Confinement effects facilitate low-concentration carbon dioxide capture with zeolites

Engineered systems designed to remove CO₂ from the atmosphere need better adsorbents. Here, we report on zeolite-based adsorbents for the capture of low-concentration CO₂. Synthetic zeolites with the mordenite (MOR)-type framework topology physisorb CO₂ from low concentrations with fast kinetics, low heat of adsorption, and high capacity. The MOR-type zeolites can have a CO₂ capacity of up to 1.15 and 1.05 mmol/g for adsorption from 400 ppm CO₂ at 30 °C, measured by volumetric and gravimetric methods, respectively. A structure–performance study demonstrates that Na⁺ cations in the O33 site located in the side-pocket of the MOR-type framework, that is accessed through a ring of eight tetrahedral atoms (either Si⁴⁺ or Al³⁺: eight-membered ring [8MR]), is the primary site for the CO₂ uptake at low concentrations. The presence of N₂ and O₂ shows negligible impact on CO₂ adsorption in MOR-type zeolites, and the capacity increases to ∼2.0 mmol/g at subambient temperatures. By using a series of zeolites with variable topologies, we found the size of the confining pore space to be important for the adsorption of trace CO₂. The results obtained here show that the MOR-type zeolites have a number of desirable features for the capture of CO₂ at low concentrations.

The anthropogenic emission of CO₂ is associated with the continuous increase in global temperature since the industrial revolution. Therefore, many CO₂ mitigation strategies have been under investigation in the past years with the goal of net-zero emission by 2050. Point-source capture provides solutions for the sustainable operation of steel industries, cement plants, coal-based power stations, and the like. Bioenergy with carbon capture and storage (BECCS) and direct air capture (DAC) are being investigated for the direct removal of CO₂ from air to address the emissions from mobile sources such as automobiles, airplanes, and cargo ships (1, 2). BECCS and DAC provide opportunities for net-negative emissions.The search for CO₂ adsorbents that are affordable, effective, energy efficient, environmentally friendly, and safe for large-scale applications poses a serious challenge for the implementation of carbon capture technologies (3–5). This is particularly significant for DAC because of the low diffusion rates and low CO₂ capacities resulting from trace concentrations of CO₂ (5). It is generally believed that physisorbents are not applicable to the DAC system due to the their weak affinity for CO₂ (6). Thus, chemisorbents have been extensively investigated for trace CO₂ capture (7). Liquid amine and alkaline adsorbents as well as other types of chemisorbents (e.g., ionic liquids (8) and electric based membranes (9)) have been investigated for the capture of CO₂ from low-concentration environments. However, the intensive energy requirements for desorption (60–120 kJ/mol) and slow kinetics may be problematic for processing the large quantities needed for the implementation of DAC with chemisorbents. Amines supported on porous materials have also been studied for DAC to increase surface exposure and diffusion kinetics as compared to the liquid analogs (1, 10–14). The time-dependent oxidative degradation and evaporation of amines are intrinsic challenges to the use of these methods (15). The development of new physisorbents that display high stability, low energy cost for desorption, fast sorption kinetics, and high capacity, as well as that possess moderate adsorption heat of 30–60 kJ/mol and fully reversible physisorption properties, could be enabling adsorbents for large-scale DAC (16).The most widely studied physisorbents for DAC are metal–organic frameworks (MOFs) (5). Promising CO₂ capture performances are reported for hybrid ultramicroporous materials, a subgroup of MOFs (17–20). The high performance of these solids originates from the strongly electronegative, fluorine-based adsorption centers as well as the well-controlled pore size (20). However, it is still a challenging task to obtain a MOF sorbent for DAC with cost-effective scalability, high performance, and long-term stability (18, 20). Zeolites are another type of microporous materials with vast structural and physicochemical properties and high stability. They can be synthesized in large quantities in cost-effective processes and have a long history in the industry for catalysis and adsorption (21). For carbon capture, they often possess faster kinetics than supported amines (22). These merits have made zeolites interesting candidates for the capture of high-concentration CO₂ (23–25). The known challenges for the application of zeolites for DAC are the detrimental effect of water as well as capacities for low-concentration CO₂ capture. The former issue can be addressed by engineering multibed systems with a desiccant bed upstream of the zeolitic adsorbents (26). For DAC applications, the capture of atmospheric water could be a useful endeavor to complement the removal of CO₂ in areas where fresh water is badly needed. To address the later issue, recent research has been focused on maximizing the number (22, 27) of adsorption sites by using low-silica zeolites or adjusting the type of extraframework cations (28–30) by incorporating Zn²⁺ and Ca²⁺ ions. These approaches have given high capacities of 0.4 and 0.87 mmol/g for Na-FAU zeolites with Si/Al = 1.2 (zeolite X) and 1.0 (low-silica zeolite X), respectively, as well as 0.67 mmol/g for Zn-CHA with Si/Al = ∼2.0 and 1.8 mmol/g for Ca-LTA with Si/Al = 1 (the three letter codes of zeolites are assigned by the Interantional Zeolite Association for indicating their framework topologies). However, the low thermostability for low-silica zeolites and irreversible adsorption of CO₂ in Ca²⁺-containing zeolites will probably present challenges for commercial-scale implementation of DAC. Therefore, there remains a need for a zeolitic adsorbent with competitive capacity, high stability, and cyclability (31, 32).In this work, we report that the confinement effect in zeolites greatly affects the adsorption of low-concentration CO₂. MOR-type zeolites with eight-membered ring (8MR) side-pockets synthesized with or without (33) organic structure-directing agents (OSDAs) can give a CO₂ capacity of ∼1.15 mmol/g, among the highest reported for physisorbents for DAC. This capacity results in approximately an order of magnitude improvement of adsorption efficiency (i.e., CO₂ per adsorption site), compared to the standard 13X zeolite adsorbent. The O33 site in the 8MR side-pocket is the primary adsorption site of MOR-type zeolites, and the size of the confined space for the adsorption site in zeolites dictates their properties for the adsorption of 400 ppm CO₂.     

Preparation and Properties of Different Polyether-Type Defoamers for Concrete

In this study, a series of polyether-type defoamers for concrete which consist of the same alkyl chain (hydrophobic part) but different polyether chains (hydrophilic part) was prepared, and the structure–property relationship of the defoamers was investigated for the first time. Using oleyl alcohol (OA) as the starting agent (alkyl chain), the polyether defoamers with different polyether chains were prepared by changing the amount and sequence of ethylene oxide (EO) and propylene oxide (PO) units. The properties of different defoamers were tested in aqueous solutions, and fresh and hardened mortars; the structure–property relationship of the defoamers was thus studied. The results indicated that the defoaming capacity of the polyether defoamers decreased with an increased EO amount, and the defoamers linked with both EO and PO units (PO before EO) had a stronger defoaming capacity than those linked with EO only. This study is beneficial for the development and applications of novel synthetic polyether-type defoamers for concrete.     

Experimental Study on the Stability and Distribution of Air Voids in Fresh Fly Ash Concrete

The air void system purposely introduced by an air-entraining admixture (AEA) is of great significance for the protection of concrete from freeze–thaw damage. Fly ash has been globally used in concrete, while the unburnt carbon in fly ash can adsorb AEA molecules and, thus, increase the AEA demand. Previous studies primarily focused on the air content of fresh fly ash concrete. This paper aimed to explore the stability and distribution of air voids in fly ash concrete at the fresh state. To achieve this goal, eleven different fresh fly ash concrete mixtures with an initial air content of 6 ± 1% were prepared in the laboratory. Samples were taken at various times within 75 min after initial mixing to investigate the air content and air void distribution in fly ash concrete at the fresh state using a super air meter (SAM). The results indicated that there was no significant correlation between loss on ignition (LOI) of fly ash and AEA demand to achieve the initial air content of 6 ± 1%. Class C fly ash concrete tended to have a better air content retention than Class F fly ash concrete. Compared with LOI, AEA demand had a stronger correlation with air content retention. Most of the fly ash concrete mixtures had a satisfactory air void system immediately after mixing, but the SAM number showed an increasing trend over time, suggesting the coarsening of the air void system with time.     

To explore the prognostic value of spread through air spaces and develop a nomogram combined with spread through air spaces in lung squamous cell carcinoma

BackgroundSpread through air spaces (STAS), as a new pattern of invasion, was officially proposed by the World Health Organization (WHO) in 2015, and its importance was reiterated in 2021. Since it was proposed, numerous studies have confirmed that STAS is associated with poor prognosis, but there are relatively few studies related to the prognosis of postoperative patients with lung squamous cell carcinoma. By synthesizing different predictive variables, nomogram can obtain the individual digital probability of clinical events succinctly and intuitively, which can meet our needs for personalized medicine. In this study, our goal is to explore the prognostic value of STAS in lung squamous cell carcinoma and establish a prognostic prediction model.MethodsUnder six inclusion criteria, 540 postoperative patients were enrolled in the study. STAS was re-evaluated by pathologists at Ningbo Clinicopathological Diagnosis Center. Progression-free survival (PFS) referred to the time from randomization to the first occurrence of disease progression or death of any cause. Recurrences were confirmed by clinical, radiological or pathological assessment. The survival information was collected by telephone and outpatient follow-up. A total of 540 patients were randomly divided into groups in a 6:4 ratio for survival analysis to determine the correlation between STAS and prognosis. Cox regression was used for univariate and multivariate analysis, so as to establish a predictive model. The assessment of the nomogram was carried out by receiver operating characteristic (ROC) curve analysis, calibration curve analysis and decision curve analysis (DCA).ResultsThe overall 5-year survival rate was 70.35% in STAS-negative patients and 42.35% in STAS-positive patients. In all cohorts, STAS-negative patients had longer 5-year PFS than STAS-positive patients (P<0.001). Multivariate analysis showed that stage [stage II P=0.008, hazard ratio (HR) =1.792; stage III P<0.001, HR =3.148], tumor differentiation (well-differentiation P=0.021, HR =0.436), and STAS (P=0.026, HR =1.470) were independent predictors of PFS. The area under the curve (AUC) of model 5 in discovery cohort is 0.720, while the AUC of model 5 in validation cohort is 0.693.ConclusionsThe nomogram combined with STAS can provide a personalized visual survival probability prediction map for postoperative patients with lung squamous cell carcinoma, so as to aid in the pursuit of personalized medicine to a certain extent.     

Location-specific strategies for eliminating US national racial-ethnic [... formula ...] exposure inequality

Air pollution levels in the United States have decreased dramatically over the past decades, yet national racial-ethnic exposure disparities persist. For ambient fine particulate matter (PM2.5), we investigate three emission-reduction approaches and compare their optimal ability to address two goals: 1) reduce the overall population average exposure (“overall average”) and 2) reduce the difference in the average exposure for the most exposed racial-ethnic group versus for the overall population (“national inequalities”). We show that national inequalities in exposure can be eliminated with minor emission reductions (optimal: ~1% of total emissions) if they target specific locations. In contrast, achieving that outcome using existing regulatory strategies would require eliminating essentially all emissions (if targeting specific economic sectors) or is not possible (if requiring urban regions to meet concentration standards). Lastly, we do not find a trade-off between the two goals (i.e., reducing overall average and reducing national inequalities); rather, the approach that does the best for reducing national inequalities (i.e., location-specific strategies) also does as well as or better than the other two approaches (i.e., sector-specific and meeting concentration standards) for reducing overall averages. Overall, our findings suggest that incorporating location-specific emissions reductions into the US air quality regulatory framework 1) is crucial for eliminating long-standing national average exposure disparities by race-ethnicity and 2) can benefit overall average exposures as much as or more than the sector-specific and concentration-standards approaches.

The Clean Air Act has dramatically reduced outdoor air pollution levels in the United States, with (during 1990 through 2020) aggregate benefits exceeding costs 30-to-1 ($2 trillion versus $65 billion) (1). Important regulatory strategies include the National Ambient Air Quality Standards (NAAQS) and sector-specific emission-reduction technology requirements (e.g., Best Achievable Control Technology [BACT] standards). However, exposure inequalities persist (2–7). Disparities by race-ethnicity are larger than, and distinct from, those by income (4–6, 8, 9). Racial-ethnic inequalities in US ambient air pollution and subsequent exposures are attributable in part to racist planning, including historical, race-based housing segregation and land-use practices (10–18). Environmental racism scholars have suggested that strategies and policies for eliminating disparities will be most effective when racial-ethnic injustices are centered and directly addressed (19–22).The existing literature documents exposure inequities (3–7, 9, 23–26) and investigates the impacts on inequities of emission changes for specific sources (e.g., refs. 27–36) or locations (37–43). However, the scientific literature has not investigated how to eliminate national racial-ethnic inequalities in air pollution or what level of emission reduction would be required to do so (44).We examine three potential approaches to reduce or eliminate national exposure inequalities: 1) location-specific emission reductions (hereafter, “location”), 2) sector-specific emission reductions (“sector”; analogous to BACT-type approaches), and 3) requiring regions to meet a concentration standard (“NAAQS-like”). Approaches 2 and 3 mirror aspects of current regulations; approach 1 would be a new regulatory approach. We find that the location approach is by far the most effective (can eliminate national disparities with only small absolute emission reductions); the sector approach is poor (can reduce disparities, but requires substantially larger emission reductions; cannot eliminate disparities except by eliminating nearly all emissions); and NAAQS-like is the least effective (does not eliminate disparities). The location approach is also the strongest of the three for reducing population-average exposures.To quantitatively compare the three approaches, we use the publicly available InMAP (Intervention Model for Air Pollution) source-receptor matrix (ISRM) (45) to estimate long-term average ambient fine particulate matter (PM2.5) concentrations across the contiguous United States caused by anthropogenic emissions in 2014. Disparity here refers to the difference between population-weighted average PM2.5 concentrations for the most exposed racial-ethnic group minus the overall population (in sensitivity analyses, we instead investigate government-designated “high vulnerability” [HV] locations; Materials and Methods). ISRM predicts the concentration of primary PM2.5 and secondary PM2.5 formed from nitrogen oxides (NOx), sulfur oxides (SOx), ammonia (NH3), and volatile organic compounds (VOCs). We employ the 2014 US Environmental Protection Agency (EPA) National Emission Inventory, grouped into 14 source sectors (see Fig. 2B, SI Appendix, and below). ISRM contains 52,411 grid cells (locations) with size (i.e., spatial resolution) ranging from 1 km in densely populated urban centers to 48 km in sparsely populated rural areas; the average spatial resolution is 2.6 km in Urban Areas and 22.6 km in non-Urban Areas (13.2 km overall). Emissions reductions for location and sector are an optimization to maximally reduce disparities for the most exposed group relative to the overall population average. They use the spatial resolution of the simulation grid and the 14 source sectors, respectively. Thus, our results inform what that method could optimally do to reduce or eliminate racial-ethnic exposure disparities. The NAAQS-like approach simulates successive, proportional emission reductions in each region violating the hypothetical NAAQS (e.g., 6 µg/m3), until the NAAQS-like standard is met.Open in a separate windowFig. 2.Emission reductions for the three approaches: by location (i.e., corresponding to the green lines, Fig. 1) (A), by sector (corresponding to blue lines, Fig. 1) (B), and NAAQS-like (orange lines, Fig. 1) (C). A displays national results (Left) and zoomed-in results for 10 large areas (Right). Spatial units displayed in C are CBSAs, the geographic unit for NAAQS evaluation. The three approaches offer fundamentally different ways of formulating and prioritizing emission reductions. Ag., agriculture; Const., construction; Elec., electricity; HD, heavy duty; LD, light duty; Misc., miscellaneous; Res., residential; Veh., vehicle.     

Short-term exposure to stone minerals used in asphalt affect lung function and promote pulmonary inflammation among healthy adults

ObjectiveStone minerals are a partially ignored environmental challenge but a significant contributor to urban air pollution. We examined if short-term exposure to two stone minerals – quartz diorite and rhomb porphyry – commonly used in asphalt pavement would affect lung function, promote pulmonary inflammation, and affect bronchial reactivity differently.MethodsOur randomized crossover study included 24 healthy, non-smoking young adults exposed to the stone minerals quartz diorite, rhomb porphyry, and control dust (lactose). Exposure occurred in an exposure chamber, in three separate 4-hour exposure sessions. Fractional exhaled nitric oxide (FeNO) and lung function were monitored before exposure, then immediately following exposure, and 4 and 24 hours after exposure. In addition, methacholine was administered 4 hours following exposure, and exhaled breath condensate (EBC) was collected before exposure, then immediately and 4 hours after exposure. EBC was analyzed for pH, thiobarbituric acid reactive substances (TBARS), intercellular adhesion molecule 1 (ICAM-1), interleukin-6 (IL-6), IL-10, P-Selectin, surfactant protein D (SP-D), and tumor necrosis factor-α (TNF-α).ResultsOur results showed significantly elevated concentrations of FeNO after exposure to quartz diorite compared to rhomb porphyry, suggesting that quartz diorite is more likely to trigger pulmonary inflammation after short-term exposure. Moreover, short-term exposure to rhomb porphyry was associated with a modest but statistically significant decline in forced vital capacity (FVC) compared to quartz diorite.ConclusionThese results emphasize that using stone material in asphalt road construction should be reconsidered as it may affect lung inflammation and lung function in exposed subjects.     

小儿急性肠套叠的诊断与治疗

目的 :探讨小儿急性肠套叠的诊断与治疗。方法 :对 2 0 0 1年 1月～ 2 0 0 4年 2月间收治的小儿肠套叠 4 2例临床资料进行回顾性分析。结果 :34例男患儿好发年龄为 4个月～ 10个月 ,以回结型最多见 (6 6 .6 % )。空气灌肠复位成功 31例 ,其余均手术治疗。死亡 1例 ,其余均治愈出院。结论 :早期诊断、早期治疗是小儿急性肠套叠空气灌肠复位成功的关键 ,发病超过 4 8h、血便超过 2 4h者不宜行空气灌肠复位术 ,必须手术治疗。     

沙美特罗替卡松联合BiPAP在慢性阻塞性肺疾病治疗中的应用研究

目的：探讨沙美特罗替卡松联合双水平气道正压通气（BiPAP）在慢性阻塞性肺疾病（COPD）合并呼吸衰竭治疗中的应用价值。方法：选取本院2007年7月~2011年3月收治的250例COPD合并Ⅱ型呼吸衰竭患者的临床资料,随机分为治疗组（130例）和对照组（120例）,对照组患者采用沙美特罗替卡松粉吸入剂治疗,治疗组患者采用沙美特罗替卡松粉吸入剂联合BiPAP呼吸机治疗,随访4周,比较两组患者动脉血气分析及肺功能变化情况。结果：治疗组患者肺功能及动脉血气分析明显优于对照组,两组患者比较差异有统计学意义（P〈0.05）。结论：沙美特罗替卡松联合BiPAP呼吸机治疗慢性阻塞性肺疾病,疗效满意,值得在临床推广。     

Computational fluid dynamics (CFD) assisted performance evaluation of the Twincer™ disposable high-dose dry powder inhaler

Objectives To use computational fluid dynamics (CFD) for evaluating and understanding the performance of the high‐dose disposable Twincer? dry powder inhaler, as well as to learn the effect of design modifications on dose entrainment, powder dispersion and retention behaviour. Methods Comparison of predicted flow and particle behaviour from CFD computations with experimental data obtained with cascade impactor and laser diffraction analysis. Key findings Inhaler resistance, flow split, particle trajectories and particle residence times can well be predicted with CFD for a multiple classifier based inhaler like the Twincer?. CFD computations showed that the flow split of the Twincer? is independent of the pressure drop across the inhaler and that the total flow rate can be decreased without affecting the dispersion efficacy or retention behaviour. They also showed that classifier symmetry can be improved by reducing the resistance of one of the classifier bypass channels, which for the current concept does not contribute to the swirl in the classifier chamber. Conclusions CFD is a highly valuable tool for development and optimisation of dry powder inhalers. CFD can assist adapting the inhaler design to specific physico‐chemical properties of the drug formulation with respect to dispersion and retention behaviour.