Sequestration Applications Research Articles

Hierarchical TiO2:Cu2O Nanostructures for Gas/Vapor Sensing and CO2 Sequestration.

We investigate the effect of high-surface-area self-assembled TiO2:Cu2O nanostructures for CO2 and relative humidity gravimetric detection using polyethylenimine (PEI), 1-ethyl-3-methylimidazolium (EMIM), and polyacrylamide (PAAm). Introduction of hierarchical TiO2:Cu2O nanostructures on the surface of quartz crystal microbalance sensors is found to significantly improve sensitivity to CO2 and to H2O vapor. The response of EMIM to CO2 increases fivefold for 100 nm-thick TiO2:Cu2O as compared to gold. At ambient CO2 concentrations, the hierarchical assembly operates as a sensor with excellent reversibility, while at higher pressures, the CO2 desorption rate decreases, suggesting possible application for CO2 sequestration under these conditions. The gravimetric response of PEI to CO2 increases by a factor of 3 upon introduction of a 50 nm TiO2:Cu2O layer. The PAAm gravimetric response to water vapor also increases by a factor of 3 and displays improved reversibility with the addition of 50 nm TiO2:Cu2O structures. We found that TiO2:Cu2O can be used to lower the detection limits for CO2 sensing with EMIM and PEI and lower the detection limits for H2O sensing with PAAm by over a factor of 2. Coarse-grained and all-atom molecular dynamics simulations indicate the dissociative character of ionic liquid assembly on TiO2:Cu2O interfaces and different distributions of CO2 and H2O molecules on bare and ionic liquid-coated surfaces, confirming experimental observations. Overall, our results show high potential of hierarchical assemblies of TiO2:Cu2O/room temperature ionic liquid and polymer films for sensors and CO2 sequestration.

Role of B. Licheniformis in bio mineralization of calcium carbonate and its biological applications

Bio mineralization is a significant process carried out by living organisms in which minerals are produced through the hardening of biological tissues. Herein, the current study focus on calcium carbonate precipitation, as part of bio mineralization, to be used in applications for CO2 sequestration, material technology, and other fields. A strain B. licheniformis, isolated from marine water, was investigated for its ability to produce urease and induce calcium carbonate precipitation in a metabolic process. It was discovered that B. licheniformis, resisted high concentrations of urea up to 60 g/L. In order to optimize the calcification process of B. licheniformis, the Calcium carbonate precipitation media is used respectively, pH of 10, and culture time of 96 h. Using X-ray diffraction and Scanning Electron Microscopy analysis, the calcium carbonate polymorphs produced by B. licheniformis, were proven to be mainly calcite. The results of this research provide evidence that B. licheniformis can biologically induce calcification and suggest that B. licheniformis may play a potential role in the synthesis of new bio minerals and in bioremediation or bio recovery.

Effects of Hydrophobic and Hydrophilic Graphene Nanoflakes on Methane Hydrate Kinetics

Gas hydrate technologies have steadily gained interest in several industries for their potential use in natural gas transport and carbon dioxide sequestration applications. To further develop these emerging technologies, significant focus has been placed on additives, and particularly nanoparticles, which optimize their efficiencies. The addition of materials such as graphene nanoflakes (GNFs) has previously been proven to enhance the production of methane hydrates and other hydrate systems. In this study, the growth rates of methane hydrates were measured in the presence of both hydrophobic (as-produced) and hydrophilic (plasma-functionalized) GNFs at 2 °C and 4646 kPa. The effect of GNF loading in the aqueous phase for both types was also determined. Small-scale agglomeration limited the growth rate enhancement effect of hydrophobic GNFs at low concentrations of around 0.5 ppm while significantly increasing the formation kinetics by about 101% at concentrations of 5 ppm. At even higher concentrations (10 ppm), the performance decreased due to large-scale agglomeration. Enhancement rose rapidly at low concentrations (0.1–1 ppm) of hydrophilic GNFs, peaking at about 288% before dropping to around 215% at 5 ppm due to mean free path limitations then rising again as surface area increased.

Removal of the synthetic hormone methyltestosterone from aqueous solution using a β-cyclodextrin/silica composite

Contamination of water with steroid residues can cause a number of environmental damages, affecting exposed organisms including man. The development of technologies for treatment or removal of this type of micropollutant from water is of paramount importance. In this study, citric acid was used to functionalize β-Cyclodextrin (bCD) on the silica surface generating an organic-inorganic hybrid composite for application in molecular sequestration. The functionalization percentage was high, with about 62.6% of the composite mass corresponding to the organic part of the material. 13C NMR and infrared spectroscopic analysis indicate that the functionalization mechanism occurs by an esterification reaction between the citric acid with the silanol groups from silica and the primary hydroxyls of the bCDs. Fast adsorption of the methyltestosterone steroid was observed at acid pH, with a high adsorption capacity of 11 mg g−1. The best kinetic and isotherm models fit indicated that the adsorption occurred by a physical mechanism at independent sites with the steroid molecule possibly captured by two bCDs. The removal process was spontaneous and exothermic, with the existence of weak interactions between the hormone and the composite, and its regeneration is quite fast efficient with the displacement of the complexation equilibrium. The results obtained in this study demonstrate the considerable potential of the composite for use in the treatment of wastewater containing the steroid studied, and its efficacy should be evaluated for other steroid molecules.

CO2 Storage in Low Permeable Carbonate Reservoirs: Permeability and Interfacial Tension (IFT) Changes During CO2 Injection in an Iranian Carbonate Reservoir

The lack of fundamental experimental studies on low permeable carbonate reservoirs for CO2 sequestration purposes is essential for further application of CO2 sequestration as a highly-anticipated CO2 mitigation method in deep saline aquifers, specifically those with low permeabilities. The core samples were taken from a carbonate reservoir in Iran and the brine composition was based on that of the same formation. The objective of this study is to investigate permeability alteration during CO2 sequestration in the aquifers of a low permeable Iranian carbonate reservoir. Various parameters have been investigated. The effects of different parameters such as injection pressure, confining pressure, and temperature on permeability alteration of the cores was investigated. Moreover, the interfacial tension (IFT) of CO2/brine was also determined at pressures and temperatures up to 7 MPa and 100 °C, respectively. The experimental results showed CO2 solubility and rock dissolution to be the governing mechanism when CO2 was injected into carbonate cores. The permeability measurements showed that permeability increases by increasing injection pressure and decreases by increasing confining pressure and temperature. The IFT measurement results showed that the IFT decreases significantly when there is an increase in pressure and temperature.

Utilization of Malaysia EAF slags for effective application in direct aqueous sequestration of carbon dioxide under ambient temperature

Iron and steel industries are among the contributors of CO2 emission in large volume into the atmosphere, causing detrimental effects to the environment and the ecosystem at large scale. These industries also generate solid wastes in the form of electric arc furnace (EAF) slag during operations which result in about 10–15% slag wastes per ton of steel produced. In this study, the EAF slags from an iron and steel-making factory in Klang, Malaysia was utilized for CO2 sequestration through direct aqueous mineral carbonation. According to the surface area analysis, the fresh EAF slag has a mesoporous structure, its elemental composition shows the presence of 20.91 wt.% of CaO that was used for the sequestration of CO2 through carbonation. The sequestration capacity was found to be 58.36 g CO2/kg of slag at ambient temperature in 3 h, with the liquid/solid (L/S) ratio of 5:1 and using <63μm particle size. Moreover, the shrinking core model (SCM) was used to analyze the solid-fluid reaction in a heterogeneous phase and the CO2 sequestration shows to be controlled by the product layer phase. The EAF slag is demonstrated to have the potential of CO2 sequestration at ambient temperature.

Mineral carbonation of yellow phosphorus slag and characterization of carbonated product

A procedure for producing high-purity CaCO3 by yellow phosphorus slag carbonation was proposed. The impacts of technological parameters on acid-leaching and carbonation results were discussed. The calcium leaching rate was 99.8%, while the acid-leaching product was amorphous silicon dioxide with granular morphology and some pores in the surface. The carbonation ratio was 98.10%: 1 t of yellow phosphorus slag can be used to produce 881 kg of CaCO3 and sequester 388 kg of CO2 under the optimized conditions. The CaCO3 satisfied the Chinese recommended industrial standard of HG/T 2226-2010. The products with a single calcite or vaterite structure, or binary and trinary mixed structure of calcite, vaterite and aragonite were all successfully prepared. A preliminary economic evaluation predicted that our yellow phosphorus slag carbonation procedure held a promising application for CO2 sequestration.

Comprehensive studies on polyethylenimine filled polypropylene and its potential application in carbon dioxide sequestration

Polypropylene (PP) was blended with branched polyethylenimine (PEI) with the aim to prepare blends having CO2 adsorption property. The CO2 adsorption properties will be conferred due to the presence of variety of amine functionality in PEI. PEI contains primary, secondary as well as tertiary amine groups. Before testing CO2 adsorption, PP–PEI blends were characterized using variety of techniques, for example, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, scanning electron microscopy, and polarized light optical microscopy. In this work, we have studied in detail both compatibilized as well as noncompatibilized blends of PP and PEI. The compatibilization was achieved via addition of maleic anhydride grafted PP. Finally, all the compatibilized as well as noncompatibilized blends were studied for CO2 adsorption. The compatibilized blends showed better thermal, mechanical as well as CO2 adsorption properties as compared to the noncompatibilized blends. POLYM. ENG. SCI., 59:2092–2102, 2019. © 2019 Society of Plastics Engineers

Modified mineral carbonation of phosphogypsum for CO2 sequestration

A modified phosphogypsum carbonation was systematically investigated, and ammonium acetate was used to separate Ca2+ and concentrate impurity ions from PG. The effect of technological conditions on salt-leaching and carbonation results were discussed. The calcium leaching rate was 98.1%, and the only crystal phase of salt-leaching product was quartz with granular morphology and some pores in the surface. The carbonation ratio (η) was 98.32%, and 1000 kg of phosphogypsum produced 510 kg of high-purity CaCO3 and sequestered 224 kg of CO2 under the optimized conditions. The spherical vaterite carbonation product met the recommended Chinese standard (HG/T 2226-2010). The carbonation filtrate can be reused for salt-leaching experiments. Various polymorph and morphology of CaCO3 were achieved by adjusting the carbonation temperature and ammonia dosage. The mechanism of phosphogpysum carbonation was studied by using thermodynamics research. All of this indicated that the whole procedure setup of phosphogypsum carbonation showed potential application for phosphogypsum utilization and CO2 sequestration.

Mineral carbonate dissolution with increasing CO2 pressure measured by underwater laser induced breakdown spectroscopy and its application in carbon sequestration

In this study, the ability of laser-induced breakdown spectroscopy (LIBS) to measure the in situ aqueous dissolution of various mineral carbonates with increasing CO2 pressure was examined. Dissolution experiments included four geologically common mineral carbonates (CaCO3, MgCO3, MnCO3, SrCO3) and the CO2 pressure ranged from ambient to 250 bar. The ensuing plasma emission was spectrally analyzed, and the intensities of Ca, Mg, Mn, and Sr emission lines were used to monitor the respective metal cations released to the aqueous solution. The strong emission lines of Ca (Ca II 393.36, Ca II 396.84, Ca I 422.67 nm), Mg (unresolved magnesium doublet: Mg I 383.230, Mg I 383.829 nm), Mn (unresolved manganese triplet: Mn I 403.076, Mn I 403.307, Mn I 403.449 nm), and Sr (Sr II 407.77, Sr II 421.55, Sr I 460.73 nm) were identified in the spectra. The amounts of metals released from their respective carbonates were estimated at different time intervals following the CO2 injection (5 m, 1, 2, 3, 4, 24 h) and at different pressures (50, 100, 150, 200, 250 bar) using calibration models developed at corresponding pressure settings. The results demonstrated that the pressure-induced dissolution of all carbonates was consistent with their expected and selective pH-dependent solubility. The dissolution rate of CaCO3, MgCO3, and SrCO3 was found to be higher than that of MnCO3. The dissolution of constituents in a Mt. Simon sandstone associated with a deep saline reservoir at elevated CO2 pressure was also studied and Ca release was quantified. The results demonstrated that real-time monitoring of carbonate dissolution by LIBS may provide a useful indirect detection system indicative of CO2 leakage from geologic carbon storage sites.

Comparison of life-cycle assessment between bio-catalyzed and promoted potassium carbonate processes and amine-based carbon capture technologies

Up until today, the technology used for the capture and production of pure CO2 in post-combustion applications for both use and sequestration relies primarily on the use of chemical amine solvents such as monoethanolamine (MEA). However, these solvents require significant amounts of valuable, high-grade process heat for solvent regeneration and suffer from substantial operational and environmental issues including degradation, toxic aerosol emissions, sensitivity to flue gas contaminants, and corrosivity. CO2 Solutions Inc (CSI) recently developed and deployed a new technology to solve these challenges by employing a non-toxic low-cost, stable salt solution as an absorption solution and the carbonic anhydrase enzyme as a catalyst for carbon management. The result is both fast CO2 absorption kinetics and significantly reduced energy costs by allowing to use low-grade heat to drive the solution regeneration. This study aims to analyze and compare the environmental profile of capture processes such as CSI, MEA and UNO MK3 (a precipitating potassium carbonate separation process). The context of the study is CO2 capture from the flue gas stream of a 550 MW coal-fired power station in the midwestern USA. To fulfill the objective, we performed an attributional cradle-to-gate LCA comparing the three systems. This study was conducted according to the requirements of ISO 14040 & 14044 and reviewed by an independent panel which concluded that “The LCA requirements of ISO 14040 and ISO 14044 have been answered in the best possible manner.”Data were mainly based on process simulation of the three technologies. The impact assessment was carried out with the Impact 2002+ method. This method considers four indicators at endpoint level (Climate change, Human health, Ecosystem quality and Resources) and sixteen indicators at midpoint level (for instance Aquatic Acidification or Ozone formation).Results show that the CSI carbon capture unit has significantly lower potential impacts than the MEA and UNO MK3 units. The CSI system presents lower scores than the MEA and the UNO MK3 systems for all midpoint and endpoint indicators. The operation stage, and more especially its energy consumption, is the main contributor to the environmental profile of all three systems. The CSI system differs radically from the MEA and UNO MK3 systems as it can use hot water instead of steam for its regeneration step. Hot water is a waste from the power plant, whereas steam consumption reduces the production of electricity at the power plant, which needs to be compensated elsewhere. In this study, it is considered that these losses of electricity production will affect the regional market in which the power plant is located, and therefore the lost electricity is produced by an average electricity grid mix coming from this regional market.Other inputs do not contribute significantly to the environmental profile of the systems at endpoint level. Among them, chemical inputs are the top contributors. However, the midpoint category where CSI technology differentiates itself the most from other technologies is when comparing the MEA Respiratory Organics score, which is 3.5 times higher than CSI. The several sensitivity analysis conducted typically do not affect the conclusion.

Playing with covalent triazine framework tiles for improved CO2 adsorption properties and catalytic performance.

The rational design and synthesis of covalent triazine frameworks (CTFs) from defined dicyano-aryl building blocks or their binary mixtures is of fundamental importance for a judicious tuning of the chemico-physical and morphological properties of this class of porous organic polymers. In fact, their gas adsorption capacity and their performance in a variety of catalytic transformations can be modulated through an appropriate selection of the building blocks. In this contribution, a set of five CTFs (CTF1–5) have been prepared under classical ionothermal conditions from single dicyano-aryl or heteroaryl systems. The as-prepared samples are highly micro-mesoporous and thermally stable materials featuring high specific surface area (up to 1860 m2·g−1) and N content (up to 29.1 wt %). All these features make them highly attractive samples for carbon capture and sequestration (CCS) applications. Indeed, selected polymers from this series rank among the CTFs with the highest CO2 uptake at ambient pressure reported so far in the literature (up to 5.23 and 3.83 mmol·g−1 at 273 and 298 K, respectively). Moreover, following our recent achievements in the field of steam- and oxygen-free dehydrogenation catalysis using CTFs as metal-free catalysts, the new samples with highest N contents have been scrutinized in the process to provide additional insights to their complex structure–activity relationship.

Modified phosphogypsum sequestrating CO2 and characteristics of the carbonation product

A method of PG carbonation to produce polymorphs of high-purity CaCO3 was proposed. The effect of experimental conditions on transformation process from PG to calcium carbonate was systematically discussed. PG transformed into granular portlandite and fibrous quartz under the action of caustic soda at room temperature for 10 min. The carbonation ratio (η) was 98.57%, and 1000 kg of PG could produce 519 kg of high-purity CaCO3 and sequestrated 228 kg of CO2. The spherical vaterite carbonation product met the relevant standards for the industrial precipitated calcium carbonate. A reaction mechanism of PG carbonation was also proposed by thermodynamic research of the gas-liquid-solid reaction. The products with a single vaterite structure, or a vaterite and calcite mixing structure or a vaterite, aragonite and calcite mixing structure were all successfully prepared. All of these indicated that the whole procedure setup of PG carbonation showed potential application for PG utilization and CO2 sequestration.

Heat capacity and thermodynamic functions of crystalline forms of the metal-organic framework zinc 2-methylimidazolate, Zn(MeIm)2

Zeolitic imidazolate frameworks (ZIFs) are composed of metal atoms connected with imidazole-like linkers, and these frameworks have potential for applications in molecular sieving, gas sequestration, and catalysis. In addition, these materials form true polymorphs with the same chemical composition but different topologies. In this paper, we present the results of low temperature heat capacity and inelastic neutron scattering studies of the sodalite (SOD) and diamondoid (dia) topologies of the popular zinc 2-methylimidazolate framework, Zn(MeIm)2. Molar heat capacities from 1.8 K to 300 K are presented, along with theoretical fits and the values of Cp,m°, Δ0TSm°, Δ0THm°, andΦm°calculated from those fits. The Gibbs energy of the transformation from SOD to dia is −(4.6 ± 2.2) kJ, and this transformation is primarily enthalpically driven. The results of this study are compared with previous measurements on the zinc 2-ethylimidazolate framework, Zn(EtIm)2. Inelastic neutron scattering measurements confirm the presence of low energy modes and suggest that the higher heat capacity of SOD at low temperatures is due to the dynamics of the methyl groups on the methylimidazolate linkers.

Exfoliation of Titanium Aluminum Carbide (211 MAX Phase) to Form Nanofibers and Two-Dimensional Nanosheets and Their Application in Aqueous-Phase Cadmium Sequestration.

A green approach was adopted to exfoliate a Ti2AlC MAX phase. The exfoliated nanostructures (Alk-Ti2Cfibr and Alk-Ti2Csheet) with exceptional mechanical, thermal, and water stabilites, as well as abundant oxygenated active binding sites, were synthesized via a controlled hydrothermal treatment in an alkaline environment. The successful synthesis of nanofibers and sheetlike nanostructures was inferred with scanning electron microscopy and X-ray diffraction analyses. Field emission scanning electron microscopy, field-emission transmission electron microscopy, Raman spectroscopy, Brunauer-Emmett-Teller surface area, ζ-potential analyses, and X-ray photoelectron spectroscopy were utilized to investigate the material's characteristics and its structural changes after metal ion adsorption. Heavy metal ion adsorption of the synthesized nanostructures was assessed in batch tests based on Cd2+ ion sequestration; the maximum adsorption capacity for Cd2+ was 325.89 mg/g, which is among the highest values reported for similar materials such as graphene oxide and its derivatives. The detailed quantitative investigation confirmed the interaction of hydroxyl groups with Cd2+ ions by electrostatic interactions, adsorption-coupled oxidation, and complex formation. Owing to their unique structure, high porosity, large specific surface area, and oxygenated functional groups, Alk-Ti2Csheet nanosheets were highly time-efficient for Cd2+ removal. Moreover, Alk-Ti2Cfibr and Alk-Ti2Csheet nanostructures were tested for simulated groundwater, showing that synthesized nanostructures were capable for removing Cd2+ ions at the ppb level. The results obtained from this study suggested that nanostructures synthesized using this route could provide a new approach to prepare and exfoliate additional MAX phases for the removal of heavy metal ions and other pollutants in the environment.

Propagation of toughness-dominated fluid-driven fractures in reactive porous media

Fluid-driven open-mode fractures in porous media are the result of multiple physical processes governed by fluid properties, porous media properties, geometrical fracture properties, and fluid injection parameters. For example, a propagating open-mode fracture in which most work is spent on creating new fracture surface rather than on moving fluid through the fracture is said to be in a “toughness-dominated” regime. However, other multiphysical phenomena such as thermal dilation and mineral-dissolution can also affect fracture propagation. This study focuses on the facilitation of fracture propagation in toughness-dominated regime by weakening of the rock at the fracture tip by injection of a reactive fluid that causes mineral dissolution. We explore this coupled problem through numerical simulation using a finite element method (FEM) formulation based on the phase-field approach in order to solve equations for fluid flow, poroelasticity, linear elastic fracture mechanics and reactive transport. We couple mechanics and reactive fluid flow by assuming that fracture toughness decreases due to increases in rock porosity caused by mineral dissolution. The numerical simulation results show that acid injection and mineral dissolution (1) lower fracture breakdown pressure and (2) can bridge a transition from toughness-dominated to viscosity-dominated fracture propagation at constant injection pressure. Our results demonstrate that acid injection can change fracture propagation regimes and enable new phenomena that are not possible in unreactive porous media. The understanding of fracture propagation patterns and geometry manipulation is critical for safe and effective use of reactive fluids in the subsurface, such as in hydraulic fracturing, harnessing of deep geothermal energy, and carbon geological sequestration applications.

Fracture Propagation in Heterogeneous Porous Media: Pore-Scale Implications of Mineral Dissolution

Open-mode fractures in sediments and rock occur both in natural processes and in engineering practice. In contrast to long planar fractures predicted by solutions in homogeneous media, laboratory and field observations often evidence complex and non-planar open-mode fracture networks in geological media. One cause of fracture complexity is the heterogeneity of material mechanical properties. This study focuses on the effects of mineral dissolution on pore structure modification in heterogeneous porous media and ensuing changes on fracture propagation characteristics. We performed semicircular bending experiments on limestone samples pre- and post-acidizing, mapped 3-D pore structure with X-ray microtomography, and used a finite element formulation based on the phase-field approach and linear elastic fracture mechanics to model initiation and propagation of open-mode fractures. Semicircular bending experiments on acidized carbonate rock samples show that non-planar fractures follow high porosity regions and large pores, and that fracture toughness correlates well with local porosity. Numerical modeling shows that a direct relationship between fracture toughness and porosity permits replicating fracture stress intensity at initiation and non-planar fracture propagation patterns observed in experiments. The results of this study indicate that mineral dissolution can affect fracture propagation patterns and that a coupling of mechanical and reactive processes in porous media formulations can be achieved through porosity and toughness. The understanding of fracture propagation patterns and geometry manipulation is critical for safe and effective use of reactive fluids in the subsurface, such as in hydraulic fracturing and carbon geological sequestration applications.

Flexibility and Efficiency of Steam Turbine Extraction vs Gas Fired Generation as Steam Source for Post Combustion CO2 Capture on Coal Fired Power Plant

CO2 emissions from electrical power generation must be reduced if global climate change mitigation targets are to be met. Expansion of renewable sources of power generation and the application of carbon capture and sequestration are two strategies required to reduce the CO2 emissions from this sector. As the penetration of renewable resources increases, non-renewable generation will need to become more flexible in order to back-up the intermittent renewable energy sources. Post combustion CO2 capture is the only proven full scale option currently available for reducing emissions from existing coal fired power plants. Post combustion capture processes however require significant quantities of thermal energy (or steam) to regenerate the solvent used for CO2 capture. This requirement for thermal energy can represent almost half of the de-rate associated with CO2 capture. Numerous studies have evaluated sources of this thermal energy; such as the existing steam turbine, or the integration of new gas fired sources. Most studies that have compared these sources of thermal energy have evaluated only performance at full load but this study focuses on flexibility and efficiency of these two configurations over a broader range of output. The conclusion of the study is that the existing steam turbine of the associated power plant can be re-engineered to become a more efficient and a more flexible source of the thermal energy than the addition of a gas fired generation source.

The application, required investments and operational costs of geological CO2 sequestration: a case study

The integrity of natural systems is already at risk because of climate change caused by the intense emissions of greenhouse gases in the atmosphere. The goal of geological carbon sequestration is to capture, transport and store CO2 in appropriate geological formations. In this review, we address the geological environments conducive to the application of CCS projects (Carbon Capture and Storage), the phases that make up these projects, and their associated investment and operating costs. Furthermore it is presented the calculations of the estimated financial profitability of different types of projects in Brazil. Using mathematical models, it can be concluded that the Roncador field presents higher gross revenue when the amount of extra oil that can be retrieved is 9.3% (US$ 48.55 billions approximately in 2018). Additional calculations show that the Paraná saline aquifer has the highest gross revenue (US$ 6.90 trillions in 2018) when compared to the Solimões (US$ 3.76 trillions approximately in 2018) and Santos saline aquifers (US$ 2.21 trillions approximately in 2018) if a CCS project were to be employed. Therefore, the proposed Carbon Capture and Storage method in this study is an important scientific contribution for reliable large-scale CO2 storage in Brazil.

Iodine sequestration using cyclophosphazene based inorganic-organic hybrid nanoporous materials: Role of surface functionality and pore size distribution

Cyclophosphazene based inorganic-organic hybrid nanoporous materials having triazine and pyrrolic functionality named as HNM-1 and CHNM-1, respectively, with varying nitrogen content, hierarchical pore size and high specific surface area have been explored for iodine sequestration application. The presence of electron rich functionality in the HNM-1 and CHNM-1 provides a large number of active sites for the adsorption of iodine. Maximum gravimetric iodine capture capacity of 223 and 120 wt% were estimated in HNM-1 and CHNM-1 specimens, respectively, under fuel processing condition i.e. 75 °C and ambient pressure. Moreover, both the specimens have shown very good iodine release behavior in organic solvents. The recyclability of HNM-1 and CHNM-1 for iodine sorption has shown the retention of adsorption capacity by 80 and 86%, respectively, even after five cycles. The iodine sorption both in vapor as well as solution phases is greatly influenced by the nitrogen content and pore size distribution of the framework materials.