Catalytic Oxidation Process Research Articles

A novel copper ion enhanced electrochemical DNA biosensor for the determination of epinephrine

A novel electrochemical biosensor was developed for the detection of epinephrine (EP) by immobilizing double-strand DNA (dsDNA) bound with copper ions on a gold electrode (Cu2+/dsDNA/MCH/AuE). The electrochemical behavior of EP at Cu2+/dsDNA/MCH/AuE was examined, and the results demonstrated a significant enhancement in the electrocatalytic oxidation peak current of EP due to the formation of a stable G-Cu(II)-G sandwich structure between Cu2+ and guanine at the modified electrode. The modification process of the electrode was characterized by scanning electron microscopy, infrared spectroscopy, electrochemical impedance spectroscopy, and differential pulse voltammetry. A study on the effect of pH in phosphate buffer solution on the electrochemical oxidation of EP indicated that the catalytic oxidation process was pH-dependent. A plot of catalytic current versus EP concentration exhibited a dual-linear relationship within two ranges: 1.0–12.5 μM and 12.5–1000.0 μM, with correlation coefficients of 0.995 and 0.997, respectively. The limit of detection was determined to be 47 nM (S/N = 3). According to the calculated Hill coefficient (0.99), it can be concluded that the electrocatalytic process followed the Michaelis-Menten kinetic mechanism. The maximum catalytic current Im was 25 μA, while the apparent Michaelis-Menten constant Km was 1.425 mM. These findings indicated excellent electrocatalytic activity of the modified electrode towards oxidation of EP. The developed biosensor successfully detected EP in spiked mouse serum as well as epinephrine hydrochloride injection with high selectivity, sensitivity, stability, and accuracy.

Ultrasound‒induced facile synthesis of spinel CoFe2O4‒PAC magnetic nanocatalyst for remediation of hypersaline petrochemical wastewater: Degradation mechanism, biodegradability enhancement and phytotoxicity mitigation

In this study, magnetic CoFe2O4−PAC nanocatalysts were synthesized through facile hydrothermal and co‒precipitation approaches with ultrasonic irradiation, which were used for the treatment of hypersaline petrochemical wastewater (HPCW). When an ultrasound‒induced synthesis process (US@CoFe2O4‒PAC) was used, a more efficient and stable magnetic spinel CoFe2O4‒PAC nanocatalyst was developed. The application of this nanocatalyst as a PMS activator, not only caused eradication of 90.4% of chemical oxygen demand (COD) of a HPCW after 90 min reaction time under the optimum conditions (pH 5−6, catalyst dose 1.0 g/L and 1.0 mM PMS), but also led to marginal leaching of iron (314 μg/L) and cobalt (95 μg/L) from the nanocatalyst. Recycling experiments over five consecutive runs showed a negligible decrease (7.2%) in COD removal efficiency which proved the stability and reusability of magnetic US@CoFe2O4−PAC. Two main mechanisms of adsorption and catalytic oxidation processes (homogeneous and heterogeneous PMS) are involved simultaneously in the PMS/US@CoFe2O4−PAC system, which are responsible for the destruction of refractory contaminants of HPCW through the generation of SO4•‒ and OH• radicals. COD of HPCW was mainly removed through SO4•− radical attack (73.6%) and the biodegradability of HPCW was enhanced dramatically after 90 min reaction time. The germination index (GI) of raw HPCW was increased 17.1 ± 4.2% and 24.3 ± 8.8% after 15 and 90 min reaction time, respectively, even PMS/US@CoFe2O4−PAC system showed less impact on phytotoxicity mitigation. Hence, it can be recommended to dilute the effluent before using for irrigational purpose. The findings of this study present practical significance of spinel US@CoFe2O4−PAC, which is an environment‒friendly catalyst, easy to handle and can sustain long‒term operation for the treatment of recalcitrant hypersaline wastewater and the other potential practical applications.

Plasma driven exsolution of Ca as the adjacent dechlorinated site in La0.8Ca0.2MnO3 perovskite: A highly mineralization chlorobenzene oxidation catalyst

The degradation of chlorine-containing volatile organic compounds (CVOCs) catalytic combustion technology is subject to the catalyst chlorine poisoning, which is resulted from the chlorination of active phases, even though the structural stable perovskite. The reaction between Ca species and dissociated chlorine species is demonstrated as an efficient way to inhibited chlorine poisoning of the active phase. Herein, a Ca substituted partial La prepared La0.8Ca0.2MnO3 (named as L8C2MO) perovskite was treated by 5% H2/Ar plasma driven route (the treated sample was denoted as L8C2MO-P), which was applied for the chlorobenzene oxidation removal. The integrated characterization results of XRD, XPS, HRTEM, etc. confirmed that Ca (mainly exhibited as CaCO3) was successfully exsolved from La0.8Ca0.2MnO3 and simultaneously leaved oxygen vacancies on the surficial layers. The continuous catalytic oxidation experiments illustrated that the conversion efficiency of L8C2MO was unexpectedly decreased compared with that of LaMnO3 (LMO in short) sample, while that of L8C2MO-P was nearly maintained the oxidation capacity, with approximately 12 °C of 90% chlorobenzene conversion temperature (T90) higher than that of LMO. Importantly, the CO2 and inorganic chlorine species yields were significantly enhanced for L8C2MO and L8C2MO-P. The characteristic of used samples showed a possible chlorinated Ca species formation while the status of Mn phases was hardly changed, suggesting the exsolved Ca could inhibit the poison of Mn sites by binding with dissociative chlorine species. Additionally, oxygen vacancies that generated along with Ca exsolution process was definitely contributed to the deep oxidation of chlorobenzene. The possible reaction route was also studied by in situ DRIFTS and GCMS. The work provides a potential route as in situ growth of adjacent sites to protect active phases from chlorine poison in CVOCs catalytic oxidation process.

Cyclodextrin-boosted photocatalytic oxidation for efficient bisphenol A removal

Wastewater contains various high-risk trace organic pollutants, such as antibiotics and endocrine disruptors, which seriously restrict wastewater reuse. Cyclodextrin-based functional materials show great potential in the removal of trace pollutants because of their adsorption catalytic synergy. Clarifying the synergistic mechanism of cyclodextrin in oxidation is the key issue in confined catalytic oxidation process design. In this work, we fabricated a BiOIO3@BiOBr/β-CD heterojunction photocatalyst to study the synergistic mechanism of cyclodextrin in the photocatalytic oxidation process. The synergistic mechanism of cyclodextrin was investigated by combining radical chemistry, electrochemistry, spectroscopy, and time-dependent density functional theory. Results showed that the excited intermediate free radicals played an important role in promoting the photocatalytic degradation process. The heterojunction photocatalyst loaded with β-cyclodextrin (β-CD) at the electronic end (C[Cat.] = 0.2 mg/mL) removed about 97% of bisphenol A (BPA) within 30 min, and the first-order kinetic constant (kCDBIB = 0.112 min−1) was about twice that of the unloaded β-CD (kBIB = 0.057 min−1). Cyclodextrin loading improved the photocatalytic performance of the heterojunction and stimulated the intermediate to increase the free radical yield and regulate the reaction path.

Against catalyst deactivation during toluene oxidation on CuCeOx in flue gas: High oxidation efficiency and rapid oxidation pathway

The removal of volatile organic compounds (VOCs) from flue gas by a tightly coupled catalytic oxidation process in the NH3-SCR unit is a cost-effective approach. A CuCeOx bimetallic mixed oxide catalyst prepared by the co-precipitation method has demonstrated the ability to completely convert toluene at 350 ℃ under simulated flue gas conditions. Cu oxide is considered as the main active site for toluene oxidation, and the introduction of Ce induced a synergistic effect which enhanced the surface adsorbed oxygen and oxidation performance. The CuCeOx catalyst was found to outperform commercial VOC catalysts (Pt/Al2O3) and SCR catalysts (V2O5-WO3/TiO2) under the influence of different flue gas components. The negative effect of the flue gas on CuCeOx almost diminished at 350 ℃. The mechanism study showed that toluene on CuCeOx underwent a rapid oxidation pathway, thereby avoiding the potential interaction between intermediates and flue gas components. The superior catalytic performance of CuCeOx in the simulated flue gas conditions were attributed to the higher toluene adsorption efficiency and weaker adsorption towards the flue gas components.

Designing ammonia oxidation catalysts via physical mixing of Pt/SiO2 and Cu/ZSM-5

Ammonia (NH3) is emerging as a carbon-neutral fuel alternative; however, its use poses environmental and health risks due to NH3 slip. The NH3-selective catalytic oxidation (NH3-SCO) process, which converts NH3 into N2 and H2O, offers a solution. However, it faces challenges with respect to the formation of byproducts, particularly N2O and NOx. This study focuses on designing NH3-SCO catalysts to enhance low temperature NH3 conversion efficiency while minimizing undesired byproducts. Pt/SiO2 catalysts were synthesized with adjusted Pt particle sizes to improve the NH3-SCO activity and were physically mixed with Cu/ZSM-5 to overcome the low N2 selectivity of Pt-based catalysts by utilizing the selective catalytic reduction (SCR) ability of Cu/ZSM-5. Pt1Cu3 catalyst, a physical mixture of Pt/SiO2 and Cu/ZSM-5 in a 1:3 mass ratio, was found to be the most effective, achieving complete NH3 oxidation at 250 ℃ while maintaining a high N2 selectivity of approximately 80%. Further investigation revealed that the performance of the Pt1Cu3 catalyst was significantly influenced by the arrangement and physical proximity of the Pt/SiO2 and Cu/ZSM-5 catalysts, with a closely contacted mixture showing synergistic effects that enhanced activity and selectivity. These results suggest that the Pt1Cu3 catalyst offers a promising solution for NH3 emission control by utilizing a balanced approach that combines SCO and SCR reactions.

Versatile Fe3O4-impregnated catalytic ceramic membrane for effective atrazine removal: Confined catalytic oxidation processes, reactive oxygen species selectivity and performance in real wastewater

An Fe3O4-impregnated catalytic ceramic membrane (CCM) was fabricated through a facile ethylene glycol-gel-assisted wet impregnation method. Ethylene glycol played a dual role, acting as a reducing agent for iron (III) nitrate salt and a chelating agent to disperse catalyst uniformly in the CCM. The resulting 5xFe3O4-CCM efficiently activated peroxymonosulfate (PMS) to generate reactive oxygen species (ROS), achieving a 99% removal of atrazine (ATZ) within a short hydraulic retention time (HRT) of 5.7 s. This was facilitated by the spatial confinement effect in CCMs, enhancing the interaction among ATZ, ROS and CCM. The versatile 5xFe3O4-CCM could also effectively activate H2O2 and peroxydisulfate (PDS). It demonstrated robustness in real wastewater matrices (settled water and RO-reject) collected from local water reclamation and treatment plants. The 5xFe3O4-CCM exhibited self-cleaning properties in reducing fouling of CCM by humic acid. ROS scavenging experiments and electron paramagnetic resonance (EPR) spectroscopy revealed the pivotal role of SO4•-, •OH, and 1O2 in ATZ removal. The co-existing anion species HCO3- showed a strong inhibitory effect on ATZ degradation compared to other ionic species (NO3- and Cl-), attributed to different scavenging reaction rate of both SO4•- and •OH by anions in generating less reactive species. Possible degradation pathways of 5xFe3O4-CCM/PMS were proposed based on the LC-QTOF analysis, including oxidation, dealkylation, dealkylation-hydroxylation, dechlorination-hydroxylation of both s-triazine ring and side chain. The toxicity of the ATZ by-products was assessed, revealing reduced toxicity after treatment. With optimized operating parameters, Fe3O4-CCM can be utilized effectively in different advanced oxidation processes (AOPs) and real wastewater matrices.

Enhanced peroxymonosulfate activation for degradation of iodinated contrast media by microwave-induced bimetallic carbon-based catalysts: Insight into the synergistic mechanism between microwaves and bimetallic sites

Microwave-assisted catalytic oxidation process was a promising wastewater treatment technology for the disposal of refractory organic contaminants. Nevertheless, its practical implementation was limited by the high energy consumption of microwaves and the poor sustainable reactivity of catalysts. To address these issues, the microwave-assisted dielectric-activation double-responsive Co/Fe carbon-based catalyst (CoFe/NC-3) was used to activate peroxymonosulfate (PMS) for oxidative degradation of refractory diatrizoate (DTZ). The results showed that the DTZ was completely degraded within 6 min in the MW/CoFe/NC-3/PMS reaction system, and the degradation efficiency increased by 82.38% compared with the MW/Fe/NC/PMS system. It was attributed to the enriched active sites and prolonged redox cycling capability of the bimetallic catalysts. Moreover, microwave enhanced electron migration ability to accelerate the circulation of Fe3+/Fe2+/Fe0 and Co3+/Co2+ and generate more reactive oxygen species (ROSs) for the high-efficiency degradation of DTZ. The degradation pathways of DTZ were elucidated by LC-MS in combination with DFT calculation and the product toxicity was evaluated using ecological structure-activity relationship software (ECOSAR). The results showed that the majority of intermediate degradation products were not acute or chronic toxicity to fish, daphnia, and green algae. Overall, these results revealed that the MW/CoFe/NC-3/PMS system was a cost-effective and stable method for wastewater treatment.

Carbon redirection via tunable Fenton-like reactions under nanoconfinement toward sustainable water treatment

The ongoing pattern shift in water treatment from pollution control to energy recovery challenges the energy-intensive chemical oxidation processes that have been developed for over a century. Redirecting the pathways of carbon evolution from molecular fragmentation to polymerization is critical for energy harvesting during chemical oxidation, yet the regulation means remain to be exploited. Herein, by confining the widely-studied oxidation system—Mn3O4 catalytic activation of peroxymonosulfate—inside amorphous carbon nanotubes (ACNTs), we demonstrate that the pathways of contaminant conversion can be readily modulated by spatial nanoconfinement. Reducing the pore size of ACNTs from 120 to 20 nm monotonously improves the pathway selectivity toward oligomers, with the yield one order of magnitude higher under 20-nm nanoconfinement than in bulk. The interactions of Mn3O4 with ACNTs, reactant enrichment, and pH lowering under nanoconfinement are evidenced to collectively account for the enhanced selectivity toward polymerization. This work provides an adaptive paradigm for carbon redirection in a variety of catalytic oxidation processes toward energy harvesting and sustainable water purification.

Research into arsenic (III) effective catalytic oxidation in an aqueous solution on a new active manganese dioxide in a flow column

Groundwater in many places on Earth contains arsenic compounds. Arsenic (III) compounds must be oxidised to purify water containing arsenic effectively. The subject of this study is oxidation of arsenic (III) compounds in an aqueous solution. Today’s most common industrial arsenic oxidation method using aggressive oxidising agents such as chlorine or ozone has a number of serious disadvantages. The most problematic of these include extremely high risks to human health and the environment, the cost and overall complexity of the process. Catalytic oxidation of arsenic (III) compounds using atmospheric oxygen is an alternative free from the above disadvantages, yet, to date, no information about effective catalysts for this process has been presented in the literature. The arsenic (III) catalytic oxidation process is studied in an aqueous solution on a new active manganese dioxide (NAMD) synthesised by the author. A comparative experimental analysis is performed with other known modifications of manganese dioxide. It is shown that the new active manganese dioxide (NAMD) has high catalytic activity towards arsenic (III), this being confirmed experimentally in both a limited volume and a flow column mode. Some theoretical aspects of the mechanism for catalytic oxidation of arsenic (III) with oxygen on active manganese dioxide in an aqueous solution are also discussed on the basis of the research results. Experimental work is required at pilot plants in the field for successful industrial implementation of the technology for catalytic oxidation of arsenic (III) compounds on NAMD. Further laboratory research is necessary for developing a detailed theoretical basis for catalytic oxidation of arsenic in aqueous solutions. The results of this research are of interest to industrial companies specialising in removing arsenic compounds from water, to scientists and researchers studying catalytic oxidation of arsenic (III), as well as heterogeneous catalytic oxidation with oxygen in general.

Crystal Plane Regulation Promotes the Oriented Conversion of Radicals in Heterogeneous Persulfate Catalyzed Oxidation Process.

In heterogeneous persulfate-catalyzed oxidation systems, the mechanism underlying the crystal plane effects of the catalyst on the selective conversion of reactive oxygen species (ROS) remains ambiguous. In this study, nano-Co3O4 catalysts with varying crystallinity and exposure levels of (111) crystal planes are prepared via a hydrothermal method. Compared to low crystalline catalysts, high crystallinity catalysts predominantly expose (111) planes containing higher concentrations of Co2+ and oxygen vacancies (Ov), resulting in an increase degradation efficiency of p-nitrobenzaldehyde (4-NBA) from 74.5% to 100%. Radical quenching experiments and EPR characterization reveal that the degradation of 4-NBA occurs through a radical pathway, and quantification of radicals demonstrates that increasing exposure levels of (111) planes effectively promote radical yield (CSO4•- increase from 18.2 to 172.8 µm and C•OH increase from 1 to 58.9 µm). Furthermore, XPS and DFT calculations indicate that high crystallinity catalyst possesses more Ov active sites on (111) planes. The presence of Ov not only facilitates the adsorption of PMS molecules but also enhances electron transfer from Co2+ to PMS, leading to directed formation and efficient transformation of radicals. This study presents a novel strategy for promoting efficient radical formation in persulfate-activated systems.

Activation of peroxymonosulfate using heterogeneous Fe-doped carbon-based catalyst to generate singlet oxygen for the degradation of sulfamethoxazole

Non-radical catalytic oxidation processes can eliminate refractory pollutants from wastewater containing complex substrates such as dissolved organic matter, but the production of selective non-radicals is challenging during the activation of peroxymonosulfate (PMS). Herein, a novel magnetic carbon-based catalyst (Fe3O4@CD-8, where 8 represents an annealing temperature of 800 ℃) with N and Fe species as catalytic active sites was fabricated to remediate sulfamethoxazole (SMX)-containing water. It showed excellent SMX removal efficiency and facilitated singlet oxygen (1O2) production. The characterization results revealed that Fe3O4@CD-8 had a microscopically hierarchical pore structure and an overall core–shell-like structure. Due to its large specific surface area, N-containing species, and Fe nanoparticles, 0.1 g/L Fe3O4@CD-8 removed almost 100% SMX (24 min) and achieved a 44.1% mineralization (40 min) efficiency in the presence of 0.5 mM PMS. This catalytic system also maintained its removal performance in the presence of inorganic anions and humic acids and over a wide pH range of 3–11, showing good tolerance to various environmental factors. 1O2 was confirmed to be the predominant active species for SMX degradation using the Fe3O4@CD-8/PMS system. Density functional theory (DFT) calculations, intermediate monitoring, and toxicity evaluation demonstrated that SMX was transformed into low-toxicity molecules and completely mineralized into CO2 and H2O. The addition of Fe nanoparticles enhanced PMS adsorption and facilitated the Fe(III)/Fe(II) redox cycle to accelerate the activation of PMS. This study provides new insights and strategies for the controlled production of non-radicals for remediating antibiotic-containing wastewater.

A novel method for the remediation of o‐ and p‐aminophenol from industrial wastewater by hexacyanoferrate (III) ions using Ir‐complex catalyst

AbstractIn this manuscript o‐ and p‐aminophenols model environmental pollutants are being remedied by catalytic oxidation process. A kinetic‐spectrophotometric technique was used to study the remediation of o‐ and p‐aminophenol by hexacyanoferrate (III) ions as an oxidant and synthesized Ir‐DTPy complex as a catalyst in aqueous alkaline medium. The optimum pH for these experiments was 9.0 and 11.0 for o‐ and p‐aminophenol respectively at the constant temperature 25°C. It has been studied how variations in the concentration of the catalyst (Ir‐DTPy), the hexacyanoferrate (III) ions, and substrate affect the rate of the reaction. At four different temperatures, ranging from 25 to 40°C, the change in reaction rate has been analyzed with thermodynamic variables like free energy of activation, enthalpy, frequency factor, and activation energy. FTIR, UV‐Vis, and ESI‐MS spectroscopic analytical methods have been used to identify the oxidized products. 2‐aminophenoxazin‐3‐one and NN'‐bis‐(p‐hydroxyphenyl)‐2‐hydroxy‐5‐amino‐1, 4‐benzoquinone di‐imine are the main products of oxidation of o‐and p‐aminophenol, respectively. Therefore, this technique for removing o‐ and p‐aminophenol from contaminated water resources is very effective and environmentally safe.

Study on the Catalytic Oxidation Modification Effect of Heavy Oil at Low Temperature under the Action of Different Ligand Ferric-Based Systems

This work explores the low-temperature catalytic oxidation of heavy oil (140 °C), resulting in structural changes with reduced heavy components and increased light components. The catalytic oxidation system consists of a catalyst, an oxidant, and a proton donor. Four different complexes of iron-based catalysts were utilized: ferric oleate, iron naphthenate, EDTA–FeNa, and EDDHA–FeNa. Catalytic oxidation processes with these catalysts produced four types of oxygenated oil, which were then analyzed using group composition analysis and a viscosity test. The results show that EDDHA–FeNa is more favorable for the catalytic oxidation of heavy oil in a low-temperature environment, achieving a viscosity reduction rate of 78.57%. Furthermore, the catalytic performance of heavy oil oxidation was investigated using EDDHA–FeNa as catalyst under three conditions: the amount of catalyst, oxidant and reaction temperature. These findings may provide researchers valuable guidance and principles for the investigation and development of advanced catalytic viscosity reduction of heavy oil.

Catalytic combustion of toluene performance over MnOx catalysts: Effect of KMnO4 content

MnOx samples were prepared and applied to the catalytic combustion of toluene. The results indicated that the KMnO4 content was important to the catalytic performance. Cat‐0.2 (0.2 g KMnO4) possessed the best catalytic performance, and more than 90% of toluene conversion was 255°C. Moderate amounts of KMnO4 facilitated the generation of mixed crystalline phases and structural defects, which led to the generation of more oxygen vacancies. In addition, the Cat‐0.2 possessed high contents of Oads/(Oads + Olatt) and Mn3+/(Mn3+ + Mn4+), which promoted the emergence‐annihilation cycle of oxygen vacancies and facilitated the reaction process of toluene. The reaction pathway of toluene was investigated via in situ DRIFTS, in which the by‐products included benzyl alcohol, benzaldehyde, benzoate, maleic anhydride, and short‐chain carbonate. Among them, benzoate was the main intermediate in the catalytic oxidation process of toluene.

Channel Confinement Enables K Species with Rich Electrons in α‐MnO2 for Water Molecules Activation

AbstractWater molecules are actively involved in many catalytic oxidation processes, which require the construction of highly active sites for their activation to accelerate the reaction rate, especially over non‐noble metal catalysts. Herein, K species is embeded into the natural 2*2 channel of α‐MnO2 by a hydrothermal coupled molten salt method, which would make these K species behave in an electron‐rich state and provide more electrons for the activation of water molecules. Compared with surface K modification (namely, the electron‐deficient K species), channel K confinement can lower the activation energy barrier of H2O dissociation on α‐MnO2 to generate hydroxyl species with more nucleophilic oxygen atoms, contributing to the superior HCHO catalytic oxidation activity with a fourfold enhancement. The internal relationship among the confined channel, K species, and catalytic performance is systematically elucidated at the molecular level. This work offers a new ion confinement method and opens up new avenues to construct electron‐rich metal sites with channel structures for the activation of water molecules.

Theory-guided unraveling of the mechanism underlying Cu1.0/Mn1.0-ZnO with dual reaction centers for enhanced peroxymonosulfate activation

Developing efficient catalytic systems for water contamination removal is a topic of great interest. However, the use of heterogeneous catalysts faces challenges due to insufficient active sites and electron cycling. In this study, results from first-principles calculations demonstrate that dual reaction centers (DRCs) are produced around the Cu and Mn sites in Cu1.0/Mn1.0-ZnO due to the electronegativity difference. Experimental results reveal the material with DRCs greatly enhances electron transfer efficiency and significantly impacts the oxidation and reduction of peroxymonosulfate (PMS). In addition, the self-consistent potential correction (SCPC) method was introduced to correct the energy and charge of charged periodic systems simulating a catalytic process, resulting in more precise catalytic results. Specifically, the material exhibits a preference for adsorbing negatively charged PMS anions at electron-deficient Mn sites, facilitating PMS oxidation for the generation of 1O2, and PMS reduction around the electron-rich Cu for the formation of •OH and SO4•−. The major reactive oxygen species is 1O2, showcasing effective performance in various degradation systems. Overall, our work provides novel insights into the persulfate-based heterogeneous catalytic oxidation process, paving the way for the development of high-performance catalytic systems for water purification.

Ozone oxidation of nitric oxide: Promoting effect of phosphorus and inhibitory effect of phosphoric acid

AbstractThis work presents experimental and density functional theory theoretical methods to carry out the catalytic role and reaction mechanism of phosphorus (P4) for liquid phase catalytic oxidation nitric oxide. Meanwhile, it carries out the promoting effect of phosphorus and inhibitory effect of phosphoric acid in the ozone oxidation of nitric oxide. The work reveals the significant involvement of P4 in facilitating the NO catalytic oxidation process by generating O3. Meanwhile, the presence of phosphoric acid (H3PO4) hindered the NO catalytic removal process. The calculation results highlight that P4 promoted the formation of O3 and favoured the oxidation pathway (oxidation‐hydration, NO ➔ NO2 ➔ HNO3). During the liquid‐phase NO catalytic removal process, O2 and NO dissolved into the solution, where O2 exhibited preferential adsorbed on P4, promoting the O3 formation. Subsequently, O3 first oxidized NO to NO2. Then, HNO2 and HNO3 were generated under the hydration reaction of NO2 and H2O. Next, O3 further oxidized the generated HNO2 to HNO3, realizing the complete oxidation of NO. The hydration step of NO2 was identified as the key step in the O3 oxidation processes. Furthermore, the generation of H3PO4 led to the consumption of P4 and inhibited the NO removal process. O3 played the crucial role in liquid phase NO oxidation.

Experimental study of CeO2 after hydrothermal aging on emission characteristics of carbon black oxidation process

The CeO2 catalyst is commonly utilized in diesel particulate filter (DPF) to promote soot regeneration. It is necessary to give a particular attention to the performance of hydrothermal aging and the effect on DPF regeneration characteristics. Based on the fixed-bed test bench, the gas and particle emission characteristics of carbon black (PU) oxidation following hydrothermal aging and sieving treatment of CeO2 are investigated under a 3% water concentration condition. CeO2 is subjected to characterization and analysis combined with X-ray Photoelectron Spectroscopy (XPS), Electron Spin Resonance Spectroscopy (ESR), X-ray Powder Diffraction (XRD), and Scanning Electron Microscopy (SEM). The results indicate that the addition of fresh CeO2 proves beneficial in improving the oxidation efficiency (η) of PU, reducing CO emission and the total average particle number (PN). Meanwhile, CO2 emission rapidly increases. After hydrothermal aging, the average catalyst size and agglomeration degree of CeO2 increase, resulting in an increase in lattice defects and bulk oxygen vacancies (VO-b). The reduction of surface oxygen vacancies (VO-s) plays a dominant role in the catalytic oxidation process of PU, leading to a decrease in η and CO2 emission, while CO increase; And the contact mode between CeO2 and PU, as well as alterations in the microstructure of CeO2, consequently contributing to hindering particle movement and reducing total PN. Furthermore, the sieving treatment of catalyst increases particle emission, but significantly promotes the η and reduces harmful gas CO. This research establishes a theoretical and experimental foundation for enhancing the hydrothermal stability of catalysts and controlling particle emission at the DPF outlet.

Studies on adsorption properties of magnetic composite prepared by one-pot method for Cd(II), Pb(II), Hg(II), and As(III): Mechanism and practical application in food

A one-pot synthesis afforded a magnetic, crosslinked polymer adsorbent (m-P6) with a variety of functional groups to realize simultaneous adsorption of Cd2+, Pb2+, Hg2+, and As3+. The material was characterized by TEM-EDS, XRD, FT-IR, VSM, and XPS. Kinetic and isothermal analyses suggested mainly chemisorption processes of heavy metal ions that form multiple layers on heterogeneous surfaces. Theoretical adsorption capacities calculated by a pseudo-2nd-order kinetic model and the Sips isothermal model were 282.88 mg/g for Cd2+, 326.18 mg/g for Pb2+, 117.85 mg/g for Hg2+, and 320.29 mg/g for As3+. m-P6 not only can efficiently adsorb divalent heavy metals (Cd2+, Pb2+, Hg2+), but also demonstrate a process of adsorption-driven catalytic oxidation by single-electron transfer (SET) from As3+ to As5+. In application, in addition to adsorption in water, m-P6 is capable of minimizing matrix interference, and extracting trace heavy metals in a complex environment (cereal) through easy operations for improving the detection accuracy, as well as it is potential for application in detection of trace heavy metals in foodstuffs. m-P6 can be readily regenerated and efficiently recycled for 5 cycles using eluent E12 and dilute acid.