Binary Mixtures Of CO2 Research Articles

Assessment of Neurotoxic Mechanisms of Individual and Binary Mixtures of Cobalt, Nickel and Lead in Hippocampal Neuronal Cells.

Many studies have focused on the neurotoxic effects of single metals, while investigation on the exposure to metal mixtures, which mainly occur in real-life situations, is scarce. This study sought to assess the neurotoxic effect of Ni, Co, and Pb binary mixtures and their individual effects in hippocampal neuronal cells (HT-22). Cells were exposed to Ni, Co, and Pb separately for 48 h at 37°C and 5% CO2, and cell viability was assessed. Morphological assessment of the cells exposed to binary mixtures of Co, Ni, and Pb and single metals was assessed using a microscope. Furthermore, acetylcholinesterase (AChE) activity, oxidative stress biomarkers (glutathione [GSH] and malondialdehyde [MDA] levels, catalase [CAT], and glutathione-S transferase [GST] activities) and nitric oxide [NO] levels were evaluated after treatment with the binary mixtures and single metals. Binary mixtures of the metals reduced cell viability, exerting an additivity action. The combinations also exerted synergistic action, as revealed by the combination index. Furthermore, a significant reduction in AChE activity, GSH levels, CAT and GST activities, and high MDA and NO levels were observed in neuronal cells. The additive interactions and synergistic actions of the binary mixtures might contribute to the significant reduction of AChE activity, GSH levels, GST, and CAT activities, and an increase in MDA and NO levels. The findings from this study revealed significant evidence that binary mixtures of Co, Pb, and Ni may induce impaired neuronal function and, ultimately, neurodegeneration.

Performance of a high-temperature transcritical pumped thermal energy storage system based on CO2 binary mixtures

Pumped thermal energy storage is a novel energy storage technology with features of high efficiency, geographical independence and suitable for bulk capacity energy storage. As a subset of pump thermal energy storage system, the transcritical CO2 arrangements have received widespread attention due to their excellent thermodynamic performance. However, the high cost and low efficiency of heat exchange progress caused by CO2 phase transition hinder the transformation of this system from scientific theory to practical application. CO2 binary mixtures is innovatively employed as working fluid in proposed system. The temperature of mixture is variable rather than remaining constant during the evaporation and condensation progresses. R134a, R290, R600 and R601 are selected respectively to mix with CO2 to form the new working fluids. Advanced thermodynamic and economic models are established to investigate the performance of novel systems. Results indicate that the system driven by CO2/R134a with a refrigerant mass fraction of 0.15 exhibits the optimal overall performance. At the optimal point of the 10 MW/8h system, the round trip efficiency and levelized cost of storage are 66.18 % and 0.146 $/kWh, respectively. Moreover, the investigation of system performance with various energy storage capacities is put forward. It is shown that when the energy system capacity reaches 300 MW, the levelized cost of storage can be reduced to 0.122 $/kWh. To adapt to different peak and valley periods in different regions, systems with different charge and discharge times are investigated and it is found that the charge duration should better be equal to the discharge duration.

Experimental isochoric apparatus for bubble points determination: Application to CO2 binary mixtures as advanced working fluids

Carbon dioxide binary mixtures are increasingly considered as working fluids in transcritical power cycles, due to the capability to perform liquid-phase compression even at high environmental temperatures. However, a robust thermodynamic model is essential for optimal and reliable design conditions. It is widely recognised that fine-tuning the equation of state with experimental vapour-liquid equilibrium data of the mixture significantly enhances its reliability.In this work, a new apparatus dedicated to vapour-liquid equilibrium measurements of mixtures is presented. The proposed method consists of a constant-volume system, where bubble points are identified from the divergence of slope of the isochoric lines between the two-phase and liquid regions, in the temperature-pressure plane. The temperature and pressure limits of the apparatus are 503 K and 25 MPa.Bubble points of CO2 binary mixtures with hexafluorobenzene (C6F6) and n-pentane (C5H12) have been measured and compared with previous literature data for validation purposes. Then, the CO2 mixture with octafluorocyclobutane (c-C4F8) is experimentally studied, addressing a literature gap in bubble point data. The data are used to calibrate the thermodynamic model, leading to affordable design conditions of the power cycle compared to the non-optimised thermodynamics scenario, in a concentrated solar power tower plant.

Importance of Bridging Molecular and Process Modeling to Design Optimal Adsorbents for Large-Scale CO2 Capture.

ConspectusCarbon capture, utilization, and storage have been identified as key technologies to decarbonize the energy and industrial sectors. Although postcombustion CO2 capture by absorption in aqueous amines is a mature technology, the required high regeneration energy, losses due to degradation and evaporation, and corrosion carry a high economic cost, precluding this technology to be used today at the scale required to mitigate climate change. Solid adsorbent-based systems with high CO2 capacities, high selectivity, and lower regeneration energy are becoming an attractive alternative for this purpose. Conscious of this opportunity, the search for optimal adsorbents for the capture of CO2 has become an urgent task. To accurately assess the performance of CO2 separation by adsorption at the needed scale, adsorbents should be synthesized and fully characterized under the required operating conditions, and the proper design and simulation of the process should be implemented along with techno-economic and environmental assessments. Several works have examined pure CO2 single-component adsorption or binary mixtures of CO2 with nitrogen for different families of adsorbents, primarily addressing their CO2 adsorption capacity and selectivity; however, very limited data is available under other conditions and/or with impurities, mainly due to the intensive experimental (modeling) efforts required for the large number of adsorbents to be studied, posing a challenge for their assessment under the needed conditions. In this regard, molecular simulations can be employed in synergy with experiments, reliably generating missing adsorption properties of mixtures while providing understanding at the molecular level of the mechanism of the adsorption process.This Account provides an outlook on strategies used for the rational design of materials for CO2 capture from different sources from the understanding of the adsorption mechanism at the molecular level. We illustrate with practical examples from our work and others' work how molecular simulations can be reliably used to link the molecular knowledge of novel adsorbents for which limited data exist for CO2 capture adsorption processes. Molecular simulation results of different adsorbents, including MOFs, zeolites, and carbon-based and silica-based materials, are discussed, focusing on understanding the role of physical and chemical adsorption obtained from simulations and quantifying the impact of impurities in the performance of the materials. Furthermore, simulation results can be used for screening adsorbents from basic key performance indicators, such as cycling the working capacity, selectivity, and energy requirement, or for feeding detailed dynamic models to assess their performance in swing adsorption processes on the industrial scale, additionally including monetized performance indicators such as operating expenses, equipment sizes, and compression cost. Moreover, we highlight the role of molecular simulations in guiding strategies for improving the performance of these materials by functionalization with amines or creating hybrid solid materials. We show how integrating models at different scales provides a robust and reliable assessment of the performance of the adsorbent materials under the required industrial conditions, rationally guiding the search for best performers. Trends in additional computational resources that can be used, including machine learning, and perspectives on practical requirements for leveraging CO2 capture adsorption technologies on the needed scale are also discussed.

Effects of non‐condensable CCUS impurities (CH4, O2, Ar and N2) on the saturation properties (bubble points) of CO2‐rich binary systems at low temperatures (228.15–273.15 K)

AbstractThe present work investigated the effects of some non‐condensable impurities (i.e., N2, O2, CH4, and Ar) on the phase behaviour of CO2‐rich systems at low temperature conditions (228.15–273.15 K). The study focused on bubble point measurements of CO2‐rich systems using the isothermal (pressure–volume) method at different mole fractions of CO2 (99.5%–95%). The obtained experimental data were used to validate multi‐fluid Helmholtz energy approximation (MFHEA) and Peng–Robinson (PR) equations of state (EoSs). For all data points, the measurements’ uncertainties for temperature and pressure were 0.14 K and 0.03 MPa, respectively. While the composition uncertainty of the CO2 systems was a maximum of 0.024%. The findings reveal that as the mole fractions of the impurities increased, the bubble point pressures of the binary mixtures were elevated. Among all the investigated impurities, N2 has the most significant effect on the bubble point pressures of CO2 binary mixture at all the isotherms and compositions. Both MFHEA and PR models agreed well with the measured equilibrium points. For all systems, the average absolute deviations of the measured experimental data against the MFHEA and PR EoSs, were found to be less than 3.4% and 2.2%, respectively. Although the MFHEA EoS overpredicted most of the data points, the overall trend agreed with the experimental data and was consistent with the data available in the literature. The findings imply that the presence of these non‐condensable impurities (even as low as 0.5% mole fraction) increases the risk of two‐phase flow at higher pressures in a CO2‐rich system. © 2023 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd.

Simultaneous Detection of CO and NO2 Gases using Interaction Analysis of SnS2 Sensor Array Response

Developing a multi-analyte gas sensing system that simultaneously detects trace levels of CO and NO2 at low temperatures is necessary for the Internet of Things (IoT) based air quality monitoring applications. Nevertheless, gas sensors operating at low temperatures are nonspecific and rarely detect target gases at lower ppb levels in the air. Herein, an array of two SnS2 sensors with different bias voltages has been developed and characterized upon exposure to individual and binary mixtures of CO and NO2 gases at different concentrations. The developed gas sensors array achieved the lower detection limit of 45 ppb for NO2 and 150 ppb for CO. Further, co-adsorption-induced interaction analysis was carried out to predict the target gas concentration in the binary mixture using the mixed gas response. The mean absolute percentage error of 7.86% is observed in predicting the target gas concentrations in the binary mixture, which indicates the high prediction accuracy of proposed method. As a minimal resource intensive approach, the proposed method can be used in air quality monitoring applications that require low-power and low-cost sensors.

CO2 Dissociation in Barrier Corona Discharges: Effect of Elevated Pressures in CO2/Ar Mixtures

The formation of carbon monoxide, oxygen and ozone in a barrier corona discharge (BCD) operating in pure carbon dioxide (CO2) and binary mixtures of CO2 and argon is studied. The asymmetric electrode configuration of the BCDs allows plasma operation at pressures exceeding 1 atm, up to 6 bar, at moderate high-voltage amplitudes below 15 kV. Charge–voltage plots and an equivalent circuit model are employed to characterize the electrical parameters at different pressures and gas compositions. Depending on these conditions and the voltage amplitude, full or partial coverage of the electrodes with plasma is obtained. The existence of an optimum pressure for power dissipation for each given operation voltage amplitude and gas composition can be confirmed and explained by the equivalent circuit model. Increasing the CO2 concentration in the working gas increases the mean reduced electric field strength E/N while pressure reduces it in the BCD. The CO2 conversion shows a maximum efficiency of about 4% at 1.5 bar for the gas mixture Ar/CO2 = 1:1 and a voltage amplitude of about 10 kV. The calculation of thermodynamic equilibrium parameters reveals that a relatively small increase in pressure can affect both, the equilibrium parameters and the reaction rates. As a result, the specific required energy for the reaction (ΔH/SEI\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta \\mathrm{H}/\\mathrm{SEI}$$\\end{document}) shows an optimum, but only 8% of the electrical input energy is spent for CO2 dissociation at these optimum conditions.

Molecular dynamics investigation on Widom line of binary mixtures of supercritical carbon dioxide containing noble gases

This work focuses on the effects of the addition of noble gases (Xe and Kr) at different concentrations on the thermodynamic properties and Widom line (WL) of supercritical carbon dioxide (S-CO2), as well as the microstructures of the binary mixture at different thermodynamic state points. Three thermodynamic properties (volume expansivity αp, isothermal compressibility κT, and isobaric heat capacity Cp) of CO2 + Xe and CO2 + Kr binary mixtures are investigated in the near-critical region (280–370 K, 8–14 MPa), and both of them significantly reduce the peaks of the three thermodynamic properties compared to pure CO2, and this effect enhances as the concentration of noble gases increases. The WL constructed by the maxima of the three thermodynamic properties of the CO2 + Xe binary mixture rotates clockwise around the critical point on the P-T plane as the concentration of Xe increases, while the same WL of the CO2 + Kr binary mixture shifts in the direction of temperature decrease on the P-T plane as the concentration of Xe increases. The Radial distribution function (RDF) of Xe and Kr in CO2 binary mixtures both exhibit significant first and blurry second peaks of RDF in the near-critical region consistent with pure CO2, which suggests the miscibility and homogeneity between CO2 and the two noble gases combined with visualization of the simulated mixture system.

Thermodynamic modeling of a residential heat pump for combined space and water heating using binary CO2-based mixtures

The residential sector answers for a considerable share of the energy consumption worldwide. An alternative to meet technical and environmental requirements of space heating and hot water demanded by this sector uses CO2 mixtures as a refrigerant in compression-based cycles. However, while CO2 is nonflammable and has low GWP and ODP, it performs poorly due to its low specific refrigerating effect and large throttling losses. Differently, mixtures with a low-GWP refrigerant and CO2 could enhance the performance of these cycles while attending the environmental requirements. Therefore, this study considered the use of a combined heat pump for space and water heating using binary mixtures of CO2 and several refrigerants. Through a computational model, three configurations were tested, along with different ratios of space heating to hot water demands, and different CO2 mass fractions on the mixture. The heat pump configuration with the best performance range was the one with three gas coolers, where the low temperature gas cooler preheats the water, the intermediate equipment heats the space, and the high temperature gas cooler heats the already preheated water to the operating temperature. For this arrangement, heat pumps primarily dedicated to space heating benefit from mixtures with low mass fractions of CO2, approximately 10%. In contrast, heat pumps primarily attending water heating perform better for high mass fractions of CO2 (∼ 90%). Furthermore, in this combined configuration, about 87% of the mixtures analyzed could have higher coefficient of performance than pure fluids, indicating an improvement of CO2 heat pumps.

A step towards dynamic: An investigation on a carbon dioxide binary mixtures based compressed gas energy storage system using energy and exergy analysis

A dynamic model of a compressed gas energy storage system is constructed in this paper to discover the system's non-equilibrium nature. Meanwhile, the dynamic characteristics of the CO2 binary mixture (i.e., CO2/propane, CO2/propylene, CO2/R161, CO2/R32, and CO2/DME) based system are first studied through energy and exergy analyses. Performance indicators are considered, including round trip efficiency, exergy efficiency, energy density, discharge time, and average power output. The effects of tank volume and ambient temperature on the system performance are analyzed. According to the results, although the round trip efficiency of the CO2 mixture system is reduced by about 0.68%–11.97% compared to pure CO2, the compressor performance and the system pressure stability are improved. When the tank volume increases from 10,000 m3 to 15,000 m3, the system round trip efficiency increases by 0.16%–0.33%. A further improvement of round trip efficiency for the CO2 mixture is found compared to pure CO2 at higher ambient temperature. This paper demonstrates the dynamic operational characteristics of the compressed gas energy storage system when using different CO2 binary mixtures, providing a reference for optimizing related systems. Potential scenarios and applications for the CO2 binary mixture are discussed for future research.

Thermodynamics analysis of the supercritical CO2 binary mixtures for Brayton power cycles

Supercritical CO2 Brayton-based cycles are a promising technology for concentrated solar power plants. Their high efficiency can be improved by using CO2 mixtures as working fluid instead of pure CO2. This work studies 3 cycle topologies: simple recompression (RCC), recompression with main compressor intercooling (RCMCI) and partial cooling recompression (PCRC), across a range of regenerator conductance (UA), compressor and turbine inlet temperatures. Each topology is simulated with different working fluids: CO2, CO2–NH3, CO2–SO2, CO2–COS and CO2–H2S. The influence of the working fluid, operating conditions and cycle irreversibility on the overall efficiency has been analyzed in depth, finding two interesting, opposing trends. The mixtures with higher critical pressure improve the heat absorption and rejection temperatures of the cycles, but also increase irreversibility. The combination of topology and mixture that achieves the best compromise between both trends will have the higher efficiency. In general, using RCMCI instead of PCRC or RCC can improve efficiency by up to 4% depending on the working fluid and operating conditions. Using a mixture instead of pure CO2 by up to near 3%.

Kerogen Differential Swelling during CO2-CH4 Adsorption: Mechanism and Significance

There exists differential swelling during the pure and competitive adsorption of CO2-CH4, whose mechanism was of broad interest to CO2-ESGR (CO2 enhanced shale gas recovery) and CCUS (carbon capture, utilization, and storage) engineering. However, the kerogen differential swelling during CO2-CH4 adsorption has been rarely reported, and so is its mechanism and significance. Here, the differential swelling mechanism of kerogen atomic representation was investigated using molecular simulation and the poromechanical model. Results indicated that swelling ratios for the systems of pure CO2, pure CH4, and a binary mixture of CO2 + CH4 (mole ratio = 1:1) gradually increase with the increasing temperature, pressure, and bulk mole of CO2. The activation energy of swelling deformation can be calculated via the Arrhenius formula, where they were 1.58 and 1.33 kJ/mol for CO2 and CH4, respectively, at 0.1 MPa, indicating that the swelling deformation of CO2 adsorption requires more energy to trigger than CH4. CO2 plays a dominant role in triggering the swelling deformation of competitive adsorption system. The swelling activation energy of pressure dependence firstly increases and then decreases with the increasing pressure. The outcomes of this paper have a higher fidelity than many previous efforts and were expected to be of broad interest to CCUS and CO2-ESGR.

Alternative CO2-based blends for transcritical refrigeration systems

The extensive use of CO2 in commercial refrigeration system has grown in the last two decade thanks to the development of new components and configurations that allows working in transcritical conditions efficiently. However, using these arrangements increases the cost and complexity of the refrigerating plant, making it challenging to implement them in medium or low-capacity systems. As an alternative, CO2-based binary mixtures report attractive improvements that allow for enhancing the COP of the system by minimising its complexity and maintaining the safety and environmental conditions of CO2. This manuscript analyses five binary mixtures of CO2 with the refrigerants R32, R152a, R1234yf, R1234ze(E) and R1270, determining the optimal mixture composition for maximising the COP of a CO2 transcritical refrigeration plant in a wide range of environmental temperatures (0 to 40°C). Fixing the operating conditions for a medium-temperature application, the binary mixtures of CO2/R32 (81/19% in mass) and CO2/R1270 (92.5/7.5% in mass) reported the best COP enhancements results with increments up to +21.4% and +8.7%, respectively, at high environmental temperatures.

Theoretical studies on the role of water in ionic liquids at ZIF (IL@ZIF) complex and its effect on selective CO2 separation

One of the major problems we have always faced and still facing is the vast amount of toxic gases expelled into the atmosphere mainly during the manufacture of many of the day-to-day commodities we all use. The selective adsorption and storage of gases from various industrially important gaseous mixtures are studied in order to find a suitable method as a sustainable solution for this concern. This study is conducted in order to get a perspective on the gas separation and storage capabilities of large framework molecules like zeolitic imidazolate frameworks (ZIFs) by incooperation of ionic liquids (ILs). Here, the gas adsorption efficiency of IL@ZIF-8 composite materials is studied in the presence of a single water molecule. We have selected 1-butyl-3-methylimidazolium [BMIM]+ cation along with five different anions as the ILs. We used both hydrophilic and hydrophobic ILs in this study. The IL@ZIFs complexes are prepared by adding ILs in two different approaches to the ZIF pore. A single water molecule is added into the previously optimized geometries of IL@ZIF in the first method (Approach-I), while we added water and an IL to the ZIF simultaneously in the second method (Approach-II). The selection of the different approaches for water addition helps to gather information about the interaction pattern of water with the IL and ZIF and also of these molecules with one another in the presence of water. We used these complexes to study their adsorption capabilities towards CO2 and also their selectivity nature towards CO2 in a binary mixture of CO2 and N2. Computational approaches such as density functional theory (DFT) and grand canonical Monte Carlo (GCMC) are used in this study.

Adoption of CO2-based binary mixture to operate transcritical Rankine cycle in warm regions

This paper investigates the potential of CO2-based binary mixtures to operate a Rankine cycle with low-grade heat sources in warm regions. Utilizing low-grade heat sources in warm regions is a challenging task due to lower turbine inlet temperatures and higher pump inlet temperatures. A transcritical Rankine cycle with heat recuperation is implemented to minimize the heat losses linked with the isothermal phase change process of the working fluid. A proper selection of the working fluid suitable for a given scenario is one of the crucial tasks to maximize the thermal efficiency of the cycle. Energy and exergy analyses are presented for the cycle running with pure CO2 and CO2-based binary mixtures as a working fluid. Five different organic fluids (n-pentane, cyclopentane, cyclohexane, R1336mzz, and R600) are selected as additives to make a binary mixture. The effect of additive concentration in the mixture on the thermodynamic performance of the cycle is investigated. The cycle is found to perform significantly better if operated with a binary mixture than pure CO2. Binary mixtures of CO2 with n-pentane, cyclopentane, and cyclohexane perform substantially better than the rest with an increase in the thermal efficiency by more than 30% in comparison to the thermal efficiency of the cycle operating with pure CO2. The results indicate that the adoption of the CO2-based binary mixture for a transcritical Rankine cycle not only improves the overall thermodynamic performance but also reduces the operating pressures of the cycle which may lead to less expensive materials needed for the various components of the plant. Exergy analysis reveals that the irreversibility losses in the system during the heat transfer process are much larger than in the turbomachinery.

The Effect of Surface Composition on the Selective Capture of Atmospheric CO2 by ZIF Nanoparticles: The Case of ZIF-8.

We performed theoretical studies of CO2 capture in atmospheric conditions by the zeolitic imidazolate framework-8 (ZIF-8) via classical Monte Carlo (MC) simulations with Metropolis sampling and classical molecular dynamics (MD) simulations in the NVT and NPT ensembles and different thermodynamic conditions. The ZIF-8 framework was described by varying unit cell dimensions in the presence of pure gases of CO2, N2, O2, Ar, and H2O steam as well as binary mixtures of CO2:N2 and CO2:H2O in s 1:1 concentration. Different chemical compositions of the framework surface was considered to provide an accurate treatment of charge and charge distribution in the nanoparticle. Hence, surface groups were represented as unsaturated zinc atom (Zn+2), 2-methylimidazole (mImH), and deprotonated 2-methylimidazole (mIm-). Force field reparameterization of the surface sites was required to reproduce the interactions of the gas molecules with the ZIF-8 surface consistent with quantum mechanics (QM) calculations and Born-Oppenheimer molecular dynamics (BOMD). It was observed that ZIF-8 selectively captures CO2 due to the negligible concentrations of N2, O2, Ar, and H2O. These molecules spontaneously migrate to the inner pores of the framework. At the surface, there is a competitive interaction between H2O, CO2, and N2, for the positively charged ZIF-8 nanoparticle with a large binding energy advantage for water molecules (on average -62, -15, and -8 kcal/mol respectively). For the neutral ZIF-8 nanoparticle, the water molecules dominate the interactions due to the occurrence of hydrogen bond with the imidazolate groups at the surface. Simulations of binary mixtures of CO2/water steam and CO2/N2 were performed to investigate binding competition between these molecules for the framework positively charged and neutral surfaces. It was found that water molecules drastically block the interaction between CO2 molecules and the framework surface, decreasing CO2 capture in the central pore, and CO2 molecules fully block the interaction between N2 molecules and the framework. These findings show that CO2 capture by ZIF-8 is possible in atmospheric environments only upon dehydration of the atmospheric gas. It further shows that ZIF-8 capture of CO2 from the atmospheric environment is dependent on thermodynamic conditions and can be increased by decreasing temperature and/or increasing pressure.

Tuning N-doping thermal-process enables biomass-carbon surface modification for potential separation effect of CO2/CH4/N2

• The optimal N-doping temperature of 600 ℃ for biomass activated carbon was validated. • The detailed comparative studies of two types of activated carbon were conducted. • The thermal stability of N-doping activated carbon was improved from 403 ℃ to 541 ℃. • The adsorption ability of the optimized sample for CO 2 was drastically enhanced. • The N-doping activated carbon afford great potential for separation of CO 2 /CH 4 /N 2 . Gas-adsorption-Sieving especially for CO 2 /CH 4 /N 2 became attractive in flue-gas separation, natural-gas energy upgrading, and gas-layer-methane recovery. Herein, a detailed study on the potential adsorption separation effect of CO 2 /CH 4 /N 2 using two kinds of synthesized temperature-tuning N-doping biomass activated carbon (BCx and GCx) derived from banana peel and grapefruit peel was explored. A comprehensive comparison of the structural properties and surface character of N-doping carbon was conducted through various characterizations, revealing that two N-doping AC both afford a better doping effect and higher post-implanted surface skeleton N species at 600 °C. Impressively, CO 2 adsorption capacity of optimal GC600 and BC600 at 0 °C/25 °C and 1 bar reaches 5.09/3.05 mmol g −1 and 3.04/3.57 mmol g −1 , respectively, which have exceeded most reported AC adsorbents. Especially, BC600 affords appreciable N and O component proportion, which renders better surface affinity for CO 2 adsorption at 25 °C. While GC600 endows better CO 2 adsorption at 0 °C by right of the highest occupation fraction of pore-volume-selected corresponding to specific pore-size of 1.2 nm and post-implanted beneficial surface N species. The tentative linear fitting among CO 2 adsorption performance with surface N species state and structural properties validates their comprehensive influence on CO 2 adsorption. Through the rational correlation of the adsorption of pure components, the adsorption selectivity to the binary mixture of CO 2 /N 2 (15/85), CO 2 /CH 4 (10/90), and CH 4 /N 2 (30/70) is predicted for optimized GC600 and BC600 through Ideal Adsorbed Solution Theory(IAST), which reaches 22.84/3.46/5.84 and 17.45/3.66/3.98, respectively and reveals obvious improvements compared to original biomass-carbon and traditional AC adsorbents. Most importantly, the optimal adsorbent afford extremely low-level adsorption heat for CO 2 , thereby rendering the good reversibility and reusability during 7 cycles at room temperature without any extra thermal process.

Preliminary thermodynamic analysis of a carbon dioxide binary mixture cycled energy storage system with low pressure stores

The liquid CO2 energy storage has considerable potential for power supply-demand management, but its low energy density, harsh condensation condition and high operation pressure are substantial obstacles. It is the first time to design energy storage system with high energy density and low-pressure stores by cycling the CO2 binary mixtures. By using CO2 mixtures, the pressure in storage tanks can be as low as ambient pressure (0.1 MPa) and two-tank cold energy storage with liquid storage materials can be used to complete the evaporation and condensation processes of working fluid in subcritical pressure. A large number of refrigerants are discussed and nine of them are selected as preliminary candidate additives into CO2. The performance of newly proposed system cycled with these additives is further analyzed by utilizing an in-house code developed with established thermodynamic models. The numerical results demonstrate that the mass fraction of additives is suggested to be higher than 0.12, otherwise there is high required capacity of cold storage material although a larger energy density. By and large, the mixtures CO2/R161 (0.7/0.3) and CO2/R1270 (0.82/0.18) are the first two most suitable selections among the CO2 mixtures, the round trip efficiency and energy density of which at basic design condition are 52.95% and 29.74 kWh/m3 and 52.12% and 29.83 kWh/m3, respectively. Both the optimal charge and discharge pressures can be identified for round trip efficiency while the energy density increases monotonically with charge pressure and the increasing trend is first steep and gradually becomes slow.

Preparation of Magnetic Surface Ion-Imprinted Polymer Based on Functionalized Fe3O4 for Fast and Selective Adsorption of Cobalt Ions from Water

A novel cobalt ion-imprinted polymer (Co(II)-MIIP) based on magnetic Fe3O4 nanoparticles was prepared by using Co(II) as the template ion, and bis(2-methacryloxyethyl) phosphate and glycylglycine as dual functional monomers. The fabricated material was analyzed by Fourier transform infrared spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, Brunauer–Emmett–Teller, X-ray diffraction, and vibrating sample magnetometer. The adsorption experiments with Co(II)-MIIP, found that the maximum adsorption capacity could reach 33.4 mg·g−1, while that of the non-imprinted polymer (Co(II)-NIP) was found to reach 15.7 mg·g−1. The adsorption equilibriums of Co(II)-MIIP and Co(II)-NIP was established within 20 min and 30 min, respectively. The adsorption process could be suitably described by the Langmuir isotherm model and the pseudo-second-order kinetics model. In binary mixtures of Co(II)/Fe(II), Co(II)/Cu(II), Co(II)/Mg(II), Co(II)/Zn(II), and Co(II)/Ni(II), the relative selectivity coefficients of Co(II)-MIIP toward Co(II)-NIP were 5.25, 4.05, 6.06, 11.81, and 4.48, respectively. The regeneration experiments indicated that through six adsorption–desorption cycles, the adsorption capacity of Co(II)-MIIP remained nearly 90%.

Nanocellular foaming of poly (methyl methacrylate) with chlorodifluoromethane (HCFC-22)/CO2 binary mixtures as a model blowing agent

A foaming process for polymethylmethacrylate (PMMA) using a chlorodifluoromethane (HCFC-22) and carbon dioxide (CO2) binary mixture as a blowing agent at 40 MPa and 353.2 K was studied for the production of foams with high porosity and uniformity. HCFC-22 was employed as a model blowing agent because of (1) much larger solubility to polymers than CO2 and (2) well known phase diagram and physicochemical property. HCFC-22/CO2 binary mixtures improved the homogeneity of the cellular structure. The micrometer-sized cell structures seen in the foams with pure CO2 used as blowing agent were decreased in HCFC-22/CO2 binary mixtures. Homogeneous structure with cells from 0.07 µm to 0.35 µm were obtained in the binary mixtures. The binary mixtures were also effective in increasing the cell nucleation density of nanometer-sized cell structures. We were able to determine the optimal composition of HCFC-22/CO2 to coexist the high expansion ratio and homogeneous structure for PMMA foams.