Том 1, № 5 (2019)

Hybrid membranes based on pyridine-containing polybenzimidazole (PBI–Py) and silica containing sulfonic groups on the surface have been synthesized by two methods, namely, by casting a polymer solution with ready-prepared oxide particles and with a precursor for their synthesis. The effect of the synthesis method on the morphology, conductivity under various conditions, and gas permeability of the hybrid membranes has been studied. It has been shown that the membrane modification with silica leads to an increase in conductivity at a low silica content (2–5 wt %) and an increase in gas permeability. The highest proton conductivity (58 mS/cm at 160°C) has been found for the sample synthesized by casting a PBI–Py solution with a precursor that contains 2 wt % of silica modified with sulfonic groups. Possible mechanisms of proton transport in the synthesized systems have been discussed.

Aspects of the interaction of organic pollutants of natural water with nanofiltration and reverse osmosis membranes have been considered on the basis of experimental results and summarized literature data. Experimental studies have been carried out to determine the rates of membrane fouling by various organic substances including humic acids (imparting the color) and low-molecular-weight organics (responsible for the oxygen demand) during the treatment of river water and pretreated water. The effect of membrane material on the rate of organic deposition on them has been studied. Relationships have been obtained for calculating the rates of buildup of organics on membranes depending on their concentration in the feed water, the nature and molecular weight of foulants, the membrane material, the flow rates in device channels, and the recovery. Experimental determination of the rates of adsorption of organic substances of various natures has made it possible to measure the sorption capacity of the membrane surface. It is likely that in the case of simultaneous fouling of the membrane with poorly soluble salts (calcium carbonate), colloidal and organic substances, iron compounds, etc., the effect of the set of foulants and scalants on the membranes surface may differ significantly from the results obtained in this study. Predicting the amount of organic foulants will help to correctly select the composition of solutions for chemical cleaning of membranes and eliminate the influence of organics on scale dissolution.

Chitosan pressure-driven filtration membranes have been studied. The factors affecting the solubility of high-molecular-weight chitosan have been analyzed, and the optimal procedure for preparing its concentrated solutions has been proposed. Formulations of casting solutions for fabricating micro-, ultra-, and nanofiltration and reverse osmosis membranes based on chitosan have been developed. The membranes obtained using the dry and dry/wet casting techniques have been tested to determine their porosity, specific flux, and rejection ability. It has been established that the performance characteristics of the developed chitosan membranes are similar to those of pressure-driven filtration membranes made from other polymers.

A unique method for producing Polikon cation–anion exchange mosaic materials has been proposed. The materials were prepared by the polycondensation filling of polymer composites and via synthesis and curing of a weakly basic anion exchanger and a strongly acidic sulfonated cation exchanger on the surface and in the structure of a fibrous novolac phenol–formaldehyde matrix. Molecular models that characterize the chemical composition of the developed composites are given. The effect of the composition that facilitates the formation of a material with stable performance characteristics has been studied. The cause-and-effect relationships of the structural, physicochemical, and operational properties of the heterogeneous cation–anion-exchange mosaic materials Polikon under thermomechanical action at the stage of polymer matrix curing were investigated. Empirical equations that refine these relationships were obtained. The morphology and internal structure of the test heterogeneous membranes were characterized by scanning electron microscopy and energy-dispersive elemental analysis. The viscoelastic properties of the samples were studied by dynamic thermomechanical analysis.