Vol 57, No 6 (2017)

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.

Asymmetric track-etched membranes based on polyethylene terephthalate have been prepared using two-sided irradiation on the heavy-ion accelerator DC-60. A process for cyclotron adjustment to bombardment of a polymer material has been described. A procedure for preparing asymmetric track-etched membranes with different pore lengths and sizes has been specified. The strength characteristics of the resulting membrane have been evaluated. It has been shown that the membrane can be used in processes in which the driving force is hydraulic or osmotic pressure.

The formation of organic colloidal particles in the pores and on the surface (fouling) of membranes used in the food industry is a significant constraint on the further development of membrane technology. A model to describe the effect of these particles on electric conductivity and diffusion permeability has been proposed. It is based on a microheterogeneous two-phase model constructed in terms of the concepts of nonequilibrium thermodynamics and effective medium theory. The model takes into account the presence of two phases: (i) the gel phase comprising a polymer matrix and fixed ions whose charge is compensated for by mobile ions and (ii) the electrically neutral solution filling the intergel spaces. Each of the phases is characterized by intrinsic thermodynamic and kinetic parameters. The model takes into account changes in the values of these parameters caused by the formation of organic nanoparticles in meso- and macropores (fouling). It is assumed that the formation of colloidal particles in the intergel solution leads to a decrease in the ion mobility. In addition, these particles are capable of deprotonating a portion of the fixed ions and thereby decreasing the exchange capacity of the membrane. A high degree of hydration of these particles is responsible for an increase in the volume fraction of intergel spaces. Selection of relevant model parameters provides good agreement between calculation and experimental results.

The possibility of using the seeded calcium carbonate precipitation technology developed previously by the author for the utilization of concentrates of existing reverse osmosis units has been explored. In modern reverse osmosis plants, scale inhibitors are used to prevent calcium carbonate scaling of membranes; the role of antiscalants consists of adsorption on the surface of forming crystals and slowing down their growth. The presence of antiscalants in the concentrate decreases the growth rate of the “seed” crystals and hampers the utilization of the concentrate. To increase the rate of crystallization, it is necessary to increase the supersaturation of the solution or increase the amount of seed crystals to be introduced. The dependence of the calcium carbonate growth rate in the antiscalant-containing concentrate on the added “seed” dose, recovery, and the pH has been studied. Various antiscalants have been compared in terms of performance, and their type most suitable for the process has been chosen. The results of comparison of the operating costs of a reverse osmosis plant involving concentrate utilization, depending on the antiscalant type used, are presented.

Experimental data on the pressure gradient-dependent flux through UPM-50M, UFM-50, OPMN-P, and OFAM-K membranes in the separation of molasses distillery slop have been obtained. During the separation of the molasses distillery slop, a dynamic fluid membrane forms above the surface of the active layer on the test semipermeable membrane, which is compacted with increasing pressure and serves as an additional membrane. Evidence has been presented that the reverse osmosis membrane OFAM-K is superior for use at an effective working pressure of P = 4.0 MPa in the separation of the molasses distillery slops to the OPMN-P, UPM-50M, and UFM-50 membranes in terms of performance criteria (environmental friendliness, economy, import substitution, production of a discolored flow (volume) of permeate with good solute permeation and retention parameters) based on the results of statistical processing of experimental data.