafting isocyanate-terminated castor oil, a kind of natural vegetable oil, onto their surface. The existence of castor oil component in the modified cellulose nanocrystals was verified by Fourier transform infrared spectroscopy, solid-state ¹³C NMR spectra and X-ray photoelectron spectroscopy. At the same time, X-ray diffraction and transmission electron micrographs further proved that the crystalline structure and large aspect ratio of cellulose nanocrystals were essentially preserved after chemical grafting. Furthermore, the surface of modified cellulose nanocrystals appeared to be hydrophobic as indicated by contact angle measurements. The value of the polar component of surface energy decreased from 21.5 mJ/m² to almost zero via grafting castor oil. These novel hydrophobic castor oil-grafted cellulose nanocrystals appear as valuable alternatives to formulate bionanocomposites with non-polar polymers for optimized performances.     

Photochemically Produced Superhydrophobic Silane@polystyrene-Coated Polypropylene Fibrous Network for Oil/Water Separation

Cost-effective separation of oil and immiscible organic contaminants from water has become an urgent challenge to protect aquatic and human life from devastating effects. Therefore, it has become imperative to develop super-selective materials for efficiently separating oil from water. In this work, a superhydrophobic surface has been formed that consists of a silane@polystyrene-coated polypropylene fibrous network (silane@PS-PPF) for efficient separation of accidentally spilled oil from water. The superhydrophobic PPFs were designed by a simple, cost-effective two-step process that includes photochemically controlled polymerization of styrene and subsequent dip coating in octadecyltrichlorosilane solution. The hydrophobic surface (CA=129°±4°) of the PS coated PPF after treating with silane was turned into a superhydrophobic body (CA=161°±2°). The achieved silane@PS-PPF fibrous network selectively allowed the fast permeation of the oils and non-polar organic liquids by altogether rejecting water during operation. The separation efficiency for various oils from the contaminated water was 96 to 99%, with a high flux in the range of 7606±312 L m⁻²h⁻¹ to 9870±151 L m⁻²h⁻¹. Apart from being used as a filter, the silane@PS-PPF was also used as an oil absorber and has shown an absorption capacity in the range of 1185 to 1535% for various oils. We anticipate that the developed silane@PS-PPF, due to its facile synthetic route, cost-effectiveness, and high performance, can be effectively used in oily wastewater treatment and clean-up of large oil spills from water.     

Intermolecular Interactions and the Adhesion of Oleic Acid

The method presented by Good, van Oss, and Chaudhury was applied to characterize intermolecular interactions and the adhesion of oleic acid to selected model surfaces. Interfacial tensions of oleic acid were on the order 11–12 mJ/m² in aqueous solutions and 31–32 mJ/m² at air. The dispersive contribution to the surface tension of oleic acid against different neutral interfaces was determined to be 24–31 mJ/m² in air. Contact angles of oleic acid on selected hydrophilic and hydrophobic model surfaces were measured both in air and in aqueous solution. Van der Waals (dispersive) interactions determined the wetting properties of oleic acid in air both on nonpolar and basic surfaces. As expected, the adhesion of oleic acid to hydrophilic surfaces was much lower and to hydrophobic surfaces higher in aqueous environment than in air. The adhesion in aqueous environment is mainly governed by the cohesive and adhesive properties of water. It was concluded that the GvOC method in this case was only capable to give qualitative information about Lewis acid-base and van der Waals properties of surfaces and liquids, an important limiting factor being the asymmetry of oleic acid and the common probe liquids (diiodomethane and water).     

Hydrophobic cellulose nanopaper through a mild esterification procedure

Films of cellulose nanofibrils (CNF) (referred to as nanopaper) present a great potential in many applications due to the abundance, low environmental impact, excellent oxygen barrier properties and good mechanical performance of CNF. However, the strong hygroscopic character of the natural nanofibers limits their use in environments with high relative humidity. In this paper, we introduce a simple route for the esterification and processing of CNF with the aim of reducing their hydrophilicity, and producing hydrophobic cellulose nanopaper with reduced moisture sensitivity. The preparation steps of hydrophobic nanopapers involve vacuum filtration, solvent exchange from water to acetone, and reaction with anhydride molecules bearing different hydrophobic alkyl chains by hot pressing. Porous films having a surface area between 38 and 47 g/m² and pore sizes in the 3–200 nm range are obtained. This method preserves the crystalline structure of native cellulose, and successfully introduces hydrophobic moieties on CNF surface as confirmed by FTIR, XPS and elemental analysis. As a result, modified nanopapers have a reduced moisture uptake, both higher surface water contact angle and wet tensile properties as compared with reference non-modified nanopaper, thus illustrating the benefit of the modification for the use of cellulose nanopaper in humid environments.     

Direct observation of cellulose dissolution in subcritical and supercritical water over a wide range of water densities (550–1000 kg/m<Superscript>3</Superscript>)

Direct observations of the heating of microcrystalline cellulose (230 DP) in water at temperatures up to 410 °C and at pressures up to 700 MPa were made with a batch-type microreactor. Cellulose particles were found to dissolve with water over temperatures ranging from 315 to 355 °C at high pressures. Dissolution temperatures depended on water density and decreased from about 350 °C at a water density of 560 kg/m³ to a minimum of around 320 °C at a water density of 850 kg/m³. At densities greater than 850 kg/m³, the dissolution temperatures increased and reached a value of about 347 °C at 980 kg/m³. The cellulose dissolution temperatures were independent of heating rates for values ranging from 10 to 17 °C/s. The low dependence of dissolution temperatures on the heating rates is strong evidence for simultaneous dissolution and reaction of the cellulose. Different phenomena occurred depending on water density. At low densities, particles turned transparent and seemed to dissolve into the aqueous phase from the surface. From 670 to 850 kg/m³, the cellulose particles visibly swelled just before completely collapsing and dissolving into the aqueous phase. The swelling probably increased water accessibility and particle surface area and thus lead to the lower dissolution temperatures observed. From 850 to 1000 kg/m³, the particles required longer times to dissolve and many fine brown-like particles were generated as the particles dissolved. FT-IR spectra of the residues were analyzed. Residues formed from heating cellulose at high densities still retained some cellulose character whereas those as low densities had little cellulose character, especially in the O–H stretching vibration region.     

Superhydrophobic surfaces from surface-hydrophobized cellulose fibers with stearoyl groups

In this report, surface-hydrophobized cellulose fibers by stearoyl groups were used for the construction of superhydrophobic surfaces. The product after the synthesis contains two components: cellulose microfibers as the major component and nanoscaled segments in small amounts. The crystalline structure of cellulose was maintained after surface modification based on solid-state ¹³C NMR spectroscopy. Superhydrophobic surfaces showing static water contact angles of >150° were fabricated using freshly prepared products containing both components via the facile route, e.g., solvent casting. The cellulose types, microcrystalline cellulose or cotton linter cellulose fibers, did not significantly affect the chemical modification of cellulose fibers, but the superhydrophobic surfaces using surface-hydrophobized cotton linters as starting materials exhibited higher surface hydrophobicity and better impact stability in comparison to shorter microcrystalline cellulose. Due to the presence of a crystalline cellulose skeleton, the obtained superhydrophobic surfaces are stable during the heat treatment at 80 °C.     

Fabrication of AgNPs/Silane coated mechanical and washing durable hydrophobic cotton textile for self-cleaning and oil-water separation application

This study deals to develop a simple and facile two-step dip-coating method using silver nanoparticles (AgNPs) and fluorine-free silane monomer, 3-(Trimethoxysilyl) propyl methacrylate (TMSPM) for the fabrication of hydrophobic coating on cotton fabric. The anti-wetting properties, surface morphology, chemical composition, and functionality of the cotton fabric before and after modification were well characterized by contact angle measurement, scanning electron microscope (SEM), and energy-dispersive X-ray spectrum (EDX) and FT-IR respectively. The fabricated cotton fabric displays strong durability against different pH solutions, different soft/hard mechanical treatments including adhesive peeling test, abrasion with tissue paper and finger wiping, home laundering, without losing the hydrophobic property. The contact angle values (water contact angle of 148.3 ?± ?2° and oil contact angle of 0°) imply that the modified cotton has considerable hydrophobic/oleophilic properties. Additionally, the modified hydrophobic/oleophilic cotton fabric exhibits self-cleaning and oil-water separation behavior for both industrial and household importance.     

Surface functionalized waste-silk fabric engineered with polylactic acid & activated charcoal for oil/solvent recovery from oily wastewater

The present study reports using waste silk fabric functionalized using Polylactic acid (PLA) and Activated charcoal for oil/solvent recovery from simulated seawater (3.5% NaCl-based water). An average of 91% separation was visible in the functionalized waste silk fabric with an efficiency up to 20 cycles towards petroleum oils/solvents from simulated seawater. Further, the functionalized waste fabric showed hydrophobic properties with a water-based contact angle of 105° and oil/solvent absorption towards petroleum oils and organic solvent, with a surface free energy of 52.46 mN m⁻¹. The functionalized waste silk also showed permeation flux of 658, 386, and 993 L m⁻² h⁻¹, for Petrol, Diesel, and n-Hexane, respectively. The results show that PLA/Activated-charcoal engineered waste silk can be effectively applied for practical oil/solvent recovery from simulated seawater. Utilizing waste silk fabric further supports in reducing the global carbon footprints as silk does not emit and/-or produce carbon dioxide due to its green origin and generating the circular economy approach.     

Epoxy Coatings with Low Surface Energy from Powdered Compounds Modified with Finely Dispersed Polytetrafluoroethylene Particles

Highly hydrophobic epoxy coatings with the surface energy as low as 14.5 mJ m^–2 and contact angles with water of 120°–150° were prepared from powdered compounds modified with less than 2 wt % finely dispersed polytetrafluoroethylene particles by dry mixing. As shown by scanning electron microscopy, EDX microanalysis, and atomic-force microscopy, the film formation at 180°С and formation of a polymer network matrix are accompanied by predominant migration of polytetrafluoroethylene particles to the air/coating interface, leading to gradient distribution of fluorine across the film and significant enrichment of the coating surface with fluorine. By varying the polytetrafluoroethylene content, it is possible to obtain hydrophobic coatings with satisfactory physicomechanical properties, smooth or rough surface, including micrometric and nanometric roughness, and different surface energy.     

Long-term stabilization of foams and emulsions with in-situ formed microparticles from hydrophobic cellulose

We report a simple method to produce foams and emulsions of extraordinary stability by using hydrophobic cellulose microparticles, which are formed in situ by a liquid-liquid dispersion technique. The hydrophobic cellulose derivative, hypromellose phthalate (HP), was initially dissolved in water-miscible solvents such as acetone and ethanol/water mixtures. As these HP stock solutions were sheared in aqueous media, micron sized cellulose particles formed by the solvent attrition. We also designed and investigated an effective and simple process for making HP particles without any organic solvents, where both the solvent and antisolvent were aqueous buffer solutions at different pH. Consequently, the HP particles adsorbed onto the water/air or water/oil interfaces created during shear blending, resulting in highly stable foams or foam/emulsions. The formation of HP particles and their ability for short-term and long-term stabilization of interfaces strongly depended on the HP concentration in stock solutions, as well as the solvent chemistry of both stock solutions and continuous phase media. Some foams and emulsion samples formed in the presence of ca. 1 wt% HP were stable for months. This new class of nontoxic inexpensive cellulose-based particle stabilizers has the potential to substitute conventional synthetic surfactants, especially in edible, pharmaceutical and biodegradable products.     

Cellulose II nanoelements prepared from fully mercerized, partially mercerized and regenerated celluloses by 4-acetamido-TEMPO/NaClO/NaClO2 oxidation

A softwood bleached kraft pulp (SBKP) and cotton lint cellulose were fully or partially mercerized, and these along with celluloses and commercially available regenerated cellulose fiber and beads were oxidized by 4-acetamido-TEMPO/NaClO/NaClO₂ at 60 °C and pH 4.8. Weight recovery ratios and carboxylate contents of the oxidized celluloses were 65–80% and 1.8–2.2 mmol g⁻¹, respectively. Transparent and viscous dispersions were obtained by mechanical disintegration of the TEMPO-oxidized celluloses in water. These aqueous dispersions showed birefringence between cross-polarizers, indicating that mostly individualized cellulose nanoelements dispersed in water were obtained by these procedures. Transmission electron microscopy observation showed that the cellulose nanoelements prepared from mercerized SBKP, repeatedly mercerized SBKP, mercerized cotton lint cellulose, regenerated cellulose beads and 18% NaOH-treated SBKP, i.e. partially mercerized SBKP, had similar morphologies and sizes, 4–12 nm in width and 100–200 nm in length. The 18% NaOH-treated SBKP was converted to cellulose nanoelements consisting of both celluloses I and II.     

Synthesis and Surface Active Properties of Ethoxyalted 4,5-Dihydroimidazoline Surfactants

Pure oleic acid and four hydrolyzed products of locally fatty oils (namely, coconut, soybean, linseed, and castor oils) were monoesterified individually with two different polyalkylene polyamines. The produced monoesters were used as precursors for imidazoline derivatives. These oil soluble imidazolines were ethoxylated by ethylene oxide gas with different ethylene oxide contents (5, 10, and 20) to prepare water soluble stable imidazoline ethoxylates. The chemical structure of the synthesized imidazoline ethoxylates were justified through spectroscopy and surface active properties of the compounds were investigated. The obtained data were discussed on the basis of variation chemical structure.     

Surface Thermodynamic Properties of Micas and Related Layer Silicate Minerals

The surface tension values for a series of 2:1 phyllosilicate minerals with different structural characteristics and layer charges ranging from 0 to 2 per O₁₀ group have been examined. The average Lifshitz-van der Waals component (Γ^LW)value is 40.3 ± 1.9 mJ/m², and the average Lewis acid (®) parameter is 1.2 ± 0.6 mJ/² for those minerals with a layer charge greater than zero. In contrast, the Lewis base parameter (γ^e) varied greatly from a maximum of 59.7 mJ/m to a minimum of 23.7 mJ/m². Those minerals with a layer charge of zero (three samples) had smaller γ^LW values of 32.0 ± 1.6 mJ/m², slightly larger γ® values of 2.0 ± 0.4 mj/m² and significantly smaller values of γ® of 4.5 ± 1.6 mJ/m². The hydrophobic versus hydrophilic character of these materials is largely governed by the value of γ° which is strongly related to the value of the layer charge.

Thus, the hydrophilicity of a smectite is determined by the charge unbalancing ionic substitutions which attract hydrophilic interlayer cations and render adjacent oxygen atoms of the panicle surface hydrophilic.     

The influence of vegetable oils on biosurfactant production by Serratia marcescens

The production of biosurfactant, a surface-active compound, by two Serratia marcescens strains was tested on minimal culture medium supplemented with vegetable oils, considering that it is well known that these compounds stimulate biosurfactant production. The vegetable oils tested included soybean, olive, castor, sunflower, and coconut fat. The results showed a decrease in surface tension of the culture medium without oil from 64.54 to 29.57, with a critical micelle dilution (CMD⁻¹) and CMD⁻² of 41.77 and 68.92 mN/m, respectively. Sunflower oil gave the best results (29.75 mN/m) with a CMD⁻¹ and CMD⁻² of 36.69 and 51.41 mN/m, respectively. Sunflower oil contains about 60% of linoleic acid. The addition of linoleic acid decreased the surface tension from 53.70 to 28.39, with a CMD⁻¹ of 29.72 and CMD⁻² of 37.97, suggesting that this fatty acid stimulates the biosurfactant production by the LB006 strain. In addition, the crude precipitate surfactant reduced the surface tension of water from 72.00 to 28.70 mN/m. These results suggest that the sunflower oil’s linoleic acid was responsible for the increase in biosurfactant production by the LB006 strain.     

Extraction of male steroids and progesterone from water by vegetable oil gels and their determination by partial filling capillary micellar electrokinetic chromatography

Microemulsion gels were synthetized from macadamia, linseed, olive, walnut, rapeseed, sesame, and coconut oils and frying oil made from sunflower, palm, and rapeseed oils. The gels were similar as polyacrylamide–based gels with exception of replacing dodecyl sulfate with vegetable oils. The gels were modified with celluloses, cotton, or lignin to make the emulsions sustainable for water purification. They were used to compare sorption properties when they were used as solid‐phase adsorbents in isolation of steroids from water. Hydrophobicity features of the gels were compared by detecting adsorption and extraction efficiency of nonpolar androstenedione, testosterone, and progesterone, which exist in wastewater and drinking water. Quantification was done with partial filling–micellar electrokinetic chromatography with 29.5 mM sodium dodecyl sulfate–3.4 mM sodium taurocholate as the micelle and 20 mM ammonium acetate (pH 9.68) as the electrolyte. UV‐detection was used. Methanol was the best eluent for extraction of steroids from gels. The highest recoveries were from frying oil and rapeseed oil gels modified with celluloses. They also possessed the best floating properties on water surface. Lignin modified gels were too hydrophilic, when in touch with water they filled up with water. They also had the lowest capacity.     

Analysis of the thermal decomposition of commercial vegetable oils in air by simultaneous TG/DTA

This work presents a study of the thermal decomposition of commercial vegetable oils and of some of their thermal properties by termogravimetry (TG), derivative termogravimetry (DTG) and by differential thermal analysis (DTA). Canola, sunflower, corn, olive and soybean oils were studied. A simultaneous SDT 2960 TG/DTA from TA Instruments was used, with a heating rate of 10 K min^-1 from 30 to 700°C. A flow of 100 mL min^-1 of air as the purge gas was used in order to burnout the oils during analysis to estimate their heat of combustion. From the extrapolated decomposition onset temperatures obtained from TG curves, it can be seen that corn oil presents the highest thermal stability (306°C), followed by the sunflower one (304°C). Olive oil presents the lowest one (288°C). The heat of combustion of each oil was estimated from DTA curves, showing the highest value for the olive oil. Except for corn oil, which presents a significantly different thermal decomposition behavior than the other oils, a perfect linear correlation is observed, with negative slope, between the heat of combustion of an oil and its respective extrapolated onset temperature of decomposition in air. This revised version was published online in August 2006 with corrections to the Cover Date.     

Flame-retarded hydrophobic cellulose through impregnation with aqueous solutions and supercritical CO2

We have developed flame-retarded hydrophobic cellulose-based materials by producing in situ water-soluble and insoluble inorganic microparticles on various surfaces of native cellulose (filter paper and pure cotton textile). The nanoparticles were produced by simple impregnation of cellulose with two different aqueous solutions followed by a third impregnation with supercritical CO₂. Finally, the composite cellulose materials were covered by a silicon-based polymer thin film, to turn it into hydrophobic and prevent the water-soluble particles from absorbing humidity. The obtained flame-retardant behaviour is due to a combination of mechanisms. The total treatment of cellulose has an impact on, both its surface morphology and its hydrophilicity. Thus, the hydrophobic nature of the silicon-based polymer film along with the roughness caused by the presence of the inorganic particles and the inherent roughness of native cellulose resulted in superhydrophobic behaviour. The same process-concept was also applied to regenerated (from newspaper) cellulose with ionic liquids. The produced materials were characterised by thermogravimetric analysis, differential scanning calorimetry, infrared spectroscopy, scanning electron microscopy and water contact angle measurements.     

A Scalable Chemical Approach for the Synthesis of a Highly Tolerant and Efficient Oil Absorbent

In the past, bio‐inspired extreme water repellent property has been strategically embedded on commercially available sponges for developing selective oil absorbents. However, most of the reported materials lack physical and chemical durability, limiting their applicability at practically harsh settings. Herein, a stable dispersion of polymeric nanocomplexes was exploited to achieve a chemically reactive coating on the highly compressible melamine foam. A superhydrophobic melamine foam (SMF) was achieved after post‐covalent modification of the reactive coating through 1,4‐conjugate addition reaction at ambient conditions. The durability of the embedded extreme water repellent property in the as‐modified melamine foam has been elaborately demonstrated through exposing it to severe physical manipulations, chemically harsh aqueous media including pH 1, pH 12, surfactant contaminated water, river water, seawater and prolonged UV irradiation. Thus, the highly tolerant SMF was utilized as an efficient oil absorbent wherein oils of varying densities could be selectively recovered from an oil/water interface with high (e.g., 137 g g^?1 for chloroform and 83 g g^?1 for diesel) oil absorption capacity. Moreover, the selective oil absorption capacity of the as‐synthesized material remained unaffected at practically relevant severe chemical and physical settings, and the extreme water repellency of the material remained unaltered even after repetitive (at least 50 cycles) use for oil/water separation.     

树莓状超疏水多孔复合棉纤维的制备及油水分离性能

基于聚多巴胺（PDA）的化学性质和树莓状纳米粒子的粗糙结构,以聚多巴胺包覆的棉纤维为基底,制备了具有多重粗糙度的树莓状超疏水多孔复合棉纤维材料.通过扫描电子显微镜观察树莓状超疏水多孔复合棉纤维表面的微观形貌,PDA-SiO₂纳米粒子稳定地固定在聚多巴胺涂覆的棉纤维表面.经过氟化改性的树莓状超疏水多孔复合棉纤维具有超疏水性,水接触角为158.2°,油接触角为0°.油/水分离实验结果表明,树莓状超疏水多孔复合棉纤维对己烷/水混合物的分离效率可达99.4%以上,使用20次后仍维持较高的分离效率.同时,其具有较高的溶剂吸附能力（13~34 g/g）、重复使用性及机械稳定性,吸油能力可与硅气凝胶相媲美.     

PREPARATION OF CLOUDY COCONUT OIL EMULSIONS CONTAINING DISPERSED TiO2 USING ATOMIZER

ABSTRACT

Food Grade Rutile TiO₂ was dispersed in coconut oil with the help of hydrophobic emulsifiers such as sorbitan esters and lecithin. The dispersed mixture was melted and blended with hydrophilic emulsifiers such as ethoxylated sorbitan esters and the preheated (60°C) blend was further sprayed by atomizer into cold water (20°C). The oil in water emulsions contained encapsulated TiO₂ in the internal phase. The technique is simple and allows preparation of stable emulsions with average droplets size of 1-10 microns.