Hexadecane Research Articles

Simultaneous hexadecane and oxygen transfer rate on the production of an oil-degrading consortium in a three-phase airlift bioreactor

The hexadecane (HXD) transfer rate (HTR) and the oxygen transfer rate (OTR) were simultaneously evaluated as a single engineering criterion to enhance the production of an oil-degrading bacterial consortium. In order to accomplish the task, a 10-L three-phase airlift bioreactor (ALB) was used. Oxygen transfer volumetric coefficient (kLaO2) values of 25–49h−1 were found for several superficial gas velocities (Ug 0.15–2.7cms−1). HXD transfer volumetric coefficient (kLaHXD) values of 0.005–0.041h−1 were obtained for the same range of Ug values. OTR and HTR were calculated as the product of kLaO2 or kLaHXD and the respective concentration gradient. HXD transfer parameters were evaluated by using an early reported novel technique. During 14 days culture, using constant Ug values, the ratio of HTR to OTR (HTR/OTR) never reached the stoichiometric ratio (0.25±0.05g HXD (gO2)−1). However, the productivity at the higher assayed constant Ug (2.7cms−1) was as good as 1.02±0.03g SS (Ld)−1. We propose a variable Ug strategy that consumes 33% less energy than a higher constant Ug strategy to achieve the same yield and productivity. In this study, the oil-degrading consortium, able to remediate contaminated soils and water, productivity was successfully enhanced with simultaneous HXD and oxygen transfer considerations.

Forced Unbinding of Individual Urea–Aminotriazine Supramolecular Polymers by Atomic Force Microscopy: A Closer Look at the Potential Energy Landscape and Binding Lengths at Fixed Loading Rates

Atomic force microscopy-based single-molecule force spectroscopy (AFM-SMFS) was used to study the forced unbinding of quadruple self-complementary hydrogen-bonded urea-aminotriazine (UAT) complexes in hexadecane (HD). To elucidate the bond strength of individual linkages the unbinding forces of UAT supramolecular polymers were investigated for the first time. The bond rupture was probed at three different, fixed piezo retraction rates in far from equilibrium conditions. The number of supramolecular bonds (N) between AFM tip and the surface was determined by independent knowledge of the linker length. The observed rupture force of urea-aminotriazine (UAT)-based supramolecular polymer chains was found to decrease with increasing rupture length. The dependence of the most probable rupture force on N was in quantitative agreement with the theory of uncooperative bond rupture for supramolecular linkages switched in series. Experiments with three different, fixed loading rates provided identical values (within the experimental error) for the characteristic bond length x(β) and the off-rate constant in the absence of force k(off)(f = 0). The value of x(β) was found to agree with literature data on the hydrogen-bond distance obtained via crystallographic data of the hydrogen-bonded dimer. This work broadens the scope of our previous report showing that relevant parameters of the bond energy landscape can be derived from a single data set of rupture events at a fixed loading rate for supramolecular linkages switched in series.

Preparation, characterization and thermal properties of nanocapsules containing phase change material n-dodecanol by miniemulsion polymerization with polymerizable emulsifier

Nanocapsules containing phase change material (PCM) n-dodecanol as core and polymethyl methacrylate (PMMA) as shell were synthesized by miniemulsion polymerization with polymerizable emulsifier DNS-86 and co-emulsifier hexadecane (HD). The nanocapsules were characterized by using Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and laser particle diameter analyzer. The effects of polymerizable emulsifier and co-emulsifier on the properties of nanocapsules were studied. The results show that thermal properties of nanocapsules are affected greatly by the addition methods of HD and the amounts of DNS-86 and HD. Adding HD into water phase is helpful for the encapsulation of n-dodecanol. When the mass ratios of DNS-86 to n-dodecanol and the mass ratios of HD to n-dodecanol were 3% and 2%, the phase change latent heat and the encapsulation efficiency of nanocapsules reached to the maximum value of 98.8 J/g and 82.2%, respectively. Spherical nanocapsules with mean diameter of 150 nm and phase change temperature of 18.2 °C are obtained, which are sure to have a good potential for energy storage.

Evaluating the link between self-assembled mesophase structure and drug release

Lipid-based liquid crystalline materials are of increasing interest for use as drug delivery systems. The intricate nanostructure of the reversed bicontinuous cubic (V2) and inverse hexagonal (H2) liquid crystal matrices have been shown to provide diffusion controlled release of actives of varying size and polarity. In this study, we extend the understanding of release to other self-assembled phases, the micellar cubic phase (I2) and inverse micelles (L2). The systems are comparable as they were all prepared from the one lipid, glyceryl monooleate (GMO), which sequentially forms all four phases with increasing hexadecane (HD) content in excess water. Phase identity was confirmed by small angle X-ray scattering (SAXS). SAXS data indicated that four mesophases were formed with increasing HD content at 25°C: V2 phase (Pn3m space group) formed at 0–4% (w/w) HD, H2 phase formed at 4–25% (w/w) HD, I2 phase (Fd3m space group) formed at 25–40% (w/w) HD and finally L2 phase formed at >40% (w/w) HD. Analogous compositions using phytantriol rather than GMO as the core lipid did not produce the I2 phase, with only V2 to H2 to L2 transitions being apparent with increasing HD concentration. In order to relate the liquid crystal phase structure to drug release rate, in vitro release tests were conducted by incorporating radio-labelled glucose as a model hydrophilic drug into the four GMO-based mesophases. It was found that the drug release followed first-order diffusion kinetics and was fastest from V2 followed by L2, H2, and I2. Drug release was shown to be significantly faster from bicontinuous cubic phase than the other mesophases, indicating that the state of the water compartments, whether open or closed, has a great influence on the rate of drug release. It is envisioned that liquid crystalline mesophases with slower release characteristics will more likely have potential applications as sustained release drug delivery systems, and hence that the bicontinuous cubic phase is not necessarily the best choice for a sustained release matrix.

Effect of mixed costabilizers on Ostwald ripening of monomer miniemulsions

The role of the mixed costabilizers of cetyl alcohol (CA) and hexadecane (HD) in retarding Ostwald ripening occurring in the three-component disperse phase monomer miniemulsions at 25 °C was investigated. The modified Kabalnov equation failed to describe the Ostwald ripening behavior. Thus, the miniemulsion disperse phase comprising monomer (methyl methacrylate (MMA) or styrene (ST)) and the mixed costabilizers of CA and HD was simply treated as a pseudo-two-component disperse phase miniemulsion system. All the results that are self-consistent with one another justify the validity of the proposed pseudo-two component disperse phase miniemulsion model. A unique feature observed in this study is the synergistic effect of the mixed costabilizers of CA and HD in retarding the Ostwald ripening process.

Synthesis, characterization and properties of a novel fluorinated methacrylate polymer

A fluorinated monomer of 2-(2,2,2-trifluoroethoxy)ethyl methacrylate (FEMA) was prepared by a “one pot” process and then a novel fluorinated methacrylate polymer, poly[2-(2,2,2-trifluoroethoxy)ethyl methacrylate] (PFEMA), was successfully synthesized via miniemulsion polymerization using cetyltrimethyl ammonium bromide (CTAB) as emulsifier, hexadecane (HD) as co-stabilizer and 2,2′-azobisisobutyronitrile (AIBN) as initiator. The chemical structure of PFEMA was characterized by FT-IR, 1H NMR and 19F NMR. GPC results show that the number average molecular weight ( M n) of PFEMA was as high as 8.5 × 10 5 g/mol and the polydispersity index (PDI) was only 1.3. SEM and DLS characterizations showed that the morphology of PFEMA latex was uniform spheres with the diameter of about 110–125 nm. It was also found that PFEMA has high thermo-stability ( T d > 200 °C), low glass transition temperature ( T g = 13.0 °C), and nice hydrophobicity ( θ water = 99.9°). Comparison studies on PFEMA and poly(2,2,2-trifluoroethyl methacrylate) show that an introduced functional group (–CH 2CH 2O–) has a significant effect on lowering T g and improving hydrolysis resistance without impairing surface properties.

Preparation and characterization of poly(MMA–BA)/nano-ATO hybrid latex via miniemulsion polymerization

The poly(methyl methacrylate–n-butyl acrylate)/nano-antimony-doped tin oxide (ATO) hybrid latices were prepared successfully via miniemulsion polymerization in the presence of emulsifier sodium dodecyl sulfate (SDS) and costabilizer hexadecane (HD). Several factors affecting the encapsulation efficiency of nano-ATO were studied. The prepared hybrid latices were characterized using transmission electron microscopy, dynamic light scattering particle size analysis, thermogravimetric analysis, and ultraviolet–visible-near infrared (NIR) spectra. The results show that the encapsulation efficiency of nano-ATO reaches the maximum value of 78.0% with 3 wt% of nano-ATO, 4 wt% of SDS, and 4 wt% of HD, and the mean diameter of hybrid latex particles is 87.5 nm. Both the weight loss ratio and the transmittance in NIR region of hybrid film decrease with the increasing nano-ATO amount. The prepared hybrid film containing nano-ATO exhibits excellent ability for shielding IR light with high transmittance in visible region, which can be used as transparent a heat-insulating coating for energy savings.

Preparation of Raspberry-like Nanocapsules by the Combination of Pickering Emulsification and Solvent Displacement Technique

Well-defined raspberry-like nanocapsules were prepared by the combination of Pickering emulsification and solvent displacement technique by using silica particles as stabilizer and hexadecane (HD) as soft template. The formation of the capsule morphology is caused by the phase separation of poly(styrene-co-4-vinyl pyridine) (poly(St-co-4-VP)) in the droplets due to the diffusion of good solvent for the (co)polymer to the aqueous continuous phase. The size of capsules was successfully reduced from tens of micrometers in the dispersion by simply stirring to the nanorange by the employment of sonication and Ostwald ripening. The formation of silica-particles-armored nanocapsules was confirmed by transmission electron microscopy (TEM), high-resolution scanning electron microscopy (HRSEM), dynamic light scattering (DLS), and zeta potential measurement. The colloidal stability and particle properties, including size and morphology, depend on the amount of HD, and copolymers, the sonication time, the dispersion pH value, the type of solvent, and the copolymer composition.

Dielectric properties of quinoline, 4,6-dimethyldibenzothiophene and hexadecane as model compounds in the upgrading of LCO

The dielectric properties of 4,6-dimethyldibenzothiophene (DMDBT), hexadecane (HD), quinoline (QL), and HD/QL mixtures were investigated at six microwave frequencies (0.4, 0.9, 1.4, 1.9, 2.5 and 3.0 GHz) and temperatures ranging from 297 K to 624 K. While both DMDBT and HD exhibited limited response under these conditions, QL demonstrated high dielectric loss with a penetration depth comparable to that of water. Through the use of the Debye relationship and solvent mixing rules, a model is proposed to predict the dielectric constant and loss factor for HD/QL mixtures. Based on the observed dielectric behaviour of QL, microwave-assisted separation/conversion may be effective during upgrading of light cycle oil (LCO) for similar, difficult-to-remove nitrogen compounds.

Dynamic Technique to Determine Hexadecane Transfer Rate from Organic Phase to Aqueous Phase in a Three-Phase Bioreactor

Determination of mass transfer of non-water soluble substrates, as hexadecane (HXD), is an important constraint in three-phase airlift bioreactor. A new simple dynamic technique able to measure the hexadecane transfer rate (HTR) in a three-phase airlift bioreactor (ALB) was studied in this work. The image analyses technique allowed measuring the resulting specific mass transfer area (aHXD). Gas chromatography was used to measure time-dependent transferred HXD and therefore the HXD transfer coefficient (kLHXD). Finally, HTR was calculated by using the equation HTR = kLaHXD•(CHXD* - CHXD) where CHXD* and CHXD are the saturation HXD-aqueous interphase and HXD aqueous phase concentration, respectively. As case study, we successfully applied to the measurement of HTR during a typical ALB microbial consortium culture; values from 0.010 to 0.042 mg HXD (L h)-1 were found. This technique could be used to compare similar simultaneously occurring parameters to assess mass transfer constraints in three-phase systems.

Dynamic Technique to Determine Hexadecane Transfer Rate from Organic Phase to Aqueous Phase in a Three-Phase Bioreactor

Determination of mass transfer of non-water soluble substrates, as hexadecane (HXD), is an important constraint in three-phase airlift bioreactor. A new simple dynamic technique able to measure the hexadecane transfer rate (HTR) in a three-phase airlift bioreactor (ALB) was studied in this work. The image analyses technique allowed measuring the resulting specific mass transfer area (aHXD). Gas chromatography was used to measure time-dependent transferred HXD and therefore the HXD transfer coefficient (kLHXD). Finally, HTR was calculated by using the equation HTR = kLaHXD•(CHXD* - CHXD) where CHXD* and CHXD are the saturation HXD-aqueous interphase and HXD aqueous phase concentration, respectively. As case study, we successfully applied to the measurement of HTR during a typical ALB microbial consortium culture; values from 0.010 to 0.042 mg HXD (L h)-1 were found. This technique could be used to compare similar simultaneously occurring parameters to assess mass transfer constraints in three-phase systems.

Surfactant-Free Miniemulsion Polymerization as a Simple Synthetic Route to a Successful Encapsulation of Magnetite Nanoparticles

Due to the existing interest in new hybrid particles in the colloidal range based on both magnetic and polymeric materials for applications in biotechnological fields, this work is focused on the preparation of magnetic polymer nanoparticles (MPNPs) by a single-step miniemulsion process developed to achieve better control of the morphology of the magnetic nanocomposite particles. MPNPs are prepared by surfactant-free miniemulsion polymerization using styrene (St) as a monomer, hexadecane (HD) as a hydrophobe, and potassium persulfate (KPS) as an initiator in the presence of oleic acid (OA)-modified magnetite nanoparticles. The effect of the type of cross-linker used [divinylbenzene (DVB) and bis[2-(methacryloyloxy)ethyl] phosphate (BMEP)] together with the effect of the amount of an aid stabilizer (dextran) on size, particle size distribution (PSD), and morphology of the hybrid nanoparticles synthesized is analyzed in detail. The mixture of different surface modifiers produces hybrid nanocolloids with various morphologies: from a typical core-shell composed by a magnetite core surrounded by a polymer shell to a homogeneously distributed morphology where the magnetite is uniformly distributed throughout the entire nanocomposite.

Synthesis of raspberry‐like organic–inorganic hybrid nanocapsules via pickering miniemulsion polymerization: Colloidal stability and morphology

AbstractRaspberry‐like hybrid nanocapsules with a hydrophobic liquid core were successfully prepared via the copolymerization of styrene, divinylbenzene (DVB), and 4‐vinyl pyridine (4‐VP) in Pickering‐stabilized miniemulsions by using silica particles as the sole emulsifier and hexadecane (HD) as liquid template. When compared with conventional Pickering miniemulsions and Pickering suspensions, the colloidal stability of the current systems is much more sensitive to the variation of reaction parameters such as pH, size, amount of silica particles, and content of 4‐VP. The systems without coagulum were only obtained in a narrow pH range at around 9.5 and by using 12 nm silica particles as emulsifier. The formation of well‐defined raspberry‐like capsules was confirmed by transmission electron microscopy (TEM) and high‐resolution scanning electron microscopy (HRSEM). The stable attachment of silica particles on the surface of hybrid particles was verified by centrifugation and subsequent characterizations, such as Fourier transform infrared spectroscopy, TEM, and HRSEM. The influence of pH and weight content of HD, DVB, and 4‐VP on the particle morphology was extensively investigated. Interestingly, the particle morphology strongly depends on the particle size. When compared with the organic surface‐active surfactant, the formation of capsule morphology could be promoted by the application of silica particles taking advantage of their surface inactivity. The formation mechanisms of capsules/solid particles are discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Controlling morphology of polymer microspheres by Shirasu porous glass (SPG) membrane emulsification and subsequent polymerization: from solid to hollow

In this study, the solid, porous, and hollow polymer microspheres were prepared using a simple and novel production method based on Shirasu porous glass (SPG) membrane emulsification and suspension polymerization. With the SPG membrane, uniform-sized emulsion monomer droplets containing divinyl benzene (DVD), styrene (St), hexadecane (HD), and an initiator were prepared in an aqueous phase using a membrane emulsification technique. The aqueous phase contained hydroquinone (HQ) as a water-soluble inhibitor and polyvinylpyrrolidone (PVP) as a stabilizer. The morphology of the particles was affected by the stabilizer, St/DVB ratio, hexadecane amount, and initiator amount. Through this study, the porous polymer microspheres were achieved when the HD content was 30 wt% relative to the monomer and the hollow polymer microspheres was achieved when the HD content was more than 62.5 wt% relative to the monomer. These results highlight the phase separation speed between polystyrene (PSt) and HD.

Poly(BMA-co-NVP)/NiS core-shell hybrid materials via Interfacial-initiated miniemulsion copolymerization and gamma-irradiation

In this work, N-butyl methacrylate (BMA)/N-vinyl-2-pyrrilidone (NVP) amphiphilic core-shell nanoparticles were successfully prepared via miniemulsion copolymerization, the emulsion was initiated by the redox initiation couple of cumene hydroperoxide (CHPO) and ferrous sulfate hydrate (FS). The synthetic waterborne polyurethane (WPU) was used as surfactant and hexadecane (HD) as co-stabilizer, respectively. FTIR and XPS were used to confirm the occurrence of copolymerization between two monomers. TEM and DLS were used to observe the particle morphology and determine the particle size and its polydispersity index (PDI). It was found that the core-shell poly(BMA-co-NVP) nanoparticles prepared via interfacial-initiated miniemulsion copolymerization (IMEP) had relatively small diameters (40–120 nm) and narrowly particle size distribution (0.066–0.243). Only about 2 wt% surfactants based on the solution was enough to prepare a stable miniemulsion. The results demonstrated that IMEP prompted the copolymerization of water-soluble NVP monomer with oil-soluble BMA monomer to form core-shell nanoparticles. The effects of surfactant and co-stabilizer affect on the miniemulsion copolymerization were discussed. All the results indicate that the fabrication amphiphilic core-shell nanoparticles via IMEP were successful. Then the poly(BMA-co-NVP)/NiS hybrid materials were fabricate via the reaction of NiSO4 and CH3CSNH2 on the copolymers surface under 60Co γ-irradiation at room temperature and ambient pressure. The hybrid materials were characterized by FESEM.

Enhanced hexadecane degradation and low biomass production by Aspergillus niger exposed to an electric current in a model system

The effects of an electric current on growth and hexadecane (HXD) degradation by Aspergillus niger growth were determined. A 450-mL electrochemical cell with titanium ruthenium-oxide coated electrodes and packed with 15 g of perlite (inert biomass support) was inoculated with A. niger (2.0×10(7) spores (g of dry inert support)(-1)) and incubated for 12 days (30 °C; constant ventilation). 4.5 days after starting culture a current of 0.42 mA cm(-2) was applied for 24h. The current reduced (52±11%) growth of the culture as compared to that of a culture not exposed to current. However, HXD degradation was 96±1.4% after 8 days whereas it was 81±1.2% after 12 days in control cultures. Carbon balances of cultures not exposed to current suggested an assimilative metabolism, but a non-assimilative metabolism when the current was applied. This change can be related to an increase in total ATP content. The study contributes to the knowledge on the effects of current on the mycelial growth phase of A. niger, and suggests the possibility of manipulating the metabolism of this organism with electric current.

Preparation of polymer nanocapsules for use as carriers via one-step redox interfacially initiated miniemulsion polymerization

In this work, one-step redox interfacially initiated miniemulsion polymerization (IMEP) was employed to fabricate polystyrene (PS) nanocapsules 80 nm in diameter with a 2,2′-bipyridine core by the redox-initiated coupling of cumene hydroperoxide (CHPO) to iron(II) sulfate (FS) using waterborne polyurethane (WPU) as surfactant and hexadecane (HD) as costabilizer. The morphology of the nanocapsules was characterized by transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). Dynamic light scattering (DLS) was used to determine the size and polydispersity of the nanocapsules. It was found that the latexes prepared by miniemulsion polymerization via the redox-initiated method had relatively small diameters (40–100 nm) and a relatively narrow particle size distribution index (PDI: 0.086–0.124), which indicated that polymeric nanoparticles with small diameters and a narrow PDI can easily be prepared via one-step IMEP. The release of 2,2′-bipyridine from the nanocapsules was monitored by UV-visible spectroscopy. These results indicate that polymeric nanocapsules with a functional liquid core can be successfully fabricated via IMEP.

MINI-EMULSIFICATION AND MINI-EMULSION POLYMERIZATION OF METHYL METHACRYLATE/NANOSILICA DIPSERSION

The mini-emulsification and mini-emulsion polymerization of methyl methacrylate(MMA)/nanosilica dispersion were investigated.The mini-emulsification was carried out by ultrasonic treatment.It was found that more than 90% silica particles would be escaped from submicron MMA droplets to water phase after ultrasonic treatment when MMA/unmodified silica dispersion was used.Almost all silica particles stably stayed in MMA droplets when silica particles were treated by 3-(trimethoxysilyl)propyl methacrylate(MPS) coupling agent at 40℃ for 24 h before being dispersed in aqueous phase.This was caused by the effective grafting of MPS onto silica particles,and the decrease of hydrophilicity of silica particles.Poly(methyl methacrylate)/nanosilica composite latex particles were prepared by mini-emulsion polymerization of silica-containing MMA using sodium lauryl sulfate(SDS) as the surfactant and hexadecane(HD) as the costabilizer.The composite latex particles were dispersed stably,the surfaces of composite latex were sleek and the silica particles could hardly be found in the water phase.It was considered that the silica particles had been encapsulated in the composite particles.

One-step preparation of PS/TiO 2 nanocomposite particles via miniemulsion polymerization

This paper presents a one-step method to fabricate PS/TiO 2 nanocomposite particles via miniemulsion polymerization technique. In this approach, styrene (St) and acetylacetone (Acac) chelated tetra-n-butyl titanate (TBT) were confined in the miniemulsion droplets with the aid of cationic surfactant cetyl trimethyl ammonium bromide (CTAB) and co-stabilizer hexadecane (HD). During the polymerization of St, TBT diffused towards the surface of the miniemulsion droplets owing to its hydrophilicity and yielded TiO 2 particles via a sol–gel process. With the electrostatic interaction between the positively charged CTAB and negatively charged Ti-OH, TiO 2 particles were coated onto the PS cores to form PS/TiO 2 nanocomposite particles.

Fabrication method of TiO 2–SiO 2 hybrid capsules and their UV-protective property

This article presents a novel miniemulsion-combined sol–gel process to fabricate TiO 2–SiO 2 hybrid capsules. In this approach, the oil phase composed of acetylacetone (Acac) modified titanium (IV) butoxide (TBT), dimethyl benzene (DB) and hexadecane (HD) is confined in the miniemulsion droplet microreactors with the aid of a cationic emulsifier hexadecyltrimethylammonium bromide (CTAB). Then, a silica layer was coated onto the miniemulsion droplets by the co-condensation of amino-silane and tetraethyl silicate (TEOS). At the same time, TBT in the miniemulsion droplets diffused to the O/W interface and then initiated the sol–gel reaction, hence TiO 2–SiO 2 hybrid shell with TiO 2 colloids loading inside formed. TEM, FTIR, EDX and XPS indicated that TiO 2–SiO 2 hybrids possess hollow-like structure, with small titania colloids loaded in the titania/silica hybrid shells. Some influencing parameters, such as the concentrations of TBT in the oil droplet, the content of amino-silane in the silica precursor, on the morphology of the TiO 2–SiO 2 hybrid capsules were investigated. UV–vis spectra and dye degradation experiments showed that the polyurethane films doped with these hybrid colloids had a very good UV-protective property.