The article presents the results of development of a roll-type electrobaromembrane apparatus for separation of technological solutions of chemical industries with differentiated removal of ions. A ...method is described for engineering calculation of the proposed promising design of a roll-type electrobaromembrane apparatus for separation of technological solutions of chemical and engineering industries, taking account of the hydrodynamics and direction of solution movement.
A method of determining the nonstationary concentration polarization of a solution, flowing in a plane channel, in the process of nanofiltration of the solution flow is proposed. The concentration ...polarization of the aqueous solutions, containing 0.5 kg/m
3
of ZnSO
4
and SnSO
4
, in the process of their nanofiltrational separation was analyzed. It was established that an increase in the transmembrane pressure in a separation apparatus in the range P
m
= 0.5–2.0 MPa causes the coefficient of concentration polarization of the ZnSO
4
and SnSO
4
solutions in this apparatus to increase in the ranges θ = 1.340–1.436 and θ = 1.351–1.430, respectively. A calculation of the time of work of a membrane in a stationary regime and the volume of the permeate obtained in it has shown that, before a membrane is regenerated, the nanofiltrational separation of ZnSO
4
and SnSO
4
from their solutions at a definite pressure can be conducted for the times t
m
= 2070–2791 s and tm = 2893–2036 s, respectively. An increase in the transmembrane pressure causes these times to decrease and the amounts of the permeates obtained for the stationary-regime time to increase from 0.200 to 0.266 dm3 and from 0.202 to 0.262 dm
3
, respectively
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%.
The article presents the results of a study of mass transfer in the process of electrochemical extraction of iron, magnesium and manganese ions from technological solutions. Mathematical expressions ...are obtained, and numerical values of empirical coefficients are determined for theoretical calculation of specific outflow, retention coefficient, and average mass transfer coefficients of the electrochemical membrane process of separation of technological solutions. The dependence of concentration polarization on solution flow rate, pressure gradient, and concentration is analyzed.
Results of the structure evolution in MFFK-3 and PP-190 polymer films during the purification of water–organic solutions are described. X-ray diffraction analysis data show that significant changes ...in the microstructure of the working film samples occur in the intergranular amorphous phase due to the conformation of lamellar crystallites; in this case, the percentage of crystallinity of the MFFK-3 and PP-190 films decreases by 22 and 9%, respectively. Electron microscopy studies of the original and working samples of the MFFK-3 microfiltration membrane and the PP-190 prefilter on a JEOL JSM 6510 electron microscope at a magnification of 140–7000× are described. For the original and working samples of the MFFK-3 microfiltration membrane and the PP-190 prefilter, it is found that organic substances present in the feed solution are adsorbed on the surface of the active layer of the films.
In this work, experimental data on the rejection coefficient and the specific output flux are obtained. Based on the studies, graphical dependencies of the rejection coefficient on the specific ...output flux were constructed and analyzed. During the analysis, it was noted that with an increase in the output specific flow of the solvent, the rejection coefficient decreases. The reason for this is the boundary layers of fat and protein formed in the near-membrane layers, which prevents the passage of protein molecules through the pores of the membrane. For the theoretical calculation of the rejection coefficient and specific output flux, mathematical expressions are developed and numerical values of the values of empirical coefficients are obtained. The developed mathematical expressions describe the experimental data with good confidence. The obtained experimental and calculated data can be used with great reliability in the calculations of mass-transported flows of substances through semipermeable membranes, as well as in engineering methods for calculating and predicting the effectiveness of the use of membrane processes for the concentration of whey.
This work has investigated changes in crystallinity and amorphism in the surface layers of commercial microfiltration films. Experimental studies of supramolecular formations and changes in the ...structure of microfiltration films were carried out by differential scanning calorimetry and X-ray diffractometric measurements in reflection geometry in the region of large angles. In the process of water swelling of semipermeable films of the MMPA, MPS, and МFFK types, a change in the structure of the lattice of the films is observed due to an increase in the interatomic distance, that is, the size of the pore diameter is likely to change throughout the structure of both the active layer and the film substrate. The observed changes in the supramolecular structure of the films upon swelling occur to a greater extent due to the disordering of macrochains in all layers of the films. The decrease in the degree of crystallinity of the films upon sorption of water is most likely associated with the redistribution of the ratio between the number of perfect crystalline phases in polyamide crystallites with different values of the enthalpy of melting.
The objectives of this study are to perform the mathematical description of the formation of a sediment layer on the surface of membranes due to concentration polarization on the basis of the ...semi-integral method of solving the convective diffusion equation, to optimize the process of ultrafiltration and determine the sediment layer on the surface of a membrane, and to calculate the membrane operation time and the filtrate volume in a steady-state regime before regeneration. Minimization results show that the lowest function value of 1.32583 and 1.32112 is given by the Wolfram Mathematica software for the Na
3
PO
4
concentrations of 0.5 and 1 kg/m
3
, respectively. It is established that concentration polarization attains the maximum admissible value of 1.32583 and 1.298 for the solutions with concentrations of 0.5 and 1 kg/m
3
at 2.43 and 2.52 s from the beginning of the separation process, respectively. The propagation of concentration polarization throughout the entire channel length requires 5500 and 5710 s, respectively. Afterwards, the membranes require regeneration to maintain the necessary level of purification. In these time periods, 0.191 and 0.173 L of filtrate are formed.
A mathematical description of the electrobaromembrane process using an approach based on the Nernst–Planck and Poisson–Boltzmann equations is presented. The hydrodynamic conditions in the ...intermembrane channel is taken into account by a dimensionless equation based on the Reynolds criterion and a technique is presented for determining electrobaromembrane separation of solutions, taking into account the kinetics of mass transfer and the hydrodynamics of the flow of a solution in an intermembrane channel. Through the use of the technique the local mass-transfer coefficients along the length of the channel of the membrane module may be determined. The technique may also be used to predict and develop laboratory, pilot and industrial electromembrane instruments and plants.
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.
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