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CO2 mineralized all-solid waste alkali-activated cementitious materials can not only realize the storage of CO2 mineralized, but also shorten the curing cycle of alkali-activated cementitious materials and improve their compressive strength. It is a promising way of CO2 capture and utilization. The effects of the ratio of alkali-activated cementitious materials, mineralized curing pressure and mineralized curing time on the carbon fixation rate and compressive strength of CO2 mineralized cementitious materials were studied. The results show that the calcium carbide slag as alkali activator is more suitable for mineralization curing, and the sample with the highest Ca/Si ratio has the best carbon fixation ability under the same curing condition. Increasing the curing pressure and curing time of CO2 can improve the properties of the samples. Physical and chemical characterization test results show that, the microstructure of the mineralized samples is more compact than that of the natural curing samples, and the calcite-type calcium carbonate produced in the curing process is helpful to increase the compressive strength of the material. The research results provide basic data and reference for the development of CO2 mineralization curing technology of all-solid waste alkali-activated cementitious materials.

Electrochemical CO2 reduction (ECR) to value-added products is regarded as a sustainable strategy to mitigate global warming and energy crisis, and designing highly efficient and robust catalysts is essential. In this work, transition metal sulfides (TMS)-decorated CuS microflower-like structures were prepared via the one-pot hydrothermal synthesis method for ECR to CO, and the influence of TMS doping on ECR performance was demonstrated. Characterization of the catalysts was performed using XRD, FESEM-EDS, N2 physisorption, and XPS, revealing the successful loading of TMS, the formation of microflower-like architectures and the generation of sulfur vacancies. Electrochemical tests demonstrated that doping ZnS, Bi2S3, CdS and MoS2 improved the intrinsic CO2 reduction activity of the CuS catalyst. Particularly, the MoS2-CuS composite catalyst with imperfect petal-like structure showed uniform distribution of edge Mo sites, which worked synergistically with the formed grain boundaries (GBs) and undercoordinated S vacancy sites in promoting CO2 activation, stabilizing *COOH adsorption, facilitating *CO desorption, and lowering the energy barrier of the potential-limiting step for improved CO selectivity. The MoS2-CuS catalyst achieved a maximum CO selectivity of 83.2% at –0.6 V versus the reversible hydrogen electrode (RHE) and a high CO cathodic energetic efficiency of 100%. At this potential, the catalyst maintained stable catalytic activity and CO selectivity during a 333-min electrolysis process. The findings will offer a promising avenue for the development of efficient and stable catalysts for CO production from ECR. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel PEI–K2CO3/AC sorbent was prepared with the co-impregnation method. [•] The coupling characteristics of PEI and K2CO3 in the sorbent are expounded. [•] Both PEI and K2CO3 contribute to the total CO2 capture capacity of PEI–K2CO3/AC. [•] PEI–K2CO3/AC presents high CO2 capture capacity and long-term stability. [•] PEI–K2CO3/AC should be considered as a new option for post-combustion CO2 capture. [ABSTRACT FROM AUTHOR]

Highlights: [•] Several potassium-based sorbents were applied to low concentration CO2 removal at ambient temperature. [•] K2CO3/AC shows high carbonation conversion efficiency and CO2 sorption capacity. [•] K2CO3/5A, K2CO3/13X, and K2CO3/SG show low CO2 sorption capacities. [•] K2CO3/Al2O3 shows low carbonation conversion efficiency and needs high temperature of 350°C to be regenerated. [•] K2CO3/AC is a more efficacious choice for CO2 removal in confined space. [ABSTRACT FROM AUTHOR]

SEM and N2 adsorption tests show that the surface area is 3.0m2 g−1 for K2CO3 with structure of monoclinic crystal (PC#1) while that of K2CO3 with structure of hexagonal crystal (PC#2) is 0.95m2 g−1, and the pore volume of PC#1 and PC#2 are 8.0×10−3 and 2.8×10−3 cm3 g−1, respectively. Their pore size distribution curves show almost the same trends. Compared with PC#2, the particle morphology of PC#1 is better for the carbonation reaction. However, the carbonation reaction activity of PC#2 is better than that of PC#1. In order to find out the reason, the crystal structure characteristics of these sorbents are investigated with XRD and Inorganic Crystal Structure Database searching. It is shown that the difference in crystal structure causes the difference of carbonation reactivity between PC#1 and PC#2. The present work provides basic data for the technology of CO2 capture from flue gas using dry potassium-based sorbents. [Copyright &y& Elsevier]

K 2 CO 3 supported on activated carbon (K 2 CO 3 /AC) shows promise as a potential candidate for removing low-concentration CO 2 from environmental control and life support systems (ECLSS). However, K 2 CO 3 /AC would suffer a decreased CO 2 sorption capacity due to sorbent deactivation in acid impurities such as SO 2 and NO 2 . To solve this problem, water vapor pretreatment, KOH addition and polyethyleneimine (PEI) modification were proposed as efficacious means for improving its CO 2 sorption capacity and mitigating the sorbent deactivation in these acid impurities. CO 2 sorption performances of the pretreated and modified sorbents were evaluated in a fixed-bed reactor under simulated ECLSS conditions of 20 °C, 1.0% CO 2 , 2.0% H 2 O, 30 ppm SO 2 , 20 ppm NO 2 and balanced N 2 . The mechanisms for sorbent deactivation inhibition by water vapor pretreatment, KOH addition and PEI modification were revealed by N 2 adsorption-desorption, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FT-IR). Effects of water vapor pretreatment duration, KOH addition and PEI loading on sorbent deactivation inhibition performances were demonstrated. Furthermore, the long-term working stabilities of the pretreated and modified sorbents in impurities were evaluated. The results will provide fundamental support on practical application of K 2 CO 3 /AC for low-concentration CO 2 removal in ECLSS. [ABSTRACT FROM AUTHOR]

Efficient removal of low-concentration CO 2 from manned closed systems including space-crafts and submarines is critically significant for fulfilling the requirement for long-term space or deep sea explorations therein. K 2 CO 3 supported on activated carbon (K 2 CO 3 /AC) shows promise in these low-concentration CO 2 removal applications, with respect to minimizing the system mass and volume. However, the undesirable trace impurities of SO 2 and NO 2 in these systems are expected to degrade the CO 2 sorption efficiency of K 2 CO 3 /AC. In this work, K 2 CO 3 /AC is synthesized with wet impregnation method. CO 2 sorption capacity, sorbent regeneration behaviors and multiple cycle performances of K 2 CO 3 /AC in the presence of trace SO 2 and NO 2 are evaluated with a modified fixed-bed reactor system. The sorbent is characterized by N 2 adsorption–desorption, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDX) as well as elemental analysis (EA), to enable detailed mechanisms for sorbent deactivation in these impurities being fully understood. [ABSTRACT FROM AUTHOR]