Absorption with aqueous amine solvents is a well-established technology for acid gas removal and will continue to be a readily available option for post-combustion CO2 capture. Its main drawback is the solvent degradation under process conditions, due to oxygen captured from the flue gases. Dissolved O-2 oxidizes amines, forming various degradation products, including heat-stable salts (HSS), which intensify corrosion and reduce the sorption capacity of the solvent. This paper investigates direct removal of dissolved O-2 from amine solvents in gas-liquid membrane contactors. Novel composite membranes have been developed for this process. They consist of a highly permeable polymer blend, made from poly [1-(trimethylsilyl)-1-propyne] (PTMSP) and polyvinyltrimethylsilane (PVTMS), which is deposited as a thin protective layer on porous polysulfone hollow fibers and tubular ceramic supports. For the first time, a comprehensive study has been carried out on the efficiency of dissolved O-2 removal vs. contactor and process parameters (membrane support type; amine solvent type; solvent CO2 loading; driving force generation mode; solvent velocity; temperature). The deoxygenation performance of the contactors has been demonstrated in the O-2 removal process from the amine solvent under the conditions encountered in an absorber sump during the CO2 capture process (30 % aqueous monoethanolamine solvent with CO2 loading of 0.5 mol/mol at 60 degrees C). In this case, the O-2 removal efficiency of up to 46 % in an hour has been achieved for developed contactors, which reduces the estimated rate of HSS formation by similar to 2 times compared to non-deoxygenated solvents. The size of the membrane was calculated to remove 90 % of the dissolved oxygen in a hypothetical post-combustion CO2 capture plant with a solvent flow rate of 120 m(3)/h, amounting to similar to 1460 m(2) for ceramic-based membranes.

Anthropogenic CO2 emissions into the atmosphere are one of the unsolved problems of the modern world. A significant contribution to the increase in the concentration of CO2 in the atmosphere is made by the flue gases of the energy production industry. The most mature technology for post-combustion CO2 capture is absorption using amine solvents. The disadvantage of this technology is the oxidative degradation of amines due to the presence of dissolved oxygen in the solvent. A promising solution to control the cause of amine degradation is oxygen concentration maintenance. In this work, membrane contactors were developed for dissolved oxygen removal (deoxygenation) from model alkanolamine CO2 solvents. Composite and flat sheet membranes based on highly permeable glassy polymers poly[1-(trimethylsilyl)-1-propyne] and poly[vinyltrimethylsilane] were obtained. Gas-liquid and liquid-liquid membrane contactors based on the fabricated membranes were developed. A deoxygenation process was implemented using a vacuum to create a driving force in the case of a gas-liquid contactor, while a liquid-liquid membrane contactor was tested using aqueous solutions of oxygen scavengers. The various types of alkanolamines were used to test the deoxygenation process. It has been shown that 5-37% of dissolved oxygen can be removed from amine solution using the developed membrane contactors. The process efficiency was evaluated with a resistance-in-series model.

The main disadvantage of absorption with aqueous alkanolamine solvents is the solvent degradation under process conditions in the presence of oxygen captured from flue gases. In this communication, the direct dissolved oxygen removal from an amine solvent in liquid–liquid membrane contactors is examined. The membranes from ladder-like polyphenylsilsesquioxanes are used for the first time for this process. The membrane deoxygenation is demonstrated in the O2 removal process from monoethanolamine (MEA) into an aqueous solution of Na2SO3. In this case, the O2 removal efficiency reached up to 40% within 1 h.

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The process of removal of the oxygen dissolved in a monoethanolamine-based absorbent from it in gas–liquid membrane contactors for the prevention of the oxidation destruction of this absorbent in the case of its use for the absorption removal of carbon dioxide from the combustion gases was investigated. The influence of the parameters of formation of composite membranes on the basis of porous tubular ceramic substrates with a thin selective nonporous polymer layer of a mixture of poly[1-(trimethylsilyl)-1-propyne] and poly(vinyl trimethylsilane) on their gas-transfer properties was determined. With the use of the membranes obtained, the process of removal of the oxygen dissolved in the aqueous solutions of monoethanolamine from them was realized. The possibility of intensification of this process with the use of a flow turbulator installed in the liquid part of a membrane contactor was demonstrated.

The study focuses on the removal of dissolved oxygen from a model monoethanolamine (MEA)-based absorbent to prevent oxidative degradation during the absorption process of flue gas CO2 removal. A mathematical model was developed to evaluate the deoxygenation parameters in a gas-liquid membrane contactor using composite hollow-fiber membranes with a thin non-porous layer made of a blend of polytrimethylsilylpropyne and polyvinyltrimethylsilane. The modeling results were shown to be in good agreement with experimental data on O2 removal efficiency. The model was applied to assess the scaling of the membrane system for dissolved O2 removal to handle an absorbent flow rate of 120 m3/h in a hypothetical CO2 capture plant using absorption technology. The influence of system parameters (absorbent linear flow rate, membrane contactor length, number of membranes in the contactor, initial O2 concentration in the absorbent) on O2 removal efficiency was determined. It was shown that to achieve 90

This work is devoted to the removal of dissolved oxygen from a model absorbent based on monoethanolamine (MEA) to prevent its oxidative degradation during the absorption purification of flue gases from carbon dioxide. Composite membranes based on porous ceramic and polymeric supports with a thin selective layer of poly[1-(trimethylsilyl)-1-propyne] or its blend with polyvinyltrimethylsilane are developed, and gas-liquid membrane contactors are created on their basis. It is shown that the use of these contractors in the vacuum mode allows the removal of up to 60% of dissolved oxygen from the model sorbent.

Membrane gas–liquid contactors have great potential to meet the challenges of amine CO2 capture. In this case, the most effective approach is the use of composite membranes. However, to obtain these, it is necessary to take into account the chemical and morphological resistance of membrane supports to long-term exposure to amine absorbents and their oxidative degradation products. In this work, we studied the chemical and morphological stability of a number of commercial porous polymeric membranes exposed to various types of alkanolamines with the addition of heat-stable salt anions as a model of real industrial CO2 amine solvents. The results of the physicochemical analysis of the chemical and morphological stability of porous polymer membranes after exposure to alkanolamines, their oxidative degradation products, and oxygen scavengers were presented. According to the results of studies by FTIR spectroscopy and AFM, a significant destruction of porous membranes based on polypropylene (PP), polyvinylidenefluoride (PVDF), polyethersulfone (PES) and polyamide (nylon, PA) was revealed. At the same time, the polytetrafluoroethylene (PTFE) membranes had relatively high stability. On the basis of these results, composite membranes with porous supports that are stable in amine solvents can be successfully obtained to create liquid–liquid and gas–liquid membrane contactors for membrane deoxygenation.

Desalination and treatment of wastewater has become critical for Asia regions with water scarcity. In this work, the concept of thin-film distillation equipped with a porous condenser (FDPC) was considered for its implementation in a tropical climate of Vietnam. It was found that samples with a concentration of biocide of 0.5 wt.% possessed lower biofouling, in contrast to the neat membranes. The FD-PC module was developed and water desalination experiments were conducted in Russia and Vietnam. The experiments showed high reproducibility of the results; in particular, the evaporation rate was (4.9/3.0) kg/m2h in Russia and (4.1/2.0) kg/m2h in Vietnam. In addition, as part of this work, the optimal configuration of the installation was calculated using solar collectors as the main energy source. The calculation showed high energy efficiency: specific energy consumption 0.1–0.5 kWh/m3.

Amine CO2 solvents undergo oxidative degradation with the formation of heat stable salts (HSS). These HSS reduce the sorption capacity of amines and lead to intense corrosion of the equipment. In our work, we propose a membrane-supported liquid-liquid extraction of the HSS from alkanolamines. For this purpose, a hollow fiber membrane contactor was used for the first time. A lab-scale extraction system on the basis of a hollow-fiber liquid-liquid membrane contactor with hollow fiber ultrafiltration polyvinylidenefluoride and polysulfone membranes has been studied. The extraction of the HSS-ions from a 30 wt.% solution of monoethanolamine was carried out using a 0.25–1 M solution of OH-modified methyltrioctylammonium chloride in 1-octanol as an extractant. It has been shown that >90% of HSS ions can be extracted from the alkanolamine solvent within 8 h after extraction. The results obtained confirm the possibility of using membrane extraction with a liquid-liquid membrane contactor for the reclaiming of amine CO2 solvents to increase the general efficiency of carbon dioxide capture.

A new interpretation of the mechanism of the polyvinylidene fluoride (PVDF) membrane formation using the nonsolvent-induced phase separation (NIPS) method based on an analysis of the complete experimental phase diagram for the three-component mixture PVDF–dimethyl acetamide (DMAc)–water is proposed. The effects of the precipitation bath’s harshness and thermodynamic affinity of the polymer’s solvent on the morphology, crystalline structure, transport and physical–mechanical properties of the membranes are investigated. These characteristics were studied via scanning electron microscopy, wide-angle X-ray scattering, liquid–liquid porosimetry and standard methods of physico-mechanical analysis. It is established that an increase in DMAc concentration in the precipitation bath results in the growth of mean pore size from ~60 to ~150 nm and an increase in permeance from ~2.8 to ~8 L m−2 h−1 bar−1. It was observed that pore size transformations are accompanied by changes in the tensile strength of membranes from ~9 to ~11 and to 6 MPa, which were explained by the degeneration of finger-like pores and appearance of spherulitic structures in the samples. The addition of water to the dope solution decreased both the transport (mean pore size changed from ~55 to ~25 nm and permeance reduced from ~2.8 to ~0.5 L m−2 h−1 bar−1) and mechanical properties of the membranes (tensile strength decreased from ~9 to ~6 MPa). It is possible to conclude that the best membrane quality may be reached using pure DMAc as a solvent and a precipitation bath containing 10–30% wt. of DMAc, in addition to water.

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).

In this work, perspective polymeric materials were developed for membrane contactor applications, e.g., for the dissolved oxygen removal from amine CO2 capture solvents. Several polymeric blends based on poly[1-trimethylsilyl-1-propyne] (PTMSP) and poly[vinyltrimethylsilane] (PVTMS) were studied. The gas and water vapor sorption and permeability coefficients for the PTMSP/PVTMS blend membranes at different PVTMS contents (0–100%) were obtained under temperatures of 30 and 60 °C for the first time. As the PVTMS content increases, the O2 and CO2 permeabilities decrease by 160 and 195 times at 30 °C, respectively. The fractional accessible volume of the polymer blends decreases accordingly. The transport of the CO2 capture solvent vapors through the PTMSP/PVTMS blend membranes were determined in thermo-pervaporation (TPV) mode using aqueous monoethanolamine (30%), N-methyldiethanolamine (40%), and 2-amino-2-methyl-1-propanol (30%) solutions as model amine solvents at 60 °C. The membranes demonstrated high pervaporation separation factors with respect to water, resulting in low amine losses. A joint analysis of the gas permeabilities and aqueous alkanolamine TPV data allowed us to conclude that the polymer blend composition of PTMSP/PVTMS 70/30 provides an optimal combination of a sufficiently high oxygen permeability and the pervaporation separation factor at a temperature of 60 °C.

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.