Tatsiana Hliavitskaya

The effect of a natural biocide based on forest chemical raw materials as an additive to cellulose acetate (CA) casting solutions on the structure and properties of the resulting membranes was studied. The NMR method was used to determine the component composition of rosin and turpentine, from which rosin terpene maleic adduct (RTMA) was obtained. Successful modification of the AC-membranes was confirmed by the results of FTIR-spectroscopy. The operational properties of AC-membranes were studied (electron microscopy, atomic force microscopy, study of the transport properties of membranes). It was shown that the introduction of 1.5–2.0 wt % RTMA into the casting solutions does not affect the transport properties of the membranes, but decrease the surface roughness of the selective layer. At the same time, modified membranes are characterized by increased antibacterial resistance and resistance to fungal fouling.

The paper presents the results of using ultrafiltration for purification of solutions simulating liquid radioactive waste, produced during decontamination of parts by electrolytic-plasma treatment, to remove chromium(III) radionuclides (⁵¹Cr(III)). The main performance characteristics and transport properties of ultrafiltration membranes made of hydrophilized polysulfone, polyethersulfone, and regenerated cellulose with different molecular weight cutoff (MWCO) values have been determined. The dependences of membrane flux and ⁵¹Cr(III) rejection coefficient on the pH of solutions and thermostatting time have been established. It has been shown that in 8% (NH₄)₂SO₄ solution at pH 7–8, the ⁵¹Cr(III) radionuclide occurs in the form of polynuclear hydroxo complexes, which are retained by ultrafiltration membranes and precipitate during centrifugation. A regenerated-cellulose membrane with MWCO = 10 is the most effective, rejecting ∼97% of ⁵¹Cr(III) at pH 8. Increasing the time of solution thermostatting before membrane separation leads to an increase in the rejection of ⁵¹Cr(III) due to a deeper hydrolysis process with the formation of polynuclear hydroxo complexes.

The work is devoted to the fabrication of hollow fiber thin-layer composite gas separation membranes with an internal selective layer using interfacial polycondensation followed by deposition of a polydimethylsiloxane (PDMS) layer on a polysulfone membrane substrate. The effect of the concentration of amine (triethylenetetramine (TETA)) and acyl (isophthaloyl chloride (IPC)) components and the conditions of PDMS layer deposition on the change in the gas permeability of composite membranes in O₂/N₂ separation was studied. It was found that after forming the selective layer by the interfacial polycondensation method, hollow fibers with high gas permeability values (≥1000 GPU) were obtained regardless of the monomers used and their concentration, with the O₂/N₂ separation factor α being about 1. After applying an additional layer using 1–3 wt % PDMS solutions, the separation factor was 1.5–3.7. The maximum value of the separation factor was found in a fairly narrow range of TETA concentrations (0.15–0.6%) and at a certain equivalent TETA/IPC ratio. The first maximum (α O₂/N₂ = 3.5) is observed at a weight concentration ratio of TETA/IPC = 0.15/0.26, and the second maximum, at the concentration ratio of TETA/IPC = 0.6/0.15, with the permeability of the composite membranes for oxygen being 107 and 76 GPU, respectively.

A new approach to carbon membranes fabrication by IR pyrolysis of the hollow fiber (HF) porous membranes from a homopolymer (PAN) and acrylonitrile copolymers with methyl acrylate (PAN-MA) and itaconic acid (PAN-IA) was developed. The method includes thermal stabilization of membranes at 250 °С, and subsequent IR pyrolysis. It was established that the HF membranes made from PAN-IA and PAN were the least susceptible to destruction with increasing temperature. However, for samples based on PAN-MA, the significant deformation of hollow fiber membranes after IR pyrolysis occurs at temperatures above 200–300 °C. Scanning electron microscopy study showed that the presence of glycerol as an impregnating agent in membranes (regardless of the chemical composition of acrylonitrile copolymers) leads to a less regular and more defective structure of the resulting carbon membranes. It was found that the thermal stabilization at 250 °C preserves structural integrity and contributes to the production of mechanically stable carbon membranes. FTIR spectra confirmed that IR radiation catalyzes transformations in the polymer structure. As a result, the time of thermal stabilization and pyrolysis was noticeably reduced. It was shown, that 15 min pretreatment and 5 min pyrolysis is enough for effective stabilization of membrane structure.

Cutting fluids are the main source of oily wastewater in the metalworking industry. This study deals with the development of antifouling composite hydrophobic membranes for treatment of oily wastewater. The novelty of this study is that a low energy electron-beam deposition technique was applied for a polysulfone (PSf) membrane with a molecular-weight cut-off of 300 kDa, which is promising for use in the treatment of oil-contaminated wastewater, by using polytetrafluoroethylene (PTFE) as target materials. The effect of the thickness of the PTFE layer (45, 660, and 1350 nm) on the structure, composition, and hydrophilicity of membranes was investigated using scanning electron microscopy, water contact angle (WCA) measurements, atomic force microscopy, and FTIR-spectroscopy. The separation and antifouling performance of the reference and modified membranes were evaluated during ultrafiltration of cutting fluid emulsions. It was found that the increase in the PTFE layer thickness results in the significant increase in WCA (from 56° up to 110–123° for the reference and modified membranes respectively) and decrease in surface roughness. It was found that cutting fluid emulsion flux of modified membranes was similar to the flux of the reference PSf-membrane (7.5–12.4 L·m⁻²·h⁻¹ at 6 bar) while cutting fluid rejection (R_CF) of modified membranes increased compared to the reference membrane (R_CF = 58.4–93.3% for modified and R_CF = 13% for the reference PSf membrane). It was established that despite the similar flux of cutting fluid emulsion, modified membranes demonstrate 5–6.5 times higher flux recovery ratio (FRR) compared to the reference membrane. The developed hydrophobic membranes were found to be highly efficient in oily wastewater treatment.

A new approach for one‐stage facile membrane modification during non‐solvent induced phase separation (NIPS)‐process is proposed. The novelty of this study is that cheap and commercially available anionic high molecular polyacrylamide‐based flocculant (AHMPF) is applied for the first time as an additive to coagulation bath (CB). The series of polyethersulfone membranes were prepared using 0.05–0.3 wt% AHMPF aqueous solution as CB at different temperatures (25–50°C) via NIPS. The effect of AHMPF concentration on the structure, composition and hydrophilicity of membranes was investigated. The separation and antifouling performance were evaluated during filtration of bovine serum albumin (BSA) solution and thermomechanical pulp mills process water (ThMP) in order to concentrate hemicellulose. The successful immobilization of AHMPF into the structure of membranes selective layer (not bottom layer) was confirmed by FTIR spectroscopy. It was established that despite the similar rejection of hemicellulose (88.8–93%) and lignin (20–21.4), modified membranes demonstrate 3–8 times higher flux and 2 times higher FRR (43.8% for reference membrane and 86.5% for modified one) in ThMP ultrafiltration. The developed membrane was found to be highly efficient in hemicellulose concentration and purification in pulp industry.