Stoichiometry Of Reaction Research Articles

Mechanism of CaO catalyst deactivation with unconventional monitoring method for glycerol carbonate production via transesterification of glycerol with dimethyl carbonate

Glycerol carbonate (GC) was synthesized by transesterification of glycerol with dimethyl carbonate (DMC) using calcium oxide (CaO) derived from eggshell as a catalyst. The best results of 96% glycerol conversion and 94% GC yield were achieved under the following reaction conditions: 0.08 mole ratio of CaO to glycerol, 1:2.5 mole ratio of glycerol to DMC, 60°C reaction temperature, and 3 hours reaction time. As expected, CaO showed deteriorated catalytic performance when recycling as observed by a rapid decrease in GC yield. This research showed that the active CaO phase first was converted to calcium methoxide (Ca[OCH3]2) and calcium diglyceroxide (Ca[C3H7O3]2) and finally to carbonate phase (CaCO3) which can be confirmed by XRD patterns. According to the phase transformation, the basicity decreased from 0.482 mmol/g to 0.023 mmol/g, and basic strength altered from strong basic strength (15.0 < H_ < 18.4) to weak basic strength (7.2 < H_ < 9.8), resulting in the lower catalytic activity of the consecutive runs. Despite the fact that the GC selectivity was almost 100%, the reaction products (methanol and GC) were not obtained in their stoichiometric ratio and their extents corresponded with that of the catalyst phase transformation to CaCO3. The mechanism of CaO catalyzed transesterification based on the condensation reaction of glycerol and catalyst was proposed, and in situ formation of water-derivative species was hypothesized as a cause of CaO transformation. CaO could react with DMC and water, generating methanol and CaCO3. This enabled unconventional monitoring of catalyst deactivation by checking if the mole ratio of methanol to GC was higher than 2:1 of its reaction stoichiometric ratio. It was also demonstrated that calcination of post-run catalyst at 900°C to CaO exhibited almost constant catalytic activity, and the mole ratio of methanol to GC was constant at its reaction stoichiometry (2:1) for at least 4 times use.

From Food to Mobility: Investigating a Screening Assay for New Automotive Antioxidants Using the Stable Radical DPPH

AbstractBy taking inspiration from the food industry, an assay was investigated as a potential screening tool to test the efficiency of new phenolic antioxidants. The method was based on the spectrophotometric measurement of the stable free radical 1,1‐diphenyl‐2‐picryl hydrazyl (DPPH) which, in its radical form, has an absorbance maxima at 515 nm. The disappearance of this absorbance band, upon reaction with an antioxidant, was monitored to reveal the kinetic pathway of the reaction, which was defined simply as either fast, medium or slow. Adaptation of the assay was attempted for application to biofuels and oil‐based automotive fluids whereby the effect of polar and non‐polar solvents on the kinetics of the reaction was investigated. In addition, the stoichiometry of the radical scavenging reaction was also analysed to give an insight into the structure‐activity relationships of phenolic antioxidants.

Elaboration of Porous Salts.

A large library of novel porous salts based on charged coordination cages was synthesized via straightforward salt metathesis reactions. For these, solutions of salts of oppositely charged coordination cages are mixed to precipitate MOF-like permanently porous products where metal identity, pore size, ligand functional groups, and surface area are highly tunable. For most of these materials, the constituent cages combine in the ratios expected based on their charge. Additional studies focused on the rate of salt metathesis or reaction stoichiometry as variables to tune particle size or product composition, respectively. It is expected that the design principles outlined here will be widely applicable for the synthesis of new porous salts based on a variety of charged porous molecular precursors.

XPS and FTIR investigations of the transient photocatalytic decomposition of surface carbon contaminants from anatase TiO2 in UHV starved water/oxygen environments

This paper explores the transient photocatalytic oxidation mechanism of carbon contaminants from a high surface area anatase TiO2 pellet under starved water/oxygen reaction conditions created when specimens are irradiated via a 375 nm UV laser inside the UHV analysis chamber of an XPS spectrometer. Complementary results are also provided following similar UV irradiations and reaction procedures in an evacuated in situ reaction cell of a Fourier-transform infrared spectrometer (FTIR). An interactive and non-steady state transient photocatalytic reaction is observed between surface carbon species and strongly adsorbed H2O brought to the exterior surface of the pellet via UV photodesorption from within the deeper lying pores of the pellet. The reaction stoichiometry and quantum efficiency of the reaction are reported at various irradiation intensities. In situ FTIR spectral features are also presented and discussed for a non-UV treated TiO2 sample and a 2-hour UV-treated TiO2 sample under evacuated conditions also showing the decomposition of carbon contaminants species and the consumption of adsorbed water/hydroxyls with the ensuing formation of carboxyl (HO-CO) carbon species and isolated surface hydroxyls. The photocatalytic decomposition of carbon species and the concomitant consumption of oxygen containing species was also tracked by following the XPS spectral changes of a UV-irradiated area on the pellet surface compared to a dark reference spot on the same specimen. Eight different reaction cases at four different UV intensities, repeated twice each, were also investigated using separate pieces of the same TiO2 media. The measured stoichiometry for the decomposition of carbon species and consumption of oxygen ranged from 0.53 during the first 10–20 min of irradiation and increased to 0.65 with an average value of 0.59 and a standard deviation of 0.11. These data suggest that the reaction product and leaving group from the TiO2 surface is primarily CO2 during the first 10–20 min of initial reaction with perhaps a small fraction of CO toward the end of reaction. Heating the sample specimen to 100 °C for 2-hour inside the XPS-UHV analysis chamber prior to UV illumination was effective in eliminating photocatalytic oxidation and carbon removal from the surface thereby demonstrating that strongly adsorbed water (prior to heating in vacuum) was a critical and limiting reagent in the overall H2O transport and reaction process.Photon efficiencies for the reaction were calculated based on the number of carbon species removed from the XPS-observable surface versus the number of the UV photons adsorbed in the topmost 2 nm of the sample. The highest photon efficiency observed was 0.0186 after 5–10 min of UV exposure at 1.5 mW/cm2. All reaction cases showed a significant efficiency drop after 30 min of UV irradiation due to the consumption of the adsorbed reactants, both carbon and water. From detailed deconvolution of the XPS C 1s spectra, UV irradiation showed a high selectivity towards hydrocarbon contaminant decomposition, which was 75% ± 5% of all carbon species removed.

The Chemistry of Hyperalkaline Springs in Serpentinizing Environments: 1. The Composition of Free Gases in New Caledonia Compared to Other Springs Worldwide

AbstractSerpentinization is a natural process that transforms ferromagnesian minerals such as olivine into serpentine and that produces waters at very high pH and gases enriched in methane (CH4) and hydrogen (H2). We report the composition of gases venting at two springs (Bain des Japonais and Rivière des Kaoris) of the serpentinizing environment of the Prony Bay (New Caledonia) collected eight times between 2011 and 2014, along with in situ measurements (temperature, pH, oxydo‐reduction potential, dissolved oxygen content) of on‐land alkaline springs of the Southern New Caledonia ophiolite. Venting gases are mainly composed of H2, CH4, and N2 and their composition has slightly varied during the 4‐year field survey. An elevated oxygen (O2) content in a high‐pH water sample is due to air uptake during surface flow. O2‐corrected gas compositions along with those published for gas data obtained at similar serpentinizing environments (Italy, Turkey, Philippines, and Oman) show that the H2 and CH4 concentrations display a linear correlation with a slope close to the value corresponding to the CH4 production from carbon dioxide rather from a less oxidized carbon such as carbon monoxide. Although these data are consistent with the stoichiometry of the Sabatier reaction, as such in the gas phase, it is also possible that microbial hydrogenotrophic methanogenesis takes place in the aqueous phase followed by degassing. A diagram is proposed that outlines the partitioning of H2 and CH4 between the gaseous and aqueous phases and the need to consider a two‐phase flow in the hydrology of these hyperalkaline environments.

Polymorphism, Halogen Bonding, and Chalcogen Bonding in the Diiodine Adducts of 1,3- and 1,4-Dithiane.

Through variations in reaction solvent and stoichiometry, a series of S-diiodine adducts of 1,3- and 1,4-dithiane were isolated by direct reaction of the dithianes with molecular diiodine in solution. In the case of 1,3-dithiane, variations in reaction solvent yielded both the equatorial and the axial isomers of S-diiodo-1,3-dithiane, and their solution thermodynamics were further studied via DFT. Additionally, S,S’-bis(diiodo)-1,3-dithiane was also isolated. The 1:1 cocrystal, (1,4-dithiane)·(I2) was further isolated, as well as a new polymorph of S,S’-bis(diiodo)-1,4-dithiane. Each structure showed significant S···I halogen and chalcogen bonding interactions. Further, the product of the diiodine-promoted oxidative addition of acetone to 1,4-dithiane, as well as two new cocrystals of 1,4-dithiane-1,4-dioxide involving hydronium, bromide, and tribromide ions, was isolated.

The combined effects of chemical reaction order and stoichiometry on nonpremixed edge flames

We examined in this work the combined effects of chemical reaction order n and the stoichiometric mixture fraction on the propagation of nonpremixed edge flames in a counterflow configuration. We began by formulating the problem mathematically using the constant density thermo-diffusive model. The problem was then solved numerically using the finite element method. It has been shown that the reaction order and stoichiometry have an interchangeable role in modifying flame propagation. The study has shown that triple flames exist only for a limited range of values of both the chemical reaction order n and the stoichiometric mixture fraction . Over such values, modifying n and were found to have a great impact on many characteristics related to the flame structure, such as the flame location, the extent of both the premixed flame wings and the trilling diffusion flame, and the flame curvature. In addition, the flame location was found to vary subjected to the value of the reaction order in a manner similar to that observed by varying the mixture fraction. The study also identified the influence of the fuel Lewis number on the flame propagation and was found that the effect of is more pronounced when the reaction order differs from unity. Finally, the study has examined the role of the strain rate on the flame propagation and concluded that the effect of the chemical order n is negligible for stoichiometric mixtures but tends to be significant for off-stoichiometric mixtures.

Integration of complete elemental mass-balanced stoichiometry and aqueous-phase chemistry for bioprocess modelling of liquid and solid waste treatment systems – Part 1: The physico-chemical framework

Bioprocesses interact with the aqueous environment in which they take place. Currently integrated bioprocess and three-phase (aqueous–gas–solid) multiple strong and weak acid/base system models are being developed for a range of wastewater treatment applications, including anaerobic digestion, biological sulphate reduction, autotrophic denitrification, biological desulphurization and plant-wide wastewater treatment systems. In order to model, measure and control such integrated systems, a thorough understanding of the interaction between the bioprocesses and aqueous-phase multiple strong and weak acid/bases is required. This first in a series of five papers sets out a conceptual framework and methodology for deriving bioprocess stoichiometric equations. It also introduces the relationship between alkalinity changes in bioprocesses and the underlying reaction stoichiometry, which is a key theme of the series. The second paper develops the stoichiometric equations for the main biological transformations that are important in wastewater treatment. The link between the modelling and measurement frameworks, which uses summary measures such as chemical oxygen demand (COD) and alkalinity, is described in the third and fourth papers. The fifth paper describes an equilibrium aquatic speciation algorithm which can be combined with bioprocess stoichiometry to provide integrated models of wastewater treatment processes.

Monitoring a MOF Catalyzed Reaction Directly in Blood Plasma.

Herein, we establish a method to quantitatively monitor a metal-organic framework (MOF)-catalyzed, biomedically relevant reaction directly in blood plasma, specifically, the generation of nitric oxide (NO) from the endogenous substrate S-nitrosoglutathione (GSNO) catalyzed by H3[(Cu4Cl)3-(BTTri)8] (CuBTTri). The reaction monitoring method uses UV-vis and 1H NMR spectroscopies along with a nitric oxide analyzer (NOA) to yield the reaction stoichiometry and catalytic rate for GSNO to NO conversion catalyzed by CuBTTri in blood plasma. The results show 100% loss of GSNO within 16 h and production of 1 equiv. of glutathione disulfide (GSSG) per 2 equiv. of GSNO. Only 78 ± 10% recovery of NO(g) was observed, indicating that blood plasma can scavenge the generated NO before it can escape the reaction vessel. Significantly, to best apply and understand reaction systems with biomedical importance, such as NO release catalyzed by CuBTTri, methods to study the reaction directly in biological solvents must be developed.

Effect of phosphate on peroxymonosulfate activation: Accelerating generation of sulfate radical and underlying mechanism

Effect of phosphate on pollutant removal was widely investigated in various peroxumonosulfate-based advanced oxidation processes (AOPs) but the role of phosphate was controversial. Many studies also used phosphate as buffer in PMS-based AOPs. This study shows that phosphate promoted PMS activation for pollutants removal. Therefore, PMS activation capacity of some strategies may be overestimated when conducted in the phosphate buffer. Importantly, the results of radical quenching tests, radical probes and reaction stoichiometries indicated that the yields of SO4− was elevated by the presence of phosphate and linearly depended on phosphate concentration, while the yields of OH remained constant. Density Functional Theory (DFT) calculation confirmed that PO43− and HPO42− could efficiently break OO bond of PMS, promoting the generation of SO4− for contaminants decomposition. These results illuminated the role of phosphate in AOPs utilizing PMS and uncovered the underlying mechanism of PMS activation by phosphate.

Reactive Extraction of Butyric Acid from Water Using Trioctyl Amine in 1-Decanol and Green Natural Oils

In this work, butyric acid (BA) was extracted using trioctyl amine (TOA). Various temperature-dependent (298.15–318.15 K) process parameters were estimated and analyzed. To reduce the harmful effects of TOA and to avoid the detrimental effects of toxic diluents on microorganisms, green and nontoxic diluents, sunflower and soybean oils, were tested. In physical extraction, KDdil and the partition coefficient, P, decreased in the order of 1-decanol > sunflower oil > soybean oil, whereas the dimerization constant, D, showed the opposite trend. In chemical extraction, the extraction efficiencies were 85–90% for 1-decanol, 82–88% for sunflower oil, and 75–86% for soybean oil. In terms of the distribution coefficient, 1-decanol was a better diluent than sunflower oil, followed by soybean oil. The high distribution coefficients and extraction efficiencies obtained using sunflower and soybean oils were found to be encouraging for their use in biorefinery industries. (KDchem)/(KDphy) was greater than 1.0 in all of the studied cases. The best distribution coefficient model was identified. The complexation reaction stoichiometry and the equilibrium complexation reaction constant were estimated using the differential evolution technique. The order of the complex molality, [HAmSn]org, in different diluents was 1-decanol > sunflower > soybean. Different thermodynamic parameters were determined and analyzed. Variations of acid–extractant, free acid, and dimer molalities at the chemical equilibrium state were found and discussed. Analysis based on the enthalpy change due to mass transfer, (ΔH)mass tr, indicated the easiest mixing of the phases in sunflower oil and the most difficult in soybean oil. The reaction equilibrium constant, KE(m:n), had the highest value at the lowest temperature (298.15 K) and decreased with an increase in temperature and had values in the order of 1-decanol > sunflower > soybean.

Dispersing aminopolycarboxylate ionic liquids in mesoporous organic polymer for highly efficient and improved carbon capture from dilute source

Aminopolycarboxylate ILs (APC-ILs)—a kind of anion-grafted amine-functionalized ILs enabling 1:2 stoichiometry of reaction with CO2—were dispersed in mesoporous organic polymer to achieve a new class of adsorbents. The mesoporous organic polymer selected herein is polydivinylbenzene (PDVB) that can be facilely synthesized by a solvothermal route without any templates. The prepared APC-IL@PDVB samples were then systematically characterized and investigated for carbon capture performance. It is found that APC-IL@PDVB samples can efficiently adsorb CO2 from dilute source, with the highest CO2 capacity of 1.65 mmol/g and IL utilization ratio of 1.53 mol/mol at 30 ℃ for 10 vol% of CO2 balanced in N2. The CO2 capacities of APC-IL@PDVB samples surpass the values of most other solid-dispersed ILs, and the IL utilization ratios surpass the values of most non-dispersed ILs. The adsorption of CO2 by APC-IL@PDVB samples is also highly selective towards N2, and reversible throughout consecutive adsorption-desorption cycles. Therefore, dispersing APC-ILs in PDVB is an effective approach to obtain adsorbents with high efficiency and improved performance for carbon capture from dilute source.

3D printed reactor-in-a-centrifuge (RIAC): Making flow-synthesis of nanoparticles pump-free and cost-effective

It is widely recognised that flow-reactors offer greater control over the stoichiometry of chemical reactions when compared to batch methods, since they provide finer and more predictable regulation over the transport of fluids and chemical species. These characteristics are of critical importance in the context of nanoparticle production, since the physical and chemical properties of the fluidic environment within a reactor strongly influence the size and/or shape of the end-product. In the past decade, replica moulding techniques (e.g., based on soft-lithography) have been developed to manufacture flow-reactors in a relatively cost-effective and efficient fashion. However, devices are often operated using multiple syringe pumps, and several of these techniques require laborious and multi-step procedures. In this study, we developed rapidly prototyped reactors embedded within a cylindrical structure that are designed for actuation using a laboratory centrifuge (herein referred to as reactor-in-a-centrifuge, or RIAC). Using RIACs of different architecture, we demonstrated production of nanoscale liposomes of therapeutically relevant size (in the diameter range 80 – 300 nm) under varying operating conditions. We also demonstrated production of silver nanospheres (with UV–vis absorption maxima of 404 nm) at selected operating conditions. The novel concept proposed in this study has the potential to significantly simplify the synthesis of nanomaterials over more commonly used microfluidic techniques, as it relies on a cost-effective and single-step reactor manufacturing process (using a desktop 3D printer) and employs widely available laboratory centrifuges to drive reagents through the reactor. In this paper we describe RIAC’s design, manufacturing, and actuation protocols, and demonstrate its applicability to the flow synthesis of nanoparticles without relying on highly specialised instrumentation or costly procedures.

Expanding the library of nitrogen enriched polybenzoxazine thermosets prepared from side-chain type benzoxazines functionalized with polyethylenimine

We present a simple methodology to develop nitrogen enriched polybenzoxazine thermosets by integrating polybenzoxazine network with polyethylenimine (PEI). Thermosets have been developed by polymerizing side-chain type resins, which have been prepared by introducing benzoxazine moieties on the amine terminated branches of nitrogen enriched PEI, using cardanol and eugenol as bio-based phenols. The aim of this study is to investigate the potential of benoxazines synthesized using different bio-based phenols and PEI, on the performance of nitrogen enriched thermosets, as well as to contribute in the array of side-chain type benzoxazine resins. The present work is a next leg of our previously reported article on the synthesis of side-chain type benzoxazine resins using guiacol and PEI (G-pei), where the reaction parameters such as reaction medium, time, and stoichiometry were optimized. It is to be noted that, due to relatively better performance of G-pei resins prepared at 8:1:16 and 10:1:20 (phenol: amine: paraformaldehyde) molar ratio, the same stoichiometry has been specifically adopted for the preparation of cardanol and eugenol-based analogous resins in the present work. The functionalization of PEI with benzoxazine as side-chains, has been confirmed using FTIR, 1H, 13C NMR spectroscopy techniques. Polar amine groups as well as alkyl chains of phenols, are expected to alter the polymerization behaviour of oxazine moieties and the same has been investigated using DSC studies, where the curing profiles display exotherms in the temperature range of 208–222 °C. Further, rheological studies suggest solvent-less processing for cardanol based resins. Polybenzoxazine network bonded with polyethyleneimine has been confirmed from FT-IR spectra of cured thermosets, and the nitrogen content has been evidenced from elemental analysis. Furthermore, the thermal stability of the crosslinked materials has been investigated using thermogravimetric analysis (TGA), while the glass transition temperature for the cured specimens has been obtained by dynamic mechanical analysis (DMA). Moreover, polarity associated with the polybenzoxazine network as well as nitrogen enriched amine, is expected to affect the surface property of the end materials, which has been investigated by performing contact angle measurements on the surface of cured thermosets. Lap shear adhesion experiments have been additionally performed using ASTM D1002 standard, and the results indicates relatively good wettability of cardanol based resins.

Investigation of phenolic ionic liquids as efficient nitric oxide absorbents

A series of phenolic ILs with different cations were synthesized and used for the capture of nitric oxide (NO) in this work. These phenolic ILs showed excellent absorption performance because of the chemical interaction between the phenolate anion and the acidic NO. In particular, their absorbability for NO was largely affected by the cationic bond-donating ability. Tetrabutylphosphonium phenolate ([P4444][PhO]) was thus highlighted with the cation of weak bond-donating ability, reaching a maximum solubility of 1 mol NO/mol IL at 1 bar and 313.2 K. With the assumption of complex formation between NO and phenolic ILs, the reaction equilibrium thermodynamic model (RETM) was constructed to correlate the experimental solubilities. Therefore, thermodynamic parameters such as the Henry’s law constant Hm, the reaction equilibrium constants K, the enthalpy ΔHSOL and the entropy ΔSSOL could be achieved to evaluate the absorption performance of NO in the phenolic ILs. Furthermore, through a combination of experimental solubilities, RETM fitting results and spectroscopic investigations, the absorption mechanism was proposed that there was a chemical interaction between NO and the O-site on the phenolate anion, with the reaction stoichiometry of 1:1 and 2:1. All these data showed that the phenolic ILs may be used as a kind of promising absorbents for NO capture.

PENGGUNAAN STRATEGI PEMBELAJARAN AKTIF UNTUK MENINGKATKAN EFEKTIVITAS PEMBELAJARAN

: This study aims to find a strategy for effective learning and teaching materials Efficient in reaction stoichiometry for students in SMAN 5 South Bengkulu by enabling students to learning. Strategies in the classroom action research was conducted in two cycles and in each cycle includes planning, implementation, observation and reflection. Meanwhile, to enable students in this study, researchers used a worksheet given to students in large groups and small groups. Which is the subject of the study of this class action is a class X IPA.1 SMAN 5 South Bengkulu being the object is learning the material stoichiometric chemical reactions on subjects that are taught in a way to enable students in small groups and large groups. From research conducted by examining the initial conditions of students as measured by means of a written test and the results of classroom action research with two cycles seen an increase results achieved by students in mastering the material stoichiometry given. Increasing mastery of this material from the first cycle of students can be increased by 28.5% from the initial conditions being on the conditions in the first cycle after the action on the second cycle increased by 39.36%. The results of this class action, the researchers recommend the policy maker or implementer of learning in this case the teachers to teach the learning material in small groups and with techniques to enable the students. Keywords : 1. Active Learning. 2. Effective Learning. 3. reaction stoichiometry.

The role of energy, serine, glycine, and 1-carbon units in the cost of nitrogen excretion in mammals and birds

The efficiency with which dietary protein is used affects the nitrogen excretion by the animal and the environmental impact of animal production. Urea and uric acid are the main nitrogen excretion products resulting from amino acid catabolism in mammals and birds, respectively. Nitrogen excretion can be reduced by using low-protein diets supplemented with free amino acids to ensure that essential amino acids are not limiting performance. However, there are questions whether the capacity to synthesize certain nonessential amino acids is sufficient when low-protein diets are used. This includes glycine, which is used for uric acid synthesis. Nitrogen excretion not only implies a nitrogen and energy loss in the urine, but energy is also required to synthesize the excretion products. The objective of this study was to quantify the energy and metabolic requirements for nitrogen excretion products in the urine. The stoichiometry of reactions to synthesize urea, uric acid, allantoin, and creatinine was established using information from a publicly available database. The energy cost was at least 40.3, 60.7, 64.7, and 65.4 kJ/g excreted N for urea, uric acid, allantoin, and creatinine, respectively, of which 56, 56, 47, and 85% were retained in the excretion product. Data from a broiler study were used to carry out a flux balance analysis for nitrogen, serine, glycine, and so-called 1-carbon units. The flux balance indicated that the glycine intake was insufficient to cover the requirements for growth and uric acid excretion. The serine intake was also insufficient to cover the glycine deficiency, underlining the importance of the de novo synthesis of serine and glycine. One-carbon units are also a component of uric acid and can be synthesized from serine and glycine. There are indications that the de novo synthesis of 1-carbon units may be a “weak link” in metabolism, because of the stoichiometric dependency between the synthesized 1-carbon units and glycine. The capacity to catabolize excess 1-carbon units may be limited, especially in birds fed low-protein diets. Therefore, there may be an upper limit to the 1-carbon-to-glycine requirement ratio in relation to nutrients that supply 1-carbon units and glycine. The ratio can be reduced by increasing uric acid excretion (i.e., reducing protein deposition) or by dietary supplementation with glycine. The hypothesis that the 1-carbon-to-glycine requirement ratio should be lower than the supply ratio provides a plausible explanation for the growth reduction in low-protein diets and the positive response to the dietary glycine supply.

Immobilization of NPP evaporator bottom high salt-bearing liquid radioactive waste into struvite-based phosphate matrices

The high salt-bearing liquid radioactive waste (evaporator bottoms, EB) makes up the most voluminous NPP waste and needs solidification. In the paper presented, we introduce a novel formation process study of the struvite-based phosphate matrices ((K, NH4)MgPO4·6H2O) and the developed phosphate matrix compositions for the solidification of high salt-bearing solutions. The solutions simulate the EB of nuclear power plants with pressurized water reactors (NPP PWR). The effect of the EB's composition and salt content on the matrices' mechanical strength was investigated. The cesium-selective nickel-potassium ferrocyanide sorbent or 10–20% of MgO over the reaction stoichiometry, introduced at the matrix synthesis stage, allowed the production of matrices with the average 137Сs leach rate of less than 10-3 g cm-2 day-1 and the mechanical strength over 5 MPa. The matrices obtained completely satisfied the cemented radioactive waste requirements and contained up to 17–17.5 wt% of salts, which was 1.7–2.5 times higher compared to the Portland cement-based matrices.

Are seep carbonates quantitative proxies of CH4 leakage? Modeling the influence of sulfate reduction and anaerobic oxidation of methane on pH and carbonate precipitation

Seep carbonates tell us where and when CH4-charged fluids escaped from the subsurface, thus providing qualitative information to reconstruct the activity of petroleum systems. The potential of seep carbonates as quantitative proxies for the amount of CH4 leaked, however, remains largely unexplored, which limit their applicability as exploration tools. This paper tackles the quantification of the CH4 flux - seep carbonate relationship by simulating the coupled sedimentary carbon (C) – sulfur (S) cycles in a reaction-transport modeling (RTM) framework. We first establish a theoretical basis demonstrating that the stoichiometry of diagenetic reactions and the ambient pH of pore waters are the main drivers of the rate of change in the saturation state of carbonate minerals (ΩCal), while the concentrations of total dissolved inorganic carbon and sulfide are only of secondary importance. It results that anaerobic oxidation of methane (AOM) is the main driver of carbonate precipitation, while organoclastic sulfate reduction (SR) has a minor impact. We further show that SR mostly drives carbonate dissolution, but can also contribute to precipitation when pH is low (<7–7.1). The RTM simulations reveal that an increase in upward fluid flow triggers an intensification of peak AOM rates, associated to a shallowing and thinning of the zone of carbonate precipitation. Such behavior leads to an almost linear relationship between the amount of carbonate precipitated and flux of CH4 (nCH4 = 3.3–5.2 * nCaCO3), until, eventually, full cementation occurs. We thus define a “quantitative domain” at moderate fluid flow and a “threshold domain” at high fluid velocities, where full cementation solely provides a lower bound estimate of the amount of CH4 leaked. We also show that in contrast to a traditional view of seep carbonate formation mainly controlled by venting activity, sedimentation rate and water depth also play major roles, via their control on residence time and saturation concentration of CH4, respectively. The interpretation of vertical seep carbonate stacks should thus not solely focus on changes in fluid flow, but also consider changes in sedimentation rate and/or water depth.

Constructing and analysing dynamic models with modelbase v1.2.3: a software update

BackgroundComputational mathematical models of biological and biomedical systems have been successfully applied to advance our understanding of various regulatory processes, metabolic fluxes, effects of drug therapies, and disease evolution and transmission. Unfortunately, despite community efforts leading to the development of SBML and the BioModels database, many published models have not been fully exploited, largely due to a lack of proper documentation or the dependence on proprietary software. To facilitate the reuse and further development of systems biology and systems medicine models, an open-source toolbox that makes the overall process of model construction more consistent, understandable, transparent, and reproducible is desired.Results and discussionWe provide an update on the development of modelbase, a free, expandable Python package for constructing and analysing ordinary differential equation-based mathematical models of dynamic systems. It provides intuitive and unified methods to construct and solve these systems. Significantly expanded visualisation methods allow for convenient analysis of the structural and dynamic properties of models. After specifying reaction stoichiometries and rate equations modelbase can automatically assemble the associated system of differential equations. A newly provided library of common kinetic rate laws reduces the repetitiveness of the computer programming code. modelbase is also fully compatible with SBML. Previous versions provided functions for the automatic construction of networks for isotope labelling studies. Now, using user-provided label maps, modelbase v1.2.3 streamlines the expansion of classic models to their isotope-specific versions. Finally, the library of previously published models implemented in modelbase is growing continuously. Ranging from photosynthesis to tumour cell growth to viral infection evolution, all these models are now available in a transparent, reusable and unified format through modelbase.ConclusionWith this new Python software package, which is written in currently one of the most popular programming languages, the user can develop new models and actively profit from the work of others. modelbase enables reproducing and replicating models in a consistent, tractable and expandable manner. Moreover, the expansion of models to their isotopic label-specific versions enables simulating label propagation, thus providing quantitative information regarding network topology and metabolic fluxes.