Grafting of temperature sensitive PNIPAAm on hydrophilised polysulfone UF membranes

Poly(N-isopropyl acrylamide) (PNIPAAm) was grafted on a polysulfone UF membrane. The changes of permeability as well as retention of PEG (35 kg/mol) and Dextran (500 kg/mol) between 23 and 60 °C were determined for both grafted and unmodified membranes. The results showed that the viscosity corrected water permeability and solute retention were almost constant for the unmodified membranes within the measured temperature range, the permeability of the grafted membranes increased and the retention of Dextran and PEG decreased with temperature. The variation of changes was most obvious in the temperature range 27–37 °C for the modified membranes due to the lower critical solution temperature (LCST) of PNIPAAm. The location and profile of PNIPAAm inside and on the surface of the membrane were analysed by SEM and FTIR. Depth profile calculation for FTIR spectra showed that PNIPAAm was mostly placed inside the membrane (at a depth of 1.06–1.10 μm from the surface) rather than on the surface. The amount of grafted PNIPAAm was low and did not significantly affect the morphology of the membrane. Therefore, a difference in SEM pictures of modified and unmodified membranes could not be seen. The modified membrane exhibited a clearly different thermal response compared to the unmodified one.     

Pyrolysis of textile wastes: I. Kinetics and yields

Thermal behavior of textile waste was studied by thermogravimetry at different heating rates and also by semi-batch pyrolysis. It was shown that the onset temperature of mass loss is within 104–156 °C and the final reaction temperature is within 423–500 °C. The average mass loss is 89.5%. There are three DTG peaks located at the temperature ranges of 135–309, 276–394 and 374–500 °C, respectively. The first two might be associated with either with decomposition of the hemicellulose and cellulose or with different processes of cellulose decomposition. The third peak is possibly associated to a synthetic polymer. At a temperature of 460 °C, the expected amount of volatiles of this waste is within 85–89%. The kinetic parameters of the individual degradation processes were determined by using a parallel model. Their dependence on the heating rate was also established. The pyrolysis rate is considered as the sum of the three reaction rates. The pyrolysis in a batch reactor at 700 °C and nitrogen flow of 60 ml/min produces 72 wt.% of oil, 13.5 wt.% of gas and 12.5 wt.% of char. The kinetic parameters of the first peak do not vary with heating rate, while those of the second and the third peak increase and decrease, respectively, with an increasing heating rate, proving the existence of complex reaction mechanisms for both cases.     

Flash pyrolysis of Silopi asphaltite in a free-fall reactor under vacuum

Flash pyrolysis experiments on asphaltite samples were performed in a free-fall reactor under vacuum to determine the effects of pyrolysis temperature, feed rate and particle size. Maximum liquid yield of 13 wt.% was obtained in free-fall reactor under vacuum when the pyrolysis temperature was 700 °C, feed rate was 0.4 g min⁻¹ and particle sizes were between 0.075 and 0.250 mm. The liquid products obtained at various pyrolysis conditions were analyzed by gas chromatography/mass spectrometer (GC/MS) and liquid products were classified as following: C5–C10, C11–C15, C16–C20 and C20+. The amount of saturated hydrocarbons decreased while the amount of unsaturated hydrocarbons increased with increase of temperature. While percent of C5–C10 unsaturated hydrocarbons continuously increased with increase of temperature, the percent of C11–C15 unsaturated hydrocarbons increased up to 750 °C and then started to diminish. Functional group analysis of solid residue was carried out using Fourier transform infrared spectrometry (FT-IR). The proximate analysis of solid residue indicated that percent of fixed carbon and ash increased with temperature.     

Raman scattering study of highly fluorinated graphite

Raman spectra of highly fluorinated C_xF samples (1<x<2) prepared at room temperature and 515°C were measured. C_xF samples prepared at room temperature exhibited two Raman bands at 1593–1583 and 1555–1542 cm⁻¹. Graphite samples fluorinated at 515°C for 1 and 2 min also gave similar bands at 1581–1580 and 1550–1538 cm⁻¹. However, graphite samples fluorinated from 15 min to 10 h at 515°C no longer showed such spectra. The Raman peaks shifted to lower frequencies with increasing fluorine concentration in C_xF. This trend is due to the weakening of the C---C bonds of the graphene layers. Observation of both kinds of Raman bands suggests the coexistence of two highly fluorinated phases, C₂F and C₁F, in the samples. The process of formation of graphite fluoride is discussed on the basis of the Raman spectra of C_xF samples obtained at 515°C.     

Thermal behaviour of lyocell fibres

Fourier-transform infrared (FTIR) spectroscopy has been applied in combination with wide-angle X-ray diffraction and measurements of strength, fluidity, yellowness, birefringence, and moisture regain to detect microstructural changes in lyocell fibres, a regenerated cellulose fibre, subjected to direct heat and annealing treatments. TMA, and SEM were used to show the effect of direct heat and annealing on lyocell fibres. The FTIR spectroscopy results show that a decrease in intermolecular hydrogen bonding occurs at 70 and 80 °C for annealed and directly heated samples, respectively. The results demonstrate increase of the intensity of O–H stretching vibrations, this associated with hydrogen bonds reforming around 130 °C. Lyocell fibres shrink with direct heating in the temperature range 130–160 °C. The crystallinity decreases gradually with increasing temperature. There is no significant change in colour of the samples annealed up to 150 °C. A continuous increase in the fluidity occurs for the annealed samples in the range 150–230 °C. The tenacity and breaking extension of heated samples decrease with increasing temperature. The lower annealing temperatures cause no observable change in the smooth and void-free surface, but in the annealing temperature range 170–230 °C, substantial non-uniformity is apparent on the surface of the fibres.     

The direct synthesis of dimethyl ether from syngas over hybrid catalysts with sulfate-modified γ-alumina as methanol dehydration components

A series of γ-Al₂O₃ samples modified with various contents of sulfate (0–15 wt.%) and calcined at different temperatures (350–750 °C) were prepared by an impregnation method and physically admixed with CuO–ZnO–Al₂O₃ methanol synthesis catalyst to form hybrid catalysts. The direct synthesis of dimethyl ether (DME) from syngas was carried out over the prepared hybrid catalysts under pressurized fixed-bed continuous flow conditions. The results revealed that the catalytic activity of SO₄²⁻/γ-Al₂O₃ for methanol dehydration increased significantly when the content of sulfate increased to 10 wt.%, resulting in the increase in both DME selectivity and CO conversion. However, when the content of sulfate of SO₄²⁻/γ-Al₂O₃ was further increased to 15 wt.%, the activity for methanol dehydration was increased, and the selectivity for DME decreased slightly as reflected in the increased formation of byproducts like hydrocarbons and CO₂. On the other hand, when the calcination temperature of SO₄²⁻/γ-Al₂O₃ increased from 350 °C to 550 °C, both the CO conversion and the DME selectivity increased gradually, accompanied with the decreased formation of CO₂. Nevertheless, a further increase in calcination temperature to 750 °C remarkably decreased the catalytic activity of SO₄²⁻/γ-Al₂O₃ for methanol dehydration, resulting in the significant decline in both DME selectivity and CO conversion. The hybrid catalyst containing the SO₄²⁻/γ-Al₂O₃ with 10 wt.% sulfate and calcined at 550 °C exhibited the highest selectivity and yield for the synthesis of DME.     

Small-angle neutron scattering study on microstructure of poly(N-isopropylacrylamide)-block-poly(ethylene glycol) in water

By employing small-angle neutron scattering (SANS), we investigated the microstructures of, poly(N-isopropylacrylamide) (PNIPA)-block-poly(ethylene glycol) (PEG) (NE) in deuterated water D₂O, as related to macroscopic behaviors of fluidity, turbidity and synerisis. SANS revealed following results: (i) microphase separation occurs at around above 17 °C in a temperature range of transparent sol below 30 °C. In the microdomain appeared in the transparent sol state, both block chains of PNIPA and PEG are swollen by water; (ii) for the NE solution of polymer concentration W_p > 3.5% (w/v), corresponding to opaque gel above 30 °C, a percolated structure, i.e., network-like domain is formed by NE as a result of macrophase separation due to dehydration of the PNIPA chains. As the temperature increases toward 40 °C, the network domain is squeezed along a direction parallel to the NE interface, which leads to increase of the interfacial thickness given by swollen PEG chains and to the macroscopic synerisis behavior.     

A simultaneous TG–DTA study of the thermal decomposition of 2-hydroxybenzoic acid, 2-carboxyphenyl ester (salsalate)

Simultaneous thermogravimetry–differential thermal analysis (TG–DTA) and gas and liquid chromatography with mass spectrometry detection have been used to study the kinetics and decomposition of 2-hydroxybenzoic acid, 2-carboxyphenyl ester, commercially known as salsalate. Samples of salsalate were heated in the TG–DTA apparatus in an inert atmosphere (100 ml min⁻¹ nitrogen) in the temperature range 30–500 °C. The data indicated that the decomposition of salsalate is a two-stage process. The first decomposition stage (150–250 °C) had a best fit with second-order kinetics with E_a=191–198 kJ/mol. The second decomposition stage (300–400 °C) is described as a zero-order process with E_a=72–80 kJ/mol. The products of the decomposition were investigated in two ways:

(a)Salsalate was heated in a gas chromatograph at various isothermal temperatures in the range 150–280 °C, and the exit gas stream analyzed by mass spectrometry (GC–MS). This approach suggested that salsalate decomposes with the formation of salicylic acid, phenol, phenyl salicylate, and cyclic oligomers of salicylic acid di- and tri-salicylides.

(b)One gram samples of salsalate were heated in a vessel under nitrogen to 150 °C, and the residues were analyzed by liquid chromatography–mass spectrometry (LC–MS). The major compound detected was a linear tetrameric salicylate ester.

     

Thermoluminescence characteristics of minerals from irradiated potatoes of different origins of production

Thermoluminescence (TL) characteristics were investigated for minerals, which were separated from potatoes irradiated at 0–1 kGy of different origins of production in Korea. The polyminerals analyzed by X-ray diffractometer were mainly composed of quartz and feldspar, and showed varied contents with producing origins, that contributed to typical TL responses to irradiation. The glow curve of irradiated samples at 0.05–1 kGy peaked at approximately 200°C with high intensity, but that of non-irradiated potatoes was observed at approximately 300°C with low intensity. Discrimination between irradiated (more than 0.05 kGy) and non-irradiated samples was possible just on the basis of the first glow curve, however, normalization of results through a re-irradiation step greatly improved their reliability. The signal intensity of TL decreased with the lapse of post-irradiation time under different storage conditions (0±0.5°C/dark room, 25±5°C/dark room and 25±5°C/naturally lighted room) but was still distinguishable from that of the non-irradiated sample even after one year.     

Detoxification of brominated pyrolysis oils

The development of an innovative technology for the pyrolytic conversion of brominated phenols in a reductive medium aimed at product recovery for commercial use is discussed in this paper. Brominated phenols are toxic products, which contaminate pyrolysis oil of wastes from electronic and electrical equipment (WEEE). The pyrolysis experiments were carried out with 2,6-dibromophenol, tetrabromobisphenol A, WEEE pyrolysis oil and polypropylene or polyethylene in encapsulated ampoules under inert atmosphere in quasi-isothermal conditions (300–400 °C) with a different residence time (10–30 min). Optimal conditions were found to be the use of polypropylene at 350 °C with a residence time of 20 min. The main pyrolysis products were identified as HBr and phenol. A radical debromination mechanism for the pyrolytic destruction of brominated phenols is suggested.     

Correlations between distribution coefficients of various biomolecules in different polymer/polymer aqueous two-phase systems

Distribution coefficients for a variety of proteins and certain other biomolecules (peptides, amino acids, and carbohydrates) (overall 27 different solutes) were measured in aqueous two-phase systems (ATPSs) dextran (Dex)–polyethylene glycol (PEG) and Dex–Ucon 50-HB-5100 (Ucon—a random copolymer of ethylene glycol and propylene glycol) both containing 0.15 M NaCl in 0.01 M phosphate buffer, pH 7.4, at 23 °C. Distribution coefficients of some selected solutes were also measured in the above two-phase systems at three different polymer concentrations for each system. It was established that the distribution coefficients for all the proteins examined in the ATPSs are correlated according to the so-called Collander linear equation.     

Zirconia-supported phosphotungstic acid as catalyst for alkylation of phenol with benzyl alcohol

The liquid-phase alkylation of phenol with benzyl alcohol was carried out using zirconia-supported phosphotungstic acid (PTA) as catalyst. The catalysts with different PTA loadings (5–20 wt.% calcined at 750 °C) and calcination temperature (15 wt.% calcined from 650 to 850 °C) were prepared and characterized by ³¹P MAS NMR and FT-IR pyridine adsorption spectroscopy. The catalyst with optimum PTA loading (15%) and calcination temperature (750 °C) was prepared in different solvents. ³¹P MAS NMR spectra of the catalysts showed two types of phosphorous species, one is the Keggin unit and the other is the decomposition product of PTA and the relative amount of each depends on PTA loading, calcination temperature and the solvent used for the catalyst preparation. The catalysts with 15% PTA on zirconia calcined at 750 °C showed the highest Brönsted acidity. At 130 °C and phenol/benzyl alcohol molar ratio of 2 (time, 1 h), the most active catalyst, 15% PTA calcined at 750 °C gave 98% benzyl alcohol conversion with 83% benzyl phenol selectivity.     

Phase behavior, conformations, thermodynamic properties, and molecular motion of multicomponent paraffin waxes: A Raman spectroscopy study

Variable-temperature (72–20 °C) studies of Raman spectra (3100–800 cm⁻¹) and thermal analysis of multicomponent paraffin wax have been carried out. The disorder–order transition under liquid–solid transition was observed and their temperature ranges were obtained through the S_lateral order parameter as a function of temperature. From 56 to 43 °C, the paraffin undergoes a conformational state transition of non-extended chain state (NECS) to extended chain state (ECS). The enthalpy and entropy change for the transition obtained by van’t Hoff analysis were 214.286 ± 21 kJ/mol and 0.661 ± 0.066 kJ/mol/K, respectively. The enthalpy determined by differential scanning calorimetry (DSC) was 52.165 ± 5.2 kJ/mol, which is smaller than the van’t Hoff enthalpy due to larger effective non-extended chain state. The variation of Raman spectra with decreasing temperature presents the structure evolution and molecular motion during the crystallization of paraffin wax.     

Stability of phospholipid vesicles studied by asymmetrical flow field-flow fractionation and capillary electrophoresis

The stability of zwitterionic phosphatidylcholine vesicles in the presence of 20 mol% phosphatidyl serine (PS), phosphatidic acid (PA), phosphatidyl inositol (PI), and diacylphosphatidyl glycerol (PG) phospholipid vesicles, and cholesterol or calcium chloride was investigated by asymmetrical flow field-flow fractionation (AsFlFFF). Large unilamellar vesicles (LUV, diameter 100 nm) prepared by extrusion at 25 °C were used. Phospholipid vesicles (liposomes) were stored at +4 and −18 °C over an extended period of time. Extruded egg yolk phosphatidylcholine (EPC) particle diameters at peak maximum and mean measured by AsFlFFF were 101 ± 3 nm and 122 ± 5 nm, respectively. No significant change in diameter was observed after storage at +4 °C for about 5 months. When the storage period was extended to about 8 months (250 days) larger destabilized aggregates were formed (172 and 215 nm at peak maximum and mean diameters, respectively). When EPC was stored at −18 °C, large particles with diameters of 700–800 nm were formed as a result of dehydration, aggregation, and fusion processes. In the presence of calcium chloride, EPC alone did not form large aggregates. Addition of 20 mol% of negatively charged phospholipids (PS, PA, PI, or PG) to 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) vesicles increased the electrostatic interactions between calcium ion and the vesicles and large aggregates were formed. In the presence of cholesterol, large aggregates of about 250–350 nm appeared during storage at +4 and −18 °C for more than 1 day.

The effect of liposome storage temperature on phospholipid coatings applied in capillary electrophoresis (CE) was studied by measuring the electroosmotic flow (EOF). EPC coatings with and without cholesterol, PS, or calcium chloride, prepared from liposomes stored at +25, +4, and −18 °C, were studied at 25 °C. The performances of the coatings were further evaluated with three uncharged compounds. Only minor differences were observed between the same phospholipid coatings, showing that phospholipid coatings in CE are relatively insensitive to storage at +25, +4 °C or −18 °C.     

Thermal decomposition of zinc carbonate hydroxide

This study is devoted to the thermal decomposition of two zinc carbonate hydroxide samples up to 400 °C. Thermogravimetric analysis (TGA), boat experiments and differential scanning calorimetry (DSC) measurements were used to follow the decomposition reactions. The initial samples and the solid decomposition products were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and laser particle size analyzer. Results showed that zinc carbonate hydroxide decomposition started at about 150 °C and the rate of decomposition became significant at temperatures higher than 200 °C. The apparent activation energies (E_a) in the temperature range 150–240 °C for these two samples were 132 and 153 kJ/mol. The XRD analyses of the intermediately decomposed samples and the DSC results up to 400 °C suggested a single-step decomposition of zinc carbonate hydroxide to zinc oxide with not much change in their overall morphologies.     

Microporous poly(vinyl methyl ether) hydrogels prepared by γ-ray irradiation at different heating rates

We prepared thermoresponsive and microporous polymer hydrogels by γ-ray irradiation of aqueous solutions poly(vinyl methyl ether) (PVME) at different heating rates. Under all temperature programs, opaque and heterogeneous PVME gels formed, which swelled at temperatures below the lower critical solution temperature and shrank at temperatures above it. All of the samples contained porous and phase-separated structures. The shape and size of the gel pores varied depending on the temperature programs. Gels having a sponge-like continuous porous structure formed only when the radiation-induced crosslinking was carried out at an optimum heating rate, which we found to be 0.11–0.13°C min⁻¹. For temperature changes between 10°C and 40°C, gels with this structure showed rapid volume transitions on a time scale of about a minute.     

Membrane properties of mixed ganglioside GM1/phosphatidylcholine monolayers

The interaction between ganglioside G_M1 (GM1) and --dipalmitoylphosphatidylcholine (DPPC) in mixed monolayers was investigated using surface pressure measurements and atomic force microscopy (AFM), and the effects of GM1, surface pressure and temperature on the properties of the membranes were examined. Mixed GM1/DPPC monolayers were deposited on mica using the Langmuir–Blodgett (LB) technique for AFM. GM1 and DPPC were miscible below the 0.2 mole fraction of GM1 and there was attractive interaction between GM1 and DPPC. The AFM images for the GM1/DPPC monolayers (X_GM1 < 0.2) at 30 mN m⁻¹ and 25 °C indicated a percolation pattern which means a micro phase separation: namely, the mixed film composed of GM1 and DPPC phase-separated from the DPPC liquid-condensed film. The AFM images for the mixed monolayers at 33 mN m⁻¹ indicated a specific morphology when the surface pressure was varied from 30 to 40 mN m⁻¹. The percolation pattern in the AFM image at 25 °C came to be destroyed with increasing temperature and completely disappeared at 45 °C. The change in the morphology of mixed GM1/DPPC monolayers on varying the surface pressure and temperature is thought to be related to signal transduction and a preventive mechanism against viral infections in the human body.     

Polysulfone ionomers for proton-conducting fuel cell membranes: sulfoalkylated polysulfones

Polysulfones (PSUs) carrying short pendant alkyl side-chains with terminal sulfonic acid units have been prepared and studied as proton-conducting membrane materials. The first step in the preparation involved quenching of lithiated PSU with SO₂ gas, resulting in sulfinated PSU. In the second step, the lithium sulfinate units on the polymer were reacted with sodium 2-bromoethanesulfonate, sodium 3-bromopropanesulfonate, or 1,4-butane sultone to produce sulfoethylated, sulfopropylated, or sulfobutylated PSUs, respectively. Analysis by thermogravimetry showed that membranes based on the sulfoalkylated polymers were stable up to approximately 300 °C under N₂ atmosphere. Calorimetry measurements revealed that the modified polymers absorbed large amounts of non-freezing water, corresponding to 11–14 mol H₂O/mol SO₃H under immersed conditions. The proton conductivity of a membrane based on a PSU carrying 0.9 sulfopropyl chains per repeating unit was measured to be 77 mS/cm at 70 °C under humidifying conditions.     

Study of parameters associated with the determination of cadmium in lake sediments by slurry sampling electrothermal atomic absorption spectrometry

Cadmium concentration in lake sediments is determined by suspending the solid samples in a solution containing 5% (v/v) concentrated nitric acid and 0.1% (v/v) Triton X-100. Three modifiers were tested for the direct determination. The furnace temperature programmes and appropriate amount for each modifier were optimised to get the highest signal and the best separation between the atomic and background signals. The drying stage is performed by programming a 400 °C temperature, a ramp time of 25 s and hold time of 10 s on the power supply of the atomiser. No ashing step is used and platform atomisation is carried out at 2200 °C. W–Rh permanent modifier combined with conventional modifier by delivering 10 μl of 0.50% (w/v) NH₄H₂PO₄ solution was the best chemical modifier for cadmium determination. This modifier also acts as a liquid medium for the slurry, thus simplifying the procedure. Calibration is performed using aqueous standards in the 1–5 μg l⁻¹ range. The optimised method gave a limit of detection of 0.56 ng ml⁻¹, characteristic mass of 10.1±0.8 pg for aqueous standard, 9.6±0.7 pg for slurry samples containing different Cd concentrations and good precision (7.6–5.2%). The method was validated by analysing four certified reference lake sediment materials: LKSD-1, LKSD-2, LKSD-3 and LKSD-4; satisfactory recoveries were obtained (90.0–96.3%) and no statistical differences were observed between the experimental and the certified cadmium concentration. The developed methodology was used to determine cadmium in three ‘real’ sediment samples from lakes in the area of Wielkopolski National Park, Poland.     

The effect of humidity on dehydration behavior of nitrofurantoin monohydrate studied by humidity controlled simultaneous instrument for X-ray Diffractometry and Differential Scanning Calorimetry (XRD–DSC)

The dependence of thermal dehydration behavior of nitrofurantoin monohydrate on humidity was studied. Difference in observed crystallinity of resulting anhydrates under three humidity conditions is discussed in relation to the effect of water vapor molecules. Thermal dehydration of nitrofurantoin monohydrate was measured using a humidity controlled simultaneous measurement instrument for X-ray Diffractometry (XRD) and Differential Scanning Calorimetry (DSC) in dry, 27 °C 91% RH and 60 °C 90% RH nitrogen. Dehydration of nitrofurantoin in dry nitrogen gave a mixture of crystalline and amorphous anhydrates in the temperature range of 124–180 °C followed by crystallization around 185–190 °C. Whereas, dehydration in high humidity atmosphere (60 °C 90% RH or 17.7% H₂O–82.3% N₂) gave well crystallized anhydrate at 140 °C soon after dehydration. Dehydration in low humidity nitrogen (27 °C 91% RH or 3.2% H₂O–96.8% N₂) gave not totally crystalline anhydrate, which became pure crystalline at around 190 °C. The effect of high humidity on dehydration and crystallinity of the resulting anhydrate can be attributed to the role of water vapor molecules in two ways such as the acceleration of molecular mobility and high molecular diffusion rate of nitrofurantoin anhydrate, and the formation of hydrogen bonding bridges quickly connecting dehydrated molecules to one another.