RESUMEN

Carbon (C) sequestration in soils is a promising CO2 removal approach. So far, the focus has been on how to increase the content of soil organic C (SOC), while the management soil inorganic C (SIC), i.e. carbonate minerals, has received little attention, because SIC is thought to be much less involved in biotic C cycling than SOC. However, in principle SIC management potentially provides a long-term solution, with a much greater capacity for C sequestration than SOC. The forgotten link is the dissolved inorganic carbon (DIC), i.e. CO2 species dissolved in soil solution, and its fate throughout the unsaturated zone (USZ). The return of CO2 respired by deep roots to the atmosphere, either directly through CO2 degassing or indirectly through DIC leaching, may not necessarily take place over decades or centuries. CO2 diffusion decreases sharply with depth due to reduced porosity of the subsoil and more water-filled pores. The downward water percolation rate is often only a few centimeters per year, and the large amount of respired CO2 compared to the leached DIC results in a relatively small amount of CO2 being transferred to the groundwater. Therefore, respired CO2 at deeper soil depth can be defined as a hitherto unknown ecosystem service of deep-rooted plants i.e. providing a net C sink as inorganic C in the USZ. A conservative estimation suggests a C sink as SIC of at least 80 kg C ha-1 y-1, comparable to reported annual C sequestration as SOC in temperate grasslands.

RESUMEN

The circulatory and respiratory systems in humans are marvels of biological engineering that exhibit competence in maintaining homeostasis. These systems not only shield the organism from external contaminants but also orchestrate the vital gases via the bloodstream to sustain cellular respiration and metabolic processes across diverse tissues. It is noticed that spaces inhabited encounter challenges akin to those of the human body: protecting the indoor air from external pollutants while removing anthropogenic byproducts like carbon dioxide (CO2), particulate matters (PM), and volatile organic compounds (VOCs) tooutside. A biomimetic approach, composed of a microbubble-based gas exchanger and circulating liquid inspired by alveoli, capillary beds, and bloodstream of the human circulatory/respiratory system, offer an innovative solution for comprehensive air purification of hermetic spaces. Circulatory/respiratory-inspired air purification system (CAPS) ensure both continuous removal of PM and exchange of gas species between indoor and outdoor environments to maintain homeostasis. The effectiveness of this system is also supported by animal behavior experiments with and without CAPS, showing an effect of reducing CO2 concentration by 30% and increasing mice locomotor activity by 53%. CAPS is expected to evolve into robust and comprehensive air purification schemes through the networked integration of plural internal and external environments.

RESUMEN

We compare public perceptions of restoring different ecosystems to increase CO2 uptake in Germany, through focus groups and a general population survey. Among focus group participants forests were highly popular, peatlands evoked negative associations, and seagrass was largely unknown. Nevertheless, the restoration of all ecosystems was viewed positively. We contrast these reactions to those of survey respondents who had not received additional information on restoration. They voiced narrower, less diverse opinions centering around afforestation. Further, focus group participants preferred expert-led restoration decisions, citing low trust in politicians' technical competence. Contrary to common policy recommendations, also beyond the German context, participants did not emphasize the need of citizen participation and were not strongly concerned about land use conflicts or compensation of affected user groups. The results imply that the public underestimates the political complexity of negotiation processes in ecosystem governance, which are becoming increasingly relevant in the international policy landscape.

RESUMEN

BACKGROUND: Preliminary studies suggest that moderate ARDS and acute renal failure might benefit from extracorporeal CO2 removal (ECCO2R) coupled with CRRT. However, evidence is limited and potential for this coupled treatment may need to be explored. The aim of the present study was to evaluate whether a protective driving pressure was obtained applying low-flow ECCO2-R plus CRRT in patients affected by moderate ARDS with COVID-19 compared to an historical group without COVID-19. METHODS: A case-control study has been conducted comparing a group of consecutive moderate ARDS patients presenting AKI and affected by COVID-19, who needed low-flow ECCO2-R plus CRRT to achieve an ultra-protective ventilatory strategy, with historical group without COVID-19 that matched for clinical presentation and underwent the same ultra-protective treatment. VT was set at 6 mL/kg predicted body weight then ECCO2R was assessed to facilitate ultra-protective low VT ventilation to preserve safe Pplat and low driving pressure. RESULTS: ECCO2R+CRRT reduced the driving pressure from 17 (14-18) to 11.5 (10-15) cmH2O (p<0.0004) in the fourteen ARDS patients by decreasing VT from 6.7 ml/kg PBW (6.1-6.9) to 5.1 (4.2-5.6) after 1 hour (p <0.0001). In the ARDS patients with COVID-19, the driving pressure reduction was more effective from baseline 18 (14-24) cmH2O to 11 (10-15) cmH2O (p<0.004), compared to the control group from 15 (13-17) to 12(10-16) cmH2O (p< 0.03), after one hour. ECCO2R+CRRT did not affected 28 days mortality in the two groups, while we observed a shorter duration of mechanical ventilation (19 {7-29} vs 24 {22-38} days; p=0.24) and ICU length of stay (19 {7-29} vs 24 {22-78} days; p=0.25) in moderate ARDS patients with COVID-19 compared to control group. CONCLUSIONS: In moderate ARDS patients with or without COVID-19 disease, ECCO2R+CRRT may be and effective supportive treatment to reach protective values of driving pressure unless severe oxygenation defects arise requiring ECMO therapy initiation.

RESUMEN

Background: Low-flow extracorporeal CO 2 removal (ECCO 2 R), managed using a renal replacement platform, is useful in achieving lung-protective ventilation with low tidal volume. However, its capacity for CO 2 elimination is limited. Whether this system is valuable in reducing strong inspiratory efforts in respiratory failure is unclear. The combined use of alkaline agents with low-flow ECCO 2 R might be useful in hypercapnic subjects preserving inspiratory efforts. Methods: This study examined the effects of low-flow ECCO 2 R on respiratory status and investigated the effects of NaHCO 3 , trometamol, and saline on respiratory status during low-flow ECCO 2 R in CO 2 inhalation models. Results: Although low-flow ECCO 2 R did not significantly change the respiratory rate (92.2% ± 24.3% [mean ± standard deviation] of that before ECCO 2 R), it reduced minute ventilation (MV) (78.9% ± 13.5% of that before ECCO 2 R). The addition of NaHCO 3 improved acidemia but did not change MV compared with that of the saline group (0.451 ± 0.026 L/min/kg body weight [BW] vs. 0.556 ± 0.138 L/min/kg BW, respectively). The addition of trometamol improved acidemia and reduced MV compared with that of the saline group (0.381 ± 0.050 L/min/kg BW vs. 0.556 ± 0.138 L/min/kg BW, respectively). The total amounts of CO 2 removed during ECCO 2 R in the NaHCO 3 group were lower than those in the saline and trometamol groups. Conclusion: The low-flow ECCO 2 R reduced MV in subjects preserving spontaneous breathing efforts with CO 2 overload. The addition of NaHCO 3 improved acidemia but did not change MV, whereas the addition of trometamol improved acidemia and reduced MV.

RESUMEN

BACKGROUND: Lung- and diaphragm-protective (LDP) ventilation may prevent diaphragm atrophy and patient self-inflicted lung injury in acute respiratory failure, but feasibility is uncertain. The objectives of this study were to estimate the proportion of patients achieving LDP targets in different modes of ventilation, and to identify predictors of need for extracorporeal carbon dioxide removal (ECCO2R) to achieve LDP targets. METHODS: An in silico clinical trial was conducted using a previously published mathematical model of patient-ventilator interaction in a simulated patient population (n = 5000) with clinically relevant physiological characteristics. Ventilation and sedation were titrated according to a pre-defined algorithm in pressure support ventilation (PSV) and proportional assist ventilation (PAV+) modes, with or without adjunctive ECCO2R, and using ECCO2R alone (without ventilation or sedation). Random forest modelling was employed to identify patient-level factors associated with achieving targets. RESULTS: After titration, the proportion of patients achieving targets was lower in PAV+ vs. PSV (37% vs. 43%, odds ratio 0.78, 95% CI 0.73-0.85). Adjunctive ECCO2R substantially increased the probability of achieving targets in both PSV and PAV+ (85% vs. 84%). ECCO2R alone without ventilation or sedation achieved LDP targets in 9%. The main determinants of success without ECCO2R were lung compliance, ventilatory ratio, and strong ion difference. In silico trial results corresponded closely with the results obtained in a clinical trial of the LDP titration algorithm (n = 30). CONCLUSIONS: In this in silico trial, many patients required ECCO2R in combination with mechanical ventilation and sedation to achieve LDP targets. ECCO2R increased the probability of achieving LDP targets in patients with intermediate degrees of derangement in elastance and ventilatory ratio.

RESUMEN

The pressing need to mitigate the effects of climate change is driving the development of novel approaches for carbon dioxide removal (CDR) from the atmosphere, with the ocean playing a central role in the portfolio of solutions. The expansion of seaweed farming is increasingly considered as one of the potential CDR avenues among government and private sectors. Yet, comprehensive assessments examining whether farming can lead to tangible climate change mitigation remain limited. Here we examine the results of over 100 publications to synthesize evidence regarding the CDR capacity of seaweed farms and review the different interventions through which an expansion of seaweed farming may contribute to climate change mitigation. We find that presently, the majority of the carbon fixed by seaweeds is stored in short-term carbon reservoirs (e.g., seaweed products) and that only a minority of the carbon ends up in long-term reservoirs that are likely to fit within existing international accounting frameworks (e.g., marine sediments). Additionally, the tiny global area cultivated to date (0.06 % of the estimated wild seaweed extent) limits the global role of seaweed farming in climate change mitigation in the present and mid-term future. A first-order estimate using the best available data suggests that, at present, even in a low emissions scenario, any carbon removal capacity provided by seaweed farms globally is likely to be offset by their emissions (median global balance net emitter: -0.11 Tg C yr-1; range -2.07-1.95 Tg C yr-1), as most of a seaweed farms' energy and materials currently depend on fossil fuels. Enhancing any potential CDR though seaweed farming will thus require decarbonizing of supply chains, directing harvested biomass to long-term carbon storage products, expanding farming outside traditional cultivation areas, and developing robust models tracing the fate of seaweed carbon. This will present novel scientific (e.g., verifying permanence of seaweed carbon), engineering (e.g., developing farms in wave exposed areas), and economic challenges (e.g., increase market demand, lower costs, decarbonize at scale), many of which are only beginning to be addressed.

Asunto(s)

RESUMEN

In the present work, the construction, and operation of a pilot-scale biogas upgrading system is presented, employing 2 commercial polyimide (PI) membranes. The Upgrading system treats biogas produced via anaerobic digestion of the sludge, produced from the treatment of municipal wastewater in the facilities of Thessaloniki's Wastewater Treatment Plant. The goal of the separation unit is the production of high purity biomethane (>95%) for potential reuse in terms of energy. The fabrication of the pilot scale system includes the scale up of a laboratory setup separating CO2 from binary CH4-CO2 gas mixture. After the stability tests of the process, for the operation of 5 months (February to June 2023) the purity and recovery of CH4 in the final gas product. The experimental results showed an average recovery of CH4 of 95.7% for an average 55% feed composition, whereas the average purity in the final product was equal to 82.4%. The purity results were lower because of the N2 presence in the product stream (average 17.5%). After normalization with the help of the lab-scale binary results, the expected results assuming N2 absence would be 99.8% CH4 purity and 67% CH4 recovery. Finally, 3 different membrane configurations are compared in terms of their energy production, concluding to the efficiency of 2-stage configuration with recycling stream for the optimal combination of theoretical stage cut fractions.

Asunto(s)

RESUMEN

BACKGROUND: In this retrospective study, we report the effectiveness and safety of a dedicated extracorporeal carbon dioxide removal (ECCO2R) device in critically ill patients. METHODS: Adult patients on mechanical ventilation due to acute respiratory distress syndrome (ARDS) or decompensated chronic obstructive pulmonary disease (dCOPD), who were treated with a dedicated ECCO2R device (CO2RESET, Eurosets, Medolla, Italy) in case of hypercapnic acidemia, were included. Repeated measurements of CO2 removal (VCO2) at baseline and 1, 12, and 24 h after the initiation of therapy were recorded. RESULTS: Over a three-year period, 11 patients received ECCO2R (median age 60 [43-72] years) 3 (2-39) days after ICU admission; nine patients had ARDS and two had dCOPD. Median baseline pH and PaCO2 levels were 7.27 (7.12-7.33) and 65 (50-84) mmHg, respectively. With a median ECCO2R blood flow of 800 (500-800) mL/min and maximum gas flow of 6 (2-14) L/min, the VCO2 at 12 h after ECCO2R initiation was 157 (58-183) mL/min. Tidal volume, respiratory rate, and driving pressure were significantly reduced over time. Few side effects were reported. CONCLUSIONS: In this study, a dedicated ECCO2R device provided a high VCO2 with a favorable risk profile.

RESUMEN

Extracorporeal CO2 removal (ECCO2R) is a therapeutic approach that allows protective ventilation in acute respiratory failure by preventing hypercapnia and subsequent acidosis. The main indications for ECCO2R in acute respiratory failure are COPD (chronic obstructive pulmonary disease) exacerbation, acute respiratory distress syndrome (ARDS) and other situations of asthmatics status. However, CO2 removal procedure is not extended to those ARDS patients presenting an air leak. Here, we report three cases of air leaks in patients with an ARDS that were successfully treated using a new ECCO2R device. Case 1 is a polytrauma patient that developed pneumothorax during the hospital stay, case 2 is a patient with a post-surgical bronchial fistula after an Ivor-Lewis esophagectomy, and case 3 is a COVID-19 patient who developed a spontaneous pneumothorax after being hospitalized for a prolonged time. ECCO2R allowed for protective ventilation mitigating VILI (ventilation-induced lung injury) and significantly improved hypercapnia and respiratory acidemia, allowing time for the native lung to heal. Although further investigation is needed, our observations seem to suggest that CO2 removal can be a safe and effective procedure in patients connected to mechanical ventilation with ARDS-associated air leaks.

RESUMEN

Background. Pregnant women are at high risk of Coronavirus disease 2019 (COVID-19) complications, including acute respiratory distress syndrome. Currently, one of the cornerstones in the treatment of this condition is lung-protective ventilation (LPV) with low tidal volumes. However, the occurrence of hypercapnia may limit this ventilatory strategy. So, different extracorporeal CO2 removal (ECCO2R) procedures have been developed. ECCO2R comprises a variety of techniques, including low-flow and high-flow systems, that may be performed with dedicated devices or combined with continuous renal replacement therapy (CRRT). Case description. Here, we report a unique case of a pregnant patient affected by COVID-19 who required extracorporeal support for multiorgan failure. While on LPV, because of the concomitant hypercapnia and acute kidney injury, the patient was treated with an ECCO2R membrane inserted in series after a hemofilter in a CRRT platform. This combined treatment reducing hypercapnia allowed LPV maintenance at the same time while providing kidney replacement and ensuring maternal and fetal hemodynamic stability. Adverse effects consisted of minor bleeding episodes due to the anticoagulation required to maintain the extracorporeal circuit patency. The patient's pulmonary and kidney function progressively recovered, permitting the withdrawal of any extracorporeal treatment. At the 25th gestational week, the patient underwent spontaneous premature vaginal delivery because of placental abruption. She gave birth to an 800-gram female baby, who three days later died because of multiorgan failure related to extreme prematurity. Conclusions. This case supports using ECCO2R-CRRT combined treatment as a suitable approach in the management of complex conditions, such as pregnancy, even in the case of severe COVID-19.

Asunto(s)

RESUMEN

A COPD exacerbation is characterized by an increase in symptoms such as dyspnea, cough, and sputum production that worsens over a period of 2 weeks. Exacerbations are common. Respiratory therapists and physicians in an acute care setting often treat these patients. Targeted O2 therapy improves outcomes and should be titrated to an SpO2 of 88-92%. Arterial blood gases remain the standard approach to assessing gas exchange in patients with COPD exacerbation. The limitations of arterial blood gas surrogates (pulse oximetry, capnography, transcutaneous monitoring, peripheral venous blood gases) should be appreciated so that they can be used wisely. Inhaled short-acting bronchodilators can be provided by nebulizer (jet or mesh), pressurized metered-dose inhaler (pMDI), pMDI with spacer or valved holding chamber, soft mist inhaler, or dry powder inhaler. The available evidence for the use of heliox for COPD exacerbation is weak. Noninvasive ventilation (NIV) is standard therapy for patients who present with COPD exacerbation and is supported by clinical practice guidelines. Robust high-level evidence with patient important outcomes is lacking for the use of high-flow nasal cannula in patients with COPD exacerbation. Management of auto-PEEP is the priority in mechanically ventilated patients with COPD. This is achieved by reducing airway resistance and decreasing minute ventilation. Trigger asynchrony and cycle asynchrony are addressed to improve patient-ventilator interaction. Patients with COPD should be extubated to NIV. Additional high-level evidence is needed before widespread use of extracorporeal CO2 removal. Care coordination can improve the effectiveness of care for patients with COPD exacerbation. Evidence-based practices improve outcomes in patients with COPD exacerbation.

Asunto(s)

RESUMEN

INTRODUCTION: Low-flow veno-venous extracorporeal CO2 removal (ECCO2R) is an adjunctive therapy to support lung protective ventilation or maintain spontaneous breathing in hypercapnic respiratory failure. Low-flow ECCO2R is less invasive compared to higher flow systems, while potentially compromising efficiency and membrane lifetime. To counteract this shortcoming, a high-longevity system has recently been developed. Our hypotheses were that the novel membrane system provides runtimes up to 120 h, and CO2 removal remains constant throughout membrane system lifetime. METHODS: Seventy patients with pH ≤ 7.25 and/or PaCO2 ≥9 kPa exceeding lung protective ventilation limits, or experiencing respiratory exhaustion during spontaneous breathing, were treated with the high-longevity ProLUNG system or in a control group using the original gas exchanger. Treatment parameters, gas exchanger runtime, and sweep-gas VCO2 were recorded across 9,806 treatment-hours and retrospectively analyzed. RESULTS: 25/33 and 23/37 patients were mechanically ventilated as opposed to awake spontaneously breathing in both groups. The high-longevity system increased gas exchanger runtime from 29 ± 16 to 48 ± 36 h in ventilated and from 22 ± 14 to 31 ± 31 h in awake patients (p < 0.0001), with longer runtime in the former (p < 0.01). VCO2 remained constant at 86 ± 34 mL/min (p = 0.11). Overall, PaCO2 decreased from 9.1 ± 2.0 to 7.9 ± 1.9 kPa within 1 h (p < 0.001). Tidal volume could be maintained at 5.4 ± 1.8 versus 5.7 ± 2.2 mL/kg at 120 h (p = 0.60), and peak airway pressure could be reduced from 31.1 ± 5.1 to 27.5 ± 6.8 mbar (p < 0.01). CONCLUSION: Using a high-longevity gas exchanger system, membrane lifetime in low-flow ECCO2R could be extended in comparison to previous systems but remained below 120 h, especially in spontaneously breathing patients. Extracorporeal VCO2 remained constant throughout gas exchanger system runtime and was consistent with removal of approximately 50% of expected CO2 production, enabling lung protective ventilation despite hypercapnic respiratory failure.

Asunto(s)

RESUMEN

Rationale: In the EOLIA (ECMO to Rescue Lung Injury in Severe ARDS) trial, oxygenation was similar between intervention and conventional groups, whereas [Formula: see text]e was reduced in the intervention group. Comparable reductions in ventilation intensity are theoretically possible with low-flow extracorporeal CO2 removal (ECCO2R), provided oxygenation remains acceptable. Objectives: To compare the effects of ECCO2R and extracorporeal membrane oxygenation (ECMO) on gas exchange, respiratory mechanics, and hemodynamics in animal models of pulmonary (intratracheal hydrochloric acid) and extrapulmonary (intravenous oleic acid) lung injury. Methods: Twenty-four pigs with moderate to severe hypoxemia (PaO2:FiO2 ⩽ 150 mm Hg) were randomized to ECMO (blood flow 50-60 ml/kg/min), ECCO2R (0.4 L/min), or mechanical ventilation alone. Measurements and Main Results: [Formula: see text]o2, [Formula: see text]co2, gas exchange, hemodynamics, and respiratory mechanics were measured and are presented as 24-hour averages. Oleic acid versus hydrochloric acid showed higher extravascular lung water (1,424 ± 419 vs. 574 ± 195 ml; P < 0.001), worse oxygenation (PaO2:FiO2 = 125 ± 14 vs. 151 ± 11 mm Hg; P < 0.001), but better respiratory mechanics (plateau pressure 27 ± 4 vs. 30 ± 3 cm H2O; P = 0.017). Both models led to acute severe pulmonary hypertension. In both models, ECMO (3.7 ± 0.5 L/min), compared with ECCO2R (0.4 L/min), increased mixed venous oxygen saturation and oxygenation, and improved hemodynamics (cardiac output = 6.0 ± 1.4 vs. 5.2 ± 1.4 L/min; P = 0.003). [Formula: see text]o2 and [Formula: see text]co2, irrespective of lung injury model, were lower during ECMO, resulting in lower PaCO2 and [Formula: see text]e but worse respiratory elastance compared with ECCO2R (64 ± 27 vs. 40 ± 8 cm H2O/L; P < 0.001). Conclusions: ECMO was associated with better oxygenation, lower [Formula: see text]o2, and better hemodynamics. ECCO2R may offer a potential alternative to ECMO, but there are concerns regarding its effects on hemodynamics and pulmonary hypertension.

Asunto(s)

RESUMEN

The production of bioenergy with carbon capture and storage (BECCS) is a pivotal negative emission technology. The cultivation of dedicated crops for BECCS impacts the temperature through two processes: net CO2 removal (CDR) from the atmosphere (biogeochemical cooling) and changes in the local energy balance (biophysical warming or cooling). Here, we compare the magnitude of these two processes for key grass and tree species envisioned for large-scale bioenergy crop cultivation, following economically plausible scenarios using Earth System Models. By the end of this century, the cumulative CDR from the cultivation of eucalypt (72-112 Pg C) is larger than that of switchgrass (34-83 Pg C) because of contrasting contributions of land use change carbon emissions. The combined biogeochemical and biophysical effects are cooling (-0.26 to -0.04 °C) at the global scale, but 13-28% of land areas still have net warming signals, mainly due to the spatial heterogeneity of the biophysical effects. Our study shows that the deployment of bioenergy crop cultivation should not only be guided by the principles of maximizing yield and CDR but should also take an integrated perspective that includes all relevant Earth system feedbacks.

Asunto(s)

RESUMEN

Lung-protective ventilation (LPV) with low tidal volumes can significantly increase the survival of patients with acute respiratory distress syndrome (ARDS) by limiting ventilator-induced lung injuries. However, one of the main concerns regarding the use of LPV is the risk of developing hypercapnia and respiratory acidosis, which may limit the clinical application of this strategy. This is the reason why different extracorporeal CO2 removal (ECCO2R) techniques and devices have been developed. They include low-flow or high-flow systems that may be performed with dedicated platforms or, alternatively, combined with continuous renal replacement therapy (CRRT). ECCO2R has demonstrated effectiveness in controlling PaCO2 levels, thus allowing LPV in patients with ARDS from different causes, including those affected by Coronavirus disease 2019 (COVID-19). Similarly, the suitability and safety of combined ECCO2R and CRRT (ECCO2R-CRRT), which provides CO2 removal and kidney support simultaneously, have been reported in both retrospective and prospective studies. However, due to the complexity of ARDS patients and the limitations of current evidence, the actual impact of ECCO2R on patient outcome still remains to be defined. In this review, we discuss the main principles of ECCO2R and its clinical application in ARDS patients, in particular looking at clinical experiences of combined ECCO2R-CRRT treatments.

RESUMEN

The production potential of a locally isolated Chlorella vulgaris strain and a local green-algae consortium, used in municipal wastewater treatment combined with CO2 sequestration from flue gases, was evaluated for the first time by comparing the elemental and biochemical composition and heating value of the biomass produced. The microalgae were grown in outdoor pilot-scale ponds under subarctic summer conditions. The impact of cultivation in a greenhouse climate was also tested for the green-algae consortium; additionally, the variation in species composition over time in the three ponds was investigated. Our results showed that the biomass produced in the consortium/outdoor pond had the greatest potential for bioenergy production because both its carbohydrates and lipids contents were significantly higher than the biomasses from the consortium/greenhouse and C. vulgaris/outdoor ponds. Although greenhouse conditions significantly increased the consortium biomass's monounsaturated fatty acid content, which is ideal for biodiesel production, an undesirable increase in ash and chemical elements, as well as a reduction in heating value, were also observed. Thus, the placement of the pond inside a greenhouse did not improve the production potential of the green-algae consortium biomass in the current study infrastructure and climate conditions.

Asunto(s)

RESUMEN

The efficiency of a novel synthetic zeolite (Ze) prepared from stone cutting sludge and a natural zeolite (clinoptilolite, Cp) as the support of TiO2 photocatalyst was examined for the CO2 removal under solar irradiation using a designed parabolic trough collector (PTC). The used samples were characterized using XRF, BET, SEM/EDS, and XPS analyses. The enhanced sunlight irradiation obtained by PTC increased the performance of CO2 photocatalytic removal. The maximum CO2 adsorption by TiO2-Ze and TiO2-Cp composites was 21.1% and 28.4% which increased to 61.8% and 78.9% under sunlight irradiation, respectively. The efficiency of zeolite-TiO2 composites for CO2 removal was approximately two times higher than zeolites and TiO2 alone. The performance of TiO2-Ze-coated composite with lower use of photocatalyst for CO2 adsorption and photocatalytic removal was better than that of powder one. Regeneration of TiO2-Ze using NaOH solution improved its removal efficiency. The adsorption behavior of CO2 on TiO2-Ze composite was well described by the Langmuir isotherm and the pseudo-first-order kinetic model. This work promises CO2 reduction using natural and synthetic zeolite as an efficient photocatalyst support under solar irradiation.

Asunto(s)

RESUMEN

Membranes with a stable performance during the natural gas sweetening process application are highly demanded. This subject has been immensely explored due to several challenges faced by conventionally used polymeric membranes, especially the high tendency of plasticization and physical aging. In this study, polysulfone (PSf) hollow-fiber membrane was formulated and tested for its application in natural gas sweetening based on several compositions of CO2/CH4 mixed gas. The effects of operating conditions such as pressure, temperature and CO2 feed composition on separation performance were analyzed. The findings showed that the formulated membrane exhibited decreasing CO2 permeation trend with the increase in pressure. Conversely, the increase in operating temperature boosted the CO2 permeation. High productivity can be attained at higher operating temperatures with a reduction in product purity. Interestingly, since PSf has higher plasticization pressure, it was not affected by the change in CO2 percentage up to 70% CO2. The experimental study showed that the membrane material formulated in this study can be potentially evaluated at the field stage. Longer testing duration is needed with the real feed gas, appropriate pre-treatment based on the material limitations, and optimum operating conditions at the site to further confirm the membrane's long-term lifetime, resistance, and stability.

RESUMEN

The use of extracorporeal oxygenation and CO2 removal has gained clinical validity and popularity in recent years. These systems are composed of a pump to drive blood flow through the circuit and a hollow fiber membrane bundle through which gas exchange is achieved. Mathematical modeling of device design is utilized by researchers to improve device hemocompatibility and efficiency. A previously published mathematical model to predict CO2 removal in hollow fiber membrane bundles was modified to include an empirical representation of the Haldane effect. The predictive capabilities of both models were compared to experimental data gathered from a fiber bundle of 7.9 cm in length and 4.4 cm in diameter. The CO2 removal rate predictions of the model including the Haldane effect reduced the percent error between experimental data and mathematical predictions by up to 16%. Improving the predictive capabilities of computational fluid dynamics for the design of hollow fiber membrane bundles reduces the monetary and manpower expenses involved in designing and testing such devices.