In this paper, we study the structure of the surface layer of air-dry, water-saturated, and operating samples of microfiltration composite membranes based on MMK-0.45 polyamide and MFFC-2G ...fluoroplast using infrared (IR) spectroscopy. The IR spectra are analyzed in the frequency ranges of 500–1700 and 2800–3400 cm
–1
. In the case of polyamide membrane MMK-0.45, the main peaks of the functional groups of polymers in the IR spectra of dry, water-saturated, and operating samples coincide. The absorption bands of polyamides range from 650 to 5000 cm
–1
, corresponding to the peptide bond. Bending vibrations of the carbonyl group occur in the absorption band at 1650 cm
–1
while bending vibrations of the N–H bond are observed in the band at 1550 cm
–1
. The 3500–3000 cm
–1
region is the stretching vibrations of the NH, OH, and water groups. In the case of the operating sample of the MFFC-2G fluoroplastic membrane, the stretching vibrations of the fluorine-substituted groups lie in the range of 1100–1400 cm
–1
; they correspond to the C–F stretching vibrations (1198 and 1171 cm
–1
). The IR spectrum also shows two peaks in the region of 2800–3000 cm
–1
; they are characteristic of biodiesel from vegetable oils. The specific output flow and changes in the pH of the permeate depending on time and transmembrane pressure are studied. There are several periods of decrease in the specific output flow depending on time, which is most likely due to the unblocking of pores of the microfiltration membrane by substances in the solution being separated, and the possible formation of a boundary gel layer. The decrease in the pH of the permeate with an increase in the transmembrane pressure on the MMK-0.45 and MFFC-2G microfiltration membranes is due probably to an increase in the rate of migration of organic acids through the helium layer and the operating layer of the membrane.
A flat-chamber electrobaromembrane apparatus with improved design and technological characteristics for wastewater treatment and differentiated ion extraction from industrial water systems was ...developed. A method allowing the total working area of the anodic and cathodic membranes, the sizes of the anodic and cathodic outlet flows, and other parameters of the membrane process to be calculated was presented. The design and technological parameters of the chamber and electrobaromembrane apparatus as a whole were calculated.
This paper presents the results of the evolution of the structure of filtration films of the MFFC-3 and PP-190 types in the process of purification of ethereal substances. It has been established by ...thermogravimetry that a decrease in the mass of samples of working films for MFPC-3 by ~22%, and for PP-190 by 18%, which is a at temperatures of ~130–265°C, is due to the destruction of the polymer molecules of the drainage layer as a result of transmembrane pressure and diffusion of ethereal substances. For a pure MFFC-3 membrane sample, a single thermal effect is recorded at the peak melting temperature
T
max
= 247°С, typical for lavsan with melting enthalpy Δ
H
= 40 kJ/kg, and for the working sample at
T
max
= 249°C with Δ
H
= 19 kJ/kg. For a clean sample of the pre-filter PP-190, a single thermal effect is recorded at the peak melting temperature
T
max
= 160°C with Δ
H
= 68 kJ/kg, and for the working sample at
T
max
= 157°C with Δ
H
= 67 kJ/kg. The bulk crystallinity of the MFFC-3 and PP-190 films of the working samples decreased by 52 and 33%, respectively, in relation to the initial ones, according to the data of differential scanning calorimetry. X-ray diffraction data indicate changes in the microstructure of films of working samples in the intergranular amorphous phase as a result of deformation of lamellar crystallites, while the X-ray degree of crystallinity of the MFPC-3 film decreased by 12%, and that of PP-190 by 9%. On the dependence curves of the hydrodynamic permeability of MFFC-3 and PP-190 filtration films on time at different transmembrane pressures, four characteristic periods are noted, where gel clots are formed on the MFFC-3 membrane, which significantly affect the process of baromembrane separation and the PP-190 pre-filter becomes clogged.
Self-organization, physicochemical properties (specific electrical conductivity, surface tension), UV absorption, and fluorescence of aqueous herbicide compositions based on
N
...-(phosphonomethyl)glycine and plant growth regulator succinic acid (SA) were studied in a range of herbicide concentrations of 1·10
−19
−1·10
−1
g L
−1
at the constant concentrations of SA 1·10
−3
g L
−1
(series
1
) and 1·10
−13
g L
−1
(series
2
). Such compositions are used in agriculture for decreasing toxic effects on cultural plants and environment. A comparison of the nonmonotonic concentration dependences of the size and ξ-potential of the disperse phase, properties, and bioeffects of systems
1
and
2
revealed significant distinctions in these compositions in the ability of self-organization and surfactant properties, which can cause, as a whole, their substantial difference in the degree of harmful influence on aquatic life and higher plants. The influence of the compositions of series
1
is accompanied by a decrease in the harmful effect on the chosen biological test objects compared to the herbicide, and that of series
2
results in an almost complete elimination of the harmful effect against multicellular organisms (cladocerans and wheat roots) and an insignificant effect on unicellular aquatic life (infusoria and algae). The influence of the compositions of series
2
on aquatic life is related to the formation of a negatively charged disperse phase accompanied by an increase in the fluorescence intensity in a range of 300–360 nm (λ
exc
= 225 nm).
A design of a flat-chamber-type electrobaromembrane apparatus for separating industrial solutions with equal area of cathode- and anode-adjoined membranes is developed. A procedure is proposed for ...calculating (based on determination of geometric and design parameters of the flat-chamber-type electrobaromembrane apparatus) to determine such parameters of the apparatus as the total membrane area (i.e., the effective separation area), the area of cathode- and anode-adjoined membranes (with and without account of screening elements), and the total volume of the solution being separated in unit volume of the proposed device.
The pulsed operation mode of an emission–reception system consisting of two immersion piezoelectric transducers separated by a liquid (glycerine) layer has been studied. Identical piezoceramic plates ...were used as active elements in the emitter and receiver. The rear sides of the plates were loaded on air. The emitting transducer was excited by composite-waveform electric signals consisting of two sine-wave half-periods with different amplitudes (with their sign taken into account). The length of each half-period corresponded to the half-period of emitting plate vibration at the antiresonance frequency. The first half-period was the exciting one, with the second, supplied at the appropriate moment, being the compensating one. The amplitudes of the compensating half-periods were precalculated based on a mathematical algorithm developed by the authors in their previous works. It has been shown that applying composite-waveform signals allows one to considerably reduce the duration of a signal at the receiver output as compared with the case where the emitter is excited by an electric pulse in the form of one half-period of vibration at the antiresonance frequency. Experimental data are in fair agreement with computation results.
The effect of the transmembrane pressure and diffusion of essential substances on the transformation of the structure in polymer membranes of UPM-100 and PP-190 type is studied in this work. It is ...found by thermal methods that the processes of reduction of the weight of the samples of the working films by about 15% for PP-190 and 13% for UPM-100 that are observed at 160–220°C are determined by the destruction of the polymer molecules of the drainage layer. The analysis of the TG and DSC curves of the initial and working samples of the films of UPM-100 and PP-190 makes it possible to note that the transmembrane pressure and diffusion of essential substances mainly induce destruction of the molecules of the amorphous phase of the drainage layer with an insignificant decrease in the crystallinity of the polymer matrix. X-ray structural studies reveal that, in a UPM-100 composite film, transmembrane pressure initiates the conformation of the crystallites of the polymer PETF matrix with the orientation of the (
a
) and (
b
) crystallographic axes at a certain angle to the surface of the film, as well as of the macromolecule chains parallel to the surface of the film. Comparisons of the data of X-ray diffraction analysis show that substantial changes in the microstructure of the samples of the working films occur in the intercrystalline amorphous phase as a result of the conformation of the lamellar crystallites; here, the degrees of crystallinity of the polymer PP and PETF matrices decrease by ~10%.
In this work, the effects of adsorbed water on the structural evolution in the PVDF layer of composite hydrophobic MFFC-3 and hydrophilic MFFC-3G membranes were studied using ATR IR spectroscopy. It ...has been found that adsorbed water molecules initiate the conformational rearrangement of PVDF polymer molecules in the hydrophilic membrane layer, while the conformation of PVDF polymer molecules in the hydrophobic membrane layer does not change. The deconvolution of the absorption bands of the stretching vibrations of OH groups was carried out using four Gaussians. Based on the frequencies of the Gaussian peaks, the energy was calculated and the hydrogen bonds of adsorbed water were classified. It is shown that the structure of adsorbed water with hydrogen bond energies
E
OH
= 42.8, 35.7, 17.9, and 14 kJ/mol are “clusters” with three or four hydrogen bonds. Energy values
E
OH
= 17.9, 10.6, 16.8, and 14 kJ/mol correspond to OH bonds of dimeric and monomeric water molecules. It is concluded that the structure of adsorbed water in the PVDF layer can be characterized by a mixed model of hydrogen bonds, consisting of monomeric, dimeric molecules, and associated clusters with hydrogen bond energies from 10.6 to 42.8 kJ/mol. A comparative analysis of the ATR IR spectra of water-saturated samples indicates that the adsorbed water molecules in the PVDF “polymer–water” interfacial space of the hydrophobic membrane do not form a layer of bound water, while, in the hydrophilic membrane, water enters the structure of molecules, forming a layer of bound water.
Because tungsten (W) is used in present fusion devices and it is a reference material for ITER divertor and possible plasma-facing material for DEMO, we strive to understand the response of different ...W grades to ion bombardment. In this study, we investigated the behavior of mirrors made of four polycrystalline W grades under long-term ion sputtering. Argon (Ar) and deuterium (D) ions extracted from a plasma were used to investigate the effect of projectile mass on surface modification. Depending on the ion fluence, the reflectance measured at normal incidence was very different for different W grades. The lowest degradation rate of the reflectance was measured for the mirror made of recrystallized W. The highest degradation rate was found for one of the ITER-grade W samples. Pre-irradiation of a mirror with 20-MeV W6+ ions, as simulation of neutron irradiation in ITER, had no noticeable influence on reflectance degradation under sputtering with either Ar or D ions.
•The reflectance of W mirror specimens pre-damaged with W ions to a dose of 0.45 and 1.45 dpa behave just as the undamaged specimens when being subjected to sputtering with ions of Ar or D plasmas.•Behavior of the reflectance depends significantly on the W grade, namely, on the microstructure of W, such as distributions of grains on their size and orientation relative to the surface of the sample.•The dominant factor that defines the reflectance and surface roughness is the difference between the heights of grains with different sputtering rates of faces differently orientated relatively to the sample surface.
