Reactivity Of Carbon Research Articles

Polymerization kinetic pathways of epoxidized linseed oil with aliphatic bio‐based dicarboxylic acids

ABSTRACTThe curing of epoxidized linseed oil (ELO) with three different bio‐based dicarboxylic acids (sebacic acid, suberic acid, and succinic acid) has been investigated. No accelerators or catalysts were used and the resulting thermosets are 100% bio‐based. Structural investigations of the three crosslinked ELO resins were made using FTIR spectroscopy and TMA, that is, tensile tests, TGA, and DMA. As evidenced by FTIR measurements ELO and dicarboxylic acids reacts but no major differences can be distinguished between the dicarboxylic acids. Non‐isothermal curing has been conducted by rheological and DSC measurements. Advanced isoconversional analysis applied to DSC data in association with the complex viscosity variations gives new insights into the polymerization mechanism. The length of dicarboxylic acid carbon chain modifies the reaction rate. Then, a correlation between reaction rate, activation energy, pre‐exponential factors, polymerization mechanism, and change in rate‐limiting step was shown. DMA and tensile tests highlight the relationship between the carbon chain length, reactivity, and thermomechanical properties. The use of succinic acid allows reaching a higher Tg and thermal stability.

Adsorption of Mercury from a Cyanide Leaching Solution Using Various Activation Rates of Granular Activated Carbon: A Laboratory- and Industrial-Scale Study

The use of granular activated carbon (GAC) is a typical and sustainable technique for recovering precious metals from a cyanide leaching solution (CLS). The level of GAC activity is a fundamental factor in assessing the rate of precious metal adsorption; thus, it is essential to determine the efficiency of carbon elution for reproducing GACs. Since mercury (Hg) adsorption plays a critical role, economically and environmentally, in GAC efficiency, we conducted various laboratory and industrial experiments to explore the effect of different rates of GAC activation (10%, 35%, 70% and 100%) on Hg adsorption from CLS. Assessments of laboratory test results showed a direct relationship between the Hg adsorption and GAC activity; by increasing the GAC activity from 10% to 100%, the recovery of Hg was increased from 20% to 41%. Kinetic modeling results indicated that the Hg adsorption for all GAC activities followed chemisorption mechanisms. There was good agreement between the laboratory test results and the results of experiments on the industrial scale (that used a continuous circuit). These outcomes indicate that by increasing the frequency of carbon reactivation and using GAC with a high level of activity in the first tank, Hg desorption was meaningfully decreased and recovery was improved (for 10% GAC activity vs. 35% GAC activity, recovery was 40% vs. 90%, respectively).

Reactivation Process of Activated Carbons: Effect on the Mechanical and Adsorptive Properties.

Carbon reactivation is a strategy to reduce waste and cost in many industrial processes, for example, effluent treatment, food industry, and hydrometallurgy. In this work, the effect of physical and chemical reactivation of granular activated carbon (AC) was studied. Spent activated carbon (SAC) was obtained from a carbon in pulp (CIP) leaching process for gold extraction. Chemical and physical reactivations were evaluated using several acid-wash procedures (HCl, HNO3, H2SO4) and thermal treatment (650–950 °C) methods, respectively. The effect of the reactivation processes on the mechanical properties was evaluated determining ball pan hardness and normal abrasion in pulp resistance. The effect on the adsorptive properties was evaluated via the iodine number, the gold adsorption value (k expressed in mg Au/g AC), and Brunauer–Emmett–Teller (BET) surface area. Initial characterization of the SAC showed an iodine number of 734 mg I2/g AC, a k value of 1.37 mg Au/g AC, and a BET surface area of 869 m2/g. The best reactivation results of the SAC were achieved via acid washing with HNO3 at 20% v/v and 50 °C over 30 min, and a subsequent thermal reactivation at 850 °C over 1 h. The final reactivated carbon had an iodine number of 1199 mg I2/g AC, a k value of 14.9 mg Au/g AC, and a BET surface area of 1079 m²/g. Acid wash prior to thermal treatment was critical to reactivate the SAC. The reactivation process had a minor impact (<1% change) on the mechanical properties of the AC.

Organic Carbonate Production Utilizing Crude Glycerol Derived as By-Product of Biodiesel Production: A Review

As a promising alternative renewable liquid fuel, biodiesel production has increased and eventually led to an increase in the production of its by-product, crude glycerol. The vast generation of glycerol has surpassed the market demand. Hence, the crude glycerol produced should be utilized effectively to increase the viability of biodiesel production. One of them is through crude glycerol upgrading, which is not economical. A good deal of attention has been dedicated to research for alternative material and chemicals derived from sustainable biomass resources. It will be more valuable if the crude glycerol is converted into glycerol derivatives, and so, increase the economic possibility of the biodiesel production. Studies showed that glycerol carbonate plays an important role, as a building block, in synthesizing the glycerol oligomers at milder conditions under microwave irradiation. This review presents a brief outline of the physio-chemical, thermodynamic, toxicological, production methods, reactivity, and application of organic carbonates derived from glycerol with a major focus on glycerol carbonate and dimethyl carbonate (DMC), as a green chemical, for application in the chemical and biotechnical field. Research gaps and further improvements have also been discussed.

Tracking the evolution of particulate organic matter sources during summer storm events via end-member mixing analysis based on spectroscopic proxies

Despite the growing attention to the effects of hydrological precipitation on organic carbon export along the continuum land-river-ocean, limited effort has been made to understand the export and the reactivity of particulate organic carbon (POC) compared to those of dissolved organic carbon (DOC). Yet, further understanding of the controlling mechanisms on the export of particulate organic matter (POM) from terrestrial systems is fundamental. In this study, we assessed the temporal changes of the source contributions to riverine POM in two adjacent rivers of the same watershed during two summer storm events, which included the early and the late events, using end-member mixing analysis (EMMA) based on spectroscopic proxies. The EMMA showed relatively high contributions of terrestrial materials to the riverine POM for both rivers during the early summer storm event. However, this trend did not persist until the late summer storm event, which presented the decreased contributions of the terrestrial sources and less dynamic changes in the source distributions compared to those observed in the early summer rain event. These results demonstrate the combined impacts of the land use/surrounding area, the hydrology, and the intra-seasonal variations on the dominant riverine POM sources. This study provides an interesting insight into the importance of the intense hydrological events on the export of the terrestrial OM and further on the potential modification of the existing carbon mass balance along the continuum land-river-ocean.

Solvent Effects on Thiol–Ene Kinetics and Reactivity of Carbon and Sulfur Radicals

The thiol-ene reaction is one of the fundamental reactions in biochemistry and synthetic organic chemistry. In this study, the effect of polar media on the reaction kinetics is taken into account by using the transition state theory; the reactivities of the carbon and sulfur radicals have also been rationalized by using conceptual DFT. The results have shown that the solvents have more impact on hydrogen atom transfer reactions and the chain transfer rate constant, kCT, can be increased by using nonpolar solvents, while propagation reactions are less sensitive to media. Similarly, the kP/kCT ratio can be manipulated by changing the environment in order to obtain tailor-made polymers. Regarding the DFT descriptors, the local and global electrophilicity indices are well correlated with the propagation rate constant kP, whereas the global electrophilicity index is associated with the chain transfer rate constant kCT. Overall, electrophilicity indices can be used with confidence to predict the kinetics of thiol-ene reactions.

Capture and Reactivity of an Elusive Carbon-Sulfur Centered Biradical.

The initial oxidation product of dimethyl sulfide in the marine boundary layer, the methyl thiomethyl radical, has remained elusive. A structurally analogous biradical with one radical center in the α-position to a sulfur atom could now be obtained by UV irradiation of p-nitrobenzaldehyde dithiane isolated in solid dinitrogen (N2) or Ar at cryogenic temperatures. A spin-forbidden reaction with triplet dioxygen (3O2) does not occur. The dithiane of o-nitrobenzaldehyde rather undergoes a series of rearrangements under the same conditions, resulting in overall photodeprotection.

Enhanced reactivity and mechanisms of mesoporous carbon supported zero-valent iron composite for trichloroethylene removal in batch studies

Ordered mesoporous carbon (CMK-3) supported nanoscale zero-valent iron (nZVI) composites were synthesized and used for the removal of trichloroethylene (TCE). The nZVI/CMK-3 composites exhibited high TCE removal efficiency in a batch study, which was 2.5 times that of nZVI alone. They also displayed excellent reusability, with 65.2% removal efficiency after three treatments. Dechlorination dominated the process of TCE removal (75.3%–79.4%), whereas adsorption accounted for 20.6%–24.7%. CMK-3 enhanced the dechlorination rate and efficiency of TCE by nZVI, and the enhancement was favored with the increase in CMK-3 content. The Tafel analysis and H2 evolution experiments indicated the mechanisms of CMK-3 action in nZVI/CMK-3 composites for TCE removal. CMK-3 serves as a direct electron transfer, whereas CO was identified as the functional group involved; the other involved the acceleration of redox reaction of atomic hydrogen owing to the superior hydrogen adsorption capacity of CMK-3. The present study provides new perspectives for seeking more efficient nZVI to reinforce the dechlorination process; however, more studies are warranted in the long-term performance of nZVI/CMK-3 in the aquifer condition.

Separation of asphalt from carbonate ore surfaces by reactive extraction: Kinetics and modelling

Separation of asphalt from carbonate unconventional ores is a challenge due to the strong interactions between carbonate mineral surfaces and asphalt. Our previous results show that the reactive extraction process performs well in recovering both extra-heavy oil and minerals from carbonate oil ores (RSC Adv. 2019, 9: 14372–14381). Herein, further tests have been conducted to understand the kinetics of the reactive extraction. It is found that the reaction kinetics of carbonate minerals in asphalt rocks is beyond the description of traditional reaction shrinking-core model. This is mainly ascribed to the coating of asphalt on the carbonate mineral surface. To mathematically describe the reaction kinetics, a modified reaction shrinking-core model has been proposed considering the unreacted oil on the mineral surface by adding a coverage coefficient θ in the kinetic model. Results show that this modified shrinking-core kinetic model works well in describing the real reaction (R2 > 0.96) under different conditions. In addition, the thermodynamic properties, including the apparent active energy, enthalpy change, entropy change, Gibbs free energy change, and pre-exponential factor of this reactive extraction process are also determined for this kind of ores. This work would provide a primary insight into predicting the reactive extraction with different kinds of reactive carbonate minerals or other similar oil ores with dissolved minerals.

Thermochemical energy storage properties of a barium based reactive carbonate composite

A reactive carbonate composite leads to destabilisation of BaCO3 and increased reaction kinetics by the addition of CaCO3.

Dual carbon isotope (δ13C and Δ14C) characterization of particulate organic carbon in the Geum and Seomjin estuaries, South Korea

We investigated the source, composition, and reactivity of particulate organic carbon (POC) in two contrasting Korean estuary systems, a closed estuary (Geum) (i.e., with an estuary dam at the river mouth) and an open (Seomjin) estuary. A dual isotope (δ13CPOC and Δ14CPOC) approach was applied to surface water samples collected along a salinity gradient in August 2016. Our results indicate that phytoplankton-derived POC was the main contributor to the total POC pool in the reservoir of the Geum estuary, while terrestrial-derived POC predominated the upper Seomjin estuary. A simple binary mixing model using Δ14CPOC revealed a higher modern POC contribution (87–90%) in the Geum estuary reservoir than that (77%) of the upper Seomjin estuary. Accordingly, it appears that an estuary dam can alter the source and reactivity of POC in a reservoir, which can be transferred to the adjacent coastal ecosystem.

Differences in surface reactivity in two synthetic routes between HiPIMS and DC magnetron sputtered carbon

Diamond-like carbon (DLC) is an amorphous form of carbon with a significant fraction of sp3 bonds. In general, it enjoys high hardness, chemical inertness, and optical transparency. It can be deposited by various chemical (CVD) and physical (PVD) vapor deposition methods, including sputtering, which is an industrially important PVD method. Here we investigate the reactivity of carbon deposited by conventional direct current magnetron sputtering (DCMS) and by the newer high power impulse magnetron sputtering (HiPIMS). Scanning electron microscopy (SEM) showed that HiPIMS produced more compact films. Both types of carbon films were very smooth by atomic force microscopy (AFM): for HiPIMS: 1.20 ± 0.55 nm and for DCMS: 1.55 ± 0.27 nm. X-ray photoelectron spectroscopy (XPS) revealed chemical differences between the two types of carbon surfaces. Two functionalization schemes were investigated. The first consisted of amidation of the surfaces by activation with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy sulfosuccinamide (sulfo-NHS) followed by reaction with a range of water-soluble and insoluble amines, and the second consisted of activation via halogenation with PCl5 or PBr5 followed by subsequent amination. The resulting surfaces were characterized by XPS and wetting. HiPIMS-deposited carbon showed higher levels of amidation. On the other hand, the DCMS surface showed greater functionalization in the halogenation/amination route. These results are consistent with the higher level of oxidized carbon initially found on the HiPIMS surface.

Mechanically Triggered Small Molecule Release from a Masked Furfuryl Carbonate.

Stimuli-responsive polymers that release small molecules under mechanical stress are appealing targets for applications ranging from drug delivery to sensing. Here, we describe a modular mechanophore design platform for molecular release via a mechanically triggered cascade reaction. Mechanochemical activation of a furan-maleimide Diels-Alder adduct reveals a latent furfuryl carbonate that subsequently decomposes under mild conditions to release a covalently bound cargo molecule. The computationally guided design of a reactive secondary furfuryl carbonate enables the decomposition and release to proceed quickly at room temperature after unmasking via mechanical force. This general strategy is demonstrated using ultrasound-induced mechanical activation to release a fluorogenic coumarin payload from a polymer incorporating a chain-centered mechanophore.

Approaches on the understanding of nanoporous carbon reactivity with polyatomic ions

Correlations among atomic structure, chemical reactivity, charge transfer and electronic structure properties were investigated in nanoporous carbon at different mass densities. The model structures have been generated by a heat-quench procedure using Density Functional Theory calculations and first-principles quantum molecular dynamics simulations. Reactive points seem to be highly dependent of the local structure of the material. The results showed that sponge-like nanoporous carbons are good candidates to graft polyoxometalates since they presented a stronger interaction with the carbon substrate. The charge transfer is from the nanoporous carbon to the polyoxometalate and a covalent interaction was observed for a density of 0.75 g/cm3. Our materials developed an electronic band around the Fermi level.

Influence of temperature and Ca(OH)2 on releasing tar and coal gas during lignite coal pyrolysis and char gasification

Abstract The yield of tar and syngas has been investigated by catalytic pyrolysis of Pingzhuang lignite (PZL) over Ca(OH) 2 catalyst in temperature range of 600 °C-1000 °C in a tube furnace. The results show that the yield of volatile pyrolysis increases and char decreases with rising temperature for both raw and catalyzed Pingzhuang lignite. The hydrogen fraction (H 2 ) increased from 20% to 40% for the PZL sample; but, for the PZL-Ca(OH) 2 sample, H 2 fraction fluctuated randomly between 35 to 42%, with the maximum H 2 fraction found at 1000 °C. The Gas-chromatography mass-spectroscopic (GC-MS) analysis revealed that the maximum tar yield at 800 °C and 700 °C was obtained for PZL and PZL-Ca(OH) 2 , respectively. The surface morphology of PZL and PZL-Ca(OH) 2 chars underwent different transformation in the presence of catalyst as illustrated by SEM/EDX, FTIR, and BET analysis. Furthermore, char sample was investigated for the carbon conversion and reactivity index using TGA analysis under N 2 and CO atmosphere.

Lipase catalyzed modification of functionalized polyester binders

Non-toxic coating formulations, i.e. without isocyanate, formaldehyde and toxic amines are a topic in the coating industries since decades. The replacement of cross-linking agents or functional groups to non-toxic compounds reduced often the mechanical properties of the coating film or just one toxic compounds are replaced by another toxic one. In the presenting work a biocatalytic route to functionalized polyester is presented forming reactive cyclic carbonates on the resin. The resin could be cross-linked by catalytic amount of amine to form a polyester-network with promising mechanical properties in comparison to polyester-melamine networks.

Effect of bicarbonate and oxidizing conditions on U(IV) and U(VI) reactivity in mineralized deposits of New Mexico

We investigated the effect of bicarbonate and oxidizing agents on uranium (U) reactivity and subsequent dissolution of U(IV) and U(VI) mineral phases in the mineralized deposits from Jackpile mine, Laguna Pueblo, New Mexico, by integrating laboratory experiments with spectroscopy, microscopy and diffraction techniques. Uranium concentration in solid samples from mineralized deposit obtained for this study exceeded 7000 mg kg−1, as determined by X-ray fluorescence (XRF). Results from X-ray photoelectron spectroscopy (XPS) suggest the co-existence of U(VI) and U(IV) at a ratio of 19:1 at the near surface region of unreacted solid samples. Analyses made using X-ray diffraction (XRD) and electron microprobe detected the presence of coffinite (USiO4) and uranium-phosphorous‑potassium (U-P-K) mineral phases. Imaging, mapping and spectroscopy results from scanning transmission electron microscopy (STEM) indicate that the U-P-K phases were encapsulated by carbon. Despite exposing the solid samples to strong oxidizing conditions, the highest aqueous U concentrations were measured from samples reacted with 100% air saturated 10 mM NaHCO3 solution, at pH 7.5. Analyses using X-ray absorption spectroscopy (XAS) indicate that all the U(IV) in these solid samples were oxidized to U(VI) after reaction with dissolved oxygen and hypochlorite (OCl−) in the presence of bicarbonate (HCO3−). The reaction between these organic rich deposits, and 100% air saturated bicarbonate solution (containing dissolved oxygen), can result in considerable mobilization of U in water, which has relevance to the U concentrations observed at the Rio Paguate across the Jackpile mine. Results from this investigation provide insights on the reactivity of carbon encapsulated U-phases under mild and strong oxidizing conditions that have important implication in U recovery, remediation and risk exposure assessment of sites.

Multiscale modeling of CO2-induced carbonate dissolution: From core to meter scale

Reactive transport models can be used to predict the long-term storage capacity of CO2 in carbonate formations if the parameters that couple physical and chemical interactions can be calibrated from centimeters (laboratory-scale) to kilometers (field-scale). However, calibration across length scales is challenging in highly reactive and heterogeneous carbonate reservoirs. In this study we translated simulations of CO2-induced carbonate dissolution and transport processes of centimeter-sized cores to meter-sized rock blocks. The meter-sized rocks represent an intermediate scale between laboratory experiments and field demonstrations.We conducted brute-force, meter-sized simulations maintaining the same grid resolution used to successfully model rock heterogeneities and physical behaviors observed in laboratory experiments. To do this, we applied multi-point statistics to generate rock heterogeneity that honors characterization data, and adopted the reaction and transport parameters (e.g., reaction rate kinetics, porosity-permeability relationship) from models calibrated by core-flood experiments.We used the high-resolution simulation data sets to understand the interplay between carbonate reactivity, flow velocity, and rock heterogeneity on the development and consequences of dissolution fronts at a meter scale, and in particular how parameters that couple chemistry and transport change at variable length scales. The modeling results reveal scale dependence of porosity-permeability relationship and carbonate reactivity. We found that upscaling reactive transport processes from centimeters to meters requires: (1) Effective representation of initial rock heterogeneity and related preferential flow field. In more permeable rocks, several dissolution fingers or wormholes form and grow along the flow direction, competing for reactive solution and leading to fast breakthrough. In less permeable rocks, a single dissolution channel forms with a dramatic increase in lateral branching due to the resistance from low-permeability regions along the flow path. (2) Higher exponential values for porosity-permeability power-law correlations. The value of the power parameter n increases by about two times as we scale the dissolution process from centimeters to meters. (3) Lower carbonate reaction rates. Carbonate reaction rates obtained for meter-sized models are about ten times slower than those for the smaller core-flood experiments. We also used the high-resolution meter-sized simulations to upscale carbonate dissolution by coarsening the representative elementary volumes (or grids). The calibrated reactive transport parameters are consistent with those derived from scaling analysis.The upscaling analysis developed in this study improves our understanding of carbonate dissolution (especially wormhole development) and associated reactive transport across time and length scales, providing a useful basis for establishing a direct relationship between core-scale and field-scale models. Additional work is needed to see if relationships developed from single-phase reactive transport processes shown in this work are directly applicable to in-situ reservoir multiphase flow conditions arising from geological storage of CO2.

Surface reactivity of nanoporous carbons: preparation and physicochemical characterization of sulfonated activated carbon fibers

Here, we have examined the nanoporous activated carbon fibers (ACFs) sulfonated using the direct sulfonation and the staged method that included bromination, followed by sulfidation and oxidation. TEM confirmed the nanoporous structure of the prepared sulfonated ACFs. Nitrogen porometry and 2D nonlocal DFT simulations showed the nanoporosity reduction and variations of the pore size distribution because of the functionalization. Comparison of parameters of the SO3H groups confined in nanopores, e.g., the thermal stability and catalytic potential, showed that the most efficient acid sites, in the catalytic 2-propanol dehydration to propylene, are the SO3H groups grafted by the staged Houben–Weil methods. From the productivity of reactions used at the preparation stage, and in contrast to the one-staged aromatic substitution, the bromine addition to π sites of the edges of carbon matrix supplies enough active sites and is a reason for further high yields of the grafted thermostable SO3H groups. Hydrolysis of the grafted bromine and the surface oxidation of nanopores walls are parallel reactions that lowered the SO3H-related acidity, increasing the total acidity to 1.5 mmol g−1. The reported nanoporous sulfonated ACFs are effective to be used in the dehydration reactions catalyzed by solid acids.

Physical characterization and alkali carbonate reactivity (ACR) potential of the rocks from Bauhti Pind and Bajar area Hassan Abdal, Pakistan

This study is conducted to evaluate aggregate characteristics and alkali carbonate reactivity (ACR) potential of carbonate rocks of the Bouhti Pind and Bajar area, Hassan Abdal, Pakistan. Physical and chemical tests were performed to assess aggregate suitability. Mean specific gravity (2.65–2.65), water absorption (0.51–0.68%), Los Angeles abrasion (24.78–26.10%) and sulphate soundness values (2.86–4.25%) of the carbonate rocks of these areas are within specified limits of their respective standards. Petrographic studies of Bajar area reveal the presence of 96.3% calcite, 2% clays, 1% hematite and 0.7% quartz. These rocks do not contain dolomite and show no expansion in rock cylinder test. Therefore, the aggregate is not prone to ACR and can be used in cement concrete. Rocks of Bouhti Pind area have mean 92% calcite, 3.8% dolomite, 2% clays, 1.2% hematite and 1% monocrystalline quartz. The amount of deleterious minerals specifically dolomite and clays are below the maximum allowed limit to initiate ACR. However, one of the rock cylinders shows 0.043% expansion which is below threshold limit of 0.10% to cause ACR as specified in ASTM C-585. Hence, these carbonate rocks qualify physical characterization and ACR tests and can be used in the construction of roads and in cement concrete.