Journal of CO2 Utilization最新文献

The mutualistic interaction between microalgae and bacteria provides a new strategy for improving carbon fixation by microalgae. In this study, Chlorella was co-cultured with natural flora at 15 % (v/v) CO₂ concentration for 120 d. Three Chlorella symbiotic bacteria strains were identified and were co-cultured with Chlorella vulgaris HL02 (C. vulgaris HL02) to fix high concentrations of CO₂. The results showed that the symbiotic bacteria significantly enhanced the fixation of 15 % CO₂ by Chlorella, with C. vulgaris HL02 + Aeromonas GS-HL01 having the highest carbon fixation efficiency, which was 22.31 % higher than that of the sterile control, followed by C. vulgaris HL02 + Bacillus GS-F03, and C. vulgaris HL02 + Microbacterium GS-H02 (which was also 16.36 % higher than the sterile control). The composition of harvested Chlorella was not altered significantly following co-culturing with bacteria. Scanning electron microscopy and Excitation–emission matrix spectra analyses showed that at high concentrations of CO₂, Microalgae and bacteria promote mutual growth and CO₂ fixation mainly through extracellular secretion of organic matter. Our results provided a new strategy to improve the efficiency of microalgae in fixing high concentration of CO₂.

Microwave (MW) heating is proposed as a method to transform polyethylene terephthalate (PET) into porous adsorbents. The yield, textural properties, and CO₂ uptake of the PET-derived adsorbents irradiated at different durations (3 – 35 min) at 400 °C were assessed. MW activation time influenced both the physical properties and CO₂ uptake capacities of the resulting adsorbents. The yield decreased with activation time, but the surface area, total pore volume, micropore volume, and CO₂ uptake capacities all increased with MW activation time before declining. The optimal sample (produced with 5 min of MW activation time) showed improved textural properties as well as higher equilibrium and dynamic CO₂ uptakes than the commercial activated carbon used as reference. This adsorbent also possesses good selectivity for CO₂ in the binary 10:90%vol/vol CO₂: N₂ mixture. Additionally, an excellent recyclability over 20 cycles, (Regeneration Efficiency > 97%) was observed, and the CO₂ adsorption kinetics best fits Lagergren’s pseudo-second-order model. This study has shown that a low activation temperature (400 °C), a short MW activation time (5 min), and a low amount of chemical agent (KOH, 0.72 M) could produce CO₂ adsorbents from a cheap and abundant material (PET-waste) with better CO₂ uptake to that of a commercial activated carbon.

How to quantitatively account for the effect of SC-CO₂ (Supercritical Carbon) rock-breaking in different rock sites is the key concern in the engineering application of non-explosive rock-breaking technology and economic comparison and there is a lack of experimental basis for relevant studies. Through the equivalent calculation of industrial emulsion explosives, a typical representative granite and mudstone site was selected, and a field experimental program was designed to compare the equivalence of the rock-breaking effects of SC-CO₂ and industrial explosives. Based on the rock-breaking equivalent field experiment, we compared and analyzed the rock-breaking area characteristics and parameter changes, such as rock-breaking volume, the morphology of the rock-breaking area, bulk rate, and unit consumption, between SC-CO₂ and industrial explosives. A correction of the equivalent conversion formula based on the volume of broken rock was realized. The study shows that SC-CO₂ breaks the rock in an elliptical volume shape, the explosives are round, the range of SC-CO₂ fracturing breaks the rock is smaller than the range of explosives breaks the rock, and the unit consumption of CO₂ is 6–10 times of the unit consumption of explosives. The rock bulk rate is higher after SC-CO₂ breaking, while the explosive blast stress wave distribution is uniform, and the bulk rate is low. SC-CO₂ rock-breaking produced by the surface vibration velocity is much smaller than the industrial explosives rock-breaking, industrial explosives blasting point of the combined vibration velocity value of the SC-CO₂ rock-breaking point of the combined vibration velocity value of 9–11 times, SC-CO₂ rock-breaking vibration impact on the surrounding environment is relatively small. The peak combined stress at the measurement point generated by SC-CO₂ rock breaking is higher than that of industrial explosives rock breaking, which is 1.2–1.6 times the corresponding measurement point value in the explosives rock breaking test. The study provides an experimental basis for research on the equivalence of SC-CO₂ rock-breaking and industrial explosives rock-breaking.

Plasma conversion technology is an emerging technique under development to activate, convert or valorize gas molecules such as CO₂, N₂, CH₄, NH₃ and others. A large-scale application beyond the lab-scale demonstrator unit requires assessment of the efficiency of this new technology. The straightforward approach for assessment of the efficiency is benchmarking with the other well-established technologies of similar technology readiness level (TRL). In this paper we present a benchmarking of the atmospheric pressure microwave-induced CO₂ plasma splitting with electrochemical CO₂ conversion, via both low-temperature and high-temperature electrolysis. An additional step of oxygen removal in case of the plasma reactor is implemented due to the difference in the output stream of the plasma (gas mixture containing CO₂, CO, and O₂) and the electrochemical reactor (typical gas mixture on cathode containing CO₂ and CO). For the benchmarking, a comprehensive set of comparison parameters that are applicable for both the plasma and the electrochemical route is identified and grouped in three comparison categories: performance, interfaces, and economics. The comparison of these parameters demonstrates that in terms of the electric power consumption (EPC; power required for production of one Nm³_CO) plasma conversion technology (∼20 kWh/Nm³_CO) is in the ballpark with the other two electrochemical technologies (∼4–20 kWh/Nm³_CO). The key features of the plasma conversion technology are relatively large conversion (up to 56%) and moderate energy efficiencies (up to 27%). Also, CO₂ gas of reduced purity of only 98% can be used without decrease of the performance, and CO output values are currently at 3.5 slm (standard litre per minute). Fast on/off response time of order of minutes, and no need for the hot standby indicate that the plasma conversion is particularly suitable for use of intermittent renewable energy sources. The aspects that require further development include optimization of the process towards lower EPC_total values, improved oxygen gas separation, and reliable ignition of the plasma.

Waste eggshells have been investigated as biomineralised CO₂ sorbents for the calcium looping cycle due to their high Ca content, low cost, availability, and high CO₂ uptake. This work investigates a novel heat-pre-treatment using eggshells as raw material. The eggshells were simultaneously calcined and thermally pre-treated via microwave heating using different powers and times whilst maintaining the same input energy in a single mode cavity reactor. The calcined eggshells were characterised using standard characterisation techniques such as TGA and isotherms of N₂ adsorption at 77 K. The dielectric properties were measured using the cavity perturbation technique at 2.45 GHz. Numerical electromagnetic simulations were performed using COMSOL Multiphysics and results were used to optimise the experimental setup. The treated materials were subjected to carbonation/calcination cycles in order to assess their suitability as a calcium-looping sorbent. The sorbent that exhibited a more stable CO₂ uptake was the one treated at the highest power (800 W) 4.5 mmol CO₂/g sorbent after 20 cycles under mild calcination conditions. Adsorbents prepared at 400, 600 and 800 W displayed similar CO₂ uptake after 20 cycles when the calcination conditions were under more realistic conditions.

Due to the depletion of river sand, the construction industry is eager to develop upcycling techniques for transforming secondary by-products derived from construction and demolition (C&D) waste into quality fine aggregates. This paper presents a study of replacing river sand with enhanced recycled fine aggregate through a wet carbonation process developed by the authors previously. The fine recycled concrete aggregate (FRCA) ranging from 0.15 to 5 mm was prepared by demolishing a concrete with a known mixture design. After wet carbonation, the particle size, water absorption, and density of the FRCA were tested and compared with the original samples. The chemical characteristics of the original and carbonated FRCA (C-FRCA) were analyzed by a series of experiments. The results showed that (1) an increase of carbonation products and a significant reduction of hydration products; (2) microscopic observation of the C-FRCA showed a surface layer densified by calcite after wet carbonation; and (3) no significant strength loss were observed when replacing up to 50% river sand by C-FRCA in mortar specimens. The potential environmental and economic impacts were also analyzed.

The release of carbon dioxide (CO₂) into the earth's atmosphere is a substantial global environmental concern that arises from the processes of industrialization and urbanization. The increase in atmospheric CO₂ concentrations has resulted in the phenomenon of global warming and subsequent alterations in climate patterns. Accelerated CO₂ sequestration in cementitious materials is currently the subject of extensive research as a highly efficacious approach to mitigating the carbon footprint of the concrete industry. The sequestration procedure entails the transformation of gaseous CO₂ into carbonate minerals. The review presented in this paper outlines the most recent carbonation (i.e., CO₂ sequestration) techniques, such as mineral carbonation, accelerated CO₂ curing (ACC), pre-carbonation, and carbonation mixing, that have been recently explored. The potential of mineral carbonation of industrial wastes and the advantages of their incorporation in the concrete matrix is investigated. Carbonation technologies and their effect on the performance of cementitious composites are reported. Information on life cycle assessment are also included to evaluate the environmental impact associated with the production of carbonated materials. Various commercialized CO₂ utilization technologies in construction sector, such as CarbonCure, Solidia, Carbstone, Calera, and Carbon8 are reviewed. Moreover, this review offers a thorough insight into the carbonation technologies, evaluating their advantages, limitations, and the existing gaps in research.

MIL-101(Cr), a class of metal-organic framework, is a potential candidate for CO₂ capture applications because of its high capacity of adsorption and separation capability. However, the intrinsic microporous structure of this nanomaterial poses limitations on its adsorption kinetics. Techniques employed to enhance its adsorption kinetics often adversely impact its adsorption capacity at equilibrium. Herein, as a new approach, we prepared amine-functionalized FAC@MIL-101(Cr) composites with adjustable micro-mesoporous structure and tunable nitrogen content by embedding different ratios of amine-functionalized activated carbon throughout the framework of MIL-101(Cr). This led to a simultaneous improvement in both kinetics and adsorption capacity for CO₂. The best adsorbent, FAC-6@MIL-101(Cr), has excellent textural properties with a high surface area (1763.1 m².g⁻¹), great pore volume (1.29 cm³.g⁻¹), and suitable nitrogen content (4.7 wt%). The adsorption analysis revealed that the modification of MIL-101(Cr) improved its CO₂ adsorption capacity from 3.21 to 5.27 mmol/g under standard conditions of 1 bar and 25 °C. Furthermore, the FAC-6@MIL-101(Cr) adsorbent demonstrated fast CO₂ adsorption kinetics (three times more relative to the pure MIL-101(Cr)), high CO₂/N₂ selectivity, and remarkable cyclic stability. The results confirmed that hybridization enhanced the polarizability of FAC@MIL-101(Cr) samples, causing more robust CO₂-adsorbent surface interactions. Simultaneously, the existence of mesopores in the structure facilitated the transport of CO₂ into the interior pores, resulting in a more efficient contact of CO₂ molecules with all of the amine sites and a faster adsorption rate as well as more efficient regeneration. According to density functional theory (DFT) calculations, hybridization process induces significant changes in composites’ electronic structure, enhancing their capacity to interact with CO₂ molecules more effectively. On the other hand, DFT calculations confirm that N₂ molecule is less activated on the FAC@MIL-101(Cr) as evidenced by calculated small adsorption energy and charge-transfer values.

Formate dehydrogenases catalyze the reversible oxidation of formate to carbon dioxide. These enzymes play an important role in CO₂ reduction and serve as nicotinamide cofactor recycling enzymes. More recently, the CO₂-reducing activity of formate dehydrogenases, especially metal-containing formate dehydrogenases, has been further explored for efficient atmospheric CO₂ capture. In this sense, molecular hydrogen (H₂) as the fuel of the future represents an efficient, cheap and environmentally friendly reducing agent when produced from renewable sources. Hydrogenases are enzymes that catalyze the reversible oxidation of H₂. Herein, the functional interplay between the soluble [NiFe] hydrogenase from Cupriavidus necator and the molybdenum-dependent formate dehydrogenase from Rhodobacter capsulatus was investigated in a coupled biocatalytic system. H₂-driven CO₂ reduction (H₂CO₂R) using methyl viologen as an artificial electron mediator gave a higher product yield of formate than using NAD⁺ as the physiological electron mediator. The enzymes were stable under anaerobic conditions for 18 h, making the coupled reaction suitable for biotechnological purposes.

In this study, synthetic CaCO₃ materials were utilized as precursors for CaO-based CO₂ sorbents. The investigation examined how various operating parameters—such as synthesis temperature (ST), stirring rate (SR), and surfactant percentage (SP)—impact the properties of the adsorbents. Samples were firstly characterized by X-ray diffraction and Scanning Electron Microscopy (SEM), which revealed that the prevalence of calcite or aragonite crystal phases in the synthetic CaCO₃ precursors can be tuned by adequately choosing the dose of surfactant (Triton-X100®), so that it can be used as a crystal habit and growth modifier. The calcination process applied to the CaCO₃ precursors leads to the formation of partially sinterized cubic crystals of CaO, accompanied by minor quantities (< 5 %) of additional compounds like Ca(OH)₂ or CaSO₄. Specific surface area (S_BET) and porosity were determined by measuring the N₂ adsorption isotherms. A CaCO₃ sample with an unprecedented value of S_BET as large as 116 m²/g was prepared operating under optimal conditions. S_BET and pore volumes were successfully correlated with the CO₂ uptake capacity of the samples. S_BET is more influential for experiments carried out under diluted CO₂ atmosphere. When pure CO₂ is used, the influence of meso- and micropore volumes (V_me and V_mi) is clearly predominant, which suggests that in this latter case diffusion through the porous texture of the samples plays a more remarkable role. A double-way approach through Response Surface Methodology (RSM) and the use of Artificial Neural Networks (ANNs) has been used to analyze the CO₂ uptake capacity of the samples. Within the operational interval, excellent results were obtained for pure and diluted CO₂ flow, and RSM and ANNs have demonstrated to be a very efficient tool to correlate the behavior of the CaO-based materials as CO₂ sorbents with the surface area and pore volumes of the samples. Valuable information on (i) the importance of the different factors under study; (ii) their influence on the surface and porosity of the CaO-derived sorbents; and (iii) the subsequent CO₂ capture performance of the sorbents has been obtained. The results suggest that four parameters have a statistically significant influence on CO₂ uptake. These parameters are SR, the square of SR, its interaction with SP, and the square of SP. Additionally, the study assessed the stability of the CaO-based sorbents over 11 consecutive calcination-carbonation cycles. By adequately choosing the synthesis strategy and conditions, an almost negligible shrinkage effect can be achieved, resulting in a more sustained uptake capacity throughout the cycles.