Presence Of Polyethylene Oxide Research Articles

Separation of chalcopyrite from a siliceous copper ore using polyethylene oxide as a depressant: An experimental study complimented by theoretical investigation

The separation of quartz and chalcopyrite during flotation in the presence of polyethylene oxide was investigated experimentally and theoretically. It was observed that the polymer adsorbs onto chalcopyrite more than onto quartz especially in high alkaline environment and this was confirmed theoretically. FTIR results of chalcopyrite-polymer system due to complexation were unveiled theoretically using quantum theory of atoms in molecules to consist of conventional hydrogen bonding with other non-covalent bonds and partially covalent interaction, while quartz-polyethylene complex was revealed to be due to conventional hydrogen bonding only. Therefore, flotation tests were performed on a mimicked siliceous-chalcopyrite synthetic mixture for Mpanda Mineral Field from Tanzania using polyethylene oxide as a chalcopyrite depressant. Flotation tests of quartz and chalcopyrite using 60 g/t of octadecan-1-amine and potassium amyl xanthate, respectively at 100 g/t and 500 g/t of polyethylene oxide at pH 10.5 ± 0.1, yielded Cu grades of 14.7% and 16.7% with recoveries of 70.7% and 75.0%. Therefore, polyethylene oxide could be a potential chalcopyrite depressant.

Polyethylene oxide assisted separation of molybdenite from quartz by flotation

Low flotation efficiency has been suffered in beneficiation of low-grade molybdenum ores due to finer size liberation and crystal anisotropy. As reported, polyethylene oxide (PEO) was proved to improve flotation efficiency of micro-fine molybdenite particles visibly. In this study, PEO was employed to investigate the influence on flotation of micro-fine molybdenite particles from mixed ores and the underlying mechanisms were fully discussed by Atomic Force Microscopy (AFM), Focused Beam Reflectance Measurement (FBRM), Dynamic Light Scattering etc. The results showed that high consumption of kerosene could not achieve a desired recovery in flotation of micro-fine molybdenite from quartz. The introduction of PEO considerably increased flotation efficiency of molybdenite from quartz, and flotation selectivity was improved via pH and stirring speed adjustment. In the presence of PEO, pH affected flocculation capacity of molybdenite slightly while the flocculation capacity of quartz had a strong dependence on the pH. Adsorption amount and hydrodynamic radius of PEO molecules resulted in the phenomenon jointly. Stirring speed had a prominent effect on flocculation, de-flocculation and re-flocculation behaviors of molybdenite and quartz. Higher stirring speed scrubbed quartz from flocs due to weak attractive forces between molybdenite and quartz to reduce heterogeneous flocculation. Moreover, strong attractive forces drove molybdenite flocs reformation when suspensions were re-submitted to low stirring speed while quartz lost the flocculation ability. Hence, higher selectivity was achieved in the flotation of molybdenite from quartz with appropriate pH and stirring speed.

Highly Elastic and Water Stable Zein Microfibers as a Potential Drug Delivery System for Wound Healing.

The development of biomaterials for wound healing applications requires providing a number of properties, such as antimicrobial action, facilitation of cell proliferation, biocompatibility and biodegradability. The aim of the present study was to investigate morphological and mechanical properties of zein-based microfibers, ultimately aimed at creating an environment suitable for wound healing. This was achieved through co-axial electrospinning of core–shell microfibers, with zein protein in the core and polyethylene oxide (PEO) in the shell. Small amounts of PEO or stearic acid were additionally incorporated into the fiber core to modify the morphology and mechanical properties of zein fibers. The presence of PEO in the core was found to be essential for the formation of tubular fibers, whereas PEO in the shell enhanced the stability of the microfibers in water and ensured high elasticity of the microfiber mats. Tetracycline hydrochloride was present in an amorphous form within the fibers, and displayed a burst release as a result of pore-formation in the fibers. The developed systems exhibited antimicrobial activity against Staphylococcus aureus and Escherichia coli, and showed no cytotoxic effect on fibroblasts. Biocompatibility, antimicrobial activity and favorable morphological and mechanical properties make the developed zein-based microfibers a potential biomaterial for wound healing purposes.

Effect of polyethylene oxide on flotation of molybdenite fines

The processing of low-grade deposits of molybdenite is becoming more urgent with the gradual depletion of high-grade molybdenite ores in China. Low flotation efficiency has been suffered due to finer sizes liberation resulted from finely disseminated nature of low-grade ores and crystal anisotropy. In this study, kerosene was used to collect the molybdenite fines with different sizes, but even high dosage of kerosene could not achieve high flotation recovery for molybdenite particles with finer sizes. However, the presence of polyethylene oxide (PEO) considerably increased the flotation efficiency of molybdenite. The mechanism of PEO effect on the molybdenite flotation was studied by molecular dynamics simulation, Atomic Force Microscopy (AFM), Focused Beam Reflectance Measurement (FBRM), etc. Molecular dynamics calculation shows PEO molecules were more susceptible to (010) plane than (001) plane, thereby promoting the adsorption of PEO on the finer molybdenite particles. The wettability results indicate molybdenite particles become more hydrophobic in the presence of PEO, especially for the edge planes. Thereby the attachment time between bubbles and molybdenite particles reduced significantly. Moreover, in PEO solution, larger attractive forces were detected between molybdenite surfaces at >100 nm, agreeing with the rapid formation of large flocs in the molybdenite suspension. Thus, PEO not only improves the surface hydrophobicity but also induces the flocculation of fine particles, both of which improve the flotation performances of molybdenite fine particles.

Formation of Indomethacin-Saccharin Cocrystals during Wet Granulation: Role of Polymeric Excipients.

Formulation of a cocrystal into a solid pharmaceutical dosage form entails numerous processing steps during which there is risk of dissociation. In an effort to reduce the number of unit operations, we have attempted the in situ formation of an indomethacin-saccharin (INDSAC) cocrystal during high-shear wet granulation (HSWG). HSWG of IND (poorly water-soluble drug) and SAC (coformer), with polymers (granulating agents), was carried out using ethanol as the granulation liquid and yielded INDSAC cocrystal granules. Therefore, cocrystal formation and granulation were simultaneously accomplished. Our objectives were to (i) evaluate the influence of polymers on cocrystal formation kinetics during wet granulation and (ii) mechanistically understand the role of polymers in facilitating the cocrystal formation. Polyvinylpyrrolidone (PVP), hydroxypropyl cellulose (HPC), and polyethylene oxide (PEO) were chosen to investigate the influence of soluble polymers. The cocrystal formation kinetics was influenced by the polymer (PVP < HPC < PEO) and its concentration. The interaction of the polymer with cocrystal components inhibited the cocrystal formation. Complete cocrystal formation was observed in the presence of PEO, a polymer which does not interact with IND and SAC.

Highly Efficient Fluorescence Resonance Energy Transfer in Electrospun Nanofibers Containing Pyrene and Porphyrin

Anionic HA nanofibers incorporated with cationic fluorescent dyes of pyrene and porphyrin have been prepared by electrospinning in the presence of polyethylene oxide. The emission spectra of fluorescent nanofibers reveal an energy transfer from pyrene to porphyrin with high FRET efficiency of 96% upon light excitation at 342 nm.

Phosphorylated and Cross‐Linked Wheat Starches in the Presence of Polyethylene Oxide and Their Application in Biocomposite Films

Wheat starch is modified by phosphorylation and cross‐linking. Starches are evaluated for phosphorus content, amylose content, swelling power, solubility, pasting properties, crystallinity, and morphology. Films are made with phosphorylated and cross‐linked starches, and with addition of 10% (w/w) polyethylene oxide (PEO). The films are evaluated for morphology, water vapor permeability, mechanical properties, crystallinity, roughness, and angle of contact with water. Phosphorylated starch shows higher phosphorus content, amylose content, swelling power, and solubility than cross‐linked starch and native starch did. The starch film containing PEO presents discontinuous morphology, is more crystalline and rugged, and less hydrophilic than starch films without PEO. The biocomposite proves promising for usage in flexible packaging.

INFLUENCE OF POLYETHYLENE OXIDE CONTENT ON SOME CHARACTERISTICS OF PLA/CS FILMS LOADING NIFEDIPINE

This work mentions the effect of polyethylene oxide (PEO) content on some characteristics and properties of polylactic acid (PLA)/chitosan (CS) films loading nifedipine (NIF). The water contact angle, droplet size values and Field Emission Scanning Electron Microscopy (FESEM) images of the films are used to investigate their morphology and hydrophobicity. The obtained results show that the hydrophobic property of the PLA/CS/NIF films is improved by the presence of PEO. Besides, the PLA/CS/NIF films containing PEO have tighter structure and water absorbed ability less than those of the PLA/CS/NIF films

Interfaces in polyethylene oxide modified cellulose nanocrystal - polyethylene matrix composites

The interface between cellulose nanocrystals (CNCs) in thermoplastic matrices is one of the most important issues prohibiting the development of CNC-based polymeric composites prepared via melt processing. In the present work, polyethylene oxide (PEO) was used as a compatibilizer to enhance the interface with a polyethylene matrix. It was found that the composites produced using a PEO compatibilizer possess better overall mechanical properties and a higher degree of crystallinity of the polyethylene than the unmodified samples. An increase in both the tensile strength and modulus of the composites was observed for up to 1.5 wt.% of CNCs; beyond this point no significant increases were observed. When CNCs were added (up to 1.5 wt.%) to the matrix, the crystallization peak of the composites in the DSC thermograms shifted to higher temperatures. The stress-transfer process in the composites was monitored using Raman spectroscopy. Higher Raman band shift rates with respect to tensile strain of a peak corresponding to main chain molecular deformation were observed for the composites produced using the PEO compatibilizer. This demonstrates that stress is transferred from the matrix to the fillers more effectively with the presence of PEO. The simple PEO-modification approach adopted in this study avoids the classical solvent method of production of CNC-based nanocomposites which is not really applicable at an industrial scale.

Biodegradable Porous Silk Microtubes for Tissue Vascularization.

Cardiovascular diseases are the leading cause of mortality around the globe, and microvasculature replacements to help stem these diseases are not available. Additionally, some vascular surgeries needing small diameter vascular grafts present different performance requirements. In this work silk fibroin scaffolds based on silk/polyethylene oxide blends were developed as microtubes for vasculature needs and for different tissue regeneration times, mechanical properties and structural designs. Systems with 13, 14 and 15% silk alone or blended with 1 or 2% of polyethylene oxide (PEO) were used to generate porous microtubes using gel-spinning. Microtubes with inner diameters (ID) of 150-300 μm and 100 μm wall thickness were fabricated. The systems were assessed for porosity, mechanical properties, enzymatic degradability, and in vitro vascular endothelial cell attachment and metabolic activity. After 14 days all tubes supported the proliferation of cells and cell attachment increased with porosity. The silk tubes with PEO had similar crystallinity but higher elastic modulus compared with the systems without PEO. The silk (13%)/PEO (1%) system showed the highest porosity (20 μm pore diameters on average), highest cell attachment and fastest degradation profile. There was a good correlation between these parameters with silk concentration and the presence of PEO. The results demonstrate the ability to generate versatile and tunable tubular biomaterials based on silk-PEO-blends with potential for microvascular grafts.

PLA/CS/Nifedipine Nanocomposite Films: Properties and the In Vitro Release of Nifedipine

The polylactic acid (PLA)/chitosan (CS) films containing a drug, nifedipine (NIF), in the presence of polyethylene oxide (PEO) as a compatibilizer were prepared by the solution method. This method has not been used to form films containing four components (PLA, CS, NIF, PEO) up to now. The CS, PEO, and NIF contents are 25 wt.%, 6–8 wt.%, and 10–50 wt.% in comparison with PLA weight, respectively. Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FESEM) were used to characterize the interactions, properties, and morphology of the PLA/CS/PEO/NIF films. The FTIR, TGA, and DSC results show that NIF carried by PLA/CS/PEO films and PLA, CS, NIF had better interaction and were more compatible when using PEO. The surface morphology of PLA/CS/PEO/NIF films was similar to that of PLA/CS/PEO films. Moreover, this was the first time drug loading and NIF release content from PLA/CS/PEO films were determined by the ultraviolet–visible (UV–Vis) spectroscopy method. The drug loading of PLA/CS/PEO/NIF films was from 80.99% to 93.61%. The in vitro NIF release studies were carried out in pH 2, 6.8, and 7.4 solutions corresponding to the pH of stomach, colon, and duodenum regions in the human body, respectively. The NIF release content in different pH solutions is in the order: pH 2 > pH 6.8 > pH 7.4 and increases when there is increasing NIF loading. The PLA/CS/PEO films are potential materials to apply for long-circulating systems for NIF delivery.

Effect of PEO molecular weight on sunlight induced photocatalytic activity of ZnO/PEO composites

ZnO spheroidal nanoparticles, synthesized by microwave processing, were used for preparation of composites with polyethylene oxide (PEO). The phase purity and crystal structure of the composites were investigated by X-ray diffraction (XRD) and Raman spectroscopy. The composites’ particles morphology and size distributions were studied by FE-SEM and laser diffraction particle size analyzer, respectively. The optical properties were studied using UV–Vis diffuse reflectance and photoluminescence spectroscopy. It is found that in the wavelength range 550–800nm, ZnO and ZnO/PEO composites absorb about 50% of the incident light intensity. Also red-shift of band gap energy (0.12–0.15eV) compared to bulk ZnO was determined. The effect of PEO molecular weights, 200,000, 600,000 and 900,000g/mol, on photocatalytic activity of ZnO/PEO composites were examined via de-colorization of methylene blue (MB) under direct sunlight irradiation. A large efficiency of MB de-colorization was found after 6h of irradiation. The enhanced photocatalytic activity of ZnO/PEO composites is attributed to the: (1) lattice defects introduced in ZnO crystal structure by rapid microwave processing, and (2) presence of PEO as a source of oxygen interstitials. In order to confirm and further clarify the experimental results ab initio calculations based on density functional theory (DFT) were performed.

A non-ionic surfactant-mediated sol–gel coating for solid-phase microextraction of benzene, toluene, ethylbenzene and o-xylene in water samples using a gas chromatography-flame ionization detector

In this study, sol–gel hybrid organic–inorganic materials were prepared in the presence of polyethyleneoxide (PEO) non-ionic surfactants (Triton X-100), which act as co-porogenic agents. For the first time, non-ionic surfactant mediated sol–gel coatings were evaluated by analyzing benzene, toluene, ethylbenzene and o-xylene (BTEX) in the aqueous samples. Two different fiber coatings were prepared including: un-modified poly(dimethylsiloxane) (PDMS) coating prepared from PDMS in the absence of Triton X-100 as a non-ionic surfactant (PDMS-no TX100), and modified PDMS coating prepared from this polymer in the presence of Triton X-100 as a porogenic agent and conditioned at a higher temperature than decomposition temperature of a non-ionic surfactant (PDMS-TX100). After the analytical procedure was optimized, the dynamic linear range obtained using PDMS-TX100 and PDMS-no TX100 fibers was 4–200 000 and 100–200 000 pg mL−1 and the limits of detection (S/N = 3) were 1–3 and 30–300 pg mL−1, respectively. The relative standard deviations (RSDs) for one fiber (repeatability) (n = 5) were from 3.1 up to 6.2% and between fibers or batch to batch (reproducibility) (n = 3) in the range of 4.2–7.7% for three fibers. The developed method was successfully applied to the real water samples while the relative recovery percentages obtained for the spiked water samples at 20 pg mL−1 of each analyte were from 94.41 to 104.05%.

Reducing the entrainment of clay minerals in flotation using tap and saline water

High gangue entrainment is a major problem in fine particle flotation. In this study, the entrainment of kaolinite Q38 in flotation was examined in tap and saline water. High molecular weight polyethylene oxide (PEO) was used to reduce the entrainment of kaolinite Q38 by enlarging the size of kaolinite particles in flotation. It was found that PEO reduced the entrainment significantly in flotation using tap water, but in saline water, the effect of PEO was less pronounced. The aggregation behaviour of kaolinite Q38 particles in the absence and presence of PEO and its effect on the entrainment of kaolinite Q38 were studied by the in-situ measurement of flocs and the size of enlarged particles, settling tests and the measurement of froth stability in flotation. It is interesting to find that PEO did flocculate kaolinite Q38 particles and enlarge their sizes in flotation despite high agitation. However, the reduction of the entrainment of kaolinite Q38 in flotation was dependent on the type of flocs formed and froth stability which can be modified by electrolytes in water and a high addition of PEO.

Interactions between Solid Surfaces Mediated by Polyethylene Oxide Polymers: Effect of Polymer Concentration

Using total internal reflection microscopy (TIRM), we have systematically measured the interactions between a microsphere and a flat hydrophilic surface in the presence of polyethylene oxide (PEO) polymer solution. Our results reveal that PEO significantly mediates the interaction forces between the two surfaces. At low polymer concentration, the interactions between two surfaces in the presence of PEO are mainly dominated by repulsive forces, originating from diffuse layer overlap. At intermediate polymer concentration, a long-range and weak attraction sets in. This force is likely attributed to the depletion attraction due to the presence of free PEO chains in bulk solution; however, a simple hard-sphere AO model fails to precisely describe the attraction. At high polymer concentration where PEO chains overlap, the attraction disappears, and levitation of the microsphere probe is detected. We argue that at this overlapping region, the correlation length of PEO chains is much smaller than the size of single PEO molecule, leading to weakening and disappearing of the depletion attraction. Finally, at very high concentration, oscillatory structural force is obviously found, indicating the significant structural ordering of the PEO chains under confinement.

Tailoring of Morphology and Surface Properties of Syndiotactic Polystyrene Aerogels

This study evaluates a method for rendering syndiotactic polystyrene (sPS) aerogels hydrophilic using polyethylene oxide (PEO) of different molecular weights. The highly porous sPS aerogels are inherently hydrophobic although applications involving absorption of moisture and removal of particulate solids may benefit from the high surface area of sPS aerogels provided some degree of hydrophilicity is induced in these materials. In this work, sPS gels are prepared by thermo-reversible gelation in tetrahydrofuran in the presence of PEO. The gels are dried under supercritical conditions to obtain aerogels. The aerogels are characterized by scanning electron microscopy, nitrogen-adsorption porosimetry, helium pycnometry, and contact angle measurements. The data reveal that the pore structures and surface energy can be controlled by varying the concentration and molecular weight of PEO and using different cooling rates during thermo-reversible gelation. In the first case, sPS aerogels, aerogels containing PEO of a low molecular weight or low concentration show superhydrophobic surface presenting the "lotus effect". In the second case, PEO at a higher concentration or with higher molecular weight forms phase-separated domains yielding new hydrophilic macropores (>10 μm) in the aerogel structures. These macropores contribute to the superhydrophobic surface with the "petal effect". The cooling rate during gelation shows a strong influence on these two cases.

Synergistic kinetic inhibition of natural gas hydrate formation

Rocking cells were used to investigate the natural gas hydrate formation and decomposition in the presence of kinetic inhibitor, Luvicap. In addition, the influence of poly ethylene oxide (PEO) and NaCl on the performance of Luvicap was investigated using temperature ramping and isothermal experiments. Luvicap decreased the hydrate nucleation temperature in ramping and increased the hydrate nucleation time at fixed temperatures. The presence of PEO and NaCl enhanced the nucleation inhibition strength of Luvicap. However the addition of Luvicap promoted the hydrate growth after nucleation. PEO does not affect hydrate growth whereas NaCl reduced the hydrate growth both in the presence and absence of Luvicap. In addition complex two-stage hydrate growth was observed in the presence of Luvicap. Moreover, the hydrate formed in the presence of inhibitor took longer time/higher temperature to decompose completely. One should consider this complex inhibitor-mediated hydrate formation and decomposition kinetics when screening and designing kinetic inhibitors for field applications.

Enhancement of Blue Spectral Response Intensity of PbS via Polyethylene Oxide-Adding for the Application to White LEDs

In this work, we have employed chemical bath deposition (CBD) method to obtain nanocrystalline PbS thin films in the presence of polyethylene oxide (PEO). The spectral response of Au/PbS-pSi(100)/Al Schottky photodiodes at different PEO amount were studied. The response exhibits a combined effect of photogeneration in the heterojunction (HJ) Si side and PbS. Spectral response were observed progressively at shorter wavelength due to the surface absorption. The peak centered at 410 nm properly corresponds to photo-exited holes being injected from PbS to the Si substrate. The intensity of the peak of R(λ) increases with PEO amount, this increasing was attributed to the decreasing of band gap (Eg).

Enhancement of the performance of kinetic inhibitors in the presence of polyethylene oxide and polypropylene oxide for binary mixtures during gas hydrate formation in a flow mini‐loop apparatus

AbstractThe objective of this work is to demonstrate the impact of the polyethylene oxide (PEO) and polypropylene oxide (PPO) on the performance of gas hydrate kinetic inhibitors for binary mixtures during gas hydrate formation in a flow mini‐loop apparatus. PEO and PPO are commercially available polymers that they have been considered to be unable to exhibit kinetic hydrate inhibition (KHI) by their self. Prevention of gas hydrate formation experiments in the presence of the KHIs solutions were conducted in a flow mini‐loop apparatus manner under suitable pressures and temperature conditions for binary gaseous mixtures including 70% CH4/30% C3H8, 30% CH4/70% C3H8, 70% CH4/30% i‐C4H10, and 30% CH4/70% i‐C4H10. In the experiments, induction time for crystallisation of gas hydrate formation and gas consumption rate are investigated in systems without KHI, containing KHI only (such as polyvinylpyrrolidone (PVP) and L‐tyrosine) and PEO or PPO together with KHI. Pressure is maintained at a constant value during experimental runs by means of required gas make‐up. The addition of a KHI into system delayed the onset of hydrate crystal nucleation. Furthermore, addition of the PEO or PPO to a KHI solution was found to enhance the performance of KHI. In addition, under the same pressure temperature hydrate formation conditions the induction time is longer when the PPO is present. Thus, inclusion of PPO into a KHI solution shows a higher enhancement in its inhibiting performance compare to PEO. © 2011 Canadian Society for Chemical Engineering

Reducing quartz gangue entrainment in sulphide ore flotation by high molecular weight polyethylene oxide

Polyethylene oxide (PEO) was tested to flocculate and depress fine quartz particles in the batch flotation of artificial mixtures of chalcopyrite–quartz as well as a commercial Au–Cu sulphide ore sample. The aggregation/dispersion behaviors of quartz, chalcopyrite and their mixtures in the presence of PEO with and without potassium amyl xanthate (KAX) were studied by photometric dispersion analysis (PDA), scanning electron microscopy (SEM) and zeta potential measurements. Batch flotation results indicated that the addition of low dosages of PEO improved value mineral recovery and concentrate grade during the flotation of both the artificial mixtures of chalcopyrite–quartz and the Au–Cu sulphide ore sample. Aggregation/dispersion test results revealed that the PEO caused non-selective flocculation of quartz and chalcopyrite, forming large hetero-aggregates. However, the addition of KAX caused the chalcopyrite particles to break away from the hetero-aggregates, leading to separate homo-aggregates of quartz and chalcopyrite. The flotation of the fine chalcopyrite and the depression of the fine quartz were thus both improved.