Polydecylmethylsiloxane–polyperfluorooctyl methylsiloxane (PDec-PFOMS) copolymers are synthesized for the first time. NMR data are used to determine the quantitative substitution of the Si–H bond in the PDec-PFOMS. It is shown that raising the content of PFO expands the wetting angle for n-butanol. It is established that injecting the polymer with 2 mol

Preparation of composite membranes is a complex technological task. To ensure high permeability and selectivity of these membranes, preliminary preparation of a selective layer polymer solution is of importance. In this work, the copolymer of polydecylmethylsiloxane and polymethylpentafluoropropylacrylatesiloxane with a theoretical block ratio of 1 : 1 has been synthesized for the first time. According to 1Н NMR studies, with increasing the time of hydrosilylation of the reaction mixture from 10 to 50 min the degree of substitution of Si–H bonds increases, with the degree of conversion of pentafluoropropyl acrylate being close to quantitative (100 mol

A series of poly(trifluoroethylacrylatemethylsiloxane) (F3) and polydecylmethylsiloxane (C10) copolymers featuring different ratios of the side groups were synthesized for the first time. A significant change in the sorption of the components of the ABE-fermentation mixture was demonstrated when the ratio of C10 and F3 in the membrane material changed. It was established that the copolymer with the C10/F3 ratio of 1:1 exhibits the maximum value of n-butanol sorption. At the same time, the total flow through the membrane doubles in comparison with C10 and it is possible to stabilize the flow by 15% after prolonged contact with the real ABE mixture.

This work is aimed at obtaining a membrane material that is resistant to the formation of a precipitate on the surface upon contact with an ABE fermentation mixture and has a good separating ability during the pervaporation isolation of n-butanol from a water–alcohol mixture. In this regard, in this work, for the first time, the creation of pervaporation membranes based on polymethyltrifluoroethylacrylatesiloxane (F3-Acr), as well as a copolymer of polydecylmethylsiloxane and polymethyltrifluoroethylacrylatesiloxane (C10-F3-Acr) is proposed. In comparison with polydecylmethylsiloxane (C10), the structure and sorption properties of the developed membrane materials for n-butanol, ethanol and acetone were studied. It should be noted that the highest sorption of n-butanol is characteristic of C10-F3-Acr (0.46 g/g). Changes in surface properties were assessed by the contact angle and elemental composition of the surface before and after exposure for 1 month in a fermentation medium. The transport and separating properties of the synthesized membrane materials were studied in the vacuum pervaporation mode during the separation of a model ABE fermentation mixture. It was shown that the introduction of a fluorine-containing substituent into the side chain of polysiloxane made it possible to increase the hydrophilicity of the polymer: the water flow for F3-Acr was 0.7 × 10–6 kg m m–2 h–1, which is almost 3 times higher than for C10. It is worth noting the positive effect of the combination of C10 and F3-Acr groups in polysiloxane. Thus, with an increase in the total flow by 60% compared to the C10 membrane, the values of the separation factor for n-butanol, acetone, and ethanol were 40.5, 32.7, and 4.3 and increased by 6, 15, and 12%, respectively, compared to the C10 membrane. For the C10-F3-Acr membrane, the pervaporation separation index for n-butanol, acetone, and ethanol was 136, 109, and 11. Therefore, this membrane is twice as efficient as C10. Taking into account the absence of detectable contamination of the surface of the membrane material with fermentation products, one can note the high potential of the C10-F3-Acr membrane for the task of isolating alcohols from the ABE fermentation mixture.

In this paper, the process of film distillation with a porous condensing surface (FD-PCS) is studied as applied to the tasks of concentration of lithium-containing solutions. Concentration of solutions is a part of a three-stage lithium extraction cycle that includes softening of the brine by the precipitation of Ca2+/Mg2+ cations with sodium carbonate (calculated in PHREEQC) followed by an integrated system consisting of a membrane distillation unit and a crystallizer (deposition of NaCl) and membrane extraction (extraction of Li+). The productivity flows of the film distillation module are investigated (4.15–7.49 kg m−2 h−1 at the temperatures of heating of the evaporation surface of 60 and 80°C, respectively). The complex operation of the three-stage system is modeled in Simulink/MATLAB. The modeling of the process based on the experimental and published data shows a higher efficiency of film distillation with a porous condensing surface in comparison with membrane distillation with a porous condensing surface (4.2 kg of lithium versus 1.4 kg over two months of stationary operation of the system).

For the task of triethylene glycol (TEG) dehydration by thermopervaporation with a porous condenser (TPV-PC), the transport and separation characteristics of known commercial composite membranes with hydrophobic and hydrophilic properties are experimentally studied with respect to both the individual components (water, triethylene glycol) and TEG–water binary mixtures with various compositions. It is found that the most effective membrane for the TPV-PC dehydration of TEG is a PolyAn hydrophobic membrane (PolyAn GmbH, Germany) which demonstrates the maximum values of the permeate flux and pervaporation separation index. During the thermopervaporation separation of a TEG–water mixture (the water content in TEG of 30 wt %), a PolyAn membrane demonstrates the values of the water/TEG separation factor of 74 000 and permeate flux of 0.95 kg m−2 h−1. A long-term experiment on drying of 5 kg of a TEG–water solution is for the first time carried out using a PolyAn membrane. It turns out to be possible to reduce the water content from 30 down to 5 wt % over 113 hours of the thermopervaporation experiment on the dehydration of TEG.

In order to increase the efficiency of membranes in the processes of gas separation and thermopervaporative isolation of volatile organic compounds from aqueous media, mixed-matrix membranes based on polytrimethylsilylpropine (PTMSP) with an amount of hypercrosslinked polystyrene (HCPS) particles up to 50 wt

This paper provides a review of the latest developments in the design and study of pervaporation membranes based on glassy polymers with a high free volume. Such membranes demonstrate competitive results compared to other membranes described in the literature (rubbery polymers and zeolites) for the separation of alcohols and other volatile organic compounds from aqueous solutions, as well as for the separation of organic/organic mixtures such as methanol/ethylene glycol and dimethyl carbonate/methanol. Incorporation of fillers such as porous aromatic framework, hypercrosslinked polystyrenes and functionalized graphene-like fillers into glassy polymers with internal microporosity to form mixed matrix membranes can improve separation efficiency and reduce membrane aging effects. There is a wide range of materials that have yet to be explored for possible use in pervaporation, which have the potential to create customized membranes for a wide range of aqueous separations. Inexpensive and highly scalable polymers are still the dominant membrane materials for pervaporation. Stabilizing the membrane structure with minimal performance degradation associated with reducing the thickness of the defect-free separation layer is the first pursuit of membranes based on high free volume polymers in recent years.

For the first time, membranes based on poly(1-trimethylsilyl-1-propyne) (PTMSP) with 5–50 wt% loading of hyper-crosslinked polystyrene sorbent particles (HCPS) were obtained; the membranes were investigated for the problem of effective removal of volatile organic compounds from aqueous solutions using vacuum pervaporation. The industrial HCPS sorbent Purolite Macronet™ MN200 was chosen due to its high sorption capacity for organic solvents. It has been found that the membranes are asymmetric when HCPS content is higher than 30 wt%; scanning electron microscopy of the cross-sections the membranes demonstrate that they have a clearly defined thin layer, consisting mainly of PTMSP, and a thick porous layer, consisting mainly of HCPS. The transport and separation characteristics of PTMSP membranes with different HCPS loading were studied during the pervaporation separation of binary and multicomponent mixtures of water with benzene, toluene and xylene. It was shown that the addition of HCPS up to 30 wt% not only increases the permeate fluxes by 4–7 times, but at the same time leads to 1.5–2 fold increase in the separation factor. It was possible to obtain separation factors exceeding 1000 for all studied mixtures at high permeate fluxes (0.5–1 kg/m2∙h) in pervaporation separation of binary solutions.

This work is aimed at investigating a new process of film distillation with a membrane condenser (FDMC) for obtaining fresh water from a reverse osmosis concentrate. The behavior of a number of structural materials during their exposure for 4.5 months in the open air and in sea water has been investigated. In the Simulink/MATLAB program, a model of the FDMC unit with the possibility of using solar radiation as a renewable energy source has been built. The operation of the unit for one month was simulated and it was shown that the area of solar collectors has the greatest influence on the volume of water received during a month of operation. The area of the evaporator has little effect on the overall process performance, but it can reduce the initial costs while maintaining the same payback period. Modeling showed that the recovery of distilled water decreases by 2–3% (from ~71–72 to ~69%) with a decrease in the NaCl concentration of the output stream from 26 to 24 wt %. The mode with a lower concentration of the output solution was found to be optimal due to the absence of both the risk of pipeline clogging and the need for frequent flushing of the evaporating surface. The use of data on solar radiation for the most and least sunny months (April and November, respectively) shows a nonlinear drop (by 46–47%) in productivity for water, which is explained by both nonlinearity of the temperature dependence of water vapor pressure and a nonlinear relationship between the solar collector efficiency and radiation intensity and ambient temperature. Varying the temperature of the cold circuit shows that using a lower temperature increases the water productivity by 5–15%, while keeping the water recovery rate constant.

Lithium-rich geothermal waters are considered as an alternative source, and further concentration of lithium is required for its effective recovery. In this work, we have simulated a three-stage lithium recovery process including the brine softening by precipitation Ca2+/Mg2+ cations with sodium carbonate (calculated in PHREEQC), followed by an integrated system consisting of membrane distillation unit (water evaporation), crystallizer (NaCl precipitation), and membrane extraction (Li+ recovery), which was simulated in Simulink/MATLAB. It was shown that the deterioration of membrane performance in time due to scaling/fouling plays a critical role in the performance of the system resulting in the dramatic increase of the replaced membrane modules by a factor of 5. Low cost membranes are required. The process simulation based on the experimental and literature data on the high salinity solutions with the membrane distillation revealed that the specific productivity can be achieved in the range of 9.9–880 g (Li+) per square meter of membranes in the module used before its replacement. The increase of energy efficiency is needed. The mass-flow-rate of saline solution circulated to the crystallizer was set at its almost minimum value as 6.5 kg/min to enable its successful operation at the given parameters of the membrane distillation unit. In other words, the operation of the integrated system having 140 kg of saline solution in the loop and a membrane module of 2.5 m2 for concentration of lithium presence from 0.11 up to 2.3 g/kg would be associated with the circulation of about of 259 tons of saline solution per month between the distillation unit (60 °C) and the crystallizer (15 °C) to yield of up to 1.4 kg of lithium ions. The comprehensive summary and discussion are presented in the conclusions section.

The influence of hyper-crosslinked polystyrene (HCPS) MacronetTM MN200 on the gas transport properties and aging of the highly permeable glassy polymer poly(1-trimethylsilyl-1-propyne) (PTMSP) was studied and analyzed in detail. The gas transport characteristics of dense PTMSP membranes containing 0–10.0 wt % HCPS were studied. It was shown that the introduction of a small amount of HCPS into the PTMSP matrix led to a 50–60% increase of the permeability coefficients of the material for light gases (N2, O2, CO2) and slowed down the deterioration of polymer transport properties over time. The lowest reduction in gas permeability coefficients (50–57%) was found for PTMSP containing HCPS 5.0 wt % after annealing at 100 °C for 300 h. It was found that HCPS sorbed residues of tantalum-based polymerization catalyst from PTMSP. In order to investigate the influence of catalysts on transport and physical properties of PTMSP, we purified the latter from the polymerization catalyst by addition of 5 wt % HCPS into polymer/chloroform solution. It was shown that sorption on HCPS allowed for almost complete removal of tantalum compounds from PTMSP. The membrane made of PTMSP purified by HCPS demonstrated more stable transport characteristics compared to the membrane made of the initial polymer. HCPS has a complex effect on the aging process of PTMSP. The introduction of HCPS into the polymer matrix not only slowed down the physical aging of PTMSP, but also reduced chemical aging due to removal of active reagents.

A novel concept of film distillation equipped with the membrane condenser (FD-MC) was proposed and implemented for the concentration of brine salt solutions. In this thermo-gradient method, the water was evaporated from the thin liquid film flowing alongside the hot surface, and then directly condensed on the cold surface of the porous membrane placed at the distance of few millimeters from the feed. The change of the membrane positioning from the hot feed solution to the cold water stream (coolant circuit) enables to overcome the common challenges of the membrane distillation process like long-term stability towards pores wetting, membrane scaling, and latent heat loss. Comparing with the air gap membrane distillation with membrane condenser (AGMD-MC), FD-MC demonstrated higher water flux (14.7 kg/m(2).h) and stable performance during the concentration of NaCl solution from 50 up to 230 g/kg (microcrystal formation was noticed) even in the presence of organic pollutants (kerosene or surfactants). A mathematical model of heat and mass transfer in FD-MC process was proposed and successfully verified. With the respect to the temperature of hot (40-100 degrees C) and cold (10-60 degrees C) circuits, the energy consumption and thermal efficiency of FD-MC process were in the range of 2.7-3.2 MJ/kg and up to 97%, respectively.

The review summarizes the accumulated scientific results on the separation of mixtures of organic solvents by pervaporation and reverse osmosis. It has been shown that the pervaporation process makes it possible to achieve generally higher selectivity as compared to the reverse osmosis process; however, a number of developments, such as membranes from polyketone or PIM-1, make it possible to effectively separate components with similar molecular weights. Such membranes allow the main advantage of reverse osmosis—lower energy consumption due to the absence of phase transitions—to be gained. It is noted that with the use of reverse osmosis membranes, the highest efficiency can be achieved in the case of separation of mixtures of organic liquids that differ significantly in their polarity, a process that is especially important for the regeneration of polar extractants in the petrochemical industry.

A scheme of a membrane distillation unit with the possibility of using solar energy collectors has been proposed for treatment of water–salt solutions. This scheme has been tested in the Simulink (MATLAB) simulation environment using a seawater desalination process as a model system. Based on solar radiation data received in Vietnam, a distillation process has been simulated using a solar collector and an electric heater. Experimental approbation of the model has been carried out by the desalination of a NaCl solution by membrane distillation with a porous condenser. The calculated productivity of the modeled system agrees with the obtained experimental data. Simulation showed the possibility of reducing energy consumption by 61% in the process of desalination of an aqueous solution of NaCl using low-grade heat.

BACKGROUND: Fermentation broth is a complex mixture which contains target and other organic compounds which must be continuously recovered to maintain microorganism activity. To overcome this problem, a sorption‐assisted thermopervaporation (SA‐TPV) method has been proposed, which enables the removal of volatile organics by means of evaporation, and low and nonvolatile compounds by membrane adsorption. RESULTS: A dense membrane made of polymer of intrinsic microporosity in the SA‐TPV process demonstrated stable performance (butanol flux 57.7 g m⁻² h⁻¹; separation factor butanol/water 30.4) within five months of operation with cell‐free ABE fermentation broth. Scanning electron microscopy/energy dispersive X‐ray spectroscopy analysis revealed that the proposed SA‐TPV method reduced ‘external’ membrane fouling by a factor of three. Fourier transform infrared and gas chromatography/ mass spectrometry analysis confirmed that it was possible to extract ‘external’ and ‘internal’ foulants by membrane adsorption followed by in situ regeneration. CONCLUSION: The SA‐TPV approach can be effective for recovery of both volatile and nonvolatile compounds from fermentation broth, whilst maintaining stable long‐term membrane performance. © 2019 Society of Chemical Industry

A wide range of membranes (hydrophobic and hydrophilic) for the task of triethylene glycol dehydration by thermopervaporation was studied. The transport characteristics of the membranes using individual liquids (water, triethylene glycol) were determined in the thermopervaporation process with varying temperature of the feed flux (40-). The maximum water flux (3.7 kg/m 2 ∙h) in all the studied temperature ranges was demonstrated by the commercial pervaporation hydrophobic PolyAn membrane. For the commercial hydrophilic membrane MDK-I water flux at 80 °С was 2.8 kg/m 2 ∙h. During thermopervaporation of triethylene glycol in the studied temperature range, TEG flux through the membranes was not observed, which shows the advantage of this process for TEG dehydration. For the first time, experiments were provided using PolyAn membranes to removal water from TEG by thermopervaporation with porous condenser. The maximum permeate flux (1.9 kg/m 2 ∙h) was achieved for the PolyAn membrane at a concentration of 70 % wt. TEG in water