T. S. Anokhina

Cellulose composite membranes for nanofiltration of aprotic solvents

Cellulose composite membranes have been fabricated by casting a cellulose solution in N-methylmorpholine oxide on a nonwoven polyester support. The membranes have been tested for nanofiltration of aprotic solvents. The solvent permeability has changed from 0.11 ± 0.02 to 2.5 ± 0.4 kg/(m2 h bar) in the following order: DMSO > NMP > DMFA > THF > acetone, which can be attributed to a decrease in viscosity of the fluids. The rejection of the anionic dyes Orange II (MW 350) and Remazol Brilliant Blue R (MW 626) has been found to range within 15–85% and 42–94%, respectively, on the solvent nature. Sorption experiments have revealed a noticeable difference between certain solvents in interaction with the membrane material: a lower degree of cellulose swelling in THF (37%) and a higher degree in DMSO (230%). In addition, it has been found that the rejection of solutes by the composite membranes correlates with the degree of cellulose swelling. A rejection of ≥90% has been achieved for Remazol Brilliant Blue R, which has the larger molecule, at a cellulose swelling ratio of 100% or higher. Thus, it has been concluded that polymer swelling leads to narrowing the porous structure of the cellulose layer of the composite membrane and, hence, improvement in separation parameters.

Fabrication of composite nanofiltration membranes from cellulose solutions in an [Emim]OAc–DMSO mixture

The dissolution of cellulose in the [Emim]OAc ionic liquid mixed with DMSO as a cosolvent has been studied, and the possibility of fabricating composite cellulose membranes for the nanofiltration of organic media has been explored. It has been shown that the addition of DMSO to [Emim]OAc leads to a decrease in the dissolution time, which has a minimal value at a solvent ratio of 1 : 1. Composite membranes on a poly(ethylene terephthalate) support have been synthesized. The cellulose content in the casting solution was 6, 8, 12, or 16 wt %. It has been found that the rejection factor of the Remazol Brilliant Blue R dye (626 g/mol) varies from 42 to 82% depending on the composition of the casting solution.

Application of Cellophane Films as Nanofiltration Membranes

The prospects for use of commercially produced cellophane as a membrane material for organic solvent nanofiltration have been studied. The effect of cellophane film conditioning with aqueous ethanol mixtures with a gradually varying concentration (from ethanol to water and from water to ethanol) has been examined. It has been shown that such treatment increases the ethanol permeability by more than two orders of magnitude in comparison with the untreated sample. The obtained value of the ethanol permeability coefficient for the treated cellophane is comparable with that for highly permeable glassy polymers. The study of cellophane swelling in aqueous ethanol solutions has revealed that the formation of porous structure takes place during the cellophane treatment process as a result of an increase of the interchain distances in the film. The observed high permeability of ethanol is associated with the fact that the porous structure formed is preserved when water is replaced by ethanol. The main factors affecting the membrane flux are the viscosity of the liquid and degree of cellophane swelling in this liquid. It has been also shown that the rejection coefficients of some dyes with molecular mass in the range of 350 to 626 Da from ethanol agree well with the hydrophobicity/hydrophilicity of the solutes. The rejection coefficients of anionic dyes in the case of water are significantly higher than in ethanol (R(EtOH) = 55% → R(H2O) = 97% for Orange II and

Effect of coagulating agent viscosity on the kinetics of formation, morphology, and transport properties of cellulose nanofiltration membranes

R_{EtOH} = 79\% \to R_{H_2 O} = 100\%

Application of PIM-1 for solvent swing adsorption and solvent recovery by nanofiltration

for Remazol Brilliant Blue R) despite the higher swelling degree of cellophane in water. This behavior is explained by the increase of the solvation shell of the solute molecules and narrowing of the transport channels, in good agreement with the assumption of the sieving mechanism of separation by nanofiltration.

Multi-stress tolerant plant growth promoting Pseudomonas spp. MCC 3145 producing cytostatic and fungicidal pigment

The dissolution of cellulose in N-methylmorpholine-N-oxide monohydrate and the dissolution of N-methylmorpholine-N-oxide monohydrate in water have been studied via optical interferometry. A part of the phase diagram for the cellulose/N-methylmorpholine-N-oxide system has been constructed. The phase diagram is characterized by crystalline equilibrium, hysteresis of the melting temperatures of the solvents, and a region of anisotropy. Optical interferometry has been used for the first time to study the kinetics of cellulose coagulation during the interaction of cellulose solutions in N-methylmorpholine-N-oxide with water and water solutions of N-methylmorpholine-N-oxide. Information on the values of interdiffusion coefficients and the morphologies of the resulting cellulose films has been obtained. The possibility to use optical interferometry to analyze the interaction of a solution with the coagulating agent in the case of cellulose fiber and film formation has been demonstrated. The influences of temperature, the nature of the coagulating agent, and the cellulose content on the kinetics of the process and morphologies of the formed films have been shown. The use of N-methylmorpholine-N-oxide as a part of the coagulation system decreases the rate of interdiffusion of solutions, thereby resulting in a more uniform and dense morphology of cellulose films. Increased temperature causes diffusion acceleration, thereby leading to the formation of an anisotropic morphology of the cellulose films.

Cellulose-Based Membranes for Solutes Fractionation

Low-viscous coagulating agents are tradionally used to precipitate polymers from their solutions and obtain films and fibers from them; they represent, as a rule, the combinations of solvent and nonsolvent of the polymer used. At the same time, since the structure of the precipitated polymer is formed under non-equilibrium conditions, the influence of the coagulant viscosity can be quite substantial. The influence of the viscosity of the medium on the formation of structure, morphology, and transport characteristics of the precipitated polymer is studied by example of forming of the cellulose membranes from solution in N-methyl-morpholine N-oxide using some proton-donor coagulants. In this regard, the interdiffusion processes proceeding at the contact of cellulose solutions and coagulating agents (water, propylene glycol, glycerin) are explored using the laser interferometry method. Varying the precipitator viscosity allows one to change the rate of formation and correspondingly the morphology of the cellulose films. In turn, the membrane structure determines its transport characteristics, which were assessed by the filtration of aprotic media with anionic dyes—Orange II and Remazol Brilliant Blue R. The application of the low-viscous precipitator provides the formation of a uniform film structure in the bulk, but leads to development of defects close to the surface, while a viscous medium promotes the formation of a relatively thin dense shell on the films.

Bioactive pigment production by Pseudomonas spp. MCC 3145: Statistical media optimization, biochemical characterization, fungicidal and DNA intercalation-based cytostatic activity

Phase separation of polymer solutions initiated by the addition of a nonsolvent is the main method for the preparation of polymer membranes. Depending on the application, such membranes must have a different pore size, which depends on the numerous parameters of the forming process. The liquid–liquid phase separation has been considered for cellulose solutions in N-methylmorpholine N-oxide (NMMO) interacting with various alcohols (methyl, ethyl, isopropyl, and isobutyl). Kinetics of cellulose regeneration was investigated by laser interferometry technique to understand the mechanism of cellulose film structure formation in the NMMO process. Influence of temperature, coagulant nature, and cellulose content on the process kinetics and morphology of the films was studied and corresponding interdiffusion coefficients were calculated. Based on the solubility parameters, triple phase diagrams of the systems were calculated. Formation of different morphologies was explained primarily by the different position of the composition path, the bimodal curve, and the gelation line in the phase diagrams. The second important parameter was the different rate of mutual diffusion of the NMMO and coagulants, due to the difference in the viscosity of the latter. Using methanol or ethanol as coagulation baths leads to obtaining the nanoporous structure of cellulose films, whereas isopropanol and isobutanol favors macropore formation.