Second-order Reaction Research Articles

Insight into the synergistic behaviors of a hydroxyethyl cellulose-based graft copolymer in the mitigation of silica scaling: Combined static and reverse osmosis tests

Silica scaling has become a common problem in membrane systems due to the ubiquity of silica in the natural environment. In this work, a series of N-[3-(dimethylamino)propyl]methacrylamide-grafted hydroxyethyl cellulose (DHEC) with different grafting ratios was designed and used as a silica scaling inhibitor. The performances and mechanisms of DHEC in the inhibition of silica scaling were evaluated in detail by static and reverse osmosis (RO) tests. The maximum inhibition efficiency of DHEC with the grafting ratio of 97% reached as high as 77.20% ± 0.26% in the static test. The permeate flux in the presence of this DHEC gradually decreased and was eventually maintained at 89.12% after 10 h of RO operation. The efficient mitigation of silica scaling was ascribed to the synergistic effect of the grafted copolymer, specifically, the hydrophilic cellulose backbone of DHEC exerted a dispersion effect and the cationic grafted chains acted as aggregators to inhibit silica scaling in the solution and at the membrane surface. This synergistic effect cannot delay the induction time of silica polymerization but can change the dominant mode of polymerization in the solution from the first-order to the second-order reaction as confirmed by the kinetic study. Thus, DHEC is an efficient and environmentally friendly inhibitor with high application potential for membrane fouling control in RO operations.

Activation of inert triethylene tetramine-cured epoxy by sub-critical water decomposition

Cured epoxy is stable and difficult to be recycled. To make the inert cured epoxy and its derivatives or composites reactive is still a challenge. In this study, sub-critical water was used to decompose the solid diglycidyl ether-based epoxy resin (bisphenol A and bisphenol F) cured with triethylene tetramine (TETA) to reactive species. First of all, the thermally most unstable bonds in the epoxy resin underwent homogeneous cleavage reaction. Next, the generated free radicals were saturated by extracting hydrogen from the sub-critical water. The decomposition rate was improved with increasing the temperature and reaction time. During the reaction, breakage occurs preferentially in the epoxy resin main chain because of the existence of ether groups. The compounds evolved and the decomposition was analyzed. The experimental outcomes revealed that the decomposition mechanism of diglycidylether of bisphenol A (DGEBA)/TETA and diglycidylether of bisphenol F (DGEBF)/TETA resin regimes in sub-critical water may include side group elimination, random fracture and unzipping. Moreover, a segmented second-order kinetic analysis of the decomposition process was performed. The decomposition processes of two resins in sub-critical water were divided into two stages. Both stages were second-order reaction, the activation energy of DGEBA/TETA was 175 kJ/mol (Ea1(15-45min)), and 612 kJ/mol (Ea2(52.5-75min)). The activation energy of DGEBF/TETA was 258 kJ/mol (Ea1(15-45min)), and 686 kJ/mol (Ea2(52.5-75min)), respectively. This study provides a way for recycling inert epoxy wastes from different industrial fields and generating reactive and functional polymers.

Precipitation of silica by CO2 bubbles/microbubbles and kinetics research

In China, the production of silica is mainly achieved through its precipitation process. Carbonization of precipitated silica makes full use of carbon-containing flue gases, such as lime kiln gas, thereby reducing the cost of silica production and making it an effective way of CO2 resource utilization. It is an important research field of cleaner production. The research in this study focuses on the production of precipitated silica through carbonation. This study evaluated the impact of Na2O·3.45SiO2 concentration and carbonization temperature during the process. The pH and temperature of the suspension were observed in order to evaluate the proposed process and contrast it with the traditional bubble generator process. The optimization of carbonization mass transfer by microbubbles was preliminarily studied by experiments and computational analysis methods. The results demonstrated that when the Na2O·3.45SiO2 concentration was at 0.2 mol/L and the temperature was 60 °C, the microbubbles could improve the efficiency of CO2 utilization by 1.9 times. The research on the specific surface area (BET) of the prepared silica powder revealed that BET decreased with the increase of Na2O·3.45SiO2 concentration when bubbling was present. Under bubbling/microbubble conditions, when the temperature was 60 °C, with the Na2O·3.45SiO2 concentration increased from 0.1 M to 0.5 M, the BET decreased by 29.2% and 16.8%, respectively. However, when the concentration of Na2O·3.45SiO2 increased to 0.5 M, the introduction of microbubbles made the BET higher than the bubble by 13.3%. Under bubbling/microbubble conditions, when the temperature increased from 25 °C to 60 °C, BET decreased with the increase of temperature, with the BET decreased by 13.5% and 12.8%, respectively. Furthermore, the kinetics of carbonation at room temperature and 0.2 mol/L Na2O·3.45SiO2 with bubbling were calculated. The results showed that carbonation was pseudo second-order reaction process. The process realized the solid waste utilization of CO2, and had important guiding significance for the preparation of high-performance silica.

Kinetic mechanism of wheat straw pellets combustion process with a thermogravimetric analyser

In this study, the combustion characteristics of two wheat straw pellets (WSP) (T1: 100% wheat straw and T5: 70% wheat straw; 10% sawdust, 10% biochar; 10% bentonite clay) were performed at a heating rate 20 °C/min under a temperature from 25 to 1200 °C in air atmosphere. A thermogravimetric analyser (TGA) was used to investigate the activation energy (Eα), pre-exponential factor (A), and thermodynamic parameters. The DTG/TG profile of WSP was evaluated by model-free and model-based methods and found the model-based method was suitable for WSP thermal characterisation. The result demonstrates that the thermal decomposition occurred in four stages, comprising four consecutive reaction steps. A→B→C→D→E→F. Further, the model-based techniques were best fitted with kinetic reaction models like Cn (nth-order reaction with auto-catalyst), Fn (reaction of nth order), F2 (second-order phase interfacial reaction) and D3 (diffusion control). The average Eα for Fn, Cn, D3 and F2 models were 164.723, 189.782, 273.88, and 45.0 kJ/mol, respectively, for the T1 pellets. Alternatively, for T5 pellets, the A was 1.17E+2, 1.76E+16, 5.5E+23, and 1.1E+3 (1/s) for F2, D3, Cn and Fn models. Overall, the thermodynamic properties showed that WSP thermokinetic reactions were complex and multi-point equilibrium, indicating a potentiality as a bioenergy feedstock.

Exposure of the static magnetic fields on the microbial growth rate and the sludge properties in the complete-mix activated sludge process (a Lab-scale study)

BackgroundIn this study, the effect of static magnetic fields (SMFs) on improving the performance of activated sludge process to enhance the higher rate of microbial growth biomass and improve sludge settling characteristics in real operation conditions of wastewater treatment plants has been investigated. The effect of SMFs (15 mT), hydraulic retention time, SRT, aeration time on mixed liquor suspended solids (MLSS) concentrations, mixed liquor volatile suspended solids (MLVSS) concentrations, α-factor, and pH in the complete-mix activated sludge (CMAS) process during 30 days of the operation, were evaluated.ResultsThere were not any differences between the concentration of MLSS in the case (2148.8 ± 235.6 mg/L) and control (2260.1 ± 296.0 mg/L) samples, however, the mean concentration of MLVSS in the case (1463.4 ± 419.2 mg/L) was more than the control samples (1244.1 ± 295.5 mg/L). Changes of the concentration of MLVSS over time, follow the first and second-order reaction with and without exposure of SMFs respectively. Moreover, the slope of the line and, the mean of α-factor in the case samples were 6.255 and, − 0.001 higher than the control samples, respectively. Changes in pH in both groups of the reactors were not observed. The size of the sluge flocs (1.28 µm) and, the spectra of amid I' (1440 cm−1) and II' (1650 cm−1) areas related to hydrogenase bond in the case samples were higher than the control samples.ConclusionsSMFs have a potential to being considered as an alternative method to stimulate the microbial growth rate in the aeration reactors and produce bioflocs with the higher density in the second clarifiers.

Analytical refractory period distribution for a class of time-variant biochemical systems with second-order reactions.

Refractory period (RP), the waiting time between signals, can induce complex signaling dynamics, such as acceleration, adaptation, and oscillation, within many cellular biochemical networks. However, its underlying molecular mechanisms are still unclear. Rigorously estimating the RP distribution may be essential to identify its causal regulatory mechanisms. Traditional methods of estimating the RP distribution depend on solving the underlying Chemical Master Equations (CMEs), the dominant modeling formalism of biochemical systems. However, exact solutions of the CME are only known for simple reaction systems with zero- and first-order reactions or specific systems with second-order reactions. General solutions still need to be derived for systems with bimolecular reactions. It is even more challenging if large state-space and nonconstant reaction rates are involved. Here, we developed a direct method to gain the analytical RP distribution for a class of second-order reaction systems with nonconstant reaction rates and large state space. Instead of using the CME, we used an equivalent path-wise representation, which is the solution to a transformed martingale problem of the CME. This allowed us to bypass solving a CME. We then applied the method to derive the analytical RP distribution of a real complex biochemical network with second-order reactions, the Drosophila phototransduction cascade. Our approach provides an alternative to the CMEs in deriving the analytical RP distributions of a class of second-order reaction systems. Since the bimolecular reactions are common in biological systems, our approach could enhance understanding real-world biochemical processes.

Crystallization kinetics of Sb70Se30 thin films for phase change memories under the non-isothermal conditions

We investigate the non-isothermal crystallization kinetics of Sb70Se30 thin films using differential scanning calorimetry and determine the kinetic triplet of Sb70Se30 thin films at various heating rates by combining model-free and model-fitting approaches. The results indicate that the crystallization activation energy decreases with increasing crystallization fraction α, confirming the presence of multi-step crystallization mechanism. In accordance with the local Avrami index n(α), the crystallization mechanism shifts from three-dimensional growth with an increased nucleation rate at 0.05 ≤ α ≤ 0.8 to three- and two-dimensional growth with a reduced nucleation rate at α＞0.8. Afterwards, we deduce that the Sb70Se30 thin films follow a second-order reaction model within the heating rate range of 20 to 40 K/min. Moreover, the Sb70Se30 thin film shows excellent data retention capability when predicting data processing and data storage time based on phase change memory units. These findings provide valuable insights into the crystallization kinetics of Sb70Se30 thin films, contributing to the advancement of phase change materials.

Synergistic effect of process parameters and nanoparticles on spent lubricant oil waste biodegradation by UV-exposed Scenedesmus vacuolatus: Process modelling, kinetics and degradation pathways

The study examines the impact of process parameters and nanoparticles (NPs) on the degradation of spent coolant waste (SCW) by UV-exposed S. vacuolatus. The model was experimentally optimized using response surface methodology (RSM) with high coefficient of determination (R2) >0.99. Upon validation of the model, total petroleum hydrocarbon (TPH) degradation of 100 % was obtained after 15 days under the optimized conditions of 25 °C temperature, 10 % (v/v) substrate concentration and 10 % (v/v) inoculum concentration. Moreover, the sensitivity of the process parameters on the degradation process assessed using artificial neural network (ANN) revealed high sensitivity of the degradation process to operational temperature. Metabolites obtained provide strong evidence for terminal oxidation and subterminal oxidation metabolic pathways in SCW degradation. In addition, the incorporation of NPs in the SCW degradation significantly enhanced the biodegradation efficiency of UV-exposed S. vacuolatus resulting in shortened degradation period from 15 to 12 days. Likewise, the inclusion of NPs substantially improved UV-exposed S. vacuolatus affinity (1/Ks) for SCW, growth constant (Kg) and maximum specific growth rate (μmax). The degradation kinetics followed the second-order reaction with degradation rate constant (K) in the range of 0.029 to 0.288 m−1 t−1 for monoaromatics and 0.972 to 4.130 m−1 t−1 for PAHs, at half-life (T1/2) ranges of 0.75 to 1.52 day−1 and 0.08 to 0.23 day−1, respectively. This knowledge will enhance the design of waste pollutant degradation towards sustainable green environment.

Pollution Characteristics of Macrolide Antibiotics During Drinking Water Treatment and Their Chlorination Reaction Mechanism

Antibiotic contamination in drinking water has attracted widespread attention. The pollution condition of six macrolide antibiotics (erythromycin-H2[KG-*2/5]O, clarithromycin, oleandomycin, roxithromycin, leucomycin, and tylosin) in two drinking water treatment plants was monitored, and the reaction mechanism of tylosin, a typical macrolide antibiotic, during chlorination disinfection treatment was investigated. The results showed that the six macrolide antibiotics can be widely detected in the drinking water treatment processes; however, their concentrations were generally very low. The concentrations of macrolide antibiotics in the influents and effluents ranged from 0.18 ng·L-1 to 3.97 ng·L-1 and 0.02 ng·L-1 to 1.91 ng·L-1, respectively. The removal rates of the six macrolides in the drinking water treatment were different, ranging from 18% (oleandomycin) to 100% (erythromycin- H2[KG-*2/5]O). The degradation of the six macrolides during chlorination was slow and greatly affected by water quality parameters. The chlorination degradation of tylosin followed the second-order reaction kinetic mode, with the kinetic rate constant of 0.77 L·(mol·s)-1 at pH 7.0. Nine chlorination degradation products of tylosin were detected, and the reaction pathways primarily included tertiary amine hydroxylation, aromatic oxidation, and epoxy addition.

Efficient degradation of tetrabromobisphenol A using peroxymonosulfate oxidation activated by a novel nano-CuFe2O4@coconut shell biochar catalyst

In this study, a novel bimetallic complexation–curing nucleation–anaerobic calcination method was developed to synthesize a nano-CuFe2O4@coconut shell biochar (CuFe2O4@CSBC) catalyst to activate peroxymonosulfate for degradation of tetrabromobisphenol A (TBBPA). The reaction processes of the TBBPA on CuFe2O4@CSBC have been investigated using in situ characterization and metal leaching. The effects of initial reaction conditions and degradation mechanism were investigated. Greater than 99% degradation of TBBPA at 10 mg L−1 was achieved in 30 min under the condition of pH 11, a total organic carbon removal rate of up to 70.67% was achieved and the degradation efficiency was 90% after 5 cycles of CuFe2O4@CSBC use. The degradation was in a second-order reaction at a constant of 0.797 M−1 min−1 (R2 = 0.993). The degradation was attributed to the main active species (SO4·−≈·OH < 1O2), and the surface active site of CuFe2O4@CSBC was the key role. The degradation process involved three main degradation pathways. Path A: ·OH attacked the C–Br bonds (TBBPA→TriBBPA→DBBPA→MBBPA→BPA); Path B: Hydroxylation and decarboxylation; Path C: Dehydrocoupling of TBBPA. What's more, the practical application of the system was very positive, achieved >77% degradation in sewage and industrial wastewater.

Quality Assessment of Sokoto Water Distribution Networks

The research is on the quality assessment of Sokoto water distribution networks. Sample coordinates of the study area were taken using GPS, the experiments were carried out at different consumer locations with thirty (30) samples of water collected weekly for four (4) weeks, to determine various purification parameters that are related to both bulk (kb) and wall (KW) reactions coefficients for Sokoto water distribution pipe network, these include residual chlorine, pH, dissolved oxygen (DO), temperature and conductivity. pH, dissolved oxygen (DO) and conductivity have average values ranging from 6.7 to 7.5; 1.1 to 6.5ppm; 310 to 520 μs/cm respectively and conform to the Nigerian Standard for Drinking Water Quality (NSDWQ), except temperature which has the average values between 29 oC, and 32.6oC, and the individual values between 26 oC, and 38.4oC, chlorine residual average values obtained, ranging from 0.11mg/l to 0.26mg/l with the lowest individual value obtained being 0.011mg/l. The age of water supply from the treatment plants in the distribution network is 6 hours and both first and second-order decay reactions were ascertained from the graph and first-order decay having the highest number of occurrences was used in Epanet 2.0 water quality modeling. The kb values ranged from 0.0025 to 0.013md-1. A total of 86 out of the 120 samples, which constitute 71.7% were straight lines which indicate first-order and thus, the average kb was determined to be 0.006/day (0.144/hour). It was observed that of all the 120 samples examined in the study, chlorine reaction with natural organic matter (NOM) was small. The average kw for Sokoto WDS was deduced to be 0.078m/h, considering, the following steel pipe conditions used in the network area. kW (ft/h), -α =-38.5, H-W C=150, kW = 38.5/150 = 0.257ft/h = 0.078m/h (-0.078m/h).

Oxidation characteristic and thermal runaway of isoprene

In this study, the oxidation characteristics of isoprene were investigated using a custom-designed mini closed pressure vessel test (MCPVT). The results show that isoprene is unstable and polymerization occurs under a nitrogen atmosphere. Under an oxygen atmosphere, the oxidation process of isoprene was divided into three stages: (1) isoprene reacts with oxygen to produce peroxide; (2) Peroxides produce free radicals through thermal decomposition; (3) Free radicals cause complex oxidation and thermal runaway reactions. The oxidation of isoprene conforms to the second-order reaction kinetics, and the activation energy was 86.88 kJ·mol−1. The thermal decomposition characteristics of the total oxidation product and purified peroxide mixture were determined by differential scanning calorimetry (DSC). The initial exothermic temperatures Ton were 371.17 K and 365.84 K, respectively. And the decomposition heat QDSC were 816.66 J·g−1 and 991.08 J·g−1, respectively. It indicates that high concentration of isoprene peroxide has a high risk of thermal runaway. The results of thermal runaway experiment showed that the temperature and pressure of isoprene oxidation were prone to rise rapidly, which indicates that the oxidation reaction was dangerous. The reaction products of isoprene were analyzed by gas chromatography-mass spectrometry (GC–MS). The main oxidation products were methyl vinyl ketone, methacrolein, 3-methylfuran, etc. The main thermal runaway products were dimethoxymethane, 2,3-pentanedione, naphthalene, etc. Based on the reaction products, the possible reaction pathway of isoprene was proposed.

Kinetics of Fixed Bed Sorption Processes

Adsorption and ion exchange are examples of fixed-bed sorption processes that show transient behavior. This means that differential equations are needed to design them. As a result, numerical methods are commonly utilized to solve these equations. The solution frequently used in analytical methods is called the Thomas solution. Thomas gave a complete solution that adds a nonlinear equilibrium relationship that depends on second-order reaction kinetics. A computational approach was devised to solve the Thomas model. The Thomas model's validity was established by conducting three distinct sets of experiments. The first entails the adsorption of acetic acid from the air through the utilization of activated carbon. Following this, zeolite-5A adsorbs trichloroethylene (TCE) from the air. Finally, activated carbon is employed for the purpose of adsorbing o-cresol from aqueous solutions. A study was done to estimate phase equilibria and interphase mass transfer rates. To find the kinetic mass-transfer coefficient (K) for gases, the phase coefficients for mass transfer in the fluid phase ( ) and the pore phase ( ) were added together. The estimation of (K) for liquid was performed using the mass transfer coefficient for the solid phase and togather. The results suggest that the adsorption of acetic acid from air on activated carbon gives a good agreement with the Thomas model. The other sets of data demonstrate a disparity due to the underlying assumptions inherent in the Thomas model.

A simplified mesoscale 3D model for characterizing fibrinolysis under flow conditions

One of the routine clinical treatments to eliminate ischemic stroke thrombi is injecting a biochemical product into the patient’s bloodstream, which breaks down the thrombi’s fibrin fibers: intravenous or intravascular thrombolysis. However, this procedure is not without risk for the patient; the worst circumstances can cause a brain hemorrhage or embolism that can be fatal. Improvement in patient management drastically reduced these risks, and patients who benefited from thrombolysis soon after the onset of the stroke have a significantly better 3-month prognosis, but treatment success is highly variable. The causes of this variability remain unclear, and it is likely that some fundamental aspects still require thorough investigations. For that reason, we conducted in vitro flow-driven fibrinolysis experiments to study pure fibrin thrombi breakdown in controlled conditions and observed that the lysis front evolved non-linearly in time. To understand these results, we developed an analytical 1D lysis model in which the thrombus is considered a porous medium. The lytic cascade is reduced to a second-order reaction involving fibrin and a surrogate pro-fibrinolytic agent. The model was able to reproduce the observed lysis evolution under the assumptions of constant fluid velocity and lysis occurring only at the front. For adding complexity, such as clot heterogeneity or complex flow conditions, we propose a 3-dimensional mesoscopic numerical model of blood flow and fibrinolysis, which validates the analytical model’s results. Such a numerical model could help us better understand the spatial evolution of the thrombi breakdown, extract the most relevant physiological parameters to lysis efficiency, and possibly explain the failure of the clinical treatment. These findings suggest that even though real-world fibrinolysis is a complex biological process, a simplified model can recover the main features of lysis evolution.

Insight into the green route to dimethyl succinate by direct esterification of bio-based disodium succinate using CO2 and CH3OH

The fermentation for succinic acid production outperforms other methods by low energy consumption and environmental benignity, with the resulting products mainly as disodium succinate (DSA). By directly esterifying DSA using CO2 and CH3OH, it is expected to avoid the use of inorganic acids. By high-resolution mass spectrometry analysis and theoretical calculation, this study establishes that the reaction consists of three steps, i.e., first forming 3-carboxypropanoate, then monomethyl succinate (MMS), and finally dimethyl succinate (DMS). A detailed kinetic analysis is further performed, the results demonstrate that the transformation of DSA to MMS is regarded to be a second-order reaction for reactant DSA, while the transformation of MMS to DMS is a first-order reaction for reactant MMS. The activation energy for the generation of MMS from DSA is 37.15 kJ·mol−1, and that for the generation of DMS from MMS is 85.80 kJ·mol−1, indicating the latter one is the rate-determining step.

Reactivity of Acrylamides Causes Cytotoxicity and Activates Oxidative Stress Response.

Acrylamides are widely used industrial chemicals that cause adverse effects in humans or animals, such as carcinogenicity or neurotoxicity. The excess toxicity of these reactive electrophilic chemicals is especially interesting, as it is mostly triggered by covalent reactions with biological nucleophiles, such as DNA bases, proteins, or peptides. The cytotoxicity and activation of oxidative stress response of 10 (meth)acrylamides measured in three reporter gene cell lines occurred at similar concentrations. Most acrylamides exhibited high excess toxicity, while methacrylamides acted as baseline toxicants. The (meth)acrylamides showed no reactivity toward the hard biological nucleophile 2-deoxyguanosine (2DG) within 24 h, and only acrylamides reacted with the soft nucleophile glutathione (GSH). Second-order degradation rate constants (kGSH) were measured for all acrylamides with N,N'-methylenebis(acrylamide) (NMBA) showing the highest kGSH (134.800 M-1 h-1) and N,N-diethylacrylamide (NDA) the lowest kGSH (2.574 M-1 h-1). Liquid chromatography coupled to high-resolution mass spectrometry was used to confirm the GSH conjugates of the acrylamides with a double conjugate formed for NMBA. The differences in reactivity between acrylamides and methacrylamides could be explained by the charge density of the carbon atoms because the electron-donating inductive effect of the methyl group of the methacrylamides lowered their electrophilicity and thus their reactivity. The differences in reactivity within the group of acrylamides could be explained by the energy of the lowest unoccupied molecular orbital and steric hindrance. Cytotoxicity and activation of oxidative stress response were linearly correlated with the second-order reaction rate constants of the acrylamides with GSH. The reaction of the acrylamides with GSH is hence not only a detoxification mechanism but also leads to disturbances of the redox balance, making the cells more vulnerable to reactive oxygen species. The reactivity of acrylamides explained the oxidative stress response and cytotoxicity in the cells, and the lack of reactivity of the methacrylamides led to baseline toxicity.

Efficient and cost-effective fluorine recovery from liquid-phase wet-process phosphoric acid via two-step precipitation method

Fluorine (F) recovery from wet-process phosphoric acid (WPA) is essential for sustainable resource utilization and environmental protection. In this study, we have proposed a two-step precipitation strategy for recovering F from WPA using anhydrous sodium sulfate and activated silica as precipitants. The optimized F recovery yield, product purity, and maximum P2O5 loss were 87.60 %, >98.50 wt%, and 0.030 wt%, respectively. Moreover, the recovery cost was only USD 60.08 per tonne of P2O5. The precipitation reactions followed the second-order reaction model and were controlled by the moving boundary diffusion mechanism. Temperature significantly influenced the reaction process, while temperature, WPA concentration, and Al3+ content significantly influenced the morphology of the precipitated crystal. Under optimized conditions, the sodium fluorosilicate product had a hexagonal cylindrical axis, low solubility in WPA, and high purity. These findings are promising for the utilization of F resources from phosphate rock and other ores, which is of great economic and environmental significance.

Thermal stability vs. energy content of compound: Thermolysis of tetrazino-tetrazine 1,3,6,8-tetraoxide (TTTO) from a broad perspective

Tetrazino-tetrazine 1,3,6,8-Tetraoxide (TTTO) is one of the most powerful energetic materials synthesized to date. Its thermal decomposition of [1,2,3,4]tetrazino[5,6-e][1,2,3,4]tetrazine 1,3,6,8-tetraoxide (TTTO) has been investigated for the first time. The obtained formal kinetic model of thermolysis includes the two-dimensional nucleation-growth with an activation energy of 102 ± 3 kJ mol−1 and the second-order reaction with barrier of 184 ± 4 kJ mol−1. Judged by the decomposition onset (155 °C), TTTO is the most thermally stable among known top energetic substances. A broader analysis of 360 energetic and non-energetic chemicals supports the idea of general thermal stability decrease with the molecule’s energy content rise, although the relationship is built as envelope of the cloud of experimental data. Two hypotheses for high energetic materials design are formulated: the limiting value of performance achieved with stable organic species (10% over benchmark 1,3,5,7-tetranitro-1,3,5,7-tetrazocane, HMX) and the existence of top performing molecules that are more thermally stable compounds than TTTO.

Caffeic acid accelerated the Fe(II) reinvention in Fe(III)/PMS system for bisphenol A degradation: Oxidation intermediates and inherent mechanism

Fe(II)-catalyzed PMS process was widely used in the degradation of refractory pollutants in wastewater, while its performance was restricted by the slow regeneration efficiency of Fe(II). Herein, caffeic acid (CFA), a representative of hydroxycinnamic acids, was introduced into Fe(III)/PMS system to accelerate the transformation of Fe(III) to Fe(II) and promote the removal of bisphenol A (BPA). Under optimum condition of 0.1 mM CFA, 0.05 mM Fe(III), and 0.5 mM PMS, almost complete removal of BPA can be achieved within 20 min, which was roughly 6.2 times higher than that in Fe(III)/PMS system. As the addition of CFA into Fe(III)/PMS system, pH application range was widened from acidic to alkaline conditions. The reduction and chelation of CFA expedited the Fe(III)/Fe(II) cycle by forming CFA-Fe chelate, thereby facilitating the PMS activation. Based on LC-MS analysis and DFT calculation, the intermediate products of CFA were found to play a decisive role in boosting the regeneration of Fe(II), and the toxicity of these intermediates towards organisms was evaluated by ECOSAR. The alcohol-scavenging and chemical probe tests certified that hydroxyl radical (•OH), sulfate radical (SO4•-), and Fe(IV) coexisted in Fe(III)/CFA/PMS system, and the second-order reaction rate constants of •OH and SO4•- reacted with CFA were calculated to be 3.16✕109 and 2.30✕1010 M−1 s−1, respectively. Two major degradation pathways of BPA, •OH addition and SO4•- induced hydroxylation reaction, were proposed. This work presented a novel green phenolic compound that expedited the Fe(II)-catalyzed PMS activation process for the treatment of organic contaminants.

Kinetics of carbon dioxide absorption in aqueous blend of 1-(2-aminoethyl) piperazine using a stirred cell reactor.

Carbon capture utilization and storage (CCUS), the technology for decarbonizing carbon dioxide (CO2) from greenhouse gas emitters such as steel, cement, oil, gas, petrochemicals, chemicals, and fertilizers, has a critical role to play in the world to achieve industrial net zero targets by 2050. CO2 can be separated from industrial exhaust gases/flue gases using amine-based solvents utilizing the post-combustion CO2 Capture process. One most crucial solvent characterization for this application is the kinetics of CO2 absorption. This work identifies aqueous 1-(2-aminoethyl) piperazine (AEPZ) as a potential candidate for CO2 capture solvent. The kinetics of absorption of CO2 in aqueous AEPZ is studied using stirred cell reactor. The experiments are performed at temperatures ranging from 303 to 333K with weight fractions of AEPZ in an aqueous solution ranging from 0.1 to 0.4. One of the critical parameters of the kinetic study is Henry's constant which is determined experimentally using another stirred cell reactor at a similar temperature and pressure range. The experimental data shows that the overall rate constant is Kov = 2.52987 × 10-4mol/m2s-kPa for 0.1 wt fr. of AEPZ at 313K with an initial CO2 partial pressure of 10kPa. The temperature dependency relation of the second-order reaction rate constant, [Formula: see text] is found to be [Formula: see text] using the Arrhenius equation. The activation energy of 0.3 wt fr. AEPZ is found to be 42.42kJ/mol. In addition, the density and viscosity of the aqueous solvent are determined at a wide range of temperatures. The diffusivity of CO2 and physical solubility used in the model development has also been determined. The kinetic parameters obtained from this study are helpful in the process design of CO2 capture in a regenerative process with a blended solvent with AEPZ.