Chemical Sorbent Research Articles

Hydrated carboxylate ionic liquids as chemical CO2 sorbents of high capacity and moderate enthalpy of absorption

Tetralkylphosphonium carboxylate ionic liquids are herein presented as efficient carbon dioxide chemisorbents in the presence of water. The ionic liquids tetrabutylphosphonium formate and acetate, tributylmethylphosphonium formate and a series of triethylalkylphosphonium formates and acetates, have been prepared by various synthetic procedures either from hydroxide or methylcarbonate precursors, or via multiple steps starting from the parent triethylphosphine. Their physicochemical properties, namely melting or glass transition temperatures, thermal decomposition behaviour, densities and viscosities have been determined. As dry substances, they are viscous liquids or low-melting solids, whereas they show little tendency to solidify in their hydrated forms. They were used mostly as monohydrates in CO2 solubility measurements, exhibiting highest capacities (3 mol L−1, i.e. ≈ 0.9 molCO2 molIL−1, at 5 bar, 25 °C) at equimolar H2O/ionic liquid ratios, approaching those of commercial aqueous amine sorbents. Carbon dioxide chemisorption into hydrogencarbonate takes place, as demonstrated by infrared spectroscopy with isotopic labelling. CO2 absorption isotherms were recorded at various temperatures and the data used to estimate the heat of absorption according to three different thermodynamic models. Enthalpies of CO2 absorption depended heavily on the model used. Rationalisation of this was done on the grounds of the expected relevance of physical and chemical sorption processes. Average heats of CO2 absorption lie between −40 and −45 kJ mol−1, in accordance with mild chemical absorption albeit significantly lower than those for typical chemical sorbents such as amines. This reinforces the feasibility of hydrated carboxylate ionic liquids for CO2 capture technologies of low regeneration energies.

Clathrating CO2 in a Supramolecular Granatohedron Cage with Noncovalent CO2-NH3 Interactions and High CO2 Capture Efficiency under Ambient Conditions.

Organic amine (R-NH2) reagents as dominant chemical sorbents for CO2 capture in industrial processes suffer from high energy compensation for regeneration. Herein, we, for the first time, report the finding of Co(III) coordinating with NH3 molecules regulating the interaction between NH3 and CO2 to electrostatic interactions instead of a chemical reaction and achieve CO2 capture under near-ambient conditions. NH3 coordinating with Co(III) significantly reduces its alkalinity and reactivity with CO2 owing to its lone-pair electron donation during coordination. Under a simple protocol, CO2 induces the crystallization of CO2@[Co(NH3)6][HSO4][SO4] clathrate into a hydrogen-bonded granatohedron cage from a cobaltic hexammine sulfate aqueous solution under a CO2 pressure of 56 and 142 kPa at 275 and 298 K, respectively, with a CO2 uptake weight content of 11.7%. We reveal that CO2 interacts with cobaltous hexammine via supramolecular interactions rather than chemical bonding. The clathrate spontaneously separates from the solution as single crystals and readily releases CO2 under ambient conditions in water for cyclic utilization without further treatment. In such a rapid supramolecular capture process, molecular recognition ensures exclusive CO2 selectivity, and soluble clathrate enables the spontaneous CO2 release at a low energy penalty, exhibiting excellent practical potential in carbon capture.

Agricultural waste-based magnetic biochar produced via hydrothermal route for petroleum spills adsorption

Oil spills are one of the marine pollution events triggered by the results of tanker operations (air ballast), ship repairs and maintenance (docking), mid-ocean loading and unloading terminals, air bilge (drainage of water, oil, and engine-processed lubricants), ship scrapping, and the most common accidents/collisions of tankers. The impacts vary from the death of marine organisms, especially fish, changes in reproduction and behavior of organisms, plankton contamination, fish migration, as well as ecosystem damage, and economic loss. Bio-based absorbents such as biochar can be an environmentally friendly alternative to chemical sorbents that works to adsorb oil spills faster. In this study, the effectiveness of magnetic biochar in oil spill removal was investigated. It also includes the synthesisation of magnetic biochar from agricultural waste (bagasse, rice husks, and sawdust) using the hydrothermal method at a temperature of 200°C. Hydrothermal carbonization is considered a cost-effective method for biochar production because the process can be carried out at low temperatures around 180°- 250°C. Biochar characterization was carried out with a Scanning Electron Microscope and Energy Dispersive X-Ray (SEM-EDX), Fourier Transform Infrared Spectroscopy (FTIR), and X-Ray Diffraction (XRD). The Brunauer, Emmett, and Teller (BET) and Barrett–Joyner–Halenda (BJH) were used to analyse the surface area and pore size distribution. Based on the results of the SEM-EDX analysis, only biochar was made from rice husk and sugarcane bagasse which contained Fe elements, as a result of the FeCl3.6H2O reaction. This condition is also proven by the presence of the FeO on both samples based on FTIR. The three synthesized biochar are amorphous and categorized as mesopores due to pore size around 15 to 16 nm, which can absorb petroleum spills with a percentage of 81% for sugarcane bagasse-based biochar, 84% for rice husk-based biochar, and 70% for sawdust-based biochar. Biochar from rice husk has excellent adsorption effectiveness with an adsorption capacity of 0.21 g/g in 60 min due to its large functional group area and the excellent attachment of magnetic compound into the biochar surface to form magnetic biochar.

Understandings on design and application for direct air capture: From advanced sorbents to thermal cycles

Direct air capture (DAC) plays a crucial role in the carbon removal portfolio and is expected to capture over 980 MtCO2 to reach the net zero target. Despite being introduced in 1999, large-scale DAC application remains challenging. Nevertheless, various research efforts regarding material development, process construction, and application continue to expand. In 2013, our group at Zhejiang University initiated research on DAC using sorption methods. Our research focuses on advanced sorbents such as quaternary ammonium and chemical sorbents for moisture swing adsorption (MSA) and thermal-driven adsorption cycles. The working mechanism of MSA, the interfacial and structural characteristics of sorbents, and their effects on sorption performance are further analyzed. Furthermore, emphasis is placed on the significance of thermal integration in DAC, and a thermodynamic analysis is established to balance the thermal cycle and practical heat utilization of DAC. Different innovative applications of DAC are proposed based on the materials and working cycles. This account highlights that the co-development of materials, thermal cycles, and applications will facilitate the rapid deployment and engineering realization of DAC. It aims to clarify the critical challenges in DAC, and our group at Zhejiang University is committed to continuously contributing to this promising field.

Evaluation of automated clean-up for large scope pesticide multiresidue analysis by liquid chromatography coupled to mass spectrometry

Clean-up step is essential during the multiresidue sample preparation process to remove undesired matrix components that may cause analytical interferences or suppression effect. However, its application generally by specific sorbents entails time-consuming work producing low recoveries for some compounds. Moreover, it usually needs to be adapted to the different co-extractives from the matrix present in the samples by using different chemical sorbents increasing the number of validation procedures. Therefore, the development of a more efficient and automated and unified clean-up procedure means a significant time reduction and laboratory work with improved performance.In this study, extracts from different matrices (tomato, orange, rice, avocado and black tea) were purified by manual dispersive clean-up (different procedures according to the matrix group) in parallel with an automated µSPE clean-up workflow, in both cases based on QuEChERS extraction. The latter procedure employed clean-up cartridges containing a mixture of sorbent materials (anhydrous MgSO4/PSA/C18/CarbonX) suitable for multiple matrices. All the samples were analysed by liquid chromatography mass spectrometry and the results obtained from both procedures have been compared in terms of the extract cleanness, performance, interferences, and sample workflow. At the levels studied, similar recoveries were achieved by both techniques (manual and automated) except for reactive compounds when PSA was used as the sorbent material producing low recoveries. However, the µSPE recoveries were between 70–120%. Furthermore, closer calibration line slopes were provided when µSPE was applied to the different matrix groups studied. It is important to note that up to 30% more samples per day can be analysed using an automated µSPE compared to the manual method (which requires shaking, centrifuging, then taking the supernatant and adding formic acid in ACN); it also provides good repeatability - an RSD (%) < 10%. Consequently, this technique is a very useful option for routine analyses, greatly simplifying the work of muti-residue methods.

Carbon Capture Materials in Post-Combustion: Adsorption and Absorption-Based Processes

Global warming and climate changes are among the biggest modern-day environmental problems, the main factor causing these problems is the greenhouse gas effect. The increased concentration of carbon dioxide in the atmosphere resulted in capturing increased amounts of reflected sunlight, causing serious acute and chronic environmental problems. The concentration of carbon dioxide in the atmosphere reached 421 ppm in 2022 as compared to 280 in the 1800s, this increase is attributed to the increased carbon dioxide emissions from the industrial revolution. The release of carbon dioxide into the atmosphere can be minimized by practicing carbon capture utilization and storage methods. Carbon capture utilization and storage (CCUS) has four major methods, namely, pre-combustion, post-combustion, oxyfuel combustion, and direct air capture. It has been reported that applying CCUS can capture up to 95% of the produced carbon dioxide in running power plants. However, a reported cost penalty and efficiency decrease hinder the wide applicability of CCUS. Advancements in the CCSU were made in increasing the efficiency and decreasing the cost of the sorbents. In this review, we highlight the recent developments in utilizing both physical and chemical sorbents to capture carbon. This includes amine-based sorbents, blended absorbents, ionic liquids, metal-organic framework (MOF) adsorbents, zeolites, mesoporous silica materials, alkali-metal adsorbents, carbonaceous materials, and metal oxide/metal oxide-based materials. In addition, a comparison between recently proposed kinetic and thermodynamic models was also introduced. It was concluded from the published studies that amine-based sorbents are considered assuperior carbon-capturing materials, which is attributed to their high stability, multifunctionality, rapid capture, and ability to achieve large sorption capacities. However, more work must be done to reduce their cost as it can be regarded as their main drawback.

Recent Advances and Reliable Assessment of Solid‐State Materials for Hydrogen Storage: A Step Forward toward a Sustainable H2 Economy

AbstractThe hydrogen economy is an envisaged system proposed for a sustainable energy future that comprises hydrogen production, storage, transportation, and stationary/mobile applications. Recently, research efforts are devoted to build a H2 economy; however, the reduced hydrogen volumetric density hinders the effective hydrogen storage. To combat this, material‐based hydrogen storage is an emerging trend that has the potential to meet the ongoing goals of the United States Department of Energy. Herein, a critical review is presented on the state‐of‐the‐art material‐based hydrogen storage where nanostructured engineering and nanotechnology have driven a rapid growth in material design from physical sorbents (carbons, metal‐organic frameworks, and organic polymer frameworks) to chemical sorbents (complex and metal nanohydrides). The research trends in physical sorption include tailoring the textural features of porous materials and enhancing the binding energy strength by inducing hydrogen spill‐over effect and functionalization of surfaces. For chemical hydrogen storage, strategies are presented to ameliorate the sorption kinetics and thermodynamics using reactive hydrides, lightweight composites, and nanoconfinement of hydrides. Considering the long‐term hydrogen storage, the concept of para hydrogen storage is also highlighted. Finally, the challenges and their plausible solutions are discussed to attain a sustainable hydrogen economy, in the near future.

(Invited) Electrochemically Modulated Mitigation of Acid Gas Emissions

The alarming rise in anthropogenic CO2 levels in the atmosphere due primarily to fossil fuel emissions is leading to significant changes in global climate patterns and increasing ocean acidities, with their severe negative impacts on the health of our planet. The mitigation of these acid gas emissions is a daunting task, both because of the scale of the problem and because of the economic ramifications associated with the capture of the greenhouse gases and their subsequent utilization or subsurface storage. The traditional means for CO2 capture and release generally rely on either chemical or physical interactions with sorbents with subsequent temperature or pressure changes to release the captured CO2 and regenerate the sorbent. The captured CO2 can then be compressed for injection and sequestration in subsurface geological formations or converted to useful products. These processes require significant energy integration which adds complexity and cost to the overall capture operation. Isothermal operations that obviate or significantly reduce the heat integration requirements in these processes could have significant advantages over the traditional methods. One such approach is to exploit electrochemical technologies for the capture and release of CO2, which can be operated isothermally, and can rely only on renewable energy resources, if desired.The general principles underlying electrochemically modulated acid gas separation processes will be outlined, with an emphasis on the thermodynamic and transport considerations required for their effective implementation in carbon capture. In particular, we will consider electrochemical technologies for the capture of CO2 that are suitable for both point-of-use gas emissions mitigation, and for removal from the atmosphere and ocean waters, where CO2 has been accumulating for decades. Examples include an indirect approach, in which an electrochemically released species (e.g., copper ions, protons) displaces the CO2 bound to a chemical sorbent via competitive complexation; the CO2 and the sorbents are regenerated when the species is re-captured in the cathode chamber of an electrochemical cell, leaving the sorbent free to be cycled back to the absorber. An alternative approach exploits the complexation of an electroactive moiety directly with the CO2 upon activation by electrochemical reduction, and releases the CO2 when it is re-oxidized on reversal of the applied cell voltage. In general, these electrochemically based technologies hold promise for tackling the climate change challenges that we, and future generations, must face.

Study of the solidification/stabilization process in a mortar with lightweight aggregate or recycled aggregate

This study investigates the solidification/stabilization process of electroplating sludge in mortars with internal curing promoted by porous aggregates (lightweight and recycled aggregate). For that, cementitious mortars were manufactured with recycled or lightweight fine aggregates added in two conditions: saturated and dried before the mortar preparation. They were incorporated in partial replacement of the natural aggregate. As well, 8.5% and 100% of electroplating sludge (liquid) in relation to the total water content in the mortars were replaced, to assess the fixation of contaminants. For this, were determined the physical properties of aggregates (density, absorption, compliance test, and others), then the mortars were prepared and evaluated for consistency, absorption by immersion, mechanical strength, leaching and others. The results showed that the LWA and RCA presented 99.9 and 96.7% efficiency in Pb adsorption, receptively. Also, for Zn, the RCA presented 98% efficiency in adsorption in the solutions. The cement consumption was reduced, on average, from 490 kg m−3 with NA to 470 kg m−3 with RCA and to 405 kg m−3 with LWA. The leaching test of the mortars showed that 100% of the Cr and Ni from the solution was adsorbed by the mortars. In the compliance tests, the Cr metal was not leached from the crushed mortars, and in the partial-added mortars, zinc was leached in less quantity in comparison with the reference series (48% less, on average). The results show that the incorporation of electroplating sludge in mortars did not alter their properties, as well as the replacement of 25% of the natural aggregate by recycled aggregate. Finally, the recycled aggregate can be used to partially replace the natural aggregate, increasing its potential for use and without causing damage to the final material. As well as the recycled and lightweight aggregate proved to be an effective chemical sorbent for the studied electroplating residue.

Carbon Purchase Agreements, Dactories, and Supply-Chain Innovation: What Will It Take to Scale-Up Modular Direct Air Capture Technology to a Gigatonne Scale

Natural and engineered carbon dioxide removal have become regular features of climate models which limit warming to 1.5°C or even 2°C above pre-industrial levels. This gives rise to an assumption that solutions, for example direct air capture (DAC)—involving the direct removal of carbon dioxide from ambient air—can be commercialised and deployed at the necessary speed and scale to have a material impact, in the order of gigatonnes, by mid-century. Modular, solid-sorbent DAC on a gigatonne scale will require the mass mobilisation of supply chains to manufacture millions of modular DAC units−20 million of the present state of the art 50 tonne/year modules to deliver 1 gigatonne per year, as well as the large-scale production of novel chemical sorbents. To achieve a climate relevant DAC industry will demand innovative procurement models, for example carbon purchase agreements (CPAs), and dedicated DAC manufacturing facilities or dactories. In addition, insight is offered through the work of DAC start-up Carbon Infinity into the industry supply-chain position, adopting lessons from computing, and energy technologies. In particular, we look at approaches to drive demand and scale-up DAC module production, and opportunities presented in the development of an integrated DAC manufacturing industry.

Design, synthesis, and physicochemical study of a biomass-derived CO2 sorbent 2,5-furan-bis(iminoguanidine)

SummaryIn this study, the concept of biomass-based direct air capture is proposed, and the aminoguanidine CO2 chemical sorbent 2,5-furan-bis(iminoguanidine) (FuBIG) was designed, synthesized, and elucidated for the physicochemical properties in the process of CO2 capture and release. Results showed that the aqueous solution of FuBIG could readily capture CO2 from ambient air and provided an insoluble tetrahydrated carbonate salt FuBIGH2(CO3) (H2O)4 with a second order kinetics. Hydrogen binding modes of iminoguanidine cations with carbonate ions and water were identified by single-crystal X-ray diffraction analysis. Equilibrium constant (K) and the enthalpies (ΔH) for CO2 absorption/release were obtained by thermodynamic and kinetic analysis (K7 = 5.97 × 104, ΔH7 = −116.1 kJ/mol, ΔH8 = 209.31 kJ/mol), and the CO2-release process was conformed to the geometrical phase-boundary model (1-(1-α)1/3 = kt). It was found that the FuBIGH2(CO3) (H2O)4 can release CO2 spontaneously in DMSO without heating. Zebrafish models revealed a favorable biocompatibility of FuBIG.

Carbonized agrowastes uses for the removal of heavy metals Cr (VI), Ni (II), Cu (II) and Zn (II) from electroplating effluent at Agra, U.P. (India)

The physico-chemical tests were conducted using an electroplating industry effluent that contained 18.0, 18.9, 8.6 and 15.6 ppm of Cr(VI), Ni(II), Cu(II) and Zn(II) respectfully. The work aimed to evaluate the feasibility of using powdered pseudo activated carbon prepared from agro wastes for the removal of heavy metals from electroplating effluents. The ability of coconut coir carbon (CCC), sagaun sawdust carbon (SSC), wheat stem carbon (WSC) and rice husk carbon (RHC) to remove heavy metals from the effluent was studied. The sorption was in the order of Ni > Zn > Cu > Cr over a wide range of initial concentrations: 1-20 mg/l at sorbent dose 1 g/l. The sorption increased with increasing contact time but the equilibrium was attained in two hours for Cr, 3.0 h for Cu, 3.5 h for Zn and 4 h for Ni. The order of metal removal capacities for these chemical sorbents was: RHC > CCC > WSC > SSC. Electroplating effluent showed 4-10% lower removal as compared to synthetic standard solution under similar conditions.

Pathways of Chemical Recycling of Polyvinyl Chloride: Part 1

An increase in the level of production and consumption of polyvinyl chloride leads to the formation of a large volume of chlorinated waste, mostly as a component of municipal plastics waste. Incineration of such waste to produce energy results in emission of toxic gases (SO2, NOx) and of heavy metals and solid particles with flue gases, and also in formation of polychlorinated dibenzodioxins and dibenzofurans and of other aggressive chlorinated organic compounds. Therefore, recycling of waste containing chlorinated organic polymers becomes a serious problem. The review considers modern commercial processes for sorting municipal plastics waste, including various procedures for polymer waste separation. Procedures based on pyrolysis and gasification for chlorinated waste recycling are analyzed. Approaches to chemical recycling of polyvinyl chloride and of polymer mixtures and municipal waste containing polyvinyl chloride, namely, pyrolysis and low-temperature catalytic dechlorination, are described. The influence of the composition and kind of polymer waste on the degree of dechlorination is analyzed. Principles and mechanisms of mechanochemical processing of polyvinyl chloride waste in a mixture with chemical sorbents and with biological and technical wastes are presented.

Polymers of Intrinsic Microporosity Chemical Sorbents Utilizing Primary Amine Appendance Through Acid-Base and Hydrogen-Bonding Interactions.

Here, we present novel chemical sorbents based on polymers with intrinsic microporosity (PIMs). For the first time, alkylamines were incorporated in PIMs through an acid-base interaction to create a chemisorbent. The amine-appended PIMs not only showed a nearly four-fold enhancement in CO2 loading capacity (36.4 cc/g at 0.15 bar and 298 K) and very high CO2/N2 selectivity compared to neat PIM-1 but also proved to have stable performance when cycled between adsorption and desorption isotherms under both dry and humid conditions that are typical for postcombustion CO2 capture.

An eco-friendly cellulose acetate chemical sorbent for hazardous volatile organic liquid spill: a perfect material to solve the issue of evaporating hazards

Accidents related to spilling of chemicals and chemical wastes are never ceasing, especially as our reliance on chemical products increases continuously. For the sake of workers’ safety and maintenance of our environment, it is important to not only reduce the frequency of such accidents but also minimize the damage from each accident through proper spill control methods. Our focus here is to address the issues regarding rapid evaporation of the hazardous volatile organic liquids spills and propose a potential sorbent material, cellulose acetate, which can significantly reduce the rate of evaporation of highly volatile chemicals such as acetone, acrolein, and propylene oxide. Compared to conventional chemical sorbents such as activated carbon, expanded vermiculite, and cellulose, cellulose acetate not only exhibits higher vapor retention abilities, but also demonstrates comparable sorption efficiencies for sorption of acetone, acrolein, and propylene oxide. Cellulose acetate is also an environmentally friendly and economical material that is safe to use even for sorption of highly flammable chemicals, thus, its potential as a new class of commercial chemical sorbent is very promising.

Photoresponsive molecularly imprinted dendrimer-based magnetic nanoparticles for photo-regulated selective separation of azathioprine

This research describes the development of a poly (amidoamine) (PAMAM) dendrimer-based photoresponsive molecularly imprinted polymers (P-MIPs) for selective separation and determination of azathioprine. This study is the first involving a PAMAM dendrimer-coated magnetic nanoparticles (MNPs) used during the imprinting process to enhance a number of recognition sites in the polymer matrix to advance the recognition ability. The photoresponsive MIP was fabricated using azathioprine as the template, water-soluble 5-[(4-(methacryloyloxy) phenyl) diazenyl] isophthalic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. The dendrimer-magnetic nanoparticles and PAMAM dendrimer-based P-MIPs were characterized by different spectroscopic and nano structural techniques. Quantitatively release and uptake of azathioprine from the P-MIP is photoregulated by alternate irradiation with ultraviolet and visible light. This means that trans–cis isomerization could regulate the affinity for azathioprine and azobenzene groups placed inside the binding sites. Hence, this material could be used as a chemical sorbent. The recoveries for analyte were higher than 95% and relative standard deviation values were found to be in the range of 1.24–1.72%, indicating that the prepared nano-sorbent has high accuracy and precision for determining trace of azathioprine in complex biological and pharmaceutical samples.

Determination of SO2 solubility in ionic liquids: COSMO-RS and modified Sanchez-Lacombe EOS

With more stringent standards regarding the emission of greenhouse gases, capturing or removal of these detrimental pollutants has become of significant importance in industrial plants. In this presented investigation, ε∗-modified Sanchez–Lacombe equation of state and COSMO-RS-Lei and COSMO-RS-ADF models have been employed in order to estimate the solubility of sulfur dioxide (SO2) in different ionic liquids (ILs) as chemical sorbents with different cations and anions. The experimental data of Imidazolium, Pyridinium, Guanidinium and Ammonium based ionic liquids such as experimental data of density and the amount of SO2 solubility into ionic liquids in a wide range of temperature and pressure have been obtained from the literature. The characteristic parameters of the ε∗-modified Sanchez–Lacombe EOS have been adjusted by applying a database including 580 experimental data points of ILs density for 4 SO2/IL systems. In order to confirm the accuracy of the mentioned models, the phase equilibrium (PTx) diagrams of the SO2/ILs systems have been drawn and predicted data are compared with experimental data. According to the figures and also reported tables which contain the amount of calculated errors, It can be claimed that presented models in this study are capable to predict the amount of SO2 solubility into ionic liquids within the value of AARD% around 5%, 63% and 62% for ε∗-modified Sanchez–Lacombe EOS, COSMO-RS-Lei and COSMO-RS-ADF respectively.

Analysis of composite sorbents for ammonia storage to eliminate NOx emission at low temperatures

A new type of composite sorbent-SCR system has been designed for NOx elimination of diesel vehicles to promote the NOx conversion rate at low temperatures (50–250°C), with the sorption reaction temperature of 50–100°C for safety reason. NH3 is sorbed by composite sorbents with expanded natural graphite treated with sulfuric acid (ENG-TSA) matrix at room temperature, and released from composite sorbents by heating phase, which is driven by both electricity and exhaust waste heat. The composite sorbent is a porous composite of 80% chemical sorbents and 20% ENG-TSA. The NH3 sorption capacity of chemical sorbents (NH4Cl, NaBr, BaCl2, CaCl2 and SrCl2) have been evaluated and compared with traditional urea-SCR system with AdBlue, and the results are analyzed. NH3 cannot be pyrolyzed from AdBlue below 160°C, and the NOx conversion rate of the composite sorbent-SCR system is about 45% higher than the urea-SCR system (0%) at 50°C. NH4Cl and NaBr are not suitable for composite sorbent-SCR system for that the pressure is too high even at the environmental temperature. According to the NH3 sorption capacity, composite of CaCl2 with ENG-TSA and composite of SrCl2 with ENG-TSA are both optimal solid sorbents, and between them CaCl2 with ENG-TSA as matrix is the best choice for the small mass required and the low cost.

Zinc Recovery from Spent Chemical Sorbent by Dry Chlorination and Electrodeposition from Chloride Solutions

Fil: de Micco, Georgina. Comision Nacional de Energia Atomica. Gerencia de Area Investigaciones y Aplicaciones no Nucleares. Gerencia de Fisica (Centro Atomico Bariloche). Division Fisica de Metales; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

Development of carboxyl-layered double hydrotalcites of enhanced CO2 capture capacity by K2CO3 promotion

Layered double hydroxides have been comprehensively studied as adsorbent precursors for CO2 capture at 250–500 °C. Layered double hydroxides take advantages of partial reversibility by pressure change of adsorbate and good selectivity to CO2 contributed by active basic sites. However, they suffer from comparatively lower CO2 capture capacity, commonly 0.28–0.70 mmol/g in previous studies, compared with typical physical adsorbents like zeolites or chemical sorbents such as calcium oxide. In this paper, K2CO3 promoted n-caprylate (CH3(CH2)6COO−) LDH and K2CO3 promoted stearate (CH3(CH2)16COO−) LDH were synthesized by combining long carbon-chain carboxylic anion intercalation and K2CO3 promotion. K2CO3 surface promotion raised CO2 capacity to 1.36 mmol/g for K-promoted magnesium–aluminum n-caprylate LDH and 1.97 mmol/g for K-promoted magnesium–aluminum stearate LDH respectively. Thermal gravimetric analysis was used to test CO2 uptake up to 1000 kPa. It was found that adsorption kinetics fitted Elovich equation. X-ray diffraction was deployed to detect the crystal patterns of both precursors and adsorbents. In situ fourier transformation infrared spectroscopy and temperature programmed desorption were used to monitor the bonding between surface basic sites and adsorbate during adsorption and desorption process, in order to illustrate the adsorption mechanism of CO2 on LDHs only by changing the partial pressure of CO2 at the same operation temperature. Both novel LDHs show good potential for PSA application.