Unraveling Different Reaction Characteristics of Alkoxy Radicals in a Co(II)-Activated Peracetic Acid System Based on Dynamic Analysis of Electron Distribution.

Peracetic acid (PAA)-based advanced oxidation processes (AOPs) have shown broad application prospects in organic wastewater treatment. Alkoxy radicals including CH3COO• and CH3COOO• are primary reactive species in PAA-AOP systems; however, their reaction mechanism on attacking organic pollutants still remains controversial. In this study, a Co(II)/PAA homogeneous AOP system at neutral pH was constructed to generate these two alkoxy radicals, and their different reaction mechanisms with a typical emerging contaminant (sulfacetamide) were explored. Dynamic electron distribution analysis was applied to deeply reveal the radical-meditated reaction mechanism based on molecular orbital analysis. Results indicate that hydrogen atom abstraction is the most favorable route for both CH3COO• and CH3COOO• attacking sulfacetamide. However, both radicals cannot react with sulfacetamide via the radical adduct formation route. Interestingly, the single-electron transfer reaction is only favorable for CH3COO• due to its lower ESUMO. In comparison, CH3COOO• can react with sulfacetamide via a similar radical self-sacrificing bimolecular nucleophilic substitution (SN2) route owing to its high ESOMO and easy escape of unpaired electrons from n orbitals of O atoms in the peroxy bond. These findings can significantly improve the knowledge of reactivity of CH3COO• and CH3COOO• on attacking organic pollutants at the molecular orbital level.

Study on the mechanism and reaction characteristics of metal-supported phosphogypsum as oxygen carrier in a chemical looping gasification application.

This study aimed to explore the chemical looping gasification (CLG) reaction characteristics of the metal-supported composite phosphogypsum (PG) oxygen carriers (OCs) and the thermodynamic mechanism. The FactSage 7.1 thermodynamic simulation was used to explore the oxygen release and H2S removal mechanisms. The experimental results showed that the syngas yield of CLG with PG-CuFe2O4 was more than that with PG-Fe2O320/CuO40 or PG-Fe2O330/CuO30 OC at 1023 K when the water vapor content was 0.3. Furthermore, the maximum syngas yield of the CO selectivity was 70.3% and of the CO2 selectivity was 23.8%. The H2/CO value was 0.78, and the highest carbon conversion efficiency was 91.9% in PG-CuFe2O4 at the gasification temperature of 1073 K. The metal-supported PG composite oxygen carrier was proved not only as an oxygen carrier to participate in the preparation of syngas but also as a catalyst to catalyze coal gasification reactions. Furthermore, both the experimental results and FactSage 7.1 thermodynamic analysis revealed that the trapping mechanism of H2S by composite OCs was as follows: CuO first lost lattice oxygen as an oxygen carrier to generate Cu2O, which, in turn, reacted with H2S to generate Cu2S. This study provided efficient guidance and reference for OC design in CLG.

Decomplexation of Cu-1-hydroxyethylidene-1,1-diphosphonic acid by a three-dimensional electrolysis system with activated biochar as particle electrodes.

The feasibility of decomplexation removal of typical contaminants in electroplating wastewater, complexed Cu(II) with 1-hydroxyethylidene-1,1-diphosphonic acid (Cu-HEDP), was first performed by a three-dimensional electrode reactor with activated biochar as particle electrodes. For the case of 50 mg/L Cu-HEDP, Cu(II) removal (90.7%) and PO43- conversion (34.9%) were achieved under the conditions of electric current 40 mA, initial pH 7, acid-treated almond shell biochar (AASB) addition 20 g/L, and reaction time 180 min, with second-order rate constants of 1.10 × 10-3 and 1.94 × 10-5 min-1 respectively. The growing chelating effect between Cu(II) and HEDP and the comprehensive actions of adsorptive accumulation, direct and indirect oxidation given by particle electrodes accounted for the enhanced removal of Cu-HEDP, even though the mineralization of HEDP was mainly dependent on anode oxidation. The performance attenuation of AASB particle electrodes was ascribed to the excessive consumption of oxygen-containing functionalities during the reaction, especially acidic carboxylic groups and quinones on particle electrodes, which decreased from 446.74 to 291.48 µmol/g, and 377.55 to 247.71 µmol/g, respectively. Based on the determination of adsorption behavior and indirect electrochemical oxidation mediated by in situ electrogenerated H2O2 and reactive oxygen species (e.g., •OH), a possible removal mechanism of Cu-HEDP by three-dimensional electrolysis was further proposed.

Simultaneous Fe(III) reduction and ammonia oxidation process in Anammox sludge.

In recent years, there have been a number of reports on the phenomenon in which ferric iron (Fe(III)) is reduced to ferrous iron [Fe(II)] in anaerobic environments, accompanied by simultaneous oxidation of ammonia to NO2-, NO3-, or N2. However, studies on the relevant reaction characteristics and mechanisms are rare. Recently, in research on the effect of Fe(III) on the activity of Anammox sludge, excess ammonia oxidization has also been found. Hence, in the present study, Fe(III) was used to serve as the electron acceptor instead of NO2-, and the feasibility and characteristics of Anammox coupled to Fe(III) reduction (termed Feammox) were investigated. After 160days of cultivation, the conversion rate of ammonia in the reactor was above 80%, accompanied by the production of a large amount of NO3- and a small amount of NO2-. The total nitrogen removal rate was up to 71.8%. Furthermore, quantities of Fe(II) were detected in the sludge fluorescence in situ hybridization (FISH) and denaturated gradient gel electrophoresis (DGGE) analyses further revealed that in the sludge, some Anammox bacteria were retained, and some microbes were enriched during the acclimatization process. We thus deduced that in Anammox sludge, Fe(III) reduction takes place together with ammonia oxidation to NO2- and NO3- along with the Anammox process.

[Characteristics of Ozone Photochemical Reaction and Emission Reduction Strategies in Summer and Autumn in Shangqiu].

Recently, ozone （O3） pollution in Shangqiu has become increasingly prominent, especially in summer and autumn, crucially affecting the local environmental air quality. Based on the monitoring data of O3 pollution days from the Environmental Monitoring Station in June and September 2022 （representing summer and autumn） in Shangqiu, an observation-based model （OBM） was used to study the causes and photochemical reaction characteristics of O3 pollution in the city and precursor emission reduction strategies were studied. The observation results indicated that during summer in Shangqiu, the ρ（O3） and O3 daily maximum 8 h moving concentrations [ρ（MDA8-O3）] were 149.7 µg·m-3 and 195.4 µg·m-3, whereas in autumn, ρ（O3） and ρ（MDA8-O3） were 119.8 µg·m-3 and 173.9 µg·m-3, respectively； the O3 concentration in summer was significantly higher than that in autumn. Ozone sensitivity research showed that the generation of O3 in summer and autumn in Shangqiu was controlled by volatile organic compounds （VOCs）. Among them, oxygen-containing volatile organic compounds （OVOCs）, aromatic hydrocarbons, and alkenes contributed the most to the ozone generation potential （OFP） and ·OH reactivity （L·OH）, and the control must have been strengthened. The OBM simulation results indicated that the maximum O3 generation rates in summer and autumn were 23.0×10-9 h-1 and 13.6×10-9 h-1, with maximum net generation rates of 17.4×10-9 h-1 and 10.4×10-9 h-1 and the maximum and maximum net generation rates of O3 in summer were 1.68 times higher than those in autumn, indicating that the photochemical reactions in summer were significantly stronger than those in autumn. Compared with that in summer, the generation of O3 in autumn was greatly influenced by regional inputs from other regions or cities, with a maximum input of 14.2×10-9 h-1. The prevention and control of O3 pollution in the summer and autumn seasons in Shangqiu should mainly focus on controlling VOCs. The reduction ratio of VOCs/nitrogen oxides （NOx） in autumn should be greater than that in summer and the reduction ratios of 3∶1 in summer and 4∶1 in autumn could be adopted for control.

Study of reaction characteristics and controlling mechanism of chlorinating conversion of cathode materials from spent lithium-ion batteries.

Spent lithium-ion batteries (LIBs) recycling has attracted much attention because it is highly favorable to environment protection and sustainable development. Developing a cleaner method for metals extraction can greatly reduce risk of secondary pollution. Chlorinating technology has been proved as an efficient method for metals extraction instead of traditional hydrometallurgy. In this paper, cathode materials from spent LIBs could be rapidly converted into metal chlorides by NH4Cl roasting at 623 K for 20 min. The results indicated nearly 100% metal leaching rates were achieved. Further, in-depth study is performed to obtain the mechanism function of chlorinating conversion based on roasting and TGA experiments. The apparent activation energy as 73.40 kJ/mol was firstly obtained, and then the reaction model of chlorination reaction was determined by model fitting and verifying. Herein, sub-reactions of chlorination reaction were figured out and their contributions were used to determinate reaction controlling mechanisms of chlorination reaction. The results indicated that nucleation reaction played a leading role in the initial stage (0.05 <α < 0.43) while phase boundary reaction took the control in next stage (0.43 <α < 0.95), which gave a good explanation to activation energy change. Finally, our findings provided inspirations for studying the controlling mechanism of gas-solid reaction.

[Effect of Temperature and pH on Nitrogen Conversion in Feammox Process].

In recent years, the oxidation of NH4+ using Fe(Ⅲ) as an electron acceptor under anaerobic conditions (Feammox) has received significant research attention. In this study, the effect of pH and temperature on nitrogen conversion during the Feammox process was studied through activity recovery of Feammox sludge acclimated by anaerobic ammonium oxidation (ANAMMOX) sludge. Results showed that after 40 d operation, activity of Feammox sludge was recovered. There was evident ammonia nitrogen conversion and total nitrogen removal from the environment, and the products were mainly nitrate and nitrogen. The concentration of nitrite remained below 2 mg·L-1. pH value and temperature significantly influenced nitrogen transformation during the Feammox process. With pH value of 7 and temperature of 30℃ during the Feammox process, the removal rate of total nitrogen was relatively high (>50%). When the pH value was 6.5, the conversion rate of ammonia nitrogen was 80.2%. During the Feammox reaction process, precipitation of iron ion compounds and coating on the sludge surface were the main interference factors leading to continuous operation of the reactor and exploration of the reaction mechanism.

Investigation on the Reaction Energy, Dynamic Mechanical Behaviors, and Impact-Induced Reaction Characteristics of PTFE/Al with Different TiH2 Percentages.

As a novel energetic material with quite a high energy density, titanium hydride (TiH2) was introduced into a polytetrafluoroethylene/aluminum (PTFE/Al) reactive material system for the first time. The effects of TiH2 on the reaction energy, dynamic mechanical responses, and reaction properties of the composites were investigated through adiabatic bomb calorimeter, split-Hopkinson pressure bar, and drop-weight experiments. The results show that the reaction heat of the composites improved significantly as the content of TiH2 increased. Under dynamic compression, these composites show obvious strain hardening and strain rate hardening effects. Besides, a certain amount of TiH2 granules helps to improve the material's compressive strength, and the maximum would even reach 173.2 MPa with 5% TiH2 percentage, 10.1% higher than that of PTFE/Al. Mesoscale images of the samples after dynamic compression indicate that interface debonding between the particles and PTFE matrix and the fracture of the PTFE matrix are the two major mechanisms resulting in the material's failure. In addition, the drop-weight experiments indicate that the material's impact sensitivities are sensitive to the content of TiH2, which would be increased to within 20% of the content of TiH2 compared with PTFE/Al, and the reaction degree is also improved to within 10% of the content of TiH2. The retrieved reaction residues after drop-weight experiments imply that the reaction is initiated at the edges of the samples, indicating a shear-induced initiation mechanism of this kind of reactive material.

Investigation on the Thermal Behavior, Mechanical Properties and Reaction Characteristics of Al-PTFE Composites Enhanced by Ni Particle.

Al-PTFE (aluminum-polytetrafluoroethene) is regarded as one of the most promising reactive materials (RMs). In this work, Ni (Nickel) was added to Al-PTFE composites for the purpose of improving the energy density and damage effect. To investigate the thermal behavior, mechanical properties and reaction characteristics of the Al-Ni-PTFE composites, an Al-PTFE mixture and an Al-Ni mixture were prepared by ultrasonic mixing. Six types of Al-Ni-PTFE specimens with different component mass ratios were prepared by molding sintering. Simultaneous thermal analysis experiments were carried out to characterize the thermal behavior of the Al-PTFE mixture and the Al-Ni mixture. Quasi-static compression tests were performed to analyze the mechanical properties and reaction characteristics of the Al-Ni-PTFE specimens. The results indicate that the reaction onset temperature of Al-Ni (582.7 °C) was similar to that of Al-PTFE (587.6 °C) and that the reaction heat of Al-Ni (991.9 J/g) was 12.5 times higher than that of Al-PTFE (79.6 J/g). With the increase of Ni content, the material changed from ductile to brittle and the strain hardening modulus and compressive strength rose first and then subsequently decreased, reaching a maximum of 51.35 MPa and 111.41 MPa respectively when the volume fraction of Ni was 10%. An exothermic reaction occurred for the specimens with a Ni volume fraction no more than 10% under quasi-static compression, accompanied by the formation of Ni-Al intermetallic compounds. In the Al-Ni-PTFE system, the reaction between Al and PTFE preceded the reaction between Al and Ni and the feasibility of increasing the energy density and damage effect of the Al-Ni-PTFE reactive material by means of Ni-Al reaction was proved.

Experimental Study on Reaction Characteristics of PTFE/Ti/W Energetic Materials under Explosive Loading.

Metal/fluoropolymer composites represent a new category of energetic structural materials that release energy through exothermic chemical reactions initiated under shock loading conditions. This paper describes an experiment designed to study the reaction characteristics of energetic materials with low porosity under explosive loading. Three PTFE (polytetrafluoroethylene)/Ti/W mixtures with different W contents are processed through pressing and sintering. An inert PTFE/W mixture without reactive Ti particles is also prepared to serve as a reference. Shock-induced chemical reactions are recorded by high-speed video through a narrow observation window. Related shock parameters are calculated based on experimental data, and differences in energy release are discussed. The results show that the reaction propagation of PTFE/Ti/W energetic materials with low porosity under explosive loading is not self-sustained. As propagation distance increases, the energy release gradually decreases. In addition, reaction failure distance in PTFE/Ti/W composites is inversely proportional to the W content. Porosity increased the failure distance due to higher shock temperature.