Degradation Reaction Research Articles

Photo-induced ageing processes in bitumen

Asphalt roads and waterproofing membranes on roofs are exposed to sunlight, which induces irreversible changes in those materials. The underlying chemical processes initially affect the surface but later on impact the bulk chemistry and the mechanical properties. Bitumen, the binding and sealing material, is particularly susceptible to such influences. However, the molecular processes that initiate material deterioration are still poorly explored. Here, we show that ultraviolet and visible light cause the formation of a unique set of oxidation products and alter aromatic structures on the bituminous surface. Qualitative and quantitative information is obtained using infrared, fluorescence and NMR spectroscopy. Bulk ageing studies have shown a shift of molecules from the aromatics to the resins and asphaltenes fractions, potentially influencing colloidal stability. The evaluation of surface processes was facilitated in ageing studies with thin sub-µm specimens. We find that gaseous oxygen is essential for molecular changes to occur. The formation of carboxylic acids, esters and aliphatic alcohols, coupled with the degradation and restructuring of aromatic systems, demonstrates the unique nature of light ageing. This is due to a nuanced interplay between oxidation, degradation, condensation and aromatisation reactions. The ageing rates depend on the origin of the binder and increase as the wavelength of the light source decreases. Ageing follows an asymptotic growth with time. All results considered, this study enabled us to decipher critical molecular processes during photochemical ageing. In this regard, we hope to develop more effective strategies for mitigating and preventing the adverse impact of solar radiation on bituminous infrastructure in the future.

Environmental profiling of gold nanoparticles by flavonoids fractionalization from carrica papaya leaf extract for photocatalytic debasement of organic contaminants and it's cyto-toxic analysis

In present investigation, Carica papaya leaf extract has been employed as a bio-reductant agent in order to synthesize ecologically sustainable bio-coupled gold nanoparticles. The formation of gold nanoparticles was confirmed based on colour change of solution and its surface plasmon resonance peak measured using UV–Vis Spectrophotometer (UV–Vis). The Morphology and size of nanoparticles were determined using transmission electron microscope (SEM/TEM), and its crystalline structure by X-ray diffraction studies. Surface area was determined via BET isotherm analysis. The elemental composition of Au nanoparticles was developed using the technique of energy dispersive spectroscopy (EDS). Furthermore, FTIR analysis delineated the presence of functional groups present in the samples of the synthesized AuNPs. Thus, the efficiency of bio coupled Au nanoparticles in photo catalytically decomposing methylene blue was examined under the influence of visible light., the lethal MB colorant had been reduced to 95 % Within 90 min. And also 60% TOC removal was recorded after 5 min of degradation reaction, which increased to 99% after 90 min. Furthermore, cytotoxic experiments on Michigan Cancer Foundations-7 (MCF-7) cell lines showed that Au nanoparticles are effective anticancer agents with an IC50 of 87.2 g/mL on the top of the present work revealed the eco-safety and affordable production of Au nanoparticles from Carica papaya leaf extract, which displayed photocatalytic debasement of organic pollutants and cyto-toxicity effects was investigated.

Fabrication of Polycaprolactone-Based Polyurethanes with Enhanced Thermal Stability.

The benefit of being acquainted with thermal properties, especially the thermal stability of polyurethanes (PU), and simplified methods for their improvement is manifold. Considering this, the effect of embedding different amounts of unmodified and surface-modified TiO2 nanoparticles (NPs) within PU, based on polycaprolactone (PCL) and Boltorn® aliphatic hyperbranched polyester, on PU properties was investigated. Results obtained via scanning electron microscopy, swelling measurements, mechanical tests and thermogravimetric analysis revealed that TiO2 NPs can be primarily applied to improve the thermal performance of PU. Through surface modification of TiO2 NPs with an amphiphilic gallic acid ester containing a C12 long alkyl chain (lauryl gallate), the impact on thermal stability of PU was greater due to the better dispersion of modified TiO2 NPs in the PU matrix compared to the unmodified ones. Also, the distinct shape of DTG peaks of the composite prepared using modified TiO2 NPs indicates that applied nano-filler is mostly embedded in soft segments of PU, leading to the delay in thermal degradation of PCL, simultaneously improving the overall thermal stability of PU. In order to further explore the thermal degradation process of the prepared composites and prove the dominant role of incorporated TiO2 NPs in the course of thermal stability of PU, various iso-conversional model-free methods were applied. The evaluated apparent activation energy of the thermal degradation reaction at different conversions clearly confirmed the positive impact of TiO2 NPs on the thermal stability and aging resistance of PU.

Degradation of Dyes Catalyzed by Aminophenyl-Substituted Mn-Porphyrin Immobilized on Chloropropyl Silica Gel and Evaluation of Phytotoxicity.

A heterogenized Mn(III) porphyrin-based catalyst was prepared for dye degradation. The new Mn(III) complex of 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin was immobilized, via covalent bond, in chloropropyl silica gel, generating the material (Sil-Cl@MnP) with a loading of 23 μmol manganese porphyrin (MnP) per gram of Sil-Cl. This material was used as a catalyst in degradation reactions of model dyes, a cationic dye [methylene blue (MB)] and an anionic dye (reactive red 120, RR120), using PhI(OAc)2 and H2O2 as oxidants. The oxidation reactions were carried out after the dye reached adsorption/desorption equilibrium with the catalytic material, with a much higher percentage of adsorption being observed for the cationic MB dye (20%) than for the anionic RR120 dye (3%), which may be associated with electrostatic attraction or repulsion effects, respectively, with the negatively charged surface of the silica (zeta potential measurement for Sil-Cl@MnP, ζ = -19.2 mV). In general, there was a higher degradation percentage for MB than for RR120, probably because the size and charge of RR120 would hinder its approach to the MnP active species on the silica surface. With respect to the oxidant, the PhI(OAc)2-based systems showed a higher degradation percentage than those of H2O2. It was observed that the increase in the oxidant concentration promoted a significant increase in the degradation of MB, with a degradation of approximately 65%. The efficiency of the catalyst was also evaluated after successive additions of the oxidant every 2 h, and it can be seen that the catalyst had no loss of efficiency, with a degradation percentage greater than 80% being observed after 8 h of reaction. The phytotoxicity of the products formed in the system was evaluated in a 1:23.5:188 molar ratio Sil-Cl@MnP: MB:PhI(OAc)2 was used. In these studies, phytotoxicity was found for the germination of lettuce seeds when the original solution was used without dilution; however, when diluted (10% V/V), the results were close to the positive and negative controls. Thus, the material obtained proved to be a potential candidate for application in the degradation reactions of environmental pollutants.

Enhanced Degradation of Micropollutants in a Peracetic Acid/Mn(II) System with EDDS: An Investigation of the Role of Mn Species.

Extensive research has been conducted on the utilization of a metal-based catalyst to activate peracetic acid (PAA) for the degradation of micropollutants (MPs) in water. Mn(II) is a commonly employed catalyst for homogeneous advanced oxidation processes (AOPs), but its catalytic performance with PAA is poor. This study showed that the environmentally friendly chelator ethylenediamine-N,N'-disuccinic acid (EDDS) could greatly facilitate the activation of Mn(II) in PAA for complete atrazine (ATZ) degradation. In this process, the EDDS enhanced the catalytic activity of manganese (Mn) and prevented disproportionation of transient Mn species, thus facilitating the decay of PAA and mineralization of ATZ. By employing electron spin resonance detection, quenching and probe tests, and 18O isotope-tracing experiments, the significance of high-valent Mn-oxo species (Mn(V)) in the Mn(II)-EDDS/PAA system was revealed. In particular, the involvement of the Mn(III) species was essential for the formation of Mn(V). Mn(III) species, along with singlet oxygen (1O2) and acetyl(per)oxyl radicals (CH3C(O)O•/CH3C(O)OO•), also contributed partially to ATZ degradation. Mass spectrometry and density functional theory methods were used to study the transformation pathway and mechanism of ATZ. The toxicity assessment of the oxidative products indicated that the toxicity of ATZ decreased after the degradation reaction. Moreover, the system exhibited excellent interference resistance toward various anions and humid acid (HA), and it could selectively degrade multiple MPs.

Preparation of defect-enriched Cu-doped FeOCl/g-C3N4Z-scheme composites for efficient photo-Fenton-like performance

In this study, a Z-scheme heterojunction with abundant oxygen vacancies (OVs) formed by Cu-doped FeOCl (Cu-FeOCl) and graphitic carbon nitride nanosheets (CNNS) was successfully synthesized for the removal of tetracycline hydrochloride (TC). The prepared Cu-FeOCl/CNNS had excellent catalytic properties under hydrogen peroxide and light illumination, and the maximum reaction rate was nearly 156 and 48 times higher than that of FeOCl and CNNS, respectively. The enhancement of catalytic performance was due to the synergistic effect of Cu species, Fe species and Ovs, which effectively promoted the adsorption and activation of H2O2, and inhibited the recombination of photogenerated carriers. We further studied the effects of different reaction conditions (catalyst dosage, H2O2 dosage, initial pH, TC concentration, and coexisting substances) on the degradation reaction. 1O2, h+, •O2−, and •OH were active species participating in the reaction, and a possible TC degradation mechanism was studied. This work provided insights into the synergetic action of interface engineering, ion doping, and oxygen defects in the photo-Fenton-like system.

Developing of α-Fe2O3/MoS2 embedded g-C3N4 nanocomposite photocatalyst for improved environmental dye degradation and electrocatalytic hydrogen evolution reaction performance

A novel g-C3N4/α-Fe2O3–MoS2 (GFMO) ternary nanocomposite has been successfully constructed by facile calcination-hydrothermal methods. As-obtained magnetic GFMO ternary composite catalyst was investigated with the excellent degradation efficiency of organic rhodamine B (Rh B) and methylene blue (MB) pollutants in aqueous solution (95.6 % and 91.1 %) in 80 min under visible-light. The active coupling of α-Fe2O3 co-catalyst accelerated photo-electron transfer, improved visible-light fascination, suppressed the recombination rate, and sustained charge separation ability. This demonstrates the synergistic effect of the intimated heterojunction interface among g-C3N4 and MoS2, liable for efficient photo-degradation response. The scavenging tests revealed that •O2− and h+ reactive species play a most vital part in the photocatalytic degradation of both dyes. Furthermore, better electrocatalytic hydrogen evolution reaction (HER) performance in typical acidic conditions, with a lower overpotential of 305 mV and a Tafel slope of 128 mV dec−1. As an outcome, the current work offers a novel insight into the development of efficient ternary g–C3N4–based photocatalysts (PCs) for wastewater refining and electrochemical hydrogen evolution reactions.

Mechanisms underlying the formation of main volatile odor sulfur compounds in foods during thermal processing.

Volatile sulfur compounds (VSCs) significantly influence food flavor and garner considerable attention in flavor research due to their low sensory thresholds, diverse odor attributes, and high reactivity. Extensive research studies have explored VSC formation through thermal processes such as the Maillard reaction, thermal pyrolysis, oxidation, and enzymatic reactions. However, understanding of the specific reaction mechanisms and processes remains limited. This is due to the dispersed nature of existing studies, the undefined intermediates involved, and the complexity of the matrices and processing conditions. Given these limitations, the authors have shifted their focus from foods to sulfides. The structure, source, and chemical characteristics of common precursors (sulfur-containing amino acids and derivatives, thiamine, thioglucoside, and lentinic acid) and their corresponding reactive intermediates (hydrogen sulfide, thiol, alkyl sulfide, alkyl sulfenic acid, and thial) are provided, and the degradation mechanisms, reaction rules, and matrix conditions are summarized based on their chemical characteristics. Additionally, the VSC formation processes in several typical foods during processing are elucidated, adhering to these identified rules. This article provides a comprehensive overview of VSCs, from precursors and intermediates to end products, and is crucial for understanding the mechanisms behind VSC formation and managing the flavor qualities of processed foods.

Efficient bioelectro-Fenton degradation of styrene using Fe/Mn modified bimetallic catalysts as microbial fuel cell cathodes

Microbial fuel cells (MFCs) can generate electricity to drive electro-Fenton (EF) reactions for contaminant degradation. The oxygen reduction ability, catalytic ability, electron transfer efficiency, and styrene degradation efficiency of the catalysts were evaluated by loading iron and manganese ions on graphite fiber (GF) as bimetallic catalysts on the cathode of MFC/EF. The surface-loaded Fe–Mn@GF cathode had the highest reduction peak current density (−136.64 mA/cm2), which was 1.99 times that of the Fe@GF (−68.62 mA/cm2) cathode and 16.64 times that of the GF (−8.21 mA/cm2) cathode. Polymorphic crystals of Fe2O3 and MnO2 were observed in the Fe–Mn@GF-loaded cathode, resulting in many active sites on the surface of the cathode to enhance the catalytic ability of the material. The maximum power density (469.71 mW/m2) and minimum total internal resistance (189.63 Ω) of Fe–Mn@GF as the MFC cathode demonstrated that the Mn-doped cathode has superior electrical conductivity and electron transfer rate, thus significantly decreasing the electron transfer resistance. The styrene removal efficiency of MFC/EF using Fe–Mn@GF in a three-cycle run was maintained at over 90.31 %−98.14 %. The bimetallic catalyst effectively promoted hydrogen peroxide (H2O2) generation, demonstrating that the Fe–Mn@GF system could stably produce ·OH for styrene degradation, and that MFC/EF with Fe–Mn@GF had almost no remaining biotoxicity after the first run. The most novel aspect of this study is the successful application of the MFC/EF system for styrene removal, providing a new approach for treating organic pollutants. Establishing this technology has important application value for improving water quality and environmental protection.

Structural characterization of a proanthocyanidin-rich fraction from Hancornia speciosa leaves and its effect on the release of pro-inflammatory cytokines and oxidative stress in THP-1 cells

Ethnopharmacological relevanceIn Brazil, the leaves of Hancornia speciosa Gomes have a traditional use for treating hypertension and diabetes. Experimental investigations have confirmed the anti-hypertensive and hypoglycemic properties of extracts derived from H. speciosa leaves across various experimental models. These biological activities have been mostly ascribed to its major constituent, bornesitol, along with other cyclitols, flavonoids, and cinnamic acid derivatives. Aim of studyThe objective of this study was to characterize the chemical structure of proanthocyanidins from H. speciosa leaves and explore their in vitro activity on the release of pro-inflammatory cytokines and oxidative stress. Material and methodsThe acetone/water (7:3) extract of H. speciosa leaves (HsE) was prepared by percolation and fractionated by column chromatography over Sephadex LH20 to afford the proanthocyanidin-rich fraction HsFr3. Structure characterization of the proanthocyanidins constituents of HsFr3 was accomplished by extensive UPLC-DAD-ESI-MS/MS analysis coupled to degradation reaction through thiolysis. The effect of HsE, HsFr3, and bornesitol on the release of TNF, IL-1β and IL-6 in LPS-stimulated THP-1 cells was assayed by ELISA. The effect of the samples on oxidative stress induced by LPS in THP-1 cell was investigated using a DCFH-DA fluorescent assay. ResultsFractionation of HsE afforded HsFr3, primarily composed of six proanthocyanidins. Their chemical structures were characterized as dimeric (4 isomers) and trimeric (2 isomers) procyanidins C-glycosides of the B-type. HsE, HsFr3, and bornesitol reduced the release of pro-inflammatory cytokines TNF and IL-1β in LPS-stimulated THP-1 cells, while no significant effect was observed on IL-6. All samples reduced the oxidative stress induced by LPS in THP-1 cells, whereas bornesitol, tested at lower concentrations, induced an equivalent response to HsE and HsFr3. ConclusionsOur findings provide additional evidence to support the ethnomedical use of H. speciosa in managing hypertension and hyperglycemia, due to the direct association of oxidative stress, TNF, and IL-1β with the maintenance and aggravation of these deleterious conditions. The dimeric and trimeric procyanidin C-glycosides, characterized in the species, contribute to diminish oxidative stress and the release or pro-inflammatory cytokines, whereas bornesitol was shown to induce similar effect at lower concentrations.

Efficient activation of persulfate for tetracycline hydrochloride degradation by biochar prepared from corn stover doped with organic phosphorus sources

Proposed to prepare phosphorus-doped biochar catalyst materials by impregnation pyrolysis method using corn stover and different phosphorus source precursors as raw materials, and the batch-wise research revealed that the phosphorus source precursor, the doping ratio, and the pyrolysis temperature had a significant influence on the biochar properties. The biochar material Pb-C-4–600 prepared with (C4H9)3PO4 as phosphorus source precursor, 1:4 doping ratio, and pyrolysis temperature of 600 ℃ had an ID/IG = 0.914, pore size of 4.91 nm, and specific surface area of 173.9845 m²/g, which was 93.4 times higher than that of the pure biochar. The removal rate of TCH reached 99.77 % in 30 min under the reaction conditions of PMS concentration of 2 g/L, Pb-C-4–600 dosage of 1 g/L, and pH 3. Comparing the efficacy of Pb-C-4–600 and different catalysts for the degradation of TCH by activated PMS under the same reaction conditions, the degradation reaction rate of Pb-C-4–600 was 0.17663 min−1, which was 1.48 times higher than that of N-bio, 1.67 times higher than that of S-bio, and 2.64 times higher than that of B-bio, which further demonstrating the advantages of Pb-C-4–600 in similar composites. The oxidative degradation performance of other typical organic pollutants (BPA, phenol, AO7) was also good. The prominent reactive oxidizing radical in the system of Pb-C-4–600/PMS was SO4·−, and the system could adapt to a wide pH range.

Advancing Wastewater Treatment: A Comparative Study of Photocatalysis, Sonophotolysis, and Sonophotocatalysis for Organics Removal

Clear and sanitarily adequate water scarcity is one of the greatest problems of modern society. Continuous population growth, rising organics concentrations, and common non-efficient wastewater treatment technologies add to the seriousness of this issue. The employment of various advanced oxidation processes (AOPs) in water treatment is becoming more widespread. In this review, the state-of-the-art application of three AOPs is discussed in detail: photocatalysis, sonophotolysis, and sonophotocatalysis. Photocatalysis utilizes semiconductor photocatalysts to degrade organic pollutants under light irradiation. Sonophotolysis combines ultrasound and photolysis to generate reactive radicals, enhancing the degradation of organic pollutants. Sonophotocatalysis synergistically combines ultrasound with photocatalysis, resulting in improved degradation efficiency compared to individual processes. By studying this paper, readers will get an insight into the latest published data regarding the above-mentioned processes from the last 10 years. Different factors are compared and discussed, such as degradation efficiency, reaction kinetics, catalyst type, ultrasound frequency, or water matrix effects on process performance. In addition, the economic aspects of sonophotolysis, photocatalysis, and sonophotocatalysis will be also analyzed and compared to other processes. Also, the future research directions and potential applications of these AOPs in wastewater treatment will be highlighted. This review offers invaluable insights into the selection and optimization of AOPs.

Proof of ssDNA degraded from dsDNA for ET recombination

The widely used ET recombination requires an ssDNA product degraded by Rac phage protein E588 from dsDNA for strand invasion. However, proof of the ssDNA product is still elusive. The study provided three levels of proof sequentially. The probable ssDNAs degraded by E588 from the fluorescent plus-, minus-, or double-stranded dsDNA pET28a-xylanase exhibited a half fluorescence intensity of the corresponding dsDNAs, equivalent to the E588 degradation nucleotides half that of the total nucleotides degraded from the corresponding dsDNA. The ssDNA product degraded by E588 from the fluorescent minus-stranded dsDNA was confirmed by gradient gel-electrophoresis and two nuclease degradation reactions. Degraded by E588 from the dsDNA pET28a-xylanase that had a phosphorothioated plus-stranded 5′-terminus, the plus-stranded ssDNA product was separated via gel electrophoresis and recovered via a DNAclean kit. The recovered ssDNA product was proven to have intact 5′- and 3′-ends by DNA sequencing analysis. This study provides a solid foundation for the mechanism of ssDNA invasion.

NMR Analysis of Thermally‐Oxidized Hydroxyl‐Terminated Polybutadiene (HTPB)

AbstractNuclear magnetic resonance spectroscopy was employed to monitor the change in chemical structures, olefin units (cis, trans and vinyl) and hydroxyl value on stabilized Hydroxyl‐terminated polybutadiene (HTPB) under accelerated ageing condition. Thermal ageing of HTPB was carried out at 65 °C for 10‐weeks and periodically withdrawn sample for NMR analysis. 1H and 13C NMR spectroscopy provided detailed structural information for all HTPB samples, including the quantification of olefin units and the determination of hydroxyl value. The analysis revealed a decrease in signal intensity, particularly for the olefin near or at the molecular end, suggesting that they were oxidized before those in the middle position within the chain. The quantitative assessment of olefin units indicates a slight decrease of 2 % in 1,2‐vinyl unit after 10‐weeks of ageing. The NMR spectra did not show any detectable signals corresponding to epoxides, peroxides or alcohols in any HTPB samples. However, a slight increase in the OH value was observed after 8 and 10 weeks of ageing, suggesting the possible incorporation of new hydroxyl groups due to thermal‐oxidation. The antioxidants used to stabilize HTPB exhibited limited effectiveness in preventing degradation reactions, even after 4 weeks of ageing at 65 °C.

Utilization of dual Z-scheme charge transfer mechanism in novel WO3-coupled α-Fe2O3/g-C3N4 ternary nanocomposite with enriched visible-light photocatalytic degradation for emerging organic pollutants

The growing concerns over water pollution have necessitated the development of advanced photocatalytic materials for environmental remediation. This study introduces a novel WO3/α-Fe2O3/g-C3N4 (WFGC) ternary nanocomposite that was synthesised via feasible calcination with hydrothermal methods and investigated by various characterization analyses to explore the crystal structures, functional groups, surface morphology, chemical characteristics and optical properties respectively. The photocatalytic efficiency of the WFGC composite was evaluated by degrading methylene blue (MB) and crystal violet (CV) under visible-light influence, achieving remarkable degradation rates of 87.6 % and 73.4 %, respectively, within 70 minutes. The boosted degradation efficiency is attributed to the dual Z-Scheme heterojunction charge transfer way, which improves sustained charge separation capability while inhibiting recombination under visible-light impact. Moreover, the quenching trials exposed that distinct superoxide radicals (•O2-) and photo-holes (h+) played a crucial part in the degradation reaction, and the probable dual Z-scheme charge transfer path mechanism for promoted ternary WFGC photocatalysts was also proposed. This study underscores the potential of WFGC composites for practical applications in wastewater treatment, offering a sustainable and efficient alternative for environmental clean-up.

Metathesis of butadiene rubber for the sustainable production of polyesters and polyols

Synthetic rubbers and elastomers are used extensively in different industries today, and more than 11.8 million tons are consumed annually. Butadiene rubber (BR) is the second most important synthetic rubber, with a worldwide consumption of about 3.44 million tons annually. In response to the high demand, production, and waste of BR and other industrial rubbers, a global effort has been made to reduce elastomeric, plastic, and microplastic pollution by studying various mechanisms of polymer degradation, including thermal degradation, mechanical treatment, UV exposure, and chemical processes.This work reported the synthesis of polyesters and polyols via metathesis degradation reaction from BR using the fatty acid methyl 10-undecenoate and the fatty alcohol 10-undecen-1-ol as chain transfer agents (CTA), using mild reaction conditions and a Ru catalyst. Polyesters and polyols were successfully produced with 94-97% yield. The formation of polyol, polyester, and by-products was assessed by FT-IR, NMR, GC/MS, and TGA. The molecular weights (Mn, Mw, Mz, and PDI) before and after degradation of BR and the products obtained were characterized by GPC. Different mole ratios BR:CTA were used to control the molecular weights; the Mw obtained ranged from 395 to 3963 Da.The proposed metathesis route may contribute to the reuse and recycling of BR to obtain sustainable products with added value for the synthesis of new materials.

Biosynthesis and characterization of a novel supported nanocatalyst for the methylene blue dye photodegradation: Machine learning modeling and photocatalytic activity

The present work aims to evaluate the photocatalytic activity of an alternative supported nanocatalyst with copper oxide nanoparticles were the photoactive phase and the analcime nanozeolite as the catalytic support (CuO-NPs@nANA), and to carry out a Machine Learning (ML) study to propose a reaction pathway for the MB dye degradation under visible light. Two machine learning algorithms (RF and XGB) were used in the regression model development from scientific papers concerning MB degradation (by GC-MS) to identify the degradation products of the reaction. XGB algorithm resulted in the best predictive model (R² equals 0.88 and 0.89 for training and testing, RMSE = 33–37), confirming the obtention of carbon dioxide (m/z = 44), water (m/z = 18) and low-molar mass compounds at the final of MB degradation reaction. Moreover, 76.93 % MB removal was reported at pH 10, [MB] = 200 mg L−1 and [CuO-NPs@nANA] = 0.5 g L−1 after 180 min under visible light, with k = 0.0088 min−1. Feature importance study revealed that the response m/w was strongly dependent on pH and reaction time. Therefore, this work confirms the potentiality of machine learning algorithms to develop predictive models for the elucidation of the degradation reaction pathway of organic dyes through heterogeneous photocatalysis.

Enhanced Mineralization of Organic Pollutants through Atomic Hydrogen-Mediated Alternative Transformation Pathways.

Electrocatalytic hydrogen atom-hydroxyl radical (H*-·OH) redox system is a promising approach for contaminant removal and mineralization. However, its working mechanism, especially the effect of H*, remains unclear, hindering its practical application. Herein, we constructed an electrochemical reactor equipped with our self-made Pd-loaded Ti/TiO2 nanotube cathode and a commercial boron-doped diamond anode. After fulfilling the electrode characterization and free radical detection, we employed coumarin and 7-azido-4-methylcoumarin as probes to confirm the participation of H* in the transformation of organic compounds. A comprehensive study on the degradation kinetics, reaction, and mineralization mechanisms using benzoic acid (BA) and 4-chlorophenol (4-CP) as model compounds was further conducted. The rate constants and total organic carbon removal of BA and 4-CP in the redox system increased compared with those of the individual oxidation and reduction processes. Theoretical calculations demonstrate that H* opens up alternative pathways for BA and 4-CP ring cleavage, forming quinones as reactive intermediates. Furthermore, H* facilitates the mineralization of the typical intermediates, maleic acid and fumaric acid, through C=C bond addition and H-abstraction from the 1,1-diol structure. The presence of H* provides alternative pathways for pollutant transformation, consequently reducing the treatment duration.

Kinetic analysis of PA4 thermal degradation: Thermal stability with respect to crystallinity

Polyamide 4 (PA4) has garnered considerable attention due to its fully bio-based origin and biodegradability as a high-performance polyamide. Nevertheless, thermal degradation during the melting process impedes thermal processing, thereby constraining its potential for engineering plastics applications. To clarify the thermal degradation reactions of PA4 amidst intricate physical and chemical transformations, establishing a theoretical foundation for the thermal stability modification, we conducted a comprehensive analysis of PA4 thermal degradation coupled with crystallization, considering kinetics and reaction mechanisms. Calculation of reaction activation energies and mechanism functions revealed that PA4 pyrolysis is a two-stage compound process, with distinct degradation mechanisms attributed to the crystalline and amorphous regions. Additionally, the thermal degradation mechanism of the PA4-CaCl2 composite system at varying crystallinity levels was illustrated. The incorporation of Ca strengthens intermolecular forces in the samples, leading to an increased overall stability. Simultaneously, a notable alteration in the reaction mechanism was observed in the crystalline zone lacking the Ca phase.

Comparing Degradation Mechanisms, Quality, and Energy Usage for Pellet- and Filament-Based Material Extrusion for Short Carbon Fiber-Reinforced Composites with Recycled Polymer Matrices

Short carbon fiber (sCF)-based polymer composite parts enable one to increase in the material property range for additive manufacturing (AM) applications. However, room for technical and material improvement is still possible, bearing in mind that the commonly used fused filament fabrication (FFF) technique is prone to an extra filament-making step. Here, we compare FFF with direct pellet additive manufacturing (DPAM) for sCF-based composites, taking into account degradation reactions, print quality, and energy usage. On top of that, the matrix is based on industrial waste polymers (recycled polycarbonate blended with acrylonitrile butadiene styrene polymer and recycled propylene), additives are explored, and the printing settings are optimized, benefiting from molecular, rheological, thermal, morphological, and material property analyses. Despite this, DPAM resulted in a rougher surface finish compared to FFF and can be seen as a faster printing technique that reduces energy consumption and molecular degradation. The findings help formulate guidelines for the successful DPAM and FFF of sCF-based composite materials in view of better market appreciation.