Rate Of Oxidative Degradation Research Articles

Polymer encapsulation impact on potential-induced degradation in PV modules revealed by a multi-modal field study

Potential-induced degradation is a significant issue affecting the performance and reliability of photovoltaic systems, particularly in large-scale installations. Understanding the mechanisms underlying the formation of potential-induced degradation is crucial for developing effective mitigation strategies and ensuring the long-term sustainability of solar energy technologies. During the inspection of a 1.2 MWp photovoltaic power plant, various imaging methods, electrical measurements, spectroscopic characterization methods, and monitoring data analyses were utilized and combined. We observed that two percent of the photovoltaic modules at the string ends exhibited the characteristic checkerboard pattern in infrared or electroluminescence imaging, implicating issues on twelve percent of all strings. This uneven distribution of potential-induced degradation-affected modules suggests additional key factors are at play. Investigations of the backsheet and ethylene-vinyl acetate using near-infrared reflectance analysis revealed that one backsheet type and two different ethylene-vinyl acetate types were present in the installed solar panels. Yet, only one type of ethylene-vinyl acetate correlated with potential-induced degradation. The same type also exhibited a higher rate of oxidative degradation. Scanning electron microscopy and energy-dispersive X-ray spectroscopy revealed a significantly increased sodium ion content in the ethylene-vinyl acetate and glass of the potential-induced degradation-affected modules. Our findings highlight the crucial role of polymer encapsulation in the development of potential-induced degradation and underscore the importance of careful polymer selection in the design of photovoltaic module technologies.

Modified sono-Fenton process for oxidative degradation of chloramphenicol.

Oxidative degradation of chloramphenicol (CAP) using a hybrid approach (US/HA+/n-Fe2O3/SPC) involving sodium percarbonate (SPC; "solid H2O2" carrier), Fe2O3 nanoparticles (n-Fe2O3; H2O2 decomposition catalyst), hydroxylamine in its protonated form (HA+; Fe (III) to Fe (II) reducer), and ultrasonic cavitation (to increase the generation of hydroxyl radicals) has been studied for the first time. The average size of n-Fe2O3 synthesized by the sonochemical method, as calculated according to the Debye-Scherrer equation, was ~ 18nm. The maximum degradation degree of CAP (83.1%) and first-order oxidative degradation rate constant of CAP as 1.253 × 10-3s-1 were achieved using the modified sono-Fenton process under the optimized conditions as the initial concentration of CAP - 50mg/L, the molar ratio of CAP:HA+:n-Fe2O3:SPC of 1:100:100:100, pH as 3, the temperature as 318K, the specific ultrasonic power as 53.3 W/L, and the treatment duration of 7200s. In general, the efficiency and intensity of CAP degradation increased with a decrease in the pH value, an increase in the molar ratio of CAP:HA+:n-Fe2O3:SPC, a decrease in the initial concentration of CAP, an increase in temperature, and showed a minor change with the specific power of US. The synergistic coefficient for the combination of the US and the heterogeneous Fenton process was 17.9. The active participation of hydroxyl radicals in the oxidative degradation of CAP using the modified sono-Fenton process was confirmed by scavenging experiments performedusing tert-butyl alcohol. The proposed process can be a promising direction in the remediation of pharmaceutical effluents with significant potential for commercial exploitation.

Fluorocarbon polymers mediated contact-electro-catalysis activating peroxymonosulfate for emerging pollutants degradation: The key role of fluorine density in electron transfer

Peroxymonosulfate-based advanced oxidation processes (PMS-AOPs) have been extensively investigated for environmental pollutants remediation. Moreover, systematic exploration of catalysts with the high-efficient, cost-effective, and environment-durable properties has been usually recognized as the crucial pathway to boost PMS activation and enhance pollutants degradation. Herein, we demonstrated that the inert fluorocarbon polymers (FCPs) mediated contact-electro-catalysis (CEC) under ultrasound can be utilized to activate PMS (FCPs/PMS/US) for high-efficient degradation and detoxication of emerging pollutants (EPs). The catalytic EPs degradation process was dominant with 1O2 pathway, accompanied by radical pathways (•OH, SO4•−, and O2•−). Density functional theory calculations and correlation analysis provided strong evidence for the fluorine (–F) density-dependent electron transfer among H2O-FCPs-electron acceptors, which determined the generation of reactive oxidative species and EPs degradation rate in FCPs/PMS/US. Consequently, fluorinated ethylene propylene (FEP) with the highest –F density exhibited higher degradation rate of sulfadiazine (kobs = 0.043 min−1, at an FEP dosage of 0.25 g·L−1) compared to polytetrafluoroethylene and polyvinylidene fluoride. Besides, the FCPs/PMS/US system showed excellent stability, durability, and promising applicability for high-salinity seawater remediation, with the electrical energy per log order of 0.53 kWh·m−3. This study provided a novel route for PMS activation and stimulates further exploration of CEC for environmental remediation.

Enhancement of ozone dissolution and oxidation treatment of phenolic wastewater by a static spiral shear rig with a variable screw pitch

A novel static spiral shear rig (SSSR) with variable screw pitch was developed to enhance the ozone–water mass transfer and the oxidative degradation of phenolic wastewater. The effects of critical operational parameters on the dissolution and mass transfer of ozone in water and the oxidative degradation rate of phenol were investigated with the proposed SSSR. Moreover, the mass transfer and oxidative degradation of phenols with the SSSR were compared to conventional static mixer (CSM) methods. The results showed that the mass transfer coefficient obtained with the SSSR is 5.33 times greater than that obtained with CSM. With the SSSR, the degradation percentage of phenolic wastewater with an initial concentration of 100mg/L reached 97.09% within 12min, and the reaction kinetic constant for phenol degradation obtained with the SSSR is 3.68 times higher than that obtained with the CSM. The SSSR dramatically enhances ozone dissolution and mass transfer, resulting in a higher phenol oxidative degradation percentage and a constant kinetic reaction.

Qualitative and quantitative analysis of electrons donated by pollutants in electron transfer-based oxidation system: Electrochemical measurement and theoretical calculations

In order to gain a profound understanding of the fate of pollutants in advanced oxidation processes (AOPs), this study analyzed the electron contribution of pollutants qualitatively and quantitatively which rarely reported before. The rich electron transfer system was constructed by mesoporous carbon nitride (MCN) coupling with persulfate (PS) driven by visible light and the sulfanilamide antibiotics (SULs) were used as target contaminants. Firstly, the qualitative analysis of electron transfer in the system was confirmed systematically. The electron flow direction tested by i-t curves indicated that PS absorbed electrons, while SULs released electrons. The flow rate of electrons was also accelerated after the addition of SULs. The fitting curve between the kinetics and the peak potential difference tested by CV curve showed that the larger potential difference, the slower rate of oxidative degradation. Secondly, the quantification of electron transfer was achieved through theoretical calculations to simulate the interactions of the ‘catalyst-oxidant-antibiotic’ system. After the addition of SULs, the adsorption energy of the ‘catalyst-oxidant-antibiotic’ system was enhanced and the bond length of the peroxide bond was stretched. Notably, the electron transfer analysis results showed that the charge of SULs was around 0.032–0.056e, indicating that SULs pollutants played the role of electron contributors in the system. The oxidative degradation pathway included the direct cracking of S-N bond, shedding of marginal groups, ring-opening and hydroxyl addition reaction. This study clarified the electronic contribution of SULs in the oxidation system, providing necessary theoretical supplement for the analysis of the transformation of pollutants in AOPs.

Biochar-mediated synergistic promotion of DIET and IHT: Kinetic and thermodynamic insights into propionate two-step syntrophic methanogenesis

Biochar can effectively enhance the thermophilic anaerobic degradation of propionate. Nevertheless, previous studies frequently ascribed this enhancement to direct interspecies electron transfer (DIET) without considering the underlying kinetics and thermodynamics involved. Additionally, quantitative evaluation of biochar’s impact on interspecies electron transfer (IET) has been limited. In this study, we developed and optimized models for analyzing thermodynamics and electron transfer flux to elucidate the mechanism by which biochar enhances the two-step syntrophic methanogenesis of propionate. Findings revealed that biochar primarily facilitated DIET (1.78 × 10−4 A), leveraging its redox capacity. Additionally, it synergistically enhanced interspecies hydrogen transfer (4.08 × 10−10 A), significantly improving IET efficiency. This synergistic effect led to accelerated oxidative degradation rates of propionate (39.2 %) and intermediate acetate (13.5 %), expanding the thermodynamic windows for their syntrophic methanogenesis (221 % and 103 %, respectively). Accordingly, biochar increased the maximum rate of propionate methanation (71.9 %) and reduced the lag phase time (51.1 %). Moreover, biochar promoted the specific growth rates of acetogenic bacteria and methanogens while significantly increasing the abundance of Pelotomaculum, Methanoculleus, and Methanosarcina. These findings provide new insights and theoretical support for the use of biochar in promoting anaerobic digestion and facilitating IET during the process.

Effective Treatment Methodology for Environmental Safeguard Catalytic Degradation of Fluconazole by Permanganate Ions in Different Acidic Environments: Kinetics, Mechanistics, RSM, and DFT Modeling.

In this paper, the degradation of fluconazole drug (Flz) was explored kinetically utilizing permanganate ion [MnO4-] as an oxidant in different acidic environments, namely sulfuric and perchloric acids at various temperatures. Stoichiometry of the reactions between Flz and [MnO4-] in both acidic environments was attained to be 1.2 ± 0.07 mol. The kinetics of the degradation reactions in both cases were the same, being unit order regarding [MnO4-], fewer than unit orders in [Flz], and fractional second orders in acid concentrations. The rate of oxidative degradation of fluconazole in H2SO4 was higher than that in HClO4 at the same investigational circumstances. The addition of small amounts of Mg2+ and Zn2+ enhanced the degradation rates. The activation quantities were evaluated and debated. The gained oxidation products were characterized using spot tests. A mechanistic approach for the fluconazole degradation was suggested. Finally, the rate law expressions were derived which were agreed with the acquired outcomes. The rates of degradation for various [Flz] were mathematically modeled using the response surface methodology (RSM). The RSM model's conclusions and the experimental findings are in agreement. The oxidative degradation mechanism of Flz using density functional theory (DFT) was performed. The fluconazole drug degrades in acidic settings, protecting both the environment and human health, according to a method that is easy to use, powerful, inexpensive, practical, affordable, and safe.

Energy-efficient biphasic solvents for industrial CO2 capture: Absorption mechanism and stability characteristics

The traditional CO2 capture process represented by monoethanolamine has excessive energy consumption, serious oxidative degradation and metal corrosion, which limits its potential for large-scale industrial applications. This study produced a highly effective biphasic 3-amino-1-propanol (MPA)–polyethylene glycol dimethyl ether (NHD)–H2O absorbent with easy modulation of phase separation and low levels of oxidative degradation and metal corrosion. The principal absorbent was MPA, and NHD served as the phase separation solvent. NHD's solvent effect decreased the energy barrier preventing MPA from forming zwitterions (MPA+COO−) and carbamate, thus promoting chemical absorption. The large polarity difference between the reaction products and NHD triggered phase separation, producing a low-polarity CO2-lean phase and a high-polarity CO2-rich phase; 97.41% of the absorbed CO2 accumulated in 43.7% of the CO2-rich phase solution. The sensible heat and latent heat of the MPA–NHD–H2O absorbent were relatively low because of the low saturation vapor pressure, high vaporization enthalpy, and excellent phase separation performance of NHD. The regeneration energy was as low as 2.66 GJ/t CO2, which was 30% less than that for monoethanolamine. Additionally, the oxidative degradation rate for the proposed absorbent was only 10.7% of that for monoethanolamine. This study provides a theoretical reference for application of the MPA–NHD–H2O biphasic absorbent.

Oxidation and hot corrosion behaviors of NiAlTa protective material for turbine single crystal blade tips

NiAlTa alloys were prepared to improve oxidation and hot corrosion resistance of single crystal blade tips as well as the sealing performance of an engine. The oxidation and hot corrosion behaviors of NiAlTa alloys were investigated. The results showed that NiAlTa alloys exhibited low oxidative degradation rates at 1000–1100 ℃. τ1-NiTaAl and β-NiAl phases exhibited different oxidation behaviors. NiAlTa alloys were more resistant to attack by mixed salts than pure salts. NiTaAl phase accelerated the alloy failure by acting as a fast diffusion channel for corrosive media. The oxidation mechanisms, hot corrosion mechanisms, and the effects of Ta were discussed.

Development of a Predictive Model to Correlate the Chemical Structure of Amines with Their Oxidative Degradation Rate in a Post-Combustion Amine-Based CO2 Capture Process Using Multiple Linear Regression and Machine Learning Regression Approaches.

In this study, the degradation behavior of 30 different amines was investigated, which were categorized into four distinct groups: alkanolamines, sterically hindered alkanolamines, multialkylamines, and cyclic amines. These experiments were conducted over a period of 14 days at a temperature of 60 °C, with a feed gas comprising 99.9% O2 flowing at a rate of 200 mL/min. The primary objective was to establish a correlation between the chemical structures of these amines and their susceptibilities to degradation. To assess this, the concentration of the amines at various time points was measured to determine their degradation rates. Results showed that secondary amines exhibited degradation rates higher than those of primary and tertiary amines. Amines with cyclic structures demonstrated lower oxidative degradation rates. Longer alkyl chain lengths decreased degradation rates in all amine types because of their electronic and steric hindrance properties. A higher number of hydroxyl groups increased the degradation rate by destabilizing the free radical. An increase in hydroxyl groups in nonsterically hindered amines increased the degradation rate by decreasing free radical stability. In contrast, for sterically hindered amines, an increase in hydroxyl groups decreased the degradation rate because the steric hindrance effect is now more dominant than the electron-withdrawing effect. An increase in the number of amino groups led to higher degradation rates due to the presence of more reactive sites for free radical formation. Amines with tert-alkyl groups exhibited higher degradation rates than those with straight chains. Moreover, branched alkyl groups located between amino and hydroxyl groups significantly increased the degradation rates. Two degradation models, a semiempirical statistical model and a CatBoost machine learning regression model, were developed to predict amine degradation rates based on their chemical structure and relevant properties. To train these models, a data set of 27 different amines was used, while another set of 3 amines was reserved for testing the model's predictive performance. The average absolute deviations (AAD) achieved were, respectively, 22.2 and 0.3%.

Enhancements of monoethanolamine CO2 absorption rate and degradation in the presence of nickel nanoparticles catalysts

In the study of the catalytic effect of nickel nanoparticles (NiNPs) on amine-based CO2 capture systems, monoethanolamine (MEA) was subjected to a CO2 loading at greatly varying concentrations (3–30 wt%) at two temperatures (20 °C and 50 °C) for the first time in a lab study to the best of our knowledge. This study shows that NiNPs can enhance the rate of CO2 absorption into MEA and that its enhancement is greater at 20 °C than at 50 °C. Solutions were loaded with CO2 until full saturation and the mass gain was recorded. At 20 °C the overall enhancement ranged between 4.0–7.4% with the optimum (>7.0%) observed at concentrations of 5 wt% and 20 wt% of MEA with NiNPs. In addition, there were large reductions in the time that it takes to fully saturate the MEA with CO2, (up to a 42% reduction) and there were differences in peak loading (molCO2/molmea) between the NiNPs solution and the control (without NiNPs) (of up to 12.5% for the same time at 20 °C and 30 wt% of MEA with NiNPs). For the first time to the best of our knowledge, the degradation of MEA with and without NiNPs was studied; an oxidative degradation experiment (30 wt%, 0.4 molCO2/molmea, 7.5 mL/min CO2, 0.35 L/min air, 55 °C) based on typical absorber conditions and a thermal degradation experiment based on typical stripper conditions (30 wt%, 0.5 molCO2/molmea, 135 °C) were carried out. Gas chromatography-mass spectrometry was used to identify and quantify the major degradation compounds. It is found that NiNPs increase the rate of both oxidative and thermal degradation.

Stability of Coumarins and Determination of the Net Iron Oxidation State of Iron-Coumarin Complexes: Implications for Examining Plant Iron Acquisition Mechanisms.

Coumarins are exuded into the soil environment by plant roots in response to iron (Fe) deficiency. Previous studies have shown that coumarins can increase the Fe solubility upon interaction with sparsely soluble Fe(III) (hydr)oxide. However, the chemical mechanisms of Fe(III) (hydr)oxide dissolution by coumarins remain unclear. The high redox instability of dissolved coumarins and the interference of coumarins in determining the Fe redox state hinder the quantitative and mechanistic investigation of coumarin-induced Fe mobilization. In this study, we investigated the oxidative stability of three coumarins that have been found in root exudates, esculetin, scopoletin, and fraxetin, over a broad pH range under oxic and anoxic conditions. Our results show that the oxidation of coumarins is irreversible under oxic conditions and that oxidative degradation rates increased with increasing pH under both oxic and anoxic conditions. However, the complexation of Fe protects coumarins from degradation in the circumneutral pH range even under oxic conditions. Furthermore, we observed that Ferrozine, which is commonly used for establishing Fe redox speciation, can facilitate the reduction of Fe(III) complexed by coumarins, even at circumneutral pH. Reduction rates increased with decreasing pH and were larger for fraxetin than for scopoletin and esculetin. Based on these observations, we optimized the Ferrozine method for determining the redox state of Fe complexed by coumarins. Understanding the stability of dissolved coumarins and using a precise analytical method to determine the redox state of Fe in the presence of coumarins are critical for investigating the mechanisms by which coumarins enhance the availability of Fe in the rhizosphere.

Comprehensive performance of a diethylenetriamine/2-diethylaminoethanol biphasic absorbent for CO2 capture

The CO2 capture process based on amine absorption–regeneration is currently the most widely used technology, and the performance of absorbent is the key to this process. Biphasic absorbents have attracted considerable interest because of their strong potential to reduce the regeneration energy consumption and equipment investment costs. The mixed solution of diethylenetriamine (DETA) and 2-diethylaminoethanol (DEEA) has been proven to be a biphasic absorbent, but there is still a lack of comprehensive performance evaluation data. In this study, the ratio of the DETA/DEEA solution was optimized as 2 M DETA + 3 M DEEA, and its phase separation property, reaction mechanism, mass transfer kinetics, and desorption thermodynamics were investigated under various conditions. The comprehensive performance of the solution was then evaluated by further analyzing its oxidative degradation, thermal degradation, and metal corrosion characteristics. On this basis, the capital cost and operation cost of using DETA/DEEA biphasic absorbent were analyzed. Under typical coal-fired flue gas (CO2 concentration 12%), because of the high CO2 absorption capacity and excellent phase separation property, the minimal desorption energy consumption of the DETA/DEEA absorbent decreased to 2.14 GJ/t CO2, a 43.7% decrease compared with that of 5 M monoethanolamine (MEA). Under the same experimental conditions, DETA/DEEA exhibited an oxidative degradation rate of only 2.71%, which was 20.7% of 5 M MEA. In addition, the metal corrosion rate of DETA/DEEA was one order of magnitude lower than that of 5 M MEA. However, under a high CO2 loading, its thermal degradation resistance needed to be improved, and it was clear that the rates of oxidative degradation, metal corrosion, and thermal degradation of the CO2 rich lower phase were higher than those of the CO2 lean upper phase. The capital cost and operational capture cost of the DETA/DEEA biphasic process were approximately $107.8/t CO2 and $31.6/t CO2, respectively, which were 2.5% and 36.4% lower than those of the MEA process. These findings provide a theoretical basis for the industrial application of DETA/DEEA.

Photodestruction of active pharmaceutical substances in the presence of hydrogen peroxide and peroxydisulfate

Studies into photochemical oxidation can enhance the current understanding of degradation processes within aqueous solutions of active pharmaceutical ingredients (APIs). APIs are complex decomposable compounds that, once in reservoirs, cause irreversible consequences in living organisms. The results obtained on the photodestruction of various drugs in water in the presence of hydrogen peroxide and peroxydisulfate contribute to gaining new practical and theoretical knowledge in the field of water treatment, post-treatment, and purification. The paper presents laboratory results on the oxidation of model aqueous solutions of nitrofural, tetracycline, and paracetamol under the combined effect of UV radiation with micro-additives of oxidants (hydrogen peroxide and peroxydisulfate). The reaction order of APIs destruction is determined by the least square method. The results show that the combined effect of UV radiation and microadditives of hydrogen peroxide and peroxydisulfate contributes to both a high degree of purification (up to 98%) and a high rate of oxidative degradation of APIs (nitrofural, tetracycline, and paracetamol) compared to the use of UV radiation separately. The studied drugs can be arranged in the following order in terms of their oxidative degradation transformation ability: nitrofural>tetracycline>paraceta mol. The paper theoretically proves that photochemical destruction in the presence of peroxydisulfate leads to the formation of more highly reactive oxygen-containing radicals, which are involved in the decomposition of nitrofural, tetracycline, and paracetamol.

Insights into the Oxidative Degradation Mechanism of Solid Amine Sorbents for CO2 Capture from Air: Roles of Atmospheric Water

AbstractDirect air capture (DAC) processes for extraction of CO2 from ambient air are unique among chemical processes in that they operate outdoors with minimal feed pretreatments. Here, the impact of humidity on the oxidative degradation of a prototypical solid supported amine sorbent, poly(ethylenimine) (PEI) supported on Al2O3, is explored in detail. By combining CO2 adsorption measurements, oxidative degradation rates, elemental analyses, solid‐state NMR and in situ IR spectroscopic analysis in conjunction with 18O labeling of water, a comprehensive picture of sorbent oxidation is achieved under accelerated conditions. We demonstrated that the presence of water vapor can play an important role in accelerating the degradation reactions. From the study we inferred the identity and kinetics of formation of the major oxidative products, and the role(s) of humidity. Our data are consistent with a radical mediated autooxidative degradation mechanism.

Insights into the Oxidative Degradation Mechanism of Solid Amine Sorbents for CO2 Capture from Air: Roles of Atmospheric Water.

Direct air capture (DAC) processes for extraction of CO2 from ambient air are unique among chemical processes in that they operate outdoors conditions with minimal feed pretreatments. Here, the impact of humidity on the oxidative degradation of a prototypical solid supported amine sorbent, poly(ethylenimine) (PEI) supported on Al2O3, is explored in detail. By combining CO2 adsorption measurements, oxidative degradation rates, elemental analyses, solid-state NMR and in situ IR spectroscopic analysis in conjunction with 18O labeling of water, a comprehensive picture of sorbent oxidation is achieved under accelerated conditions. We demonstrated that the presence of water vapor can play an important role in accelerating the degradation reactions. From the study we inferred the identity and kinetics of formation of the major oxidative products, and the role(s) of humidity. Our data are consistent with a radical mediated autooxidative degradation mechanism.

Carbon dioxide capture in aqueous potassium serinate and piperazine solution using bubbling reactor for membrane contactor applications

There are various methods of CO2 removal, including absorption, adsorption, and membrane separation. A new method, membrane–solvent combination, involves the removal of CO2 using an absorbent in a membrane contactor. However, the absorbent causes membrane wetting, which reduces the CO2 removal efficiency. Accordingly, this study considered the use of potassium serinate (PS), an amino acid salt with high surface tension, to increase the surface tension of the absorbent and therefore reduce membrane wetting when used in a membrane contactor. Piperazine (Pz) was added to improve the absorption performance and prevent oxidative degradation. The concentration ranges of PS and Pz to apply at the membrane contactor were optimized based on the CO2 cyclic capacity and the calculated theoretical breakthrough pressure. Compared to a commercial CO2 absorbent, 30 wt% monoethanolamine (MEA), the PS + Pz absorbent had higher CO2 cyclic capacity and better wettability. Moreover, its oxidative degradation rate constant (k) in 720 h oxidative degradation experiments was 42.0 % lower than that of 30 wt% MEA, indicating that amino acid salt + Pz absorbents are promising for use in membrane contactors.

Selective recognition of neurotransmitters in aqueous solution by hydroxyphenyl aza-scorpiand ligands.

The synthesis, acid-base behaviour and anion recognition of neurotransmitters (dopamine, tyramine and serotonin) in aqueous solution of different aza-scorpiand ligands functionalized with hydroxyphenyl and phenyl moieties (L1-L3 and L4, respectively) have been studied by potentiometry, NMR, UV-Vis and fluorescence spectroscopy and isothermal titration calorimetry (ITC). The analysis of the potentiometric results shows the selective recognition of serotonin at physiological pH (Keff = 8.64 × 104) by L1. This selectivity has an entropic origin probably coming from a fine pre-organization of the interacting partners. Thus, the complementarity of the receptor and the substrate allows the reciprocal formation of hydrogen bonds, π-π and cation-π interactions, stabilizing the receptors and slowing the rate of oxidative degradation, and satisfactory results are obtained at acidic and neutral pH values. NMR and molecular dynamics studies reveal the rotation blockage in the neurotransmitter side chain once complexed with L1.

Shape Memory Polymer Foams with Phenolic Acid-Based Antioxidant Properties.

Phenolic acids (PAs) are natural antioxidant agents in the plant kingdom that are part of the human diet. The introduction of naturally occurring PAs into the network of synthetic shape memory polymer (SMP) polyurethane (PU) foams during foam fabrication can impart antioxidant properties to the resulting scaffolds. In previous work, PA-containing SMP foams were synthesized to provide materials that retained the desirable shape memory properties of SMP PU foams with additional antimicrobial properties that were derived from PAs. Here, we explore the impact of PA incorporation on SMP foam antioxidant properties. We investigated the antioxidant effects of PA-containing SMP foams in terms of in vitro oxidative degradation resistance and cellular antioxidant activity. The PA foams showed surprising variability; p-coumaric acid (PCA)-based SMP foams exhibited the most potent antioxidant properties in terms of slowing oxidative degradation in H2O2. However, PCA foams did not effectively reduce reactive oxygen species (ROS) in short-term cellular assays. Vanillic acid (VA)- and ferulic acid (FA)-based SMP foams slowed oxidative degradation in H2O2 to lesser extents than the PCA foams, but they demonstrated higher capabilities for scavenging ROS to alter cellular activity. All PA foams exhibited a continuous release of PAs over two weeks. Based on these results, we hypothesize that PAs must be released from SMP foams to provide adequate antioxidant properties; slower release may enable higher resistance to long-term oxidative degradation, and faster release may result in higher cellular antioxidant effects. Overall, PCA, VA, and FA foams provide a new tool for tuning oxidative degradation rates and extending potential foam lifetime in the wound. VA and FA foams induced cellular antioxidant activity that could help promote wound healing by scavenging ROS and protecting cells. This work could contribute a wound dressing material that safely releases antimicrobial and antioxidant PAs into the wound at a continuous rate to ideally improve healing outcomes. Furthermore, this methodology could be applied to other oxidatively degradable biomaterial systems to enhance control over degradation rates and to provide multifunctional scaffolds for healing.

Stabilisation of Soybean Oil with Pod Coat Extracts of Cowpea (Vigna unguiculata)

Background: In edible oil processing industry the main reason of lipid deterioration is oxidation. The inclusion of antioxidants is required to preserve colour, flavour and to prevent vitamin destruction. In recent years the discovery of safe antioxidants of plant origin have increased conspicuously and they have been considered as better alternative than synthetic antioxidants such as tert-butyl hydroquinone, butylated hydroxyanisole, propyl gallate etc. This study is an attempt to investigate pod coats of cowpea as potential source of natural antioxidants and to appraise their efficacy for stabilizing soybean oil. Methods: In the laboratory investigation during 2015-2018 the efficacy of cowpea pod coat extracts in stabilizing soybean oil during accelerated storage has been studied. Pod coats of cowpea were extracted with three solvents (acetone, ethyl acetate and chloroform). Soybean oil samples were stabilised by adding different pod coat extracts at 1000 and 2000 ppm concentration. Result: Our investigation allowed us to conclude that rate of oxidative degradation of soybean oil was the lowest in the sample treated with acetone extract (2000 ppm).