Addition Of CO2 Research Articles

Tailoring Electrocarboxylation Pathways on Lead Cathodes: Insights into Electrolysis Mode

AbstractElectrocarboxylation, the electrochemical addition of CO2 to organic substrates using renewable energy, offers a promising approach for carbon capture and utilization. However, commercial viability remains limited due to poor product selectivity and yields. In this work, we investigate how the electrolysis mode – chronoamperometry (CA) versus chronopotentiometry (CP) – influences the electrocarboxylation mechanisms of phenyl‐activated substrates, Benzaldehyde, Styrene, and Benzylbromide, on Lead electrodes. By employing cyclic voltammetry (CV), in situ FTIR, and bulk electrolysis, we explore how these modes affect product selectivity and reaction efficiency. Our results show that substrate‐activated mechanisms, such as those observed for Benzaldehyde and Benzylbromide, achieve higher selectivity and reduced side‐product formation under CA conditions, while CP leads to increased side reactions. In contrast, Styrene exhibits more complex behavior, with CP favoring di‐carboxylation, while CA enhances mono‐carboxylation. These findings highlight the significant impact of electrolysis mode on controlling electrocarboxylation pathways, providing valuable insights for optimizing selective and efficient synthesis processes.

Research of CO2-Responsive Surfactants for Enhanced Oil Recovery: Review and Outlook

In enhanced oil recovery (EOR), various processes have specific requirements concerning surfactant surface activity. High surface activity is essential during the oil production, whereas low or even negligible surface activity is required during the oil separation process. CO2-responsive surfactants can regulate their surface activity through the addition or removal of CO2 in their aqueous solutions. This property makes them suitable for the formulation of CO2-responsive displacement systems, including CO2-responsive foam, emulsion, and hydrogel systems. These three systems hold significant application value within the realm of enhanced oil recovery. This paper reviews the structure, types, synthesis methods, applications in EOR technology, and the effects of EOR in both field and laboratory settings. This method is both environmentally friendly and efficient for enhancing oil recovery. Furthermore, the application of CO2-responsive surfactants facilitates carbon capture, utilization, and storage, contributing to the achievement of carbon neutrality and the carbon peak.

Limited reactivity of pyroxene and plagioclase in batch experiments with supercritical CO2 in the presence of NaCl and NaHCO3 in the context of CO2 sequestration via carbonation.

One-step high-pressure and high-temperature direct aqueous mineral carbonation of tailings derived from mining of Platinum Group Metals in South Africa requires a fundamental understanding of the reactivity of the most dominant mineral phases, i.e. pyroxene and plagioclase (66 wt. % and 12 wt. % of the bulk rock respectively) that are typically found in these tailings. The silicate minerals pyroxene and plagioclase were sampled from a pyroxenite footwall mined with the ore-bearing UG2 and from the Merensky Reefs outcropping in the eastern limb of the Bushveld Complex. These pyroxene and plagioclase grains were concentrated by gravity separation from the orthopyroxenite bulk rock and batch-reacted in a sodium chloride (NaCl) brine saturated with pure carbon dioxide (CO2) gas-only or seeded with sodium bicarbonate (NaHCO3; as an additional CO2 source) for 13days at 100°C and 10MPa. Pyroxene dissolved slightly but no weathering features were observed in plagioclase. Analyses of the filtrates obtained from the pyroxene sample in the absence of NaHCO3 showed an increased concentration of magnesium and calcium ions in the solution. However, they had also reached a cation saturation sealing. On the other hand, liquid samples from reactions where both CO2 gas and NaHCO3 were added to the solution exhibited a pronounced decrease in dissolved magnesium and calcium ions. XRD patterns of some of the post-reaction solids collected from the cation-depleted solution aliquots showed peaks of newly formed secondary magnesite and vermiculite. Moreover, the presence of magnesite was further confirmed by Raman shift analysis of the dried solid products. The formation of secondary magnesite was observed only in the experiments seeded with NaHCO3, specifically where the pre-reaction solid was pyroxene rich. Some of the resultant fluid chemistry was corroborated by the geochemical model that simulated the reaction parameters using the Geochemist Work Bench (GWB) software. Overall, the results indicate low pyroxene dissolution, which leads to limited carbonation. These findings suggest that the carbonation of PGM tailings may be constrained under the evaluated physicochemical conditions.

Programming Green Light-Responsive Hydrogels: From Photo-Weakening to Photo-Unresponsiveness and Photo-Strengthening.

Light-responsive hydrogels are highly valued for their dynamic mechanical properties and biocompatibility. In this study, we present a hydrogel system that can either soften or strengthen on green light exposure, or remain unresponsive to light, depending on the addition of adenosyl cobalamin (AdoCbl) and Co2+. These protein-based hydrogels were formed using genetically encoded SpyTag-SpyCatcher chemistry and included green light-sensitive CarHc protein domains. As previously reported, these hydrogels formed in the dark with the addition of AdoCbl, due to the tetramerization of the CarHc domains. Upon green light exposure, the CarHc tetramers disassembled, leading to a rapid transition from gel to sol. Interestingly, we discovered that an excess of AdoCbl leads to photo-strengthening rather than photo-weakening. This occurred because light exposure induces interchain crosslinks between AdoCbl and poly-histidine tags (His6-tags) of the proteins. Furthermore, incorporating Co2+ ions enhanced hydrogel stiffness by coordinating to His6-tags. This not only suppressed photo-weakening but also promoted photo-strengthening behaviour. These findings highlight the role of His6-tags in photochemical crosslinking with excess AdoCbl and in coordination to Co2+ ions, providing a novel strategy for designing tuneable, light responsiveness in materials.

Simultaneously Enhanced Permeability and Selectivity of Pebax-1074-Based Mixed-Matrix Membrane for CO2 Separation.

Membrane technology is a promising methodology for carbon dioxide separation due to its benefit of a small carbon footprint. However, the trade-off relationship between gas permeability and selectivity is one obstacle to limiting its application. Herein, branched polyethyleneimine (BPEI) containing a rich amino group was successfully grafted on the surface of the metal-organic framework (MOF) of AIFFIVE-1-Ni (KAUST-8) through coordination between N in BPEI and open metal sites in the MOF and with the resultant maintained BET surface area and pore volume. Both the strengthened CO2 solubility coefficients coming from the additional CO2 adsorption sites of amino groups in BPEI and the reinforced CO2 diffusivity coefficients originating from the fast transport channels created by KAUST-8 led to the promising CO2 separation performance for KAUST-8@BPEI/Pebax-1074 MMM. With 5 wt.% KAUST-8@BPEI loading, the MMM showed the CO2 permeability of 156.5 Barrer and CO2/N2 selectivity of 16.1, while the KAUST-8-incorporated MMM (5 wt.% loading) only exhibited the CO2 permeability of 86.9 Barrer and CO2/N2 selectivity of 13.0. Such enhancement is superior to most of the reported Pebax-1074-based MMMs for CO2 separation indicating a wide application for the coordination method for MOF fillers with open metal sites.

Effects of hormones on the growth and metabolite production of Amphidinium carterae under carbon sufficient and carbon limited conditions

The dinoflagellate Amphidinium carterae produces valuable fatty acids, pigments, and bioactive polyketides (e.g., amphidinols). Despite recent advances in its intensive cultivation, challenges remain that justify further work. This study explored the effects of phytohormone supplementation on growth and metabolism using a One Strain Many Compounds (OSMAC) approach. Auxins, cytokinins, jasmonates, amines, abscisic acid, gibberellic acid, and other signaling molecules were screened in batch cultures. Synthetic auxin 2-naphthoxyacetic acid (BNOA) at a final concentration of 14.84 μM (3 mg/L) emerged as the most stimulant. On a small scale, BNOA increased biomass productivity by up to 32 % and hemolytic activity in terms of productivity by 50 %. Scaling up in 10 L bubble column photobioreactor cultures with the addition of BNOA, but without CO2 supplementation, resulted in levels of amphidinol production comparable to those achieved with CO2 addition. Compared to the control without BNOA, BNOA cultures generated 2.2-fold more biomass during the stationary growth phase, and amphidinol production increased fourfold per unit of biomass. This work reveals that the addition of exogenous phytohormones such as BNOA can sustain the production of valuable metabolites in A. carterae, eliminating the need for additional CO2 and its associated costs. This promising approach highlights the potential of hormone supplementation as a cost-effective and efficient cultivation strategy for dinoflagellate bioprocesses.

CO₂-enhanced methane production by integration of bamboo biochar during anaerobic co-digestion

This study investigates the enhancement of methane production in anaerobic co-digestion (AcoD) through the introduction of exogenous CO₂ and the application of bamboo biochar. Exogenous CO₂ boosts biogas yield by providing an additional carbon source, which requires optimized solubility and pH buffering to ensure effective methanation. Biochar serves as an electron shuttle and pH stabilizer, facilitating CO2 solubility and syntrophic interactions that enhance microbial stability. When combined, biochar and CO₂ (R2) achieved a significant synergistic effect, increasing specific methane production (SMP) by 42.56% compared to the control (R0). Independent additions of biochar (R1) and CO₂ (R3) also improved SMP, with increases of 35.50% and 28.01%, respectively. This enhancement is likely due to the elevated activity of homoacetogenic bacteria and hydrogenotrophic methanogens, with increased acsB gene expression 2.4-fold with biochar+CO₂ and 1.5-fold with CO₂ alone compared to the control. Additionally, biochar facilitated syntrophic metabolism mediated by Cytochrome-C, promoting electron transfer. The study also demonstrated that biochar and CO2 could enhance enzyme activity, including acetyl-CoA synthase, mhpF, and mhpE. Such improvements bolster AcoD efficiency and promote resource recycling within the circular economy framework.

Metal mobilisation and fines migration in pure CO2 and impure CO2-SO2-NO reactions of carbon storage site core.

Carbon dioxide geological storage is proposed as part of the solution to reach net zero emissions. The potential to mobilise heavy metals to low salinity groundwater through CO2 water rock geochemical reactions is a potential environmental risk factor, if CO2 migrates. Previous studies have focused on pure CO2 reactivity, however CO2 streams from hard to abate industries can contain gas impurities. Reservoir sandstone and mudstone drill cores from a proposed low salinity CO2 storage demonstration site were reacted at in situ conditions with pure CO2 or an impure NO-SO2-CO2 stream. Sandstones hosted Rb in illite analysed via synchrotron XFM. Arsenic (As) was hosted in pyrite; and Pb, Cr, Mn in siderite rimming intergranular pores. Mudstone contained Zn, Co, Ni, Cu, As, Pb in sphalerite, and Rb in illite and K-feldspar. In impure NO-SO2-CO2 experiments the lowered pH and oxidising conditions initially released higher concentrations of metals including Pb, Zn, Co into solution compared to pure CO2 reactions. Higher concentrations of Zn (Mn and Co) were released from sphalerite in the mudstone. Fe-chlorite, K-feldspar, and carbonate dissolution released Rb, Si, Fe, Ca, and Mg. Elevated dissolved Pb was mainly from siderite and sulphide mineral reaction in sandstones. Mobilised As was released prior to CO2 addition from desorption and ion exchange. Clay and fines migration into pores occurred in both pure and impure CO2 reactions that has the potential to impact fluid migration. A portion of metals including Fe, Ni, Cr were subsequently incorporated in precipitated Fe hydr(oxy)oxides where the co-injected NO induced oxidising conditions. Rock mineral content and the injected gas mix were the main controls on metal mobilisation to formation water. Further work should investigate new gas mixtures that may be expected in storage hubs, from blue hydrogen or from direct air capture.

Research of the Features of Stress-Corrosion Destruction of Gas Pipelines

The problems of stress corrosion or hydrogen blistering of gas pipelines are relevant and require careful study of the causes and factors that cause this type of corrosion-mechanical destruction of pipelines. The analysis of numerous publications on this problem revealed contradictions of information regarding the mechanism of stress corrosion and a lack of experimental materials on the substantiation of the nature and peculiarities of the nature of destruction on gas pipeline networks. Systematic experimental studies using different brands of pipe steels allowed to determine the brands of steels, which according to their characteristics are the most resistant to VBR in harsh operating conditions, including even in the most aggressive NACE environment with H2S and CO2 additives at a pressure of 10-15 atm. Moreover, the experimental studies were as close as possible to the operating conditions of pipelines of the gas transportation network. The obtained results of experimental studies can serve as a basis for developing methods of technical diagnostics and forecasting the actual state of pipelines, which will significantly prevent the occurrence of sudden destruction caused by stress corrosion. The influence of the service life of gas pipelines on the degree of flooding and microhardness of pipe steels was established, which made it possible to substantiate the embrittlement of the metal with the increase of service life. The values of impact toughness on samples with sharp and round notches and the amount of work of crack growth depending on the service life of the pipe steels were determined, which made it possible to choose steel grades characterized by the highest resistance to brittle fracture. It is shown that with the service life, the destruction occurs according to a brittle mechanism, which is confirmed by the increase in the share of the fibrous component in the fractured samples after impact tests. It was established that the lowest corrosion rate is possessed by new grades of improved steel grades 20А and 08 KhMChA.The PRFNV parameter proposed in the paper makes it possible to assess the susceptibility of pipe steels to stress corrosion cracking and provides an opportunity to regulate the corrosion crack resistance of pipelines by metallurgical methods.

Exploring the impact of CO2 sequestration on plastic properties, mechanical performance, and microstructure of concrete

In view of global warming, carbon sequestration techniques are being employed across the globe to minimize the damaging effects of greenhouse gases on the environment. Studies have revealed that adding CO2 during the mixing or curing stage of concrete enhances its mechanical properties and long-term durability. This study aims to examine the effect of CO2 addition during the mixing stage on the plastic, mechanical and microstructural properties of concrete. Various CO2 dosages, ranging from 0.1 to 1%, were injected during mixing to analyze the plastic and hardened properties of concrete. CO2 primarily reacts with calcium hydroxide in concrete to form calcium carbonate (CaCO3), thereby densifying its microstructure and improving its compressive strength by 10–20%. An optimum strength of up to 20% was achieved with 0.75% dosage. Additionally, the results show a 5–10% improvement in flexural and split tensile strength with CO2 addition over the control mix, with 0.75% dosage yielding optimal strength. Semi-adiabatic calorimetry test on early hydrating concrete shows a 14% peak temperature rise at 0.75% CO2 dosage compared to control concrete, indicating enhanced early-age strength development. Thermal Pyrolysis tests, microscopy and infrared spectroscopy indicated the presence of CaCO3, thereby confirming the carbonation process. However, CO2 dosages above 0.5% by weight of cement resulted in a drop in the workability of concrete in the plastic stage. This research attempts to create a simplified CO2 sequestration process in concrete, develop a predictive model to estimate the compressive strength and utilize material characterization techniques to identify the mineralization process.HighlightsInjecting CO2 into fresh concrete improves its strength and lowers its environmental impact.A multiple linear regression model predicts the compressive strength of CO2-injected concrete.Semi-adiabatic calorimetry shows that CO2 injection speeds up early hydration.Thermal Pyrolysis detects mass loss stages linked to dehydration and calcite breakdown.Microscopy and spectroscopy indicate CaCO3 crystal formation in CO2-sequestered concrete.

Structural Snapshots of Reversible Carbon Dioxide Capture and (De)oxygenation at Group 14 Diradicaloids.

Although diradicals should exhibit a rather small reaction barrier as compared to closed-shell species for activating kinetically inert molecules, the activation and functionalization of carbon dioxide with stable main-group diradicals remain virtually unexplored. In this work, we present a thorough study on CO2 activation, reversible capture, and (de)oxygenation mediated by stable Group 14 singlet diradicals (i.e., diradicaloids) [(ADC)E]2 (E = Si, Ge, Sn) based on an anionic dicarbene (ADC) framework (ADC = PhC{N(Dipp)C}2; Dipp = 2,6-iPr2C6H3). [(ADC)E]2 readily undergo [4 + 2]-cycloadditions with CO2 to result in barrelene-type bis-metallylenes [(ADC)E]2(OC═O). The CO2 addition is reversible for E = Ge; thus, CO2 detaches under vacuum or at an elevated temperature and regenerates [(ADC)Ge]2. [(ADC)Sn]2(OC═O) is isolable but deoxygenates additional CO2 to form [(ADC)Sn]2(O2CO) and CO. [(ADC)Si]2(OC═O) is extremely reactive and could not be isolated or detected as it spontaneously reacts further with CO2 to yield elusive monomeric Si(IV) oxides [(ADC)Si(O)]2(COn) or carbonates [(ADC)Si(CO3)]2(COn) (n = 1 or 2) via the (de)oxygenation of CO2. The molecular structures of all isolated compounds have been established by X-ray diffraction, and a mechanistic insight of their formation has been suggested by DFT calculations.

Characterization of Lipid Production in Chlorella sp. Cultivated in Different Plant Fertilizers

Microalgae have gained attention due to their higher reproduction rate and lipid productivity. In particular, various stress conditions lead to an overproduction of lipids in microalgae cells. The study investigated the influence of additional CO2 introduced with air into the reactor during biomass growth of Chlorella sp. Additionally, increased phosphorus concentration in the medium under stress cultivation (low nitrogen concentration) was examined. The partial pressure of CO2 and its increased availability to Chlorella sp. in the cultivation medium increased biomass growth (1.4 times) and chlorophyll content (2.5 times) in microalgae cells. A high phosphorus fertilizer significantly increased lipid production under stress conditions with CO2 supply to 85.2 mg/g (2.6 times) and without CO2 to 73.8 mg/g (2.2 times). A high concentration of phosphorus in the culture medium stimulated the synthesis of C16:0 (about 38–45%) and C18:1 CIS9 (about 24–30%). The results confirm that the fertilizers can be used as a culture medium to induce stress and stimulate lipid production. Adjusting the composition of the fertilizers and controlling the additional CO2 supply could prove beneficial to increase the content of the desired fatty acids.

The impact of global change factors on the functional genes of soil nitrogen and methane cycles in grassland ecosystems: a meta-analysis.

Soil functional genes in grasslands are crucial for processes like nitrogen fixation, nitrification, denitrification, methane production, and oxidation, integral to nitrogen and methane cycles. However, the impact of global changes on these genes is not well understood. We reviewed 84 studies to examine the effects of nitrogen addition (N), warming (W), increased precipitation (PPT +), decreased precipitation (PPT-), and elevated CO2 (eCO2) on these functional genes. For nitrogen cycling, global changes mainly boost genes involved in nitrification but reduce those in denitrification, with nirK being the most sensitive. Most nitrogen fixation-related genes did not show a significant response. Among single factors, N and PPT + have the most significant effects. The impact of global changes on nitrogen cycling genes is largely additive, and their interaction with N is particularly influential. For methane cycling, global changes notably affect mcrA, while only PPT + significantly reduces pmoA. The magnitude and duration of global change treatments are more critical than the treatment form for nitrogen cycling genes. For methane cycling, the form and intensity of nitrogen addition, along with treatment duration, affect pmoA abundance. We also identified a competitive relationship between methane oxidation and nitrification and a complex coupling with denitrification. This study provides new insights into microbial responses in nitrogen and methane cycling under global changes, with significant implications for experimental design and management strategies in grassland ecosystems.

Frustrated Lewis Pairs from Al-E{14} Bonds (E{14}=Ge, Sn, Pb).

The potassium aluminyl K[Al(NON)] ([NON]2-=[O(SiMe2NDipp)2]2-, Dipp=2,6-iPr2C6H3) reacts with group 14 chloroamidinates E{14}(Am)Cl (E{14}=Ge, Sn, Pb. [Am]-=[tBuC(NDipp)2]-) to form (NON)Al-E{14}(Am) Lewis pairs with unsupported Al-E{14} bonds, including the first structurally authenticated Al-Pb bond. Analysis using spectroscopic (NMR, UV-vis and Mössbauer for E{14}=Sn), X-ray diffraction and computational (DFT, QTAIM, TD-DFT) methods conclude an Al-E{14} σ-bond derived from a Lewis basic Al and a Lewis acidic tetrylene, with back-donation from the E{14} s-orbital lone pair donor NBO to acceptor NBOs on Al that are derived from s/p-orbitals. The reaction of the Al-Ge compound with CO2 forms the dioxocarbene (NON)Al(μ-O2C)Ge(Am), whilst under the same conditions the Al-Sn compound reacts with additional CO2 to form the carbonate, (NON)Al(μ-CO3)Sn(Am). Addition of ethene to the Al-E{14} (E{14}=Ge, Sn) compounds introduces an ethylene bridge between the aluminium and group 14 atoms forming a frustrated Lewis pair (FLP). Reaction of the (Al/Ge) FLP with CO2 forms an activation product with new Al-O and Ge-C bonds, whilst reaction with iPrN=C=NiPr proceeds with insertion into the Al-C bond to form an aluminium amidinate.

Synthesis and Structural Characterization of 2,2’-Bipyridine Zinc Formate: Analysis of Formate Bonding and Hydrosilylation of CO2 and Carbonyl Compounds

The zinc formate compound (bipy)Zn(O2CH)2 is obtained via the reaction of Zn(O2CH)2 with 2,2’-bipyridine (bipy). In addition, (bipy)Zn(O2CH)2 may be formed from zinc hydride via addition of bipy followed by addition of (i) HCO2H and (ii) CO2. The molecular structure of (bipy)Zn(O2CH)2 has been determined by X-ray diffraction, thereby demonstrating that it exists as a monomeric species with a distorted tetrahedral zinc center and κ1-monodentate formate ligands. As such, the coordination environment of the zinc provides a contrast to the octahedral sites in the isomeric 4,4’-bipyridine counterpart, (bipy4,4’)Zn(O2CH)2, and the aqua derivative, (bipy)Zn(O2CH)2(OH2)•H2O, both of which feature bridging formate ligands. Analysis of the bonding within the formate ligand indicates that the zinc–formate moiety is not best represented by a Zn–O–C(=O)H resonance structure, but instead possesses a significant ionic component that reduces the C=O bond order and increases the C–O bond order. The formate compound (bipy)Zn(O2CH)2 participates in hydrosilylation transformations involving CO2 and carbonyl compounds, including (i) the reaction of CO2 with (MeO)3SiH to afford HCO2Si(OMe)3 and (ii) insertion of Ph2CO, PhC(O)Me, Me2CO and PhCHO into the Si–H bonds of PhSiH3 to afford PhSi[OCH(R)R’]3via PhSiH2[OCH(R)R’] and PhSiH[OCH(R)R’]2.

Gene cloning and characterization of N-carbamyl-l-glutamic acid amidohydrolase involved in ergothioneine utilization in Burkholderia sp. HME13.

Burkholderia sp. HME13 utilizes ergothioneine, a strong antioxidant, as the nitrogen source. We have previously shown that ergothionase (ErtA), thiourocanate hydratase (ErtB), 3-(5-oxo-2-thioxoimidazolidin-4-yl) propionic acid desulfhydrase (ErtC), and hydantoin-5-propionic acid amidohydrolase (ErtD) may be involved in ergothioneine utilization in this strain. In this study, we identified the ertE gene in Burkholderia sp. HME13, which encodes a bivalent metal-dependent N-carbamyl-l-glutamic acid amidohydrolase. ErtE showed maximum activity at 60°C and pH 7.0 and was stable at temperatures up to 55°C and pH 6.5-8.0. The Km and Vmax values of ErtE for N-carbamyl-l-glutamic acid were 0.74 mM and 140 U/mg, respectively. EDTA-treated ErtE showed no enzymatic activity, which was restored upon the addition of Co2+, Mn2+, Ni2+, and Fe2+. Expression analyses and enzymatic assays suggested that ErtE is involved in ergothioneine utilization in this strain. Finally, we propose a mechanism for ergothioneine utilization in Burkholderia sp. HME13.

Comparative study on the adsorption performance of CO2 and Hg in flue gas using corn straw and pine biochar modified by KOH

This study presents a comparative analysis of the adsorption performance of KOH-modified biochar derived from corn straw and pine for CO2 and Hg capture from coal-fired flue gas. The results indicate that the increase in KOH-activation temperature could significantly enhance the specific surface area. Pine biochar (PACs) activated at 800 °C exhibited the highest CO2 adsorption capacity, reaching 3.79 mmol/g at 25 °C. As well as, for corn straw biochar (CACs), the activation temperature of 700 °C is the optimal condition. The isosteric heat of adsorption for PACs and CACs is less than 40 kJ/mol and the R2 of the pseudo-first-order kinetic model exceeds 0.9, demonstrating that the CO2 adsorption of biochar mainly relies on physisorption. The main factor affecting the CO2 adsorption performance is the micropore capacity (<10 Å). CO2 capture positively correlates with carbon content and graphitization degree but negatively correlates with total pore volume and specific surface area. In addition, PACs and CACs present better CO2 adsorption performance after 10 cycles. PAC-800 can achieve CO2 desorption at lower temperatures and has higher selectivity for CO2, compared with CAC-700. CO2 can enhance the mercury removal efficiency of biochar to a certain extent. However, the maximum on-line mercury removal efficiency of both pine and corn straw biochar is less than 80 % under CO2 capture conditions, indicating that it is necessary to improve Hg capture performance by constructing higher-affinity sites on the surface of the biochar.

Swelling-Shrinking Behavior of a Hydrogel with a CO2-Switchable Volume Phase Transition Temperature.

Macromolecules exhibit rich phase behavior that may be exploited for advanced material design. In particular, the volume phase transition in certain crosslinked hydrogels is a key property controlling the transition between a collapsed/dehydrated and a swollen/hydrated state, thereby regulating the release and absorption of water via a temperature change. In this work, a simple and tunable system exhibiting a carbon dioxide (CO2)-switchable volume phase transition is introduced, which displays isothermal swelling-shrinking behavior that is activated by addition and removal of CO2, respectively. Through systematic compositional studies, shifts in phase transition temperatures of up to 8.6°C are measured upon CO2 exposure, which enables pronounced isothermal swelling in response to CO2, reaching up to a fivefold increase in mass. The shift in transition temperature and the extent of swelling are controlled by the hydrogel composition, thus enabling the transition temperature and swelling degree to be tuned a priori for a particular application. Controlled release experiments from these gels upon a CO2-induced phase transition suggest viability for drug delivery applications. It is anticipated that this work will motivate and expand efforts to exploit phase behavior for smart material development.

Sustainable Desalination Waste Brine Management through Electrochemically Supported CO2 mineralization and Multiple Product Recovery

Seawater reverse osmosis desalination (SWRO) is a vital technology for low cost and energy requirement water production to ensure regional water security and continued economic development. However, the state-of-the-art technology typically exhibits a recovery rate of around 42% converting in 58% of the seawater input into desalination waste brine which are largely discharged into the sea1. Significant works on brine utilization have shown that SWRO desalination brine can be converted into usable feed for chlor-alkali process with simultaneous carbon capture capabilities2,3,4. In this work, the desalination effect of electrochemistry for simultaneous utilization and treatment of desalination brine (56.0 ± 2.1 g/L) into seawater level (32.0 ± 1.4 g/L) was explored. The results demonstrate chemical self-sufficiency for desalination brine treatment (removing Mg2+ and Ca2+ to below ppm level), electrochemically recovering chlorine (95% – 99% selectivity, and hydrogen gas (92% – 97% selectivity), and conversion of desalination brine into reclaimed seawater discharge (RSD). The RSD is further chemically dechlorinated and neutralised to pH 7.3 to be safe to discharge into the sea. The excess alkali brine is used to capture additional CO2 in the form of bicarbonates achieving net abatement in climate change impact (9.90 CO2 e/m3) after product carbon abatements are accounted. 1 Jones, E.; Qadir, M.; van Vliet, M. T. H.; Smakhtin, V.; Kang, S. The State of Desalination and Brine Production: A Global Outlook. Science of The Total Environment 2019, 657, 1343–1356. 2 Melián-Martel, N.; Sadhwani, J. J.; Ovidio Pérez Báez, S. Saline Waste Disposal Reuse for Desalination Plants for the Chlor-Alkali Industry: The Particular Case of Pozo Izquierdo SWRO Desalination Plant. Desalination 2011, 281, 35–41. 3 Du, F.; Warsinger, D. M.; Urmi, T. I.; Thiel, G. P.; Kumar, A.; Lienhard V, J. H. Sodium Hydroxide Production from Seawater Desalination Brine: Process Design and Energy Efficiency. Sci. Technol. 2018, 52 (10), 5949–5958. 4 Choi, W. Y.; Aravena, C.; Park, J.; Kang, D.; Yoo, Y. Performance Prediction and Evaluation of CO2 Utilization with Conjoined Electrolysis and Carbonation Using Desalinated Rejected Seawater Brine. Desalination 2021, 509, 115068. Figure 1

Hydrothermal synthesis of self-supported hierarchical microflowers of Co3O4 nanowires for potential supercapacitor application

This study explores the synthesis of ultrathin flower architecture of spinel-structured Co3O4 electrodes, on nickel foam using a double hydrothermal method, followed by annealing at 250 °C for 4 h. We systematically investigate the effects of varying reaction times and additional Co2+ treatment during the second hydrothermal process on the morphology and electrochemical properties of Co3O4. Field emission scanning electron microscopy (FE-SEM) images confirm the formation of self-supported hierarchical flowers, characterized by sharp, spike-like nanowires (16–33 nm in diameter) arranged radially. The self-supported optimized hierarchical Co3O4 thin film, characterized by its unique architecture and substantial mass loading of 4.6 mg cm−2, achieved an impressive specific capacitance of 749.48F g−1 at a scan rate of 10 mV s−1 (specific capacity of 182.16 mAh g−1) in 2 M KOH electrolyte and retained 64 % of its initial capacitance after 5000 cycles. Furthermore, a symmetric device demonstrated the ability to illuminate a red LED for approximately 120 s when two devices were connected in series.