Journal of CO2 Utilization最新文献

Cementitious materials as a medium of carbon capture, and utilization (CCU) have recently attracted considerable attentions. Atmospheric CO₂ can be absorbed in hardened concrete, which can be also accelerated by early age CO₂ curing. Compared to the CO₂ curing of concrete materials, in-situ CO₂ mixing technology can be widely applied because it can be used in a batch plant without an additional curing facility. In this study, the CO₂ mixing time was set as the primary variable to elucidate the precipitation of the carbonate phases in the early stages and its effect on cement hydration. The dissociated CO₂ is directly mineralized into calcium carbonate (CaCO₃) in calcite phase. In addition, the longer the CO₂ mixing time, the greater the precipitation of calcite (i.e., CCU capacity), thereby densifying the internal microstructure and improving early strength development. Interestingly, a certain amount of calcite converted to monocarboaluminate—an important factor for quantitatively assessing the degree of mineral carbonation in cementitious materials.

CO₂-mixing by directly injecting CO₂ into fresh cement-based materials is a burgeoning technology to produce low-carbon cement products. The objective of this study is to investigate the influence of the calcium carbide slag (CCS) content on the properties and carbon sequestration efficiency of cement pastes mixed under direct CO₂ injection conditions. The results indicate that the addition of CCS reduced the fluidity of the cement pastes, accelerated the setting process, increased volume shrinkage, and reduced compressive strength. Following the injection of CO₂ into the cement pastes, calcium hydroxide (CH) was carbonated to form calcium carbonate (CC) particles which fill the voids in the cement pastes, thereby reducing volume shrinkage and increasing compressive strength. A lower CO₂ inflow rate (2 L/min) was more beneficial to the workability of the cement pastes, while a high inflow rate (6 L/min) can lead to insufficient hydration and affect the development of strength. However, a higher CO₂ inflow rate was favorable for improving carbon sequestration efficiency. The highest amountof carbon sequestration can be reached at 6.93 %, when the CCS content is 10 % and the CO₂ inflow rate is 6 L/min.

As an eco-friendly alternative to the conventional anthraquinone process, electrochemical production of hydrogen peroxide (H₂O₂) through the oxygen reduction reaction has been attracting attention. The goal of this work is to derive a carbon-based material from carbon dioxide (CO₂) to achieve high performance in electrochemical H₂O₂ production. Doping heterogeneous element such as oxygen on a carbon catalyst has been mainly explored to increase the selectivity and activity, but little research has been conducted on enhancing catalytic activity with oxidized boron insertion. This study proposes porous carbon materials synthesized from CO₂ as electrocatalysts. Polyethylene oxide (PEO) was thermally treated together to increase the boron-oxygen bonding sites. As a result, the synthesized carbon materials having oxidized boron functional groups of BC₂O and BCO₂ showed high activity (1.25 mA cm⁻²) and selectivity (∼90 %) over a wide voltage range in two-electron ORR (Oxygen Reduction Reaction) at alkaline media. Furthermore, in an H-cell where 0.4 V vs. RHE was applied, the average H₂O₂ production rate was maintained at 452.96 mmol g⁻¹ h⁻¹ for four hours with a high faraday efficiency of 90 %.

Mineral carbonation stands out not only as an effective method for reducing CO₂ emissions but also as a strategic approach to upcycling industrial waste. This study introduces a novel procedure for generating high-purity nano-calcium carbonate (nCaCO₃) from waste cement powder, deploying hydrochloric acid (HCl), and sodium hydroxide (NaOH), both obtained through the electrolysis of sodium chloride (NaCl). Our approach, aimed at both environmental preservation and techno-economic feasibility, encompasses optimizing calcium extraction conditions through rigorous analysis of variables such as HCl concentration, solid-to-liquid ratio, and reaction temperature, subsequently proposing a rate law for the extraction process. Furthermore, the method emphasizes the production of high-purity CaCO₃ by meticulously removing metallic impurities from the extracted solution with 1.0 M NaOH, culminating in pure calcium hydroxide and the generation of nCaCO₃ particles with superior purity (>99 %) and a uniform particle size (80–140 nm). An exhaustive environmental and economic assessment indicates that our process, while consuming varying energy levels based on operational potentials, anticipates a significant reduction in CO₂ emissions by 46.1 %, alongside a competitive production cost (335 USD/ton of nCaCO₃), thereby demonstrating substantial advantages over traditional methods in terms of sustainability, efficiency, and cost-effectiveness.

Creating useful chemicals or fuels from CO₂ is one of the most promising ways to reach carbon neutral. In this work, through the formation of Lewis acid sites, a string of boron-atom-coordinated Ru single-atom catalysts (SACs), namely RuB_xN_4-x@TiN (x=0–4), were constructed, and their CO₂ reduction reaction (CO₂RR) was systematically studied. The results show that o-RuB₂N₂@TiN, p-RuB₂N₂@TiN, and RuB₃N₁@TiN are able to efficiently inhibit the competitive hydrogen evolution reaction (HER) and activate CO₂, with a potential-determining step lower than 0.7 eV and high selectivity for CH₄ generation. This work shows that the synergistic effect of B and Ru atoms are able to effectively improve the catalytic activity, which is expected to offer a possible tactic for the sensible creation of effective CO₂RR catalysts.

The cement industry significantly contributes to global CO₂ emissions, with a notable portion attributed to limestone calcination during cement clinker production. To promote carbon-neutral building practices, alternative approaches are being explored to replace raw materials in cement manufacturing and mitigate CO₂ emissions. Steelmaking slag, enriched with noncarbonated CaO from limestone decarbonization during steel production, shows potential as a promising raw material for cement manufacture to reduce CO₂. Despite their environmental benefits, most steelmaking slags are underutilized, with limited recognition of their CO₂ mitigation potential. Moreover, challenges to using steelmaking slag as a raw material to manufacture cement clinker exist due to the mineral and chemical compositions of each slag type. This study explored potential pretreatment methods to enhance slag's performance as a cement raw material and the research on utilizing steelmaking slag, including blast furnace slag (BFS), Kanbara reactor (KR) slag, basic oxygen furnace (BOF) slag, electric arc furnace (EAF) slag, ladle furnace (LF) slag, and stainless slag, in cement clinker manufacture. Consequently, steelmaking slag could be used as a raw material to manufacture cement clinker to reduce CO₂ emissions. However, additional research is needed, including slag pretreatment methods and cement clinker manufacturing process optimization.

Coal, one of China's most abundant natural resources, plays a crucial role in providing substantial energy and promoting economic growth. However, the disposal and storage of large quantities of coal-based solid waste (CBSW), such as coal gangue (CG), fly ash (FA), and coal gasification slag (CGS), generated during coal production and utilization processes, pose serious social and environmental challenges. The application of solid waste in the construction materials field has garnered significant attention and is anticipated to become a primary treatment method in the future. This paper comprehensively reviews the characteristics, pretreatment methods, and utilization performance of typical CBSWs, aiming to offer a basis and valuable reference for optimizing the inherent properties of solid waste and its utilization. Additionally, it discusses the influence of various carbonation curing parameters on CO₂ capture and elucidates the impact mechanism of carbonation curing on the performance of CBSW concrete. This study holds great significance for the utilization of CBSW in building materials and carbon reduction, particularly in regions with substantial solid waste and high CO₂ emissions.

The transesterification of dimethyl carbonate (DMC) with ethanol to ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) has attracted increasing attention, which could be greatly promoted by heterogeneous solid base catalysts. The K₂CO₃/Al₂O₃ solid base catalysts with different active sites such as K₂CO₃, KAl(OH)₂CO₃, and KAlO₂ were prepared for the transesterification reaction. The active sites of K₂CO₃ and KAl(OH)₂CO₃ mainly exist on the surface of KA-200 and KA-300, while K₂CO₃ and KAlO₂ were mainly present on KA-400 and KA-500. The effects of active sites and the phase of support were studied systematically. KAl(OH)₂CO₃ showed higher activity than K₂CO₃ and KAlO₂. In contrast, K₂CO₃ and KAlO₂ displayed higher stability, with the activity of KA-400 kept stable over 2000 h. The excessive OH group of γ-AlOOH and water in the reaction system have a negative effect on the activity of the K₂CO₃/Al₂O₃ catalysts. The catalytic characterizations, transesterification reactions, and DFT calculations suggested that K⁺ in the KAl(OH)₂CO₃ species, with higher electron cloud density than that in K₂CO₃/γ-Al₂O₃, could efficiently promote the dissociation of ethanol and subsequent replacement of methoxy with ethoxy. The rate-determining step for the transesterification reaction was suggested to be the dissociation of ethanol.

Glibenclamide is an antidiabetic drug that also acts as an anti-inflammatory factor and reduces oxidative stress, medullary edema, and heart attack. Glibenclamide has high permeability and poor solubility in water (BCS class II). This work addresses particle size reduction of Glibenclamide using the gas antisolvent (GAS) to improve the drug dissolution rate. Three process parameters were studied at three levels: pressure (120, 140, and 160 bar), temperature (308, 318, and 328 K), and initial solute concentration (15, 45, and 75 mg/mL). The Box-Behnken design method was applied to optimize the process conditions. The coprecipitation of Glibenclamide with polyvinyl pyrrolidone (PVP) and hydroxypropyl methylcellulose (HPMC) was investigated by GAS at optimum pressure and temperature conditions (i.e., 160 bar and 308 K). Furthermore, the particles produced were characterized by high performance liquid chromatography, powder x-ray diffraction, differential scanning calorimetry, Fourier transform infrared spectrometry, dynamic light scattering, and field emission scanning electron microscopy. The maximum dissolution rate in water obtained after 75 minutes was 36.6 %, 88.3 %, 94.1 %, and 97.7 % for unprocessed Glibenclamide, Glibenclamide nanoparticles, Glibenclamide-HPMC and Glibenclamide-PVP composites, respectively. Glibenclamide-HPMC nanocomposites produced by GAS showed the smallest particle size, while Glibenclamide-HPMC exhibited the fastest dissolution rate.

This experimental study investigates a novel approach to utilize waste concrete powder (WCP) in conjunction with metakaolin as a precursor in the production of alkali-activated binder for sustainable consumption of construction and demolition waste. A Chapelle test confirms the presence of reactive silica in thermo-mechanically activated WCP. Different alkali-activated mixtures with metakaolin replacement ranging from 0 % to 80 % were prepared. The mixture with 40 % activated WCP, with a sodium silicate to sodium hydroxide ratio of 2, achieved better compressive strength than the reference sample without WCP. Mineralogical analysis of the mixture pastes revealed that activated WCP-based mixtures developed geopolymer gel and C-S-H gel, contributing to better strength properties in the case of the mixture with 40 % activated WCP. Life cycle analysis demonstrated that incorporating 40 % thermo-mechanically activated WCP by replacing metakaolin reduces carbon dioxide emissions by 49.5 % and 2.2 % compared to Portland cement and metakaolin-based binder, respectively.