CO2 Carbon Research Articles

Increasing solar still efficiency with thermo-electric cooling: an experimental study and economic analysis

Seawater distillation often relies on fossil fuels, emitting greenhouse gases, but solar energy offers a sustainable, cost-free alternative. This study enhances solar still productivity by incorporating a condensation chamber and thermoelectric cooling using Peltier modules and fans. Two models were tested in Khemis Miliana, Algeria: a conventional solar still and a modified version with a cooling system. Experimental results from September to November showed the cooling system increased productivity by 74% compared to the uncooled system and 14% compared to the conventional still. The optimal cooling system operation was determined to be 3 minutes every 30 minutes, influenced by solar radiation. The modified system achieved a water production cost of $0.09237 per litre, with a payback time of 2.5 years. Daily output data helped evaluate CO2 emissions, mitigation potential and carbon credits over the system's lifespan. Future work includes integrating a flat plate collector and optimising the cooling system's operation relative to solar radiation for higher efficiency.

A simple and cost-effective sample preparation and storage method for stable isotope analysis of atmospheric CO2 for GasBench II/continuous flow isotope ratio mass spectrometry.

The stable isotope compositions of atmospheric CO2 can provide useful insight into various geochemical processes and carbon cycles on Earth, which is critical for understanding of Earth's changing climate. Here, we present a simple and cost-effective analytical method for the collection and measurement of carbon and oxygen isotope compositions of atmospheric CO2. Air samples of ~150 mL were collected individually or collectively using our simple active air collection system and then extracted on a vacuum purification line to remove noncondensable gases and atmospheric water vapor. The efficiency of removing atmospheric water vapor was tested by using a magnesium perchlorate desiccant trap and a dry ice/ethanol trap. Lastly, a "J-Cut tube sealing/cracking method" was developed to store and transfer purified atmospheric CO2 to the GasBench II and CF-IRMS system for δ13C and δ18O measurements. The collective active air collection method combined with the full sample air extraction method for a 3-min transfer time or "Full 3m TE" yields the best analytical precision of 0.07‰ (δ13C) and 0.04‰ (δ18O). Removing atmospheric water vapor from air samples is not necessary for δ13C, but essential for δ18O measurements. The J-Cut tube sealing/cracking method shows a near 100% effectiveness for the storage and transfer of atmospheric or any CO2. A simple and cost-effect method was developed for the collection, purification, storage, and isotopic analysis of indoor/outdoor atmospheric CO2 samples for general users. This method utilizes a popular headspace gas sample preparation system for CF-IRMS and an easy-to-build vacuum purification line without involving complex and high-cost devices for the preparation of atmospheric CO2.

Mixed matrix membrane formation with porous metal–organic nanomaterials for CO2 capture and separation: A critical review

Due to the increasingly severe global warming trend, the reduction of CO2 emission and carbon capture have attracted growing interest. The separation of CO2 from gas mixtures, especially from point source and the atmosphere, is considered as one of the most important strategies for mitigating climate change. Porous metal–organic nanomaterials (PNMs), including metal-organic frameworks (MOFs) and metal-organic polyhedra (MOPs) have been extensively investigated in the fields of carbon capture, catalysts, sensors, biomedical imaging and gas storage. Their inherent pores, diverse surface function groups and potential modification possiblities make them competitive carbon capture materials. This review will introduce detailed scientific and technological advancements in PNMs and explain their fitness for carbon capture and separation, followed by the fabrication and application of mixed matrix membranes (MMMs) with PNMs. The current challenges appreared and solutions to improve the MMMs’ CO2 separation performance will also be stressed.

CFD analysis of turbulent flow characteristics of charge inside the combustion chamber of a dual–fuel homogeneous charge compression ignition engine under varying swirl ratios

This paper discusses the effects of the swirl ratio on the distribution of turbulent kinetic energy (TKE), combustion and emissions characteristics of a dual-fuel HCCI (Homogeneous charge compression ignition) engine fed with n-dodecane (premixed) and ethanol (injection). The performance of the Internal combustion (IC) engine is investigated using STAR-CD. ECFM-3Z (Extended Coherent Flame Combustion Model-3Zones) model is considered for the computational fluid dynamics (CFD) simulations. This study also includes the influence of swirl ratio on pressure and temperature of the combustion and hence the NOx (Nitrogen oxides), soot and CO2 (Carbon dioxide) emissions. The pressure, temperature and emissions of the combustion have been dropped significantly by increasing the swirl ratio. There is an increase in the distribution of air-fuel and hence the corresponding combustion flame by increasing the swirl ratio. It is observed that the reduced emissions of the combustion were achieved in the case of swirl ratio 3 and the values of the NOx emission, soot and CO2 emission are 0.0024 g/kg fuel, 0.0022 g/kg fuel and 5.12 g/kg fuel respectively. Eventually, the paper deals with the significance of the swirl ratio on NOx and CO2 emissions with limited loss of the piston work.

Investigation of oil-based CO2 foam EOR and carbon mitigation in a 2D visualization physical model: Effects of different injection strategies

CO2 flooding in low-permeability and tight oil reservoirs often encounters gas channeling, which affects oil recovery. To address this, oil-based CO2 foam development is explored using a two-dimensional visual physical model. The study includes three experimental setups: CO2 flooding followed by oil-based CO2 foam flooding, CO2 Huff-n-Puff (HnP) followed by oil-based CO2 foam HnP, and oil-based CO2 foam HnP followed by oil-based CO2 foam flooding. Findings reveal that using oil-based CO2 foam after CO2 development increases recovery factors by 15.62% and 35.86% for HnP and flooding, respectively, and significantly boosts CO2 storage. The CO2 storage is 1.96 times and 6.03 times higher than the initial one. After oil-based CO2 foam is used, the red area near the outlet of the visualization model becomes shallower, indicating a further decrease in residual oil saturation. The oil-based CO2 foam method reduces residual oil saturation and extends production duration while decreasing gas production rates. This approach effectively plugs gas channels, enhancing CO2 sweep efficiency, crude oil mobility, and recovery. The results provide innovative strategies for oilfield development, supporting carbon sequestration and offering substantial economic and environmental benefits.

Role of intensive mariculture on CO2 absorption and carbon burial, and the carbon sink potential of Sanggou Bay, China

Suspended-raft cultivation of bivalves and seaweed significantly influences carbon transport and transformation pathways in bay ecosystems, ultimately affecting air–sea CO2 flux (FCO2) and sedimentary carbon burial. Previous studies focused on whether bivalve and seaweed individuals are a carbon source or sink, but have not discussed the effects of their large-scale cultivation on carbon dynamics from the perspective of a bay ecosystem. In this study, we compared seasonal and spatial variations in air–sea FCO2 and sedimentary carbon burial flux in seaweed culture, bivalve culture, bivalve–seaweed polyculture, and non-culture areas in Sanggou Bay, China, a bay with a long history of mariculture practices. We found that in spring and summer, the air–sea FCO2 was lowest in the seaweed area; it was lowest in the bivalve area in autumn and winter. Despite this, the seaweed area annually absorbed twice the amount of atmospheric CO2 compared to the bivalve area. The bivalve area had the highest sedimentary carbon burial flux and the non-culture area had the lowest. More inorganic carbon than organic carbon was buried in sediment. Atmospheric CO2 absorption was positively correlated with sedimentary carbon burial. Seaweed culture was the main contributor, absorbing around half of the atmospheric CO2 of the bay, whereas bivalve culture exhibited the highest carbon burial, contributing about 40 % to the bay's sediment. We constructed an annual carbon budget model, and the estimated values for atmospheric absorption, seawater dissolution, and sedimentary burial were 2.09 × 104, 1.02 × 104, and 0.78 × 104 t C a−1, respectively. Taken together, our results indicate that the large-scale mariculture of bivalves and seaweed affect both atmospheric CO2 absorption and sedimentary carbon burial, as well as their relationship. Seawater dissolution is also a substantial carbon sequestration reservoir that cannot be overlooked when assessing the biogeochemical carbon cycle of bay ecosystems.

CO2 Electrolysis Coupled with Hydrogen Oxidation Reaction in Non-Aqueous Aprotic Electrolytes

CO2 electrolysis (CO2E) coupled with renewable energy is an important strategy to mitigate the effects of the green house gas in the atmosphere. By effectively transforming CO2 into higher value chemicals and fuels, the carbon cycle can be closed.[1] In order to produce C2+ products, most of the studies have been done in aqueous electrolytes, using Cu based catalysts. Nevertheless, these systems show different critical problems. First, in low temperature CO2E, CO2 carbonation in water is the primary source of energy and carbon losses.[2] Moreover, these systems rely on low faradaic efficiencies (FE) towards the single C2+ products (ethylene, ethanol, propanol). CO2E in organic aprotic electrolyte is gaining more and more attention due to the possibility of controlling the proton dynamics and the higher FE towards target products, mainly CO and oxalate. One challenge of these systems is the counter reaction. Many are using sacrificial anodes, which are not suitable for continuous industrial application.[3] Hydrogen oxidation reaction (HOR) is a promising reaction that could lower down the overall cell voltage, and, at the same time, produce more protonated products. This approach is not new in these systems, lithium mediated ammonia electrosynthesis, for example, has achieved relevant results using HOR at the anode and aprotic based electrolytes.[4] Based on these prerogatives, this study investigates the feasibility of couple CO2E with HOR in organic aprotic systems with controlled water content. A DMF/TBAPF6 electrolyte was used due to the good CO2 solubility (194 mmol L-1)[5] and conductivity. The rotating disk electrode experiments set up in a glovebox proved the stability of the chosen electrolyte, with a potential window of 3.6V, a HOR’s onset potential at -0.5V vs Ag/AgCl, and an onset potential for CO2 reduction at around -1.5V vs Ag/AgCl. A gas diffusion electrode (GDE) cell was used to perform CA or CP studies. A sputtered Cu GDE was used at the cathode. At the anode, an electrochemical deposited Pt/Au GDE was implemented for the HOR. [4] From the gas analysis, CO, H2 and ethylene have been detected at current densities of 10 mA/cm2. To investigate further the catalyst stability, XPS and SEM were used on the catalyst before and after the electrochemical reaction. ICP-MS analyses were done on the electrolyte to assess the eventual metal leaching during reaction.

Cation Effect on the Product Selectivity of Electrochemical CO Reduction

Renewable electricity-powered reduction of CO2 (CO2R) is a promising route to upgrade CO2 to ethylene, an industrial feedstock in high demand. Compared with direct CO2 electroreduction to ethylene, CO2-CO-C2H4 tandem electrolysis is more carbon efficient, circumventing CO2 crossover and carbonate formation. However, current CO electroreduction produces a mixture of multi-carbon products (ethylene, ethanol, acetate, and propanol), and the mechanism underlying this dispersion of selectivity remains unclear.We studied the role of the microenvironment of the electrode in selectivity among C2+ products, and hypothesized that destabilizing the oxygen-containing intermediates would direct the reaction pathway toward the sole oxygen-free C2+ product, ethylene. When we explore the cations in electrolyte, we find the one with the most robust hydration shell (Li) promotes ethylene production, among C2+ products, compared to weakly hydrated cations (e.g. K). This is a distinctive trend compared to studies of activity that found reverse cation trend in jc2+. A combined study of operando Raman spectroscopy, MD simulation, and DFT calculation suggests that the strongly hydrated Li+ on the electrode surface has the greatest H2O-Ointermediate interaction and the least cation-Ointermediate interaction. This increases the difference in activation energy of the selectivity-determining step between ethylene pathway and oxygenates pathway, and hence leads to the preference of Li for hydrocarbons over oxygenates. Figure 1

Carbon Fixation for Food Production

Demand for food is ubiquitous around the globe. Different regions of the world meet their food needs in different ways, but at times the normal production and supply mechanisms are interrupted. Reasons include drought and natural disasters such as hurricanes, tornados, floods, or situations arising from conflicts. The work here pursues the vision to develop a system able to produce food from minimal resources, e.g., water, as well as N2, O2, CO2 from air, using renewable energy (wind, solar, hydro). Realization of this vision will require CO2 capture, carbon and nitrogen fixation, as well as conversion of the carbon and nitrogen substrates into biomass for subsequent processing into food formats such as shakes or puddings. This presentation will focus on developing the carbon fixation capability to help enable the vision of generating food from minimal resources. The specific approach involves the electroreduction of CO2 to CO in a membrane electrode assembly (MEA) cell, followed by the electroreduction in bipolar cells with a porous solid electrolyte of CO to acetate. This two-step approach is expected to achieve a higher selectivity for acetate than direction reduction of CO2 to acetate. An additional advantage is that the product stream of the second step is comprised of pure water with water-soluble products (acetate, traces of ethanol, etc.) without the presence of electrolyte salts, avoiding separation steps. This presentation will focus on catalyst, electrode, and cell optimization for both CO2 to CO and CO to Acetate conversion, with a focus on scaling of single cells and enhancing durability over multi-hour runs.

Engineering a novel interface structure on La0.75Sr0.25Cr0.5Mn0.5O3-δ-Gd0.1Ce0.9O2-δ fuel electrode with excellent electrochemical performance and sulfur tolerance for electrocatalytic CO2 reduction

Surface and interface engineering as an efficient and controllable strategy in designing electrode structure has been widely investigated for achieving high catalyst activity and durability of robust electrodes in solid oxide cells (SOCs). The constructed heterojunction structures favor expedited charge transfer and promote the catalytic reaction. Anti-coking La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM)-based fuel electrodes are considered as promising candidates for alternative Ni-based cermet electrodes in solid oxide electrolysis cell (SOEC), however, they suffer from insufficient electrocatalytic activity for CO2 electrolysis. Herein, Mn-containing Pr0.6Sr0.4FeO3-δ (Pr0.6Sr0.4Fe0.8Mn0.2O3-δ, PSFM) nanoparticles with excellent catalyst activity are synthesized and epitaxially grown on the surface of LSCM via infiltration technique. The spontaneous connected interface can provide direct tunnel for oxygen ion and electron transport along the (110) plane of LSCM. Meanwhile, this interface promotes an increase in oxygen vacancies and enhances both surface oxygen exchange and bulk oxygen diffusion capacities. These improvements are advantageous for CO2 adsorption and carbonate dissociation at three phase boundaries (TPBs), leading to a significant enhancement in the kinetics of CO2 reduction reaction. The electrolyte-supported single with PSFM/La0.75Sr0.25Cr0.5Mn0.5O3-δ-Gd0.1Ce0.9O2-δ (LSCM-GDC) fuel electrode exhibits an impressive current density of 1.09 A cm−2 at the applied voltage of 1.5 V and 800 °C, which increases by approximately 336 % than that of LSCM-GDC. In addition, the atomic arrangement enables in-situ formation of PSFM by trapping of surface Sr/Mn atoms on the LSCM surface, avoiding Sr segregation and enhancing the resistance to sulfur poisoning. This study demonstrates a strategy for achieving the enhanced CO2 electrolysis performance and sulfur tolerance by engineering highly active interface.

Precursor-chemistry engineering toward ultrapermeable carbon molecular sieve membrane for CO2 capture

Carbon capture is an important strategy and is implemented to achieve the goals of CO2 reduction and carbon neutrality. As a high energy-efficient technology, membrane-based separation plays a crucial role in CO2 capture. It is urgently needed for membrane-based CO2 capture to develop the high-performance membrane materials with high permeability, selectivity, and stability. Herein, ultrapermeable carbon molecular sieve (CMS) membranes are fabricated by pyrolyzing a finely-engineered benzoxazole-containing copolyimide precursor for efficient CO2 capture. The microstructure of CMS membrane has been optimized by initially engineering the precursor-chemistry and subsequently tuning the pyrolysis process. Deep insights into the structure-property relationship of CMSs are provided in detail by a combination of experimental characterization and molecular simulations. We demonstrate that the intrinsically high free volume environment of the precursor, coupled with the steric hindrance of thermostable contorted fragments, promotes the formation of loosely packed and ultramicroporous carbon structures within the resultant CMS membrane, thereby enabling efficient CO2 discrimination via size sieving and affinity. The membrane achieves an ultrahigh CO2 permeability, good selectivity, and excellent stability. After one month of long-term operation, the CO2 permeability in the mixed gas is maintained at 11,800 Barrer, with a CO2/N2 selectivity exceeding 60. This study provides insights into the relationship between precursor-chemistry and CMS performance, and our ultrapermeable CMS membrane, which is scalable using thin film manufacturing, holds great potential for industrial CO2 capture.

Techno-Economic Analysis of Grid-Connected Highway Solar EV Charging Station

AbstractSolar electric vehicle (EV) charging stations offer a promising solution to an environmental issue related to EVs by supplying eco-friendly electricity. Herein, we designed and analyzed a grid-connected highway solar EV charging station for 2022, 2030, and 2050 under two scenarios: Current policy scenario with restricted grid sales and policy mitigation scenario allowing grid sale. Future systems consider changes in EV charging station, grid CO2 emissions, carbon prices, and renewable costs. In 2022, high PV and battery costs led to a grid-only system. By 2030 and 2050, significant reductions in PV costs enabled systems with substantial PV capacity, especially under the policy mitigation scenario. Economic analysis showed that enabling grid sales reduces net present cost (NPC) by 40% in 2030 and 35% in 2050 compared to the current policy scenario, with significantly lower levelized cost of energy. CO2 emissions from EV operation are projected to be 44% and 3% of 2022 levels by 2030 and 2050, respectively. The policy mitigation scenario further reduces CO2 emissions by 22% in 2030 and 25% in 2050 compared to the current policy scenario. Sensitivity analyses reveal that increased grid sale capacity leads to higher renewable penetration and lower NPC but also increased grid congestion, highlighting the need for efficient grid management. Policymakers should consider revising regulations to support higher PV penetration and manage grid congestion. This study supports the transition to renewable systems and underscores the importance of policy measures in achieving sustainable energy goals.

Selectively electrolyzing CO2 to ethylene by a Cu-Cu2O/rGO catalyst derived from copper hydroxide nanostrands/graphene oxide nanosheets.

Electrolyzing CO2 into ethylene (C2H4) is a promising strategy for CO2 utilization and carbon neutrality since C2H4 is an important industrial feedstock. However, selectively converting CO2 into C2H4 via the CO2 electro-reduction reaction (CO2 ERR) is still a great challenge. Herein, Cu-Cu2O nanoparticles anchored on reduced graphene oxide nanosheets (Cu-Cu2O/rGO) were prepared from copper hydroxide nanostrands (CHNs) and graphene oxide (GO) nanosheets via in situ electrochemical reduction. Cu-Cu2O nanoparticles with diameter less than 10 nm were formed on the surface of rGO nanosheets. After assembling the Cu-Cu2O/rGO catalyst into a flow cell, it demonstrated high Faraday efficiencies (FEs) of 55.4%, 37.6%, and 6.7% for C2H4, C2H6, and H2, respectively, and a total 93% FE for C2 at -1.3 V vs. the standard hydrogen electrode (SHE). Moreover, its FE was 68.2% for C2H4, 10.2% for C2H6, and 20.5% for H2 at -1.4 (vs. SHE). Besides, no liquid carbon product was detected. This high selectivity is attributed to the synergistic effect arising from the small diameter of Cu-Cu2O NPs with the combination of Cu0-Cu+ and rGO nanosheets, which promotes the activation of CO2 molecules, facilitates C-C coupling, and enhances stability. This may provide a facile way for designing an efficient catalyst for selectively electrolyzing CO2 into valuable C2 chemicals.

A novel approach to accelerate the carbonation of γ-C2S under atmospheric pressure: Increasing CO2 dissolution and promoting calcium ion leaching via triethanolamine

An innovative approach to accelerate the carbonation of the γ-2CaO·SiO2 (γ-C2S) under atmospheric pressure was proposed by incorporating triethanolamine (TEA). The effect of TEA on the degree of carbonation (DOC) and the mechanical strength of γ-C2S were investigated, and the mechanism of carbonation accelerated by TEA under atmospheric pressure was analyzed. The results showed that as TEA concentration increased from 0.1 % to 5 %, the DOC initially increased and then decreased, with an optimal concentration of 1 %, where the DOC increased by 126.6 % compared to reference samples after 1 d of carbonation under atmospheric pressure, and this DOC was slightly higher than that of carbonated pastes without TEA under a CO2 pressure of 0.4 MPa. For γ-C2S mortar specimens, the flexural strength and compressive strength with 1 % TEA increased by 109.8 % and 99.3 %, respectively, and these values were slightly higher than those of specimens without TEA under CO2 carbonation pressure of 0.4 MPa. Additionally, at the optimal TEA concentration, CO2 solubility increased by 10.8 times and Ca2+ concentration increased by 94.7 %. This dual effect led to the carbonation rate under atmospheric pressure that could match or slightly exceed that under CO2 pressure of 0.4 MPa, which made this method a novel technique for accelerating carbonation.

Combining Activated Carbon Adsorption and CO2 Carbonation to Treat Fly Ash Washing Wastewater and Recover High-Purity Calcium Carbonate

Fly ash washing wastewater was carbonated with carbon dioxide (CO2) to remove calcium (Ca) by forming a calcium carbonate (CaCO3) precipitate. An investigation of the factors affecting carbonation showed that Ca removal was highly dependent on the initial pH of the wastewater. The Ca removal was 10%, 61%, 91% and more than 99% at initial wastewater pH levels of 11.8, 12.0, 12.5 and 13.0, respectively. The optimal conditions for carbonation were initial pH of 13.0, carbonation time of 30 min and CO2 flow rate of 30 mL/min. The Ca concentration in the wastewater decreased to <40 mg/L, while 73 g of CaCO3 precipitate was produced per liter of wastewater. However, heavy metals, specifically Pb and Zn, co-precipitated during carbonation, which resulted in a CaCO3 product that contained as much as 0.61 wt% of Pb and 0.02 wt% of Zn. Activated carbon modified by a quaternary ammonium salt was used to selectively adsorb the Pb and Zn first. The Pb- and Zn-free water was then carbonated. By combining adsorption with carbonation, the Ca concentration in the treated wastewater was decreased to about 28 mg/L, while the Na, Cl and K were retained. The wastewater thus treated was ready for NaCl and KCl recovery. In addition, the precipitate had a Ca content of more than 38 wt% and almost no heavy metals. The average particle size of the precipitate was 47 μm, with a uniform cubic shape. The quality of the precipitate met the requirements for the industrial reuse of CaCO3. In summary, adsorption and carbonation combined were able to remove pollutants from wastewater while recovering useful resources.

A preliminary study of carbon dioxide and methane emissions from patchy tropical seagrass meadows in Thailand.

Seagrass meadows are a significant blue carbon sink due to their ability to store large amounts of carbon within sediment. However, the knowledge of global greenhouse gas (GHG) emissions from seagrass meadows is limited, especially from meadows in the tropical region. Therefore, in this study, CO2 and CH4 emissions and carbon metabolism were studied at a tropical seagrass meadow under various conditions. CO2 and CH4 emissions and carbon metabolism were measured using benthic chambers deployed for 18 h at Koh Mook, off the southwest coast of Thailand. The samples were collected from areas of patchy Enhalus acoroides, Thalassia hemprichii, and bare sand three times within 18 h periods of incubation: at low tide at 6 pm (t0), at low tide at 6 am (t1), and at high tide at noon (t2). Seagrass meadows at Koh Mook exhibited varying CO2 and CH4 emissions across different sampling areas. CO2 emissions were higher in patchy E. acoroides compared to patchy T. hemprichii and bare sand areas. CH4 emissions were only detected in vegetated areas (patchy E. acoroides and T. hemprichii) and were absent in bare sand. Furthermore, there were no significant differences in net community production across sampling areas, although seagrass meadows were generally considered autotrophic. Koh Mook seagrass meadows contribute only slightly to GHG emissions. The results suggested that the low GHG emissions from Koh Mook seagrass meadows do not outweigh their role as significant carbon sinks, with a value 320 t CO2 -eq. This study provided baseline information for estimating GHG emissions in seagrass meadows in Thailand.

Highly enriched carbon and oxygen isotopes in carbonate-derived CO2 at Gale crater, Mars

Carbonate minerals are of particular interest in paleoenvironmental research as they are an integral part of the carbon and water cycles, both of which are relevant to habitability. Given that these cycles are less constrained on Mars than they are on Earth, the identification of carbonates has been a point of emphasis for rover missions. Here, we present carbon (δ13C) and oxygen (δ18O) isotope data from four carbonates encountered by the Curiosity rover within the Gale crater. The carbon isotope values range from 72 ± 2‰ to 110 ± 3‰ Vienna Pee Dee Belemnite while the oxygen isotope values span from 59 ± 4‰ to 91 ± 4‰ Vienna Standard Mean Ocean Water (1 SE uncertainties). Notably, these values are isotopically heavy (13C- and 18O-enriched) relative to nearly every other Martian material. The extreme isotopic difference between the carbonates and other carbon- and oxygen-rich reservoirs on Mars cannot be reconciled by standard equilibrium carbonate-CO2 fractionation, thus requiring an alternative process during or prior to carbonate formation. This paper explores two processes capable of contributing to the isotopic enrichments: 1) evaporative-driven Rayleigh distillation and 2) kinetic isotope effects related to cryogenic precipitation. In isolation, each process cannot reproduce the observed carbonate isotope values; however, a combination of these processes represents the most likely source for the extreme isotopic enrichments.

Thermodynamic simulation of stepwise precipitation of NH4VO3 and NaHCO3 from carbonating Na3VO4 solution

Thermodynamic simulation was conducted to design a new process of stepwise precipitating NH4VO3 and NaHCO3 from regulating the CO2 carbonation of Na3VO4 solution. Firstly, a new V(V) speciation model for the aqueous solution containing vanadate and carbonate is established by using the Bromley−Zemaitis activity coefficient model. Subsequently, thermodynamic equilibrium calculations are conducted to clarify the behavior of vanadium, carbon, sodium, and impurity species in atmospheric or high-pressure carbonation. To ensure the purity and recovery of vanadium products, Na3VO4 solution is initially carbonated to the pH of 9.3−9.4, followed by precipitating NH4VO3 by adding (NH4)2CO3. After vanadium precipitation, the solution is deeply carbonated to the final pH of 7.3−7.5 to precipitate NaHCO3, and the remaining solution is recycled to dissolve Na3VO4 crystals. Finally, verification experiments demonstrate that 99.1% of vanadium and 91.4% of sodium in the solution are recovered in the form of NH4VO3 and NaHCO3, respectively.

Anthropic-Induced Variability of Greenhouse Gasses and Aerosols at the WMO/GAW Coastal Site of Lamezia Terme (Calabria, Southern Italy): Towards a New Method to Assess the Weekly Distribution of Gathered Data

The key to a sustainable future is the reduction in humankind’s impact on natural systems via the development of new technologies and the improvement in source apportionment. Although days, years and seasons are arbitrarily set, their mechanisms are based on natural cycles driven by Earth’s orbital periods. This is not the case for weeks, which are a pure anthropic category and are known from the literature to influence emission cycles and atmospheric chemistry. For the first time since it started data gathering operations, CO (carbon monoxide), CO2 (carbon dioxide), CH4 (methane) and eBC (equivalent black carbon) values detected by the Lamezia Terme WMO/GAW station in Calabria, Southern Italy, have been evaluated via a two-pronged approach accounting for weekly variations in absolute concentrations, as well as the number of hourly averages exceeding select thresholds. The analyses were performed on seven continuous years of measurements from 2016 to 2022. The results demonstrate that the analyzed GHGs (greenhouse gasses) and aerosols respond differently to weekly cycles throughout the seasons, and these findings provide completely new insights into source apportionment characterization. Moreover, the results have been combined into a new parameter: the hereby defined WDWO (Weighed Distribution of Weekly Outbreaks) normalizes weekly trends in CO, CO2, CH4 and eBC on an absolute scale, with the scope of providing regulators and researchers alike with a new tool meant to better evaluate anthropogenic pollution and mitigate its effects on the environment and human health.

Exergo and enviro-economic analysis of thermal energy storage assisted finned solar still

The current investigation focuses on improving the performance of a single slope solar still integrated with Phase Change Material as energy storage media. The problem of low thermal conductivity of PCM which hinders the energy storage capability has been addressed by incorporating fins with different profiles into the energy storage unit. Initially, an experimental investigation was conducted and analyzed to assess the effective performance of a Conventional Single Slope Solar Still (CSS) using various water depth levels: 1–4 cm. The optimal basin water depth for testing solar still with energy storage material along with fins was identified as 2 cm. Subsequently, the CSS was subjected to performance enhancement investigation under three different conditions: Case 1 – Solar Still (SS) with PCM storage unit, Case 2 – SS with fins at the PCM storage unit, and Case 3 – SS with fins at the storage unit and a parallel plate attached to the other end of the fins. The experimental results demonstrated the production of fresh water and efficiency improvements are as follows 26.95%, 55.86%, 69.14% and 24.34%, 52.83%, 68.83% for cases I, II, and III, respectively. Further, it was observed that Case III exhibited a lower cost of water production and a shorter payback period compared to CSS. The enviro-economic analysis revealed that the net CO2 emissions (NCEM) and Carbon Credits Earned (CCE) for Case III were 15.60 tons and 312.07 USD respectively against 9.22 tons and 184.31 USD for CSS.