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Evaluate membrane technologies synergistic with high-temperature hydrogen-rich syngas production from biomass to determine the type and integration thereof that is most cost-effective.
Abstract BACKGROUND For improving the permeability and selectivity of adsorption separation membranes, membrane materials, structural morphology and separation technology must continue to be investigated. Development of a membrane that is environmentally friendly, cost‐effective and with high filter precision is an important direction in current research. RESULTS The air pressure spraying method was used to prepare an activated carbon (AC)–cellulose acetate/chitosan (CA/CS) composite membrane. The CA/CS fiber composite membrane was prepared as substrate layer, and AC was loaded on the surface of the CA/CS composite membrane as a functional adsorption layer. When the spraying pressure was 0.01 MPa and the mass ratio of AC/CS was 2:1, a composite membrane with even and compact morphology could be obtained. Both the compact AC functional layer and complete CA/CS substrate layer endowed the AC–CA/CS composite membrane with an excellent water filtration property. At low feeding pressure, the permeate flux and rejection rate of bisphenol A (BPA) could reach 9.27 × 10 3 L m −2 h −1 and 98.31%, respectively. Meanwhile, the adsorption capacities of the membrane were investigated. It tended to equilibrate quickly in 2 min for dyes and BPA. The equilibrium adsorption capacities of the membrane for acid blue, acid yellow and BPA were 175.80, 164.0815 and 79.58 mg g −1 , respectively. The adsorption process conformed to pseudo‐second‐order kinetics and the Langmuir monolayer adsorption model. CONCLUSIONS This work could provide a practical and effective feasibility for membrane separation technology. © 2020 Society of Chemical Industry (SCI)
Water scarcity is one of the greatest societal challenges facing humanity.
Membrane pores are implicated in several critical functions, including cell fusion and the transport of signaling molecules for intercellular communication. However, these structural features are often difficult to probe directly. Droplet interfacial bilayers offer a synthetic platform to study such membrane properties. We develop a theory that links size-selective transport across a metastable membrane with its transient structural properties. The central quantity of our theory is a dynamic permeability that depends on the mechanism of pore growth, which controls the transient distribution of pore sizes in the membrane. We present a mechanical perspective to derive pore growth dynamics and the resulting size distribution for growth via Ostwald ripening and discuss how these dynamics compare to other growth mechanisms such as coalescence and growth through surfactant desorption. We find scaling relations between the transported particle size, the pore growth rate, and the time for a given fraction of particles to cross the membrane, from which one may deduce the dominant mechanism of pore growth, as well as material properties and structural features of the membrane. Finally, we suggest experiments using droplet interfacial bilayers to validate our theoretical predictions.
A three-man urine water recovery preprototype subsystem using a new concept to provide efficient potable water recovery from waste fluids on extended duration space flights has been designed, fabricated, and tested. Low power, compactness, and gravity insensitive operation are featured in this vacuum distillation subsystem that combines a hollow fiber polysulfone membrane evaporator with a thermoelectric heat pump. Application and integration of these key elements have solved problems inherent in previous reclamation subsystem designs. The hollow fiber elements provide positive liquid/gas phase control with no moving parts other than a waste liquid recirculation pump and a product water withdrawal pump. Tubular membranes provide structural integrity, improving on previous flat sheet membrane designs. A thermoelectric heat pump provides latent energy recovery.
A single-cell electrochemical reactor that utilizes a proton exchange membrane (PEM) as a solid electrolyte is being investigated for posttreatment of reclaimed waste waters with low or negligible electrolyte content. Posttreatment is a final 'polishing' of reclaimed waste waters prior to reuse, and involves removing organic impurities at levels as high as 100 ppm to below 500 ppb total organic carbon (TOC) content to provide disinfection. The system does not utilize or produce either expendable hardware components or chemicals and has no moving parts. Test data and kinetic analysis are presented. The feasibility and application for water reclamation processes in controlled ecological environments (e.g., lunar/Mars habitats) are also presented. Test results show that the electrochemical single cell reactor provides effective posttreatment.
Perstractive fermentation is a good way to increase the productivity of bioreactors. Using Propionibacteria as the model system, the feasibility of using supported emulsion liquid membrane (SELM) for perstractive fermentation is assessed in this study. Five industrial solvents were considered as the solvent for preparing the SELM. The more polar a solvent is, the higher the partition coefficient. However, toxicity of a solvent also increases with its polarity. CO-1055 (industrial decanol/octanol blend) has the highest partition coefficient toward propionic acid among the solvents that has no molecular toxicity toward Propionibacteria. A preliminary extraction study was conducted using tetradecane as solvent in a hydrophobic hollow fiber contactor. The result confirmed that SELM eliminates the equilibrium limitation of conventional liquid-liquid extraction, and allows the use of a non-toxic solvent with low partition coefficient.
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This project will focus on diagnostics and quality control understandings of continuously produced FFI membranes [both Anion Exchange Membrane (AEM) and Proton Exchange Membrane (PEM)] and continuously produced FFI electrodes. Optimization of methods and novel quality control techniques will be developed as needed.
The inexpensive sulfur raw material is promising to enable cost-effective redox flow batteries for long duration energy storage. But the catastrophic through-membrane crossover of polysulfides remains a severe challenge resulting in irreversible performance degradation and short cycle life. In this work, we demonstrate that use of a permselective cation exchange membrane yields a two orders of magnitude enhancement in polysulfide retention compared to the benchmark Nafion membrane. Combined physico-chemical, spectroscopic, and microscopic analyses suggest more disordered sidechain structures, which lead to the more hydrophobic nature and smaller hydrophilic domains in the membrane. The microstructural features contribute to the effective mitigation of polysulfide crossover. As a result, the cycle life of polysulfide/ferricyanide flow cells is boosted over a substantially extended test time. This finding sheds light on the fundamental membrane factors that cause polysulfide permeation and can provide feasible directions in the development of permselective membranes for polysulfide flow batteries.
The development of proton exchange membrane (PEM) fuel cell power plants with high energy efficiencies and high power densities is gaining momentum because of the vital need of such high levels of performance for extraterrestrial (space, underwater) and terrestrial (power source for electric vehicles) applications. Since 1987, considerable progress has been made in achieving energy efficiencies of about 60 percent at a current density of 200 mA/sq cm and high power densities (greater than 1 W/sq cm) in PEM fuel cells with high (4 mg/sq cm) or low (0.4 mg/sq cm) platinum loadings in electrodes. The following areas are discussed: (1) methods to obtain these high levels of performance with low Pt loading electrodes - by proton conductor impregnation into electrodes, localization of Pt near front surface; (2) a novel microelectrode technique which yields electrode kinetic parameters for oxygen reduction and mass transport parameters; (3) demonstration of lack of water transport from anode to cathode; (4) modeling analysis of PEM fuel cell for comparison with experimental results and predicting further improvements in performance; and (5) recommendations of needed research and development for achieving the above goals.
Development of platinum group metal (PGM)-free catalysts for oxygen reduction reaction (ORR) has been a strategic research topic for proton exchange membrane (PEM) fuel cells. Present state-of-art PGM-free ORR catalysts are Fe, N co-doped carbon (Fe-N-C) catalysts, which unfortunately exhibit instability concerns. Herein, we report a stable atomically dispersed Co, N co-doped carbon (Co-N-C) catalyst with high Co content of 1.0 at% and the active site, i.e., the coordination of Co, is CoN2+2 in nature. The Co-N-C catalyst demonstrated high ORR activity comparable to, and high stability over 3 times better than, that of the Fe-N-C catalyst. It also achieved a high activity of 22 mA cm2 at 0.9 ViR-free and a power density of 0.61 W cm-2 under 1.0 bar H2/O2. Further, we identify two main degradation mechanisms of the PGM-free catalysts: catalyst oxidation by H2O2/radicals and demetalation. The improved stability of Co-N-C relative to Fe-N-C is attributed to less Fenton-reactive nature of Co and significantly enhanced resistance to demetalation of Co-N-C.
The development of anion-exchange membrane fuel cells (AEMFCs) has recently accelerated due to synergistic improvements yielding highly conductive membranes, stable ionomers, and enhanced alkaline electrocatalysts. However, cell durability, especially under realistic conditions, still poses a major challenge. Herein, we employ low-loadings of Pt-free Pd-based catalysts in the anode of AEMFCs and elucidate potential degradation mechanisms impacting long-term performance under conditions analogous to the real-world (high current density, H 2 –air (albeit CO 2 -free), and intermittent operation). Our high-performing AEMFCs achieve impressive performance with power densities approaching 1 W cm —2 and current densities up to 3.5 A cm —2 . Over a 200 h period of continuous operation in H 2 –air at a current density of 600 mA cm —2 , our model Pd/C–CeO 2 anode cell exhibits record stability (~30 μV h —1 degradation) compared to the literature and up to 6× better stability than our Pd/C and commercial Pt/C anode cells. Following an 8 h shutdown, the Pd/C–CeO 2 anode cell was restarted and continued for an additional 300 h with a higher degradation rate of ~600 μV h —1 . Thorough in situ evaluations and post-stability analyses provide insights into potential degradation mechanisms to be expected during extended operation under more realistic conditions and provide mitigation strategies to enable the widespread development of highly durable AEMFCs.
We report water management is critical in optimizing anion exchange membrane fuel cell (AEMFCs) performance and durability. The role of membranes on determining cell water balance in AEMFCs has received limited study. A more thorough understanding of membrane water transport parameters is necessary for thorough cell optimization. In this study, a novel method for probing limiting current based on water flux across an AEMFC is presented for the first time. The water limiting current has been investigated as a function of relative humidity of anode and cathode streams, cathode backpressure and cell operating temperature. From these studies, it is clearly shown that water diffusion through the membrane from the anode is the most critical mechanism for achieving high current density performance and durability. The developed method can act as a novel screening technique that focuses on the impacts of water transport parameters and helps identify promising membrane materials based on their water transport properties. A critical but underappreciated facet of AEMFC performance and durability.
Subunit vaccines offer advantages over more traditional inactivated or attenuated whole-cell-derived vaccines in safety, stability, and standard manufacturing. To achieve an effective protein-based subunit vaccine, the protein antigen often needs to adopt a native-like conformation. This is particularly important for pathogensurface antigens that are membrane-bound proteins. Cell-free methods have been successfully used to produce correctly folded functional membrane protein through the co-translation of nanolipoprotein particles (NLPs), commonly known as nanodiscs. This strategy can be used to produce subunit vaccines consisting of membrane proteins in a lipid-bound environment. However, cell-free protein production is often limited to small scale (<1 mL). The amount of protein produced in small-scale production runs is usually sufficient for biochemical and biophysical studies. However, the cell-free process needs to be scaled up, optimized, and carefully tested to obtain enough protein for vaccine studies in animal models. Other processes involved in vaccine production, such as purification, adjuvant addition, and lyophilization, need to be optimized in parallel. This paper reports the development of a scaled-up protocol to express, purify, and formulate a membrane-bound protein subunit vaccine
The following subjects are addressed: (1) the mechanism and kinetics of carbothermal reduction of simulated lunar ilmenite using carbon and, particularly, CO as reducing agents; (2) the determination of the rate-limiting steps; (3) the investigation of the effect of impurities, particularly magnesium; (4) the search for catalysts suitable for enhancement of the rate-limiting step; (5) the comparison of the kinetics of carbothermal reduction with those of hydrogen reduction; (6) the study of the combined use of CO and hydrogen as products of gasification of carbonaceous solids; (7) the development of reduction methods based on the use of waste carbonaceous compounds for the process; (8) the development of a carbothermal reaction path that utilizes gasification of carbonaceous solids to reducing gaseous species (hydrocarbons and carbon monoxide) to facilitate the reduction reaction kinetics and make the process more flexible in using various forms of carbonaceous feeds; (9) the development of advanced gas separation techniques, including the use of high-temperature ceramic membranes; (10) the development of an optimum process flow sheet for carbothermal reduction, and comparison of this process with the hydrogen reduction scheme, as well as a general comparison with other leading oxygen production schemes; and (11) the use of new and advanced material processing and separation techniques.
Abstract Solar steam water purification and fog collection are two independent processes that could enable abundant fresh water generation. We developed a hydrogel membrane that contains hierarchical three-dimensional microstructures with high surface area that combines both functions and serves as an all-day fresh water harvester. At night, the hydrogel membrane efficiently captures fog droplets and directionally transports them to a storage vessel. During the daytime, it acts as an interfacial solar steam generator and achieves a high evaporation rate of 3.64 kg m −2 h −1 under 1 sun enabled by improved thermal/vapor flow management. With a homemade rooftop water harvesting system, this hydrogel membrane can produce fresh water with a daily yield of ~34 L m −2 in an outdoor test, which demonstrates its potential for global water scarcity relief.
The objectives of the proposed project were to develop highly porous membrane adsorbents comprising CO 2 -philic polymers and self-assembled inorganic nanocages (SINCs) for rapid temperature swing adsorption using electricity-free solar heating and radiative cooling, enabling an economically viable approach for direct air capture (DAC). Our core technical activities combine three key innovations. (1) Highly porous flat-sheet membrane adsorbents contain CO 2 -philic amines that can be easily produced using a phase inversion method. (2) CO 2 -philic SINCs can be easily dispersed in the polymers with great stability (compared with the metal-organic frameworks or MOFs). (3) The adsorption and desorption are integrated with solar heating and radiative cooling for rapid continuous operation, in contrast to traditional long-cycle separate operation. The membrane adsorbents containing amines, polymers, and SINCs were produced using a one-step industrial process. The porous membranes coupled with porous SINCs offer low resistance for gas flow and fast CO 2 sorption/desorption cycles, while the incorporation of the additional amine groups provides high CO 2 sorption capacity. The key achievements are summarized below. (1) Membrane adsorbents with high PEI loading (>40%), high porosity of >80%, and low gasflow resistance were prepared in one step using commercially available, low-cost materials. (2) Membrane adsorbents based on Solupor and PEI show CO 2 sorption capacity of >1.5 mmol/g using air containing 400 ppm at a relative humidity of 15%. (3) Effect of the adsorbent compositions (such as PEI type, PEI content, SINC content, porosity) on the CO 2 sorption was systematically investigated. (4) Effect of the processing conditions (such as CO 2 content, temperature, and relative humidity) on the CO 2 sorption was systematically investigated; (5) The stability of the membrane adsorption against many cycles of sorption and desorption was studied. The higher molecular weight of PEI (PEI25k) shows better stability than PEI800. (6) Advanced materials with radiative cooling were developed, which can decrease the temperature by 5-7 °C compared to the ambient temperature. (7) Preliminary techno-economic analysis shows that our process may achieve a capture cost of $1,343/tonne CO 2 with a total OPEX cost of $1,112/tonne CO 2 . The adsorbent replacement cost accounted for 52% of the total OPEX cost. Membrane adsorbents with lower costs and longer operation life can significantly decrease the cost. The proposed project directly addresses the requirement of DE-FOA-0002188, i.e., novel materials with CO 2 adsorption capacity for direct air capture with integrated solar heating and radiative cooling to reduce the cost of the DAC. Our future work will focus on the development of low-cost adsorbents that can be stable at the sorption and desorption conditions for long term.