Radical Reactions Research Articles

New particle formation from isoprene under upper-tropospheric conditions

Aircraft observations have revealed ubiquitous new particle formation in the tropical upper troposphere over the Amazon1,2 and the Atlantic and Pacific oceans3,4. Although the vapours involved remain unknown, recent satellite observations have revealed surprisingly high night-time isoprene mixing ratios of up to 1 part per billion by volume (ppbv) in the tropical upper troposphere5. Here, in experiments performed with the CERN CLOUD (Cosmics Leaving Outdoor Droplets) chamber, we report new particle formation initiated by the reaction of hydroxyl radicals with isoprene at upper-tropospheric temperatures of −30 °C and −50 °C. We find that isoprene-oxygenated organic molecules (IP-OOM) nucleate at concentrations found in the upper troposphere, without requiring any more vapours. Moreover, the nucleation rates are enhanced 100-fold by extremely low concentrations of sulfuric acid or iodine oxoacids above 105 cm−3, reaching rates around 30 cm−3 s−1 at acid concentrations of 106 cm−3. Our measurements show that nucleation involves sequential addition of IP-OOM, together with zero or one acid molecule in the embryonic molecular clusters. IP-OOM also drive rapid particle growth at 3–60 nm h−1. We find that rapid nucleation and growth rates persist in the presence of NOx at upper-tropospheric concentrations from lightning. Our laboratory measurements show that isoprene emitted by rainforests may drive rapid new particle formation in extensive regions of the tropical upper troposphere1,2, resulting in tens of thousands of particles per cubic centimetre.

Unraveling the Autoxidation Mechanisms of Limonene, α-Pinene, and β-Pinene: A Computational Study with Reactivity Prediction Models.

The hydrogen shift reactions of peroxy radicals derived from the ȮH-initiated oxidation of three atmospherically important monoterpenes, limonene, α-pinene, and β-pinene, have been studied. The Bell-Evans-Polanyi relationship (BEPR), Marcus cross relationship (MCR), and Robert-Steel relationship (RSR) are employed to study the factors that contribute to the kinetics of the H-shift reactions. Our results show distinct kinetic behaviors based on the size of the transition-state ring, the functional group present at the H atom abstraction site, and the type of carbon-centered radical formed. Except for the 1,5-H-shift reactions, the MCR successfully predicts the activation enthalpy with minimal mean absolute errors by dividing it into intrinsic and thermodynamic components. The RSR, which considers the bond dissociation energy, polarity effects, and structure factor while calculating the activation enthalpy, exhibits a good correlation (R2 = 0.97) with the activation enthalpy calculated through electronic structure calculations. The present study elucidates the factors contributing to the kinetics of the H-shift reactions, aiding in the development of reactivity prediction models.

The Underestimated Role of Iron in Frontotemporal Dementia: A Narrative Review

The term frontotemporal dementia (FTD) comprises a group of neurodegenerative disorders characterized by the progressive degeneration of the frontal and temporal lobes of the brain with language impairment and changes in cognitive, behavioral and executive functions, and in some cases motor manifestations. A high proportion of FTD cases are due to genetic mutations and inherited in an autosomal-dominant manner with variable penetrance depending on the implicated gene. Iron is a crucial microelement that is involved in several cellular essential functions in the whole body and plays additional specialized roles in the central nervous system (CNS) mainly through its redox-cycling properties. Such a feature may be harmful under aerobic conditions, since it may lead to the generation of highly reactive hydroxyl radicals. Dysfunctions of iron homeostasis in the CNS are indeed involved in several neurodegenerative disorders, although it is still challenging to determine whether the dyshomeostasis of this essential but harmful metal is a direct cause of neurodegeneration, a contributor factor or simply a consequence of other neurodegenerative mechanisms. Unlike many other neurodegenerative disorders, evidence of the dysfunction in brain iron homeostasis in FTD is still scarce; nonetheless, the recent literature intriguingly suggests its possible involvement. The present review aims to summarize what is currently known about the contribution of iron dyshomeostasis in FTD based on clinical, imaging, histological, biochemical and molecular studies, further suggesting new perspectives and offering new insights for future investigations on this underexplored field of research.

Impact of niobium doping on photocatalytic degradation efficiency of iron oxide nanoparticles for methylene blue dye under UV and sunlight

Iron oxide (Fe2O3) nanoparticles were synthesized using lemon peel extract with niobium (Nb) doping (2, 4, and 6 mmol) via a hydrothermal method. Characterization techniques included FTIR, UV–Vis spectroscopy, XRD, PSA, and zeta potential measurement. FTIR confirmed Nb integration, with Fe-O and Nb-O bonds at 1.65 Å and 1.34 Å. Nb doping reduced particle size (93.74 nm to 56.01 nm) and enhanced stability (zeta potential −13.04 to −37.31 mV). XRD analysis confirmed phase purity and crystalline structure, while the Scherrer and Williamson-Hall methods revealed decreases in crystallite size and lattice strain with higher Nb concentration. Bandgap analysis showed a red shift (3.08 to 2.28 eV) due to Nb-doped energy levels. Nb-doped Fe2O3 (6 mmol) achieved 87 % degradation of methylene blue (10 ppm) under sunlight in 2 h. Enhanced photocatalysis resulted from prolonged electron-hole recombination, generating reactive radicals. These Nb-doped Fe2O3 nanostructures are promising for pollutant degradation in water environments.

Rapid photocatalytic degradation of selective organic dyes using metal oxide-metal sulphide and its inverted nanocomposites

The chemical precipitation approach was employed to synthesize novel heterostructures, namely CeO2-ZnS and SnO2-ZnS, along with inverted nanocomposites ZnS-CeO2 and ZnS-SnO2. The nanocomposites were subjected to characterization using various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis absorption spectra, and photoluminescence spectra. The TEM images demonstrated particles that were homogeneous, well-dispersed, and comparatively tiny with a sphere-like structure. This indicates successful synthesis and desirable morphological properties of the nanocomposites. The integration of varied nanoparticles within a heterostructure commonly gives rise to synergistic effects, imparting superior properties to the composite compared to the individual components. These nanocomposites tested for their photocatalytic degradation efficiency using Rose Bengal (RB) and Crystal Violet (CV) dyes under natural sunlight and they exhibited approximately 95 % degradation rate. The degradation results demonstrated a significant enhancement in the photocatalytic efficiency of ZnS-CeO2 and CeO2-ZnS nanocomposites. This improvement was attributed to the effective recombination suppression of photogenerated electron-hole pairs, leading to the generation of highly reactive free radicals. The first-order kinetic rate constant for CeO2-ZnS was determined to be 0.52 min−1 for CV and 0.53 min−1 for RB. The present research work has the potential to offer a novel approach to the construction of new heterojunction photocatalysts and to provide a more profound understanding of the treatment of textile organic dyes.

Copper@MXene quantum dots-aerogel: High-performance peroxidase mimic for direct pirimiphos-methyl pesticide detection

Due to their cost-efficiency and heightened sensitivity, the rational design of artificial nanozymes has become a paramount research direction. In this investigation, we elaborate on a simplified freeze-drying methodology for fabricating Cu@MXene quantum dots-aerogel (Cu@MQDs-aerogel), which possesses augmented peroxidase-mimicking activity. Through steady-state fluorometric analysis, we delve into the catalytic mechanism of Cu@MQDs-aerogel, uncovering its proficiency in decomposing H2O2 into reactive hydroxyl radicals (OH). Density functional theory (DFT) calculations further validate that the outstanding catalytic prowess of Cu@MQDs-aerogel stems from the interfacial Cu-Ti dimer active sites, significantly activating adsorbed H2O2 and facilitating its decomposition into OH. As a result, we introduce a sensitive colorimetric sensor for pirimiphos-methyl detection, achieving a low detection limit of 0.65 nM. Additionally, it exhibits a narrow relative standard deviation (RSD) interval spanning from 1.03 % to 2.66 %. This study introduces a novel strategy for the design and synthesis of MQDs-based peroxidase-like enzymes, highlighting their significant potential in environmental pollutant detection.

A pH-responsive copper selenide nanozyme modulates multiple enzyme activities for improved healing of infected wounds

Bacterial infections can slow down wound healing and pose a threat to human health, which remains a challenging issue in clinical practice. The rise of nanozymes has provided new therapeutic approaches for antimicrobial treatment. Here, we report pH-responsive copper selenide nanoparticles (Cu1.79Se, hereafter referred to as CuSe), which exhibits peroxidase (POD)-like activity under weakly acid bacterial infection conditions, generating highly reactive hydroxyl radicals (·OH) that kill bacteria and alleviate wound infections. In the later stages of wound healing, it is neutral or weakly alkaline, the CuSe nanoparticles shows catalase (CAT) and superoxide dismutase (SOD)-like activities, clearing excessive reactive oxygen species (ROS) and producing O2, thus protecting normal tissues from damage caused by both external and endogenous ROS. The above feature helps damaged tissue cells regain their ability to proliferate and migrate, also promotes angiogenesis, achieving a "two birds with one stone" effect. It is expected that the CuSe nanoparticles could be a promising antimicrobial agent for wound healing.

Tetracycline degradation for wastewater treatment based on ozone nanobubbles advanced oxidation processes (AOPs) – Focus on nanobubbles formation, degradation kinetics, mechanism and effects of water composition

Presence of pharmaceuticals, especially antibiotics, in industrial and domestic effluents causes serious damage to the environment. Classic wastewater treatment processes, in particular conventional biological treatment methods, are not sufficient to rapidly eliminate antibiotics. Typically, Advanced Oxidation Processes (AOPs) based on activation of hydrogen peroxide, ozone or persulfate for production of particular type of radical species or singlet oxygen are used. A one of cutting-edge technologies to increase effectiveness of AOPs based on ozone are nanobubbles based processes. Thus, this paper focuses on utilization of ozone in the form of nanobubbles for degradation of tetracycline (TC). The effects of several reaction parameters, such as antibiotic concentration, ozone intake, pH, presence of salts, were investigated. This study revealed that the presence of ozone nanobubbles had a substantial positive impact on the degradation of TC. This improvement may be attributed to the enhanced mass transfer and the production of reactive radicals that occur during the collapse of the nanobubbles. Identification of radical species revealed a significant contribution of hydroxyl radicals in the degradation of the antibiotic. AOP process based on O3 nanobubbles was most (•OH) and superoxide (O2–) effective with 100 % degradation efficiency of 100 mg/L TC within 20 min at 8 mg/L concentration of ozone. Based on identified by LC-MS intermediates a degradation mechanism has been described. Degradation of TC and intermediates transformations included methylation, hydroxylation, ring-opening steps as well as cleavage of C-N bonds. This research introduces a novel technique combining nanobubbles with advanced oxidation processes (AOPs), which is anticipated to provide enhanced efficiency and environmental sustainability.

Facile electrospinning-electrospray method to fabricate flexible rice straw-derived cellulose acetate/TiO2 nanofibrous membrane with excellent photocatalytic performance

A novel and facile electrospinning-electrospray (EE) method that based on electrospinning technique and simultaneous electrospray was proposed to anchor TiO2 (P25) nanoparticles on the surface of rice straw-derived cellulose acetate (CA) nanofiber, a series of EE-CA/P25 nanofibrous membranes with different P25 dosage were successfully fabricated, which were characterized in terms of SEM, TEM, FI-IR, XRD, DRS, PL, UV–vis and 3D-EMMs, etc. Results confirmed that P25 nanoparticles were anchored on the surface of CA nanofiber. For different organic dyes of Methylene blue (MB), Rhodamine B (RhB) and Methyl orange (MO), EE-CA/P25(0.05) nanofibrous membrane toward MB dye showed the best photocatalytic degradation efficiency of 99.13 % after 30 min of light exposure. For the different antibiotics of Tetracycline (TC), Ciprofloxacin (CIP) and Sulfamethoxazole (SMX), EE-CA/P25(0.05) exhibited the best photocatalytic degradation efficiency of 83.59 % for TC after 30 min of light exposure. Moreover, EE-CA/P25(0.05) exhibited a good antimicrobial efficiency of 98.42 % for E. coli, and maintained 97.49 % after 5 cycles. The reactive radical trapping experiments revealed that h+, •O2−, and •OH participated in the reaction, and h+ and •O2− played a major role in the photocatalytic degradation process. Moreover, EE-CA/P25(0.05) flexible membrane was easy to recycle and transform rice straw waste into treasure.

Mechanism of action of persulfate activation based on humic acid modified sludge biochar: Enhancement of electron transfer mechanism

Humic acid (HA) was used to modify sludge biochar (SBC) in order to prepare HBC with higher defect structure and abundant oxygenated functional groups. The degradation of TC by HBC was up to 90 % much higher than that of SBC (30 %). HBC possessed a large number of defective structures and oxygenated functional groups, which contributed greatly to the activation of PMS. The co-regulation of highly exposed active sites such as CO, pyrrole N and pyridine N on HBC2, which played a key role in the activation of PMS. In addition, the results of electrochemical tests indicated that an active intermediate (Persistent free radicals PFRs). Oxygen-centered PFRs were implicated in the movement of electrons through conversion to carbon centers. The conductivity of the process was enhanced by the presence of graphite N. A large number of reactive radicals made sufficient preparations for the production of PFRs. Mutual electron transfer between the oxygen and carbon centers of PFRs was the main mechanism. In addition, the PFRs mechanism and the 1O2 mechanism were subjected, which yielded that both degrade TC by electrophilic addition attack and ring-opening reaction, respectively.

Kinetic modeling of sulfonamide degradation by UV/H2O2: Deduction of ROH,UV modeling and application

Eight sulfonamide (SA) antibiotics were effectively degraded using a UV/H2O2 process in a quasi-collimated beam apparatus, utilizing optimized fluence quantification. Fluence-based rate constants (kk'SA) for the UV/H2O2 process were established. A curve-fitting method, derived from ROH,UV modeling, was developed for the UV/H2O2 process to quantitatively assess the impact of critical factors, including water quality and direct UV photolysis. It was observed that k'SA values approached a limiting value as initial H2O2 concentration increased. The specific second-order rate constants for •OH reactions with neutral and anionic SA species were determined to be within (2.2–5.7) × 10⁹ M⁻1 s⁻1, showing minimal variation among species. For the eight SAs studied, k'SA values were calculated from 3.9 × 10⁻⁴ to 6.0 × 10⁻2 cm2 mJ⁻1 across a typical pH range of 6.5–9.5. Direct UV photolysis was notably significant in SA degradation, particularly for sulfisoxazole, contributing at least 35%. An energy cost equation was formulated to evaluate the cost-effectiveness of SA degradation by UV/H2O2 and optimize operational parameters. This model, validated in real water scenarios, shows promise for predicting SA removal in UV/H2O2 processes. The developed curve-fitting method, pH-independent and accounting for both direct photolysis and OH radical reactions, is apt for modeling mixed-contaminant degradation in UV/H2O2 processes, simplifying calculations in ROH,UV modeling.

A DFT analysis of the antioxidant capacity of scopolin and scopoletin.

Scopolin and scopoletin belong to the class of coumarins and have experimentally proven natural antioxidants. Natural antioxidants are crucial in mitigating the impact of oxidants in the human body through radical scavenging. Even though scopolin and scopoletin are proven antioxidants by experimental results, their antioxidant mechanisms still remained unexplained. In this study, Density functional theory (DFT) calculations were used to study the radical scavenging mechanisms of both scopolin and scopoletin using kinetic and thermodynamics parameters. The global parameters indicated that both scopolin and scopoletin have antioxidant properties. The band gap energy revealed that scopoletin (4.18eV) has strong antioxidant activity compared to scopolin (4.31eV). These studies found that hydrogen atom transfer (HAT) is the primary mechanism for CH3OO• radical scavenging at the C-H bond in scopolin (91.98kcal.mol-1) and the O-H bond in scopoletin (77.05kcal.mol-1) due to their lowest bond dissociation energies. The calculated activation energy ( ) for the radical scavenging reaction, reconfirmed scopoletin ( =11.19kcal.mol-1) performed as a better antioxidant compared to scopolin ( =20.91kcal.mol-1). In this study, the results of DFT calculations confirmed that scopoletin exhibits a higher antioxidant capacity, and HAT mechanism is the most effective radical scavenging mechanism. The antioxidant activity of scopolin and scopoletin was determined by DFT at the B3LYP/6-31G(d) level of theory. Global parameter calculations and frontier molecular orbital analysis were conducted to assess these compounds' capacity for scavenging radicals. Hydrogen atom transfer (HAT), sequential electron transfer proton transfer (SETPT), and sequential proton loss electron transfer (SPLET) mechanisms were the three main mechanisms that were taken into consideration. The potential energy surface (PES) verified the most appropriate processes shown by the enthalpy calculations.

Fabrication and characterization of ZnO and Ag/ZnO nanoparticles for efficient degradation of crystal violet dye in aqueous solution

ZnO nanoparticles (ZnO NPs) were efficiently synthesized using three different methods: hydrothermal (ZnOhyd), solvothermal (ZnOsol), and co-precipitation (ZnOcop). The resulting ZnO NPs were further decorated with Ag NPs through photoreduction. All ZnO NPs and Ag/ZnO NPs were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier transforms infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), nitrogen adsorption-desorption at −196 °C for porous structure analysis, UV–Visible spectroscopy, and photoluminescence (PL) measurements. The results confirmed that all ZnO NPs have a wurtzite hexagonal structure and that Ag NPs were successfully incorporated into the ZnO crystal lattice. The BET surface area of Ag/ZnOcop (150 m2/g) is much higher than that of undecorated ZnOcop (34 m2/g), confirming the successful incorporation of Ag nanoparticles. A redshift in the spectral absorption towards the visible light region and a reduction in the band gap, from 3.1 eV to 2.7 eV, was observed for the Ag/ZnOcop sample. The photocatalytic activities of ZnO NPs synthesized with different methods and Ag/ZnOcop NPs were assessed by their ability to degrade crystal violet (CV) in an aqueous solution when exposed to UV light. The Ag/ZnOcop sample had the highest degradation rate (95 %) than pure ZnOcop NPs (88.9 %). This degradation process relies on dye oxidation by highly reactive hydroxyl radicals, and several factors can affect its efficiency. The reduced PL intensity of Ag/ZnOcop compared to ZnOcop indicated that Ag NPs inhibit electron-hole recombination, enhancing photocatalytic activity by promoting charge separation.

Synthesis of Diones via Visible Light‐Induced Oxidation of α‐Hydroxy Ketone Derivatives

AbstractA visible light‐induced oxidation of α‐hydroxy ketone derivatives is reported, which is carried out in the presence of CBrCl3 and ruthenium photocatalyst, and the corresponding diketones are obtained in 49‐95% yields. This reaction has the advantages of moderate to excellent yields, good functional group tolerance, and mild reaction condition. The free radical reaction process was confirmed by the addition of radical scavenger 2,2,6,6‐tetramethylpiperidi‐1‐oxy (TEMPO). The fluorescence quenching experiment indicated that CBrCl3 was participated in the oxidation quenching cycle.

Reactions of a Prototypical Phenolic Antioxidant with Radicals in Polyethylene: Insights from Density Functional Theory.

Phenolic antioxidants are widely used to prevent oxidation, which is the main degradation process for many polymers, in particular polyolefins among which polyethylene is the most employed one. Although it is generally understood that one of the main mechanisms by which phenolic antioxidants prevent or slow down oxidation is by deactivating radicals and preventing the formation of alkyl radicals, detailed understanding at the atomic scale of the hierarchy of radical reactions is still lacking. Here, we investigate the interaction of a prototypical phenolic antioxidant, butylated hydroxytoluene (BHT), with radicals in a polyethylene model by means of static and dynamic simulations based on density functional theory. We focus on the H-transfer reactions between BHT and radical species by evaluating the associated energy barriers and analyze the conditions in which these relevant reactions occur by first-principles molecular dynamics simulation. Our polyethylene model includes a realistic surface of a crystalline lamella, thus describing the local atomic environment in which the reactions mainly take place. Our results suggest that the H-transfer reaction of the BHT molecule with an alkoxy radical is spontaneous, and the energy barrier is small (∼0.1 eV) with a peroxy radical. Conversely, direct scavenging of alkyl radicals by BHT seems excluded. Our molecular dynamics simulations highlight the influence of steric hindrance and antioxidant diffusion within amorphous regions on antioxidant efficiency.

Impact of Transition-State Aromaticity on Selective Radical-Radical Coupling of Triarylimidazolyl Radicals.

Radical coupling reactions are generally known to have a low selectivity due to the high reactivity of radicals. In this study, high regio and substrate selectivity was discovered in the dimerization of triarylimidazolyl radicals (TAIR), a versatile photochromic reaction. When two different radicals, 2-(4-cyanophenyl)-4,5-diphenyl-1H-imidazolyl radical (CN-TAIR) and 2-(4-methoxyphenyl)-4,5-diphenyl-1H-imidazolyl radical (OMe-TAIR), were simultaneously generated in situ, a hexaarylbiimidazole, formed by selective coupling at the nitrogen atom at position 1 of CN-TAIR and the carbon atom at position 2 of OMe-TAIR, was isolated with high selectivity as the main product among 24 possible radical dimer hexaarylbiimidazole derivatives. This high regio and substrate selectivity cannot be explained solely by the stability of the product and/or the electrophilicity and nucleophilicity of the radicals but originates from the aromaticity of the transition state in the radical-radical coupling reaction. To date, the selectivity of radical coupling reactions has been thought to be controlled by steric hindrance and radical spin density, but this study revealed a new factor for controlling radical coupling, that is, transition-state aromaticity. Aromaticity has been reported to have an important effect not only in the reactivity and structure of ground-state molecules but also on the electronically excited states and transition states in pericyclic reactions such as the Diels-Alder reaction and the Cope-Claisen rearrangement. This study demonstrated for the first time that radical coupling reactions can also be controlled by transition-state aromaticity.

Chemical Pathways of SO2 with Hydrogen Atoms on Interstellar Ice Analogues

Sulfur dioxide (SO2) is a sulfur-containing molecule expected to exist as a solid in the interstellar medium. In this study, we have performed laboratory experiments and computational studies on the surface reactions of solid SO2 with hydrogen atoms on amorphous solid water (ASW) at low temperatures. After 40 minutes of exposure of SO2 deposited on ASW to H atoms, approximately 80% of the solid SO2 was lost from the substrate at 10–40 K, and approximately 50% even at 60 K, without any definite detection of reaction products. Quantum chemical calculations suggest that H atoms preferentially add to the S atom of solid SO2, forming the HSO2 radical. Further reactions of the HSO2 radical with H atoms result in the formation of several S-bearing species, including HS(O)OH, the S(O)OH radical, HO–S–OH, HS–OH, and H2S. In codeposition experiments involving H and SO2, we have confirmed the formation of H2S, HS(O)OH, and/or HO–S–OH. However, the yields of these S-bearing species are insufficient to account for the complete loss of the initial SO2 reactant. These findings suggest that some products are desorbed into the gas phase upon formation. This study indicates that a portion of the SO2 in ice mantles may remain unreacted, avoiding hydrogenation, while the remainder is converted into other species, some of which may be subject to chemical desorption.

Enhanced fenton-like rate and anti-interference through designing materials with specific excellent sorption to pollutant

Fenton-like application is critical especially in wastewater treatment, but current catalysts face to the lack of anti-interference and low-utilization activity in high generated rate, due to the inherent contradiction between slow-sorption rate and ineffective fast-consumption of free radicals. Here, the abundant CuO nano-blade-sheets carbon-based material (Ns-CuO-LCelC) with much higher kinetic and selective capacity to pollutant than conventional adsorbents was designed and synthesized to evaluate the role of active-sorption on performance in Fenton-like applications. Due to favorable selectivity and rapid adsorptive-concentration for pollutants, the Fenton-like process rate on Ns-CuO-LCelC is 70.83 times greater than that of CuO and 3.44 times greater than powdered cellulose synthesized-catalyst. In variable systems involving pH, ions, and different pollutants, the catalytic rate and sorption performance remain highly consistent. This mitigates low-quality ROS conversion and self-consumption, achieving efficient pollutant elimination through concerted radical and non-radical reactions, with high peroxydisulfate (PDS) utilization efficiency (33.65 g/M) and unprecedented pollutant removal activity (rate constant: 40.54 min−1 M−1). The protection provided by the fiber structure and the electronic self-repair capability of the Cu Ns ensured strong stability in catalytic systems, with 100 % efficiency and 2800 L/m2/h/bar even after 900 min of continuous membrane operation in treating 2 mg/L TC, showing no significant decrease. It was the first case to underscores the value of fast adsorptive aggregation in Fenton-like application for eliminating interference and enhancing oxidant utilization.

Efficient removal of estradiol using MnFe2O4 microsphere and potassium persulfate complex salt

In this study, MnFe2O4 microspheres were synthesized to activate potassium persulfate complex salt (Oxone) for the degradation of 17β-estradiol (17β-E2) in aqueous solutions. The characteristic of MnFe2O4 was detected by XRD, XPS and SEM-EDS. The experimental results indicated that the degradation of 17β-E2 followed pseudo-first-order kinetics. At 25 °C, 17β-E2 concentration of 0.5 mg/L, MnFe2O4 dosage of 100 mg/L, Oxone dosage of 0.5 mmol/L, and initial pH value of 6.5, the decomposition efficiency of 17β-E2 reached 82.9% after 30 min of reaction. Additionally, free radical quenching experiments and electron paramagnetic resonance analysis demonstrated that SO4−• and •OH participated in the reaction process of the whole reaction system, with SO4−• being the main reactive oxygen species (ROS). The activation mechanism of the MnFe2O4/Oxone/17β-E2 system is proposed as follows: MnFe2O4 initially reacts with O2 and H2O in solution to generate active Fe3+-OH and Mn2+-OH species. Subsequently, Fe3+-OH and Mn2+-OH react with Oxone in a heterogeneous phase activation process, producing highly reactive free radicals. After four cycles of MnFe2O4 material, the removal rate of 17β-E2 decreased by 24.1%.

Synthesis and characterization of Z-scheme based MoS2/ GQD/Ag nanocomposite for degradation of organic pollution

The constituent composition of heterojunction composite materials can be changed to effectively segregate photogenerated charge carriers and to significantly advance the process of photocatalytic destruction of resistant pollutants under visible light irradiation. This work presents the hydrothermal synthesis of a novel ternary heterojunction composite, MoS2/GQD/Ag NPs (MS/GQD/Ag) and its photocatalytic performance in the degradation of organic dyes. In the synthesized material, the Z-scheme heterojunction demonstrated enhanced visible light-driven catalytic activity by effectively separating electrons from holes (e−/h+) and producing reactive oxygen species. In addition to producing reactive radicals, a variety of surface-bound redox cycles are important in the transmission of photogenerated charge carriers. Rhodamin B (RhB) photocatalytic degradation by MS/GQD/Ag under visible light irradiation was investigated, and results demonstrated 99 % RhB was decomposed using 0.1 g/L of ternary composite during 75 min. Experiments using scavenging techniques verified the concurrent activity of hydroxyl and superoxide radical species in the direction of degradation. The structural stability, recyclability for four cycles, and the pH effect in degradation efficiency of the synthesized photocatalyst illuminate its potential application for the degradation of organic pollutants for water treatment.