CaO-based meshed hollow spheres for CO 2 capture

CO2 Capture at Medium to High Temperature Using Solid Oxide-Based Sorbents: Fundamental Aspects, Mechanistic Insights, and Recent Advances

Carbon dioxide capture and mitigation form a key part of the technological response to combat climate change and reduce CO₂ emissions. Solid materials capable of reversibly absorbing CO₂ have been the focus of intense research for the past two decades, with promising stability and low energy costs to implement and operate compared to the more widely used liquid amines. In this review, we explore the fundamental aspects underpinning solid CO₂ sorbents based on alkali and alkaline earth metal oxides operating at medium to high temperature: how their structure, chemical composition, and morphology impact their performance and long-term use. Various optimization strategies are outlined to improve upon the most promising materials, and we combine recent advances across disparate scientific disciplines, including materials discovery, synthesis, and in situ characterization, to present a coherent understanding of the mechanisms of CO₂ absorption both at surfaces and within solid materials.

Optimization of the structural characteristics of CaO and its effective stabilization yield high-capacity CO2 sorbents

Calcium looping, a CO₂ capture technique, may offer a mid-term if not near-term solution to mitigate climate change, triggered by the yet increasing anthropogenic CO₂ emissions. A key requirement for the economic operation of calcium looping is the availability of highly effective CaO-based CO₂ sorbents. Here we report a facile synthesis route that yields hollow, MgO-stabilized, CaO microspheres featuring highly porous multishelled morphologies. As a thermal stabilizer, MgO minimized the sintering-induced decay of the sorbents’ CO₂ capacity and ensured a stable CO₂ uptake over multiple operation cycles. Detailed electron microscopy-based analyses confirm a compositional homogeneity which is identified, together with the characteristics of its porous structure, as an essential feature to yield a high-performance sorbent. After 30 cycles of repeated CO₂ capture and sorbent regeneration, the best performing material requires as little as 11 wt.% MgO for structural stabilization and exceeds the CO₂ uptake of the limestone-derived reference material by ~500%.

The economic operation of a carbon dioxide capture technique of calcium looping necessitates highly effective CaO-based CO₂ sorbents. Here, the authors report a facile one-pot synthesis approach to yield highly effective, MgO-stabilized, CaO-based CO₂ sorbents featuring highly porous multishelled morphologies.

Nano-rod Ca-decorated sludge derived carbon for removal of phosphorus

Recovering phosphorus (P) from waste streams takes the unique advantage in simultaneously addressing the crisis of eutrophication and the shortage of P resource. A novel calcium decorated sludge carbon (Ca-SC) was developed from dyeing industry wastewater treatment sludge by decorating calcium (Ca) to effectively adsorb phosphorus from solution. The X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques were used to characterize the Ca-SCs, followed by isotherm and kinetic sorption experiments. A preferred design with CaCO₃ to sludge mass ratio of 1:2 was found to have a sorption capacity of 116.82 mg/g for phosphorus. This work reveals the crucial role of well-dispersed nano-rod calcium on the Ca-SC surface for the sorption of phosphorus. Moreover, the decoration of nano-rod calcium was found to further promote the uptake of phosphorus through the formation of hydroxylapatite (Ca₅(PO₄)₃(OH)). Thus, the development of decorated Ca-SC for sorption of phosphorus is very important in solving the P pollution and resource loss.

Direct synthesis of dimethyl carbonate from CO2 and methanol over CaO–CeO2 catalysts: the role of acid–base properties and surface oxygen vacancies

The addition of CaO to the CeO₂ catalyst had a significant impact on the acid–base properties and amounts of oxygen vacancies on the surface catalyst.

Tuning organic carbon dioxide absorbents for carbonation and decarbonation

The reaction of carbon dioxide with a mixture of a superbase and alcohol affords a superbase alkylcarbonate salt via a process that can be reversed at elevated temperatures. To utilize the unique chemistry of superbases for carbon capture technology, it is essential to facilitate carbonation and decarbonation at desired temperatures in an easily controllable manner. Here, we demonstrate that the thermal stabilities of the alkylcarbonate salts of superbases in organic solutions can be tuned by adjusting the compositions of hydroxylic solvent and polar aprotic solvent mixtures, thereby enabling the best possible performances to be obtained from the various carbon dioxide capture agents based on these materials. The findings provides valuable insights into the design and optimization of organic carbon dioxide absorbents.