Search results for: photocatalytic oxidation

Authors: Kooshan Nayebzadeh, Maryam Enteshari

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In this study, the oxidative stability of soybean oil under different storage temperatures (4 and 25 ˚C) and during 6-month shelf-life was investigated by various analytical methods and headspace-liquid phase microextraction (HS-LPME) coupled to gas chromatography-mass spectrometry (GC-MS). Oxidation changes were monitored by analytical parameters consisted of acid value (AV), peroxide value (PV), p-Anisidine value (p-AV), thiobarbituric acid value (TBA), fatty acids profile, iodine value (IV) and oxidative stability index (OSI). In addition, concentrations of hexanal and heptanal as secondary volatile oxidation compounds were determined by HS-LPME/GC-MS technique. Rate of oxidation in soybean oil which stored at 25 ˚C was so higher. The AV, p-AV, and TBA were gradually increased during 6 months, while the amount of unsaturated fatty acids, IV, and OSI decreased. Other parameters included concentrations of both hexanal and heptanal, and PV exhibited increasing trend during primitive months of storage; then, at the end of third and fourth months a sudden decrement was understood for the concentrations of hexanal and heptanal and the amount of PV, simultaneously. The latter parameters increased again until the end of shelf-time. As a result, the temperature and time were effective factors in oxidative stability of soybean oil. Also intensive correlations were found for soybean oil at 4 ˚C between AV and TBA (r2=0.96), PV and p-AV (r2=0.9), IV and TBA (-r2=0.9), and for soybean oil stored at 4 ˚C between p-AV and TBA (r2=0.99).

Keywords: headspace-liquid phase microextraction, oxidation, shelf-life, soybean oil

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Authors: Hamsasew Hankebo Lemago, Dóra Hessz, Tamás Igricz, Zoltán Erdélyi, , Imre Miklós Szilágyi

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Metal oxide inverse opals are a promising class of photocatalysts with a unique hierarchical structure. Atomic layer deposition (ALD) is a versatile technique for the synthesis of high-precision metal oxide thin films, including inverse opals. In this study, we report the synthesis of TiO₂, ZnO, and Al₂O₃ inverse opal and their composites photocatalysts using thermal or plasma-enhanced ALD. The synthesized photocatalysts were characterized using a variety of techniques, including scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman spectroscopy, photoluminescence (PL), ellipsometry, and UV-visible spectroscopy. The results showed that the ALD-synthesized metal oxide inverse opals had a highly ordered structure and a tunable pore size. The PL spectroscopy results showed low recombination rates of photogenerated electron-hole pairs, while the ellipsometry and UV-visible spectroscopy results showed tunable optical properties and band gap energies. The photocatalytic activity of the samples was evaluated by the degradation of methylene blue under visible light irradiation. The results showed that the ALD-synthesized metal oxide inverse opals exhibited high photocatalytic activity, even under visible light irradiation. The composites photocatalysts showed even higher activity than the individual metal oxide inverse opals. The enhanced photocatalytic activity of the composites can be attributed to the synergistic effect between the different metal oxides. For example, Al₂O₃ can act as a charge carrier scavenger, which can reduce the recombination of photogenerated electron-hole pairs. The ALD-synthesized metal oxide inverse opals and their composites are promising photocatalysts for a variety of applications, such as wastewater treatment, air purification, and energy production. The ALD-synthesized metal oxide inverse opals and their composites are promising photocatalysts for a variety of applications, such as wastewater treatment, air purification, and energy production.

Keywords: ALD, metal oxide inverse opals, photocatalysis, composites

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Authors: Khosro Ghazvinian, Touba Khodaeian

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To improve the oxidative stability of meat products, the use of dietary form of antioxidants can extend the shelf life and acceptability of muscle food during exposition or storage condition. As shown, this method is more effective than adding direct preservatives due to uniform incorporation of dietary additives into sub cellular membrane and therefore, they can properly inhibit the oxidative reaction at their localized sites. Furthermore, postmortem addition of antioxidants to meat cannot directly inhibit the oxidation in membrane phospholipids. Therefore, this study was designed to evaluate the effects of feed supplementation with Melissa officinalis leaves on lipid peroxidation of chicken breast fillets during refrigerated storage. In this study, 72 one-day old Ross 308 broilers distributed in four groups with six replicates (3 chickens each) were fed a basal diet (CONT) or basal diet supplemented with 5, 10, and 15 gr/Kg M.officinalis, for 6 weeks. Following slaughter, fillets from breast were stored at 4 °C in the dark for 12 days, and lipid oxidation was assessed on the basis of thiobarbituric acid reactive substances (TBARS) formed. Results showed that incorporation of M.officinalis in broiler diets delayed lipid oxidation in raw breast meat during refrigerated storage comparative with CONT(p<0.05). In this regard, TBARS levels of breast samples containing higher concentrations (10 and 15 gr/Kg) of M. officinalis (625.43 and 504.32 µg/kg MDA equivalents, respectively )were significantly lower than those of control and 5g/kg samples (872.75 and 841.32 µg/kg MDA equivalents, respectively) (p<0.05). Therefore, M. officinalis might be utilized in novel applications as a nutritional supplement or a functional food component.

Keywords: breast fillet, lipid oxidation, Melissa officinalis, TBARS assay

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Authors: Ala Abdessemed, Mohamed Seddik Oussama Belahmadi, Nabil Charchar, Abdefettah Gherib, Bradai Fares, Boussadia Chouaib Nour El-Islem

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Algerian cities are confronted with large quantities of waste generated by the disposal of household and similar residues in technical landfills (CET), such as the one in the location of Batna. The interaction between waste components and incoming water generates leachates rich in organic matter and trace elements, which require treatment before discharge. The aim of this study was to propose an effective process for treating the leachates, which were subjected to an initial chemical treatment using the (H₂O₂/UV) system. Optimal treatment conditions were determined at [H₂O₂] of 0.3 M and pH of 8.6. Next, two hybrid biological treatment systems were applied: hybrid system I (H₂O₂/UV/bacteria) and hybrid system II (H₂O₂/UV/bacteria/microalgae). The three processes resulted in the following degradation rates, expressed in terms of total organic carbon (TOC) 27.4% for the (H₂O₂/UV) system; 58.1% for the hybrid system I (H₂O₂/UV/Bacteria); 67.86% for the hybrid system II (H₂O₂/UV/Bacteria/Microalgae). This study demonstrates that a hybrid approach combining advanced oxidation processes and biological treatments is a highly effective alternative to achieve satisfactory treatment.

Keywords: leachate, landfill, advanced oxidation processes, biological treatment, bacteria, microalgae, total organic carbon

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Authors: A. Masek, M. Zaborski

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Electrochemical oxidation of dodecyl gallate (lauryl gallate), the main monomer flavanol found in green tea, was investigated on platinum electrodes using cyclic voltammetry (CV) and differential pulse (DPV) methods. The rate constant, electron transfer coefficient and diffusion coefficients were determined for dodecyl gallate electrochemical oxidation. The oxidation mechanism proceeds in sequential steps related to the hydroxyl groups in the aromatic ring of dodecyl gallate. Confirmed antioxidant activity of lauryl gallate verified its use in polymers as an environment-friendly stabiliser to improve the resistance to aging of the elastomeric materials. Based on the energy change of the deformation, cross-linking density and time of the oxygen induction with the TG method, we confirmed the high antioxidant activity of lauryl gallate in polymers. Moreover, the research on biodegradation confirmed the environment-friendly influence of the antioxidant by increasing the susceptibility of the elastomeric materials to disintegration by mildew mushrooms.

Keywords: polymers, flavonoids, stabilization, ageing

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Authors: Khaled S. Al Salhen

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Aldehyde oxidase is molybdo-flavoenzyme involved in the oxidation of hundreds of endogenous and exogenous and N-heterocyclic compounds and environmental pollutants. Uncharged N-heterocyclic aromatic compounds such phenanthridine are commonly distributed pollutants in soil, air, sediments, surface water and groundwater, and in animal and plant tissues. Phenanthridine as uncharged N-heterocyclic aromatic compound was incubated with partially purified aldehyde oxidase from rainbow trout fish liver. Reversed-phase HLPC method was used to separate the oxidation products from phenanthridine and the metabolite was identified. The 6(5H)-phenanthridinone was identified the major metabolite by partially purified aldehyde oxidase from fish liver. Kinetic constant for the oxidation reactions were determined spectrophotometrically and showed that this substrate has a good affinity (Km = 78 ± 7.6 µM) for hepatic aldehyde oxidase, coupled with a relatively high oxidation rate (0.77± 0.03 nmol/min/mg protein). In addition, the kinetic parameters of hepatic fish aldehyde oxidase towards the phenanthridine substrate indicate that in vitro biotransformation by hepatic fish aldehyde oxidase will be a significant pathway. This study confirms that partially purified aldehyde oxidase from fish liver is indeed the enzyme responsible for the in vitro production 6(5H)-phenanthridinone metabolite as it is a major metabolite by mammalian aldehyde oxidase.

Keywords: aldehyde oxidase, fish, phenanthridine, specificity

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Authors: Satam Alotibi, Osama A. Hussein, Aziz H. Al-Shaibani, Nawaf A. Al-Aqeel, Abdellah Kaiba, Fatehia S. Alhakami, Mohammed Alyami, Talal F. Qahtan

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The demand for sustainable and efficient energy conversion using solar energy has grown rapidly in recent years. In this pursuit, solar-to-chemical conversion has emerged as a promising approach, with oxygen vacancies-rich tungsten trioxide (WO₃) playing a crucial role. This study presents a method for synthesizing oxygen vacancies-rich WO3, resulting in a significant enhancement of its photocatalytic activity, representing a significant step towards sustainable energy solutions. Experimental results underscore the importance of oxygen vacancies in modifying the properties of WO₃. These vacancies introduce additional energy states within the material, leading to a reduction in the bandgap, increased light absorption, and acting as electron traps, thereby reducing emissions. Our focus lies in developing oxygen vacancies-rich WO₃, which demonstrates unparalleled potential for improved photocatalytic applications. The effectiveness of oxygen vacancies-rich WO₃ in solar-to-chemical conversion was showcased through rigorous assessments of its photocatalytic degradation performance. Sunlight irradiation was employed to evaluate the material's effectiveness in degrading organic pollutants in wastewater. The results unequivocally demonstrate the superior photocatalytic performance of oxygen vacancies-rich WO₃ compared to conventional WO₃ nanomaterials, establishing its efficacy in sustainable and efficient energy conversion. Furthermore, the synthesized material is utilized to fabricate films, which are subsequently employed in immobilized WO₃ and oxygen vacancies-rich WO₃ reactors for water purification under natural sunlight irradiation. This application offers a sustainable and efficient solution for water treatment, harnessing solar energy for effective decontamination. In addition to investigating the photocatalytic capabilities, we extensively analyze the structural and chemical properties of the synthesized material. The synthesis process involves in situ thermal reduction of WO₃ nano-powder in a nitrogen environment, meticulously monitored using thermogravimetric analysis (TGA) to ensure precise control over the synthesis of oxygen vacancies-rich WO₃. Comprehensive characterization techniques such as UV-Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), FTIR, Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) provide deep insights into the material's optical properties, chemical composition, elemental states, structure, surface properties, and crystalline structure. This study represents a significant advancement in sustainable energy conversion through solar-to-chemical processes and water purification. By harnessing the unique properties of oxygen vacancies-rich WO₃, we not only enhance our understanding of energy conversion mechanisms but also pave the way for the development of highly efficient and environmentally friendly photocatalytic materials. The application of this material in water purification demonstrates its versatility and potential to address critical environmental challenges. These findings bring us closer to a sustainable energy future and cleaner water resources, laying a solid foundation for a more sustainable planet.

Keywords: sustainable energy conversion, solar-to-chemical conversion, oxygen vacancies-rich tungsten trioxide (WO₃), photocatalytic activity enhancement, water purification

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Authors: Satam Alotibi, Muhammad J. Al-Zahrani, Fahd K. Al-Naqidan, Turki S. Hussein, Moteb Alotaibi, Mohammed Alyami, Mahdy M. Elmahdy, Abdellah Kaiba, Fatehia S. Alhakami, Talal F. Qahtan

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Water pollution is a critical global challenge that demands scalable and effective solutions for water decontamination. In this captivating research, we unveil a groundbreaking strategy for harnessing solar energy to synthesize silver (Ag) clusters on stable titanium dioxide (TiO₂) nanoparticles dispersed in water, without the need for traditional stabilization agents. These Ag-loaded TiO₂ nanoparticles exhibit exceptional photocatalytic activity, surpassing that of pristine TiO₂ nanoparticles, offering a promising solution for highly efficient water decontamination under sunlight irradiation. To the best knowledge, we have developed a unique method to stabilize TiO₂ P25 nanoparticles in water without the use of stabilization agents. This breakthrough allows us to create an ideal platform for the solar-driven synthesis of Ag clusters. Under sunlight irradiation, the stable dispersion of TiO₂ P25 nanoparticles acts as a highly efficient photocatalyst, generating electron-hole pairs. The photogenerated electrons effectively reduce silver ions derived from a silver precursor, resulting in the formation of Ag clusters. The Ag clusters loaded on TiO₂ P25 nanoparticles exhibit remarkable photocatalytic activity for water decontamination under sunlight irradiation. Acting as active sites, these Ag clusters facilitate the generation of reactive oxygen species (ROS) upon exposure to sunlight. These ROS play a pivotal role in rapidly degrading organic pollutants, enabling efficient water decontamination. To confirm the success of our approach, we characterized the synthesized Ag-loaded TiO₂ P25 nanoparticles using cutting-edge analytical techniques, such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and spectroscopic methods. These characterizations unequivocally confirm the successful synthesis of Ag clusters on stable TiO₂ P25 nanoparticles without traditional stabilization agents. Comparative studies were conducted to evaluate the superior photocatalytic performance of Ag-loaded TiO₂ P25 nanoparticles compared to pristine TiO₂ P25 nanoparticles. The Ag clusters loaded on TiO₂ P25 nanoparticles exhibit significantly enhanced photocatalytic activity, benefiting from the synergistic effect between the Ag clusters and TiO₂ nanoparticles, which promotes ROS generation for efficient water decontamination. Our scalable strategy for synthesizing Ag clusters on stable TiO₂ P25 nanoparticles without stabilization agents presents a game-changing solution for highly efficient water decontamination under sunlight irradiation. The use of commercially available TiO₂ P25 nanoparticles streamlines the synthesis process and enables practical scalability. The outstanding photocatalytic performance of Ag-loaded TiO₂ P25 nanoparticles opens up new avenues for their application in large-scale water treatment and remediation processes, addressing the urgent need for sustainable water decontamination solutions.

Keywords: water pollution, solar energy, silver clusters, TiO₂ nanoparticles, photocatalytic activity

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Authors: M. Tabatabaee, R. Mohebat, M. Baranian

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Textile industries produce large volumes of colored dye effluents which are toxic and non-biodegradable. Earlier studies have shown that a wide range of organic substrates can be completely photo mineralized in the presence of photocatalysts and oxidant agents. ZnO and TiO2 are important photocatalysts with high catalytic activity that have attracted much research attention. Zinc sulfide is one of the semiconductor nanomaterials that can be used for the production of optical sensitizers, photocatalysts, electroluminescent materials, optical sensors and for solar energy conversion. The synthesis of ZnS nanoparticles has been tried by various methods and sulfide sources. Elementary sulfur powder, H2S or Na2S are used as sulfide sources for synthesis of ZnS nano particles. Recently, solar energy is has been successfully used for photocatalytic degradation of dye pollutant. Studies have shown that the use of metal oxides or sulfides with ZnO or TiO2 can significantly enhance the photocatalytic activity of them. In this research, Nano-sized zinc sulfide was synthesized successfully by a simple method using thioasetamide as sulfide source in the presence of polyethylene glycol (PEG 2000). X-ray diffraction (XRD) spectroscopy scanning electron microscope (SEM) was used to characterize the structure and morphology synthesized powder. The effect of photocatalytic activity of prepared ZnS and ZnS/ZnO, on degradation of direct Black19 under UV and sunlight irradiation was investigated. The effects of various parameters such as amount of photocatalyst, pH, initial dye concentration and irradiation time on decolorization rate were systematically investigated. Results show that more than 80% of 500 mgL-1 of dye decolorized in 60-min reaction time under UV and solar irradiation in the presence of ZnS nanoparticles. Whereas, mixed ZnS/ZnO (50%) can decolorize more than 80% of dye in the same conditions.

Keywords: zinc sulfide, nano articles, photodegradation, solar light

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Authors: Zh. Saffari, A. Naeimi, M. S. Ekrami-Kakhki, F. Hamidi

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Fe3O4 is one of the important magnetic oxides with spinel structure; it has exhibited unique electric and magnetic properties based on the electron transfer between Fe2+ and Fe3+ in the octahedral sites. Fe3O4 has received considerable attention in various areas such as cancer therapy, drug targeting, enzyme immobilization catalysis, magnetic cell separation, magnetic refrigeration systems and super-paramagnetic materials Fe3O4–TiO2 nanostructures were synthesized by simple, effective and new co-precipitation method assisted by ultrasonic reaction at room temperatures with organic surfactant. The effect of various parameters such as temperature, time, and power on the size and morphology of the product was investigated. Alternating gradient force magnetometer shows that Fe3O4 nanoparticles exhibit super-paramagnetic behaviour at room temperature. For preparation of nanocomposite, 1 g of TiO2 nanostructures were dispersed in 100 mL of ethanol. 0.25 g of Fe(NO3)2 and 2 mL of octanoic acid was added to the solution as a surfactant. Then, NaOH solution (1.5 M) was slowly added into the solution until the pH of the mixture was 7–8. After complete precipitation, the solution placed under the ultrasonic irradiation for 30 min. The product was centrifuged, washed with distilled water and dried in an oven at 100 °C for 3 h. The resulting red powder was calcinated at 800 °C for 3 h to remove any organic residue. The photocatalytic behaviour of Fe3O4–TiO2 nanoparticles was evaluated using the degradation of a Methyl Violet (MV) aqueous solution under ultraviolet light irradiation. As time increased, more and more MV was adsorbed on the nanoparticles catalyst, until the absorption peak vanish. The MV concentration decreased rapidly with increasing UV-irradiation time

Keywords: magnetic, methyl violet, nanocomposite, photocatalytic

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Authors: Maryam Enteshari, Kooshan Nayebzadeh, Abdorreza Mohammadi

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In this study, the oxidative stability of soybean oil under different storage temperatures (4 and 25˚C) and during 6-month shelf-life was investigated by various analytical methods and headspace-liquid phase microextraction (HS-LPME) coupled to gas chromatography-mass spectrometry (GC-MS). Oxidation changes were monitored by analytical parameters consisted of acid value (AV), peroxide value (PV), p-Anisidine value (p-AV), thiobarbituric acid value (TBA), fatty acids profile, iodine value (IV), and oxidative stability index (OSI). In addition, concentrations of hexanal and heptanal as secondary volatile oxidation compounds were determined by HS-LPME/GC-MS technique. Rate of oxidation in soybean oil which stored at 25˚C was so higher. The AV, p-AV, and TBA were gradually increased during 6 months while the amount of unsaturated fatty acids, IV, and OSI decreased. Other parameters included concentrations of both hexanal and heptanal, and PV exhibited increasing trend during primitive months of storage; then, at the end of third and fourth months a sudden decrement was understood for the concentrations of hexanal and heptanal and the amount of PV, simultaneously. The latter parameters increased again until the end of shelf-time. As a result, the temperature and time were effective factors in oxidative stability of soybean oil. Also intensive correlations were found for soybean oil at 4 ˚C between AV and TBA (r2=0.96), PV and p-AV (r2=0.9), IV and TBA (-r2=0.9), and for soybean oil stored at 4˚C between p-AV and TBA (r2=0.99).

Keywords: headspace-liquid phase microextraction, oxidation, shelf-life, soybean oil

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Authors: Otilia R. Vasile, Florina C. Ilie, Irina F. Nicoara, Cristina D. Ghitulica, Roxana Trusca, Ovidiu Oprea, Vasile A. Surdu, Bogdan S. Vasile, Ecaterina Adronescu

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In this work ZnO nanostructures (nanopowders and nanostars) have been synthesized via a simple sol-gel method. The used methods for synthesizing the nanostructures involve two steps as follows: (1) precipitation of zinc acetate precursor for the synthesis of ZnO nanopowders and zinc chloride precursor for the synthesis of ZnO nanostars and (2) addition of Eu2O3 in different concentrations (1%, 3%, and 5%) using europium acetate as precursor. Detailed crystalline parameters for each of the synthetized species were analysed using X-ray diffraction. Structural transitions were also discussed. The structure and morphology of the as-prepared ZnO nanopowders and nanostars were investigated by electron microscopy. TEM investigations have shown an average particle size range from 23 to 29 nm and polyhedral and spherical morphology with tendency to form aggregates for nanopowders. For nanostars structures, a star-like morphology could be observed. Cytotoxicity tests on MG-63 cell lines were also performed. Photocatalytic activity of ZnO nanopowders have reached higher values compared to ZnO nanostars.

Keywords: cytotoxicity, photocatalytic activity, TEM, ZnO

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Authors: Amal A. Al-Kahlawy, Heba H. El-Maghrabi

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Due to the increasing need to environment protection in real time need to energize new materials are under extensive investigations. Between others, TiO2 nanotubes (TNTs) nanocomposite with iron oxide and silver carbonate, are promising alternatives as high-efficiency visible light photocatalyst due to their unique properties and their superior charge transport properties. Our efforts in this domain aim the construction of novel nanocomposite of TiO2NT/Fe2O3@Ag2CO3. The structure, surface morphology, chemical composition and optical properties were characterized by X-ray diffraction (XRD), Raman, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and UV–vis diffuse reflectance spectroscopy (DRS). XRD results confirm the interaction of TiO2-NT with iron oxide. This novel nanocomposite shows remarkably enhanced performance for phenol compounds photodegradation. The experimental data shows a promising photocatalytic activity. In particular, a maximum value of 450 mg/g was removed within 60 min at solar light irradiation with degradation efficiency of 99.5%. The high photocatalytic activity of the nanocomposite is found to be related to the increased adsorption toward chemical species, enhanced light absorption and efficient charge separation and transfer. Finally, the designed TiO2NT/Fe2O3@Ag2CO3 nanocomposite has a great degree of sustainability and could has a potential application for the industrial treatment of wastewater containing toxic organic materials.

Keywords: nanocomposite, photocatalyst, solar energy, titanium dioxide nanotubes

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Authors: Mohammad Ali Karimi, Hossein Tavallali, Abdolhamid Hatefi-Mehrjardi

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In this study, an electrochemical sensor based on gold nanoparticles (AuNPs) functionalized improved graphene (AuNPs-IGE) was fabricated for selective determination of L-dopa in the presence of ascorbic acid by a novel self-assembly method. The AuNP IGE modified carbon paste electrode (AuNPs-IGE/CPE) utilized for investigation of the electrochemical behavior of L-dopa in phosphate buffer solution. Compared to bare CPE, AuNPs-IGE/CPE shows novel properties towards the electrochemical redox of levodopa (L-dopa) in phosphate buffer solution at pH 4.0. The oxidation potential of L-dopa shows a significant decrease at the AuNPs-IGE/CPE. The oxidation current of L-dopa is higher than that of the unmodified CPE. AuNPs-IG/CPE shows excellent electrocatalytic activity for the oxidation of ascorbic acid (AA). Using differential pulse voltammetry (DPV) method, the oxidation current is well linear with L-dopa concentration in the range of 0.4–50 µmol L-1, with a detection limit of about 1.41 nmol L-1 (S/N = 3). Therefore, it was applied to measure L-dopa from real samples that recoveries are 94.6-106.2%. The proposed electrode can also effectively avoid the interference of ascorbic acid, making the proposed sensor suitable for the accurate determination of L-dopa in both pharmaceutical preparations and human body fluids.

Keywords: gold nanoparticles, improved graphene, L-dopa, self-assembly

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Authors: Sudhakar Saroj, Satya Vir Singh

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Undoped and Fe doped TiO₂, Ti₁₋ₓFeₓO₂ (x=0.00, 0.01, 0.03, 0.05, 0.07 and 0.09) have been synthesized by solution combustion method using Titanium (IV) oxide as a precursor, and also were characterized by XRD, DRS, FTIR, XPS, SEM, and EDX. The formation of anatase phase of undoped and Fe TiO₂ nanoparticles were confirmed by XRD, and the average crystallite size was determined by Debye-Scherer's equation. The DRS analysis indicates the shifting of light absorbance in visible region from UV region with increasing the doping concentration in TiO₂. The vibrational band of the Ti-O lattice was confirmed by the FT-IR spectrum. The XPS results confirm the presence of elements of titanium, oxygen and iron in the synthesized samples and determine the binding energy of elements. SEM image of the above-synthesized nanoparticles showed the spherical shape of nanoparticles. The purities of the synthesized nanoparticles were confirmed by EDX analysis. The photocatalytic activities of the synthesized nanoparticles were tested by studying the degradation of dye (Direct Blue 199) in the photocatalytic reactor. The Ti₀.₉₇Fe₀.₀₃O₂ photocatalyst shows highest photodegradation activity among all the synthesized undoped and Fe doped TiO₂ photocatalyst.

Keywords: direct blue 199, nanoparticles, TiO₂, photodegradation

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Authors: Quan Li, Dongcai Shen, Zhengting Xiao, Xin Liu Mingrui Wu, Licheng Liu, Qin Li, Xianguo Li, Wentai Wang

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Direct electrocatalytic nitrogen oxidation (NOR) provides a promising alternative strategy for synthesizing high-value-added nitric acid from widespread N₂, which overcomes the disadvantages of the Haber-Bosch-Ostwald process. However, the NOR process suffers from the limitation of high N≡N bonding energy (941 kJ mol− ¹), sluggish kinetics, low efficiency and yield. It is a prerequisite to develop more efficient electrocatalysts for NOR. Herein, we synthesized double-shelled CeO₂ hollow spheres (D-CeO₂) and further modified with Ti₃C₂ MXene quantum dots (MQDs) for electrocatalytic N₂ oxidation, which exhibited a NO₃− yield of 71.25 μg h− ¹ mgcat− ¹ and FE of 31.80% at 1.7 V. The unique quantum size effect and abundant edge active sites lead to a more effective capture of nitrogen. Moreover, the double-shelled hollow structure is favorable for N₂ fixation and gathers intermediate products in the interlayer of the core-shell. The in-situ infrared Fourier transform spectroscopy confirmed the formation of *NO and NO₃− species during the NOR reaction, and the kinetics and possible pathways of NOR were calculated by density functional theory (DFT). In addition, a Zn-N₂ reaction device was assembled with D-CeO₂/MQDs as anode and Zn plate as cathode, obtaining an extremely high NO₃− yield of 104.57 μg h− ¹ mgcat− ¹ at 1 mA cm− ².

Keywords: electrocatalytic N₂ oxidation, nitrate production, CeO₂, MXene quantum dots, double-shelled hollow spheres

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Authors: Nazlı Çetindağ, Pelin Yılmaz Çetiner, Metin Mert İlgün, Emine Birci, Gizemnur Yıldız Uysal, Özcan Hatipoğlu, Ehsan Tuzcuoğlu, Gökhan Sır

Abstract:

Stressing the importance of water conservation, emphasizing the need for efficient management of household water, and underlining the significance of alternative solutions are important. In this context, advanced solutions based on technologies such as the advanced oxidation process have emerged as promising methods for treating household wastewater. Evaluating household water usage holds critical importance for the sustainability of water resources. Researchers and experts are examining various technological approaches to effectively treat and reclaim water for reuse. In this framework, the advanced oxidation process has proven to be an effective method for the removal of various organic and inorganic pollutants in the treatment of household wastewater. In this study, performance will be evaluated by comparing it with the reference case. This international criterion simulates the washing of home textile products, determining various performance parameters. The specially designed stain strips, including sebum, carbon black, blood, cocoa, and red wine, used in experiments, represent various household stains. These stain types were carefully selected to represent challenging stain scenarios, ensuring a realistic assessment of washing performance. Experiments conducted under different temperatures and program conditions successfully demonstrate the practical applicability of the advanced oxidation process for treating household wastewater. It is important to note that both adherence to standards and the use of real-life stain types contribute to the broad applicability of the findings. In conclusion, this study strongly supports the effectiveness of treating household wastewater with the advanced oxidation process in terms of washing performance under both standard and practical application conditions. The study underlines the importance of alternative solutions for sustainable water resource management and highlights the potential of the advanced oxidation process in the treatment of household water, contributing significantly to optimizing water usage and developing sustainable water management solutions.

Keywords: advanced oxidation process, household water usage, household appliance waste water, modelling, water reuse

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Authors: Shu-Chuan Liao, Chia-Ti Chang, Ko-Shao Chen

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Titanium and its alloy are widely used in many fields such as dentistry or orthopaedics. Due to their high strength low elastic modulus that chemical inertness and bio inert. The micro-arc oxidation used to formation a micro porous ceramic oxide layer film on Titanium surface and also to improve the resistance corrosion. For improving the biocompatibility, micro-arc oxidation surfaces bio-inert need to introduce reactive group. We introduced boundary layer by used plasma enhanced chemical vapor deposition of hexamethyldisilazane (HMDS) and organic active layer by UV light graft reactive monomer acrylic acid (AAc) therefore we can immobilize Chondroitin sulphate on surface easily by crosslinking EDC/NHS. The surface properties and composition of the modified layer were measured by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) and water contact angle. Water contact angle of the plasma-treated Ti surface decreases from 60° to 38°, which is an indication of hydrophilicity. The results of electrochemical polarization analysis showed that the sample plasma treated at micro-arc oxidation after plasma treatment has the best corrosion resistance. The result showed that we can immobilize chondroitin sulfate successful by a series of modification and MTT assay indicated the biocompatibility has been improved in this study.

Keywords: MAO, plasma, graft polymerization, biomedical application

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Authors: Yu-Jen Shih, Juan-Zhang Lou

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Nitrogenous compounds, such as NH4+/NH3 and NO3-, have become important contaminants in water resources. Excessive concentration of NH3 leads to eutrophication, which poses a threat to aquatic organisms in the environment. Electrochemical oxidation emerged as a promising water treatment technology, offering advantages such as simplicity, small-scale operation, and minimal reliance on additional chemicals. In this study, a nickel-based metal-organic framework (Ni-MOF) was synthesized using 2-amino terephthalic acid (BDC-NH2) and nickel nitrate. The Ni-MOF was further carbonized as derived nickel oxide and nitrogen-carbon composite, Ni/NiOx/NC. The nickel oxide within the 2D porous carbon texture served as active sites for ammonia oxidation. Results of characterization showed that the Ni-MOF was a hexagonal and flaky nanoparticle. With increasing carbonization temperature, the nickel ions in the organic framework re-crystallized as NiO clusters on the surfaces of the 2D carbon. The electrochemical surface area of Ni/NiOx/NC significantly increased as to improve the efficiency of ammonia oxidation. The phase transition of Ni(OH)2⇌NiOOH at around +0.8 V was the primary mediator of electron transfer. Batch electrolysis was conducted under constant current and constant potential modes. The electrolysis parameters included pyrolysis temperatures, pH, current density, initial feed concentration, and electrode potential. The constant current batch experiments indicated that via carbonization at 800 °C, Ni/NiOx/NC(800) was able to decrease the ammonium nitrogen of 50 mg-N/L to below 1 ppm within 4 hours at a current density of 3 mA/cm2 and pH 11 with negligible oxygenated nitrogen formation. The constant potential experiments confirmed that N2 nitrogen selectivity was enhanced up to 90% at +0.8 V.

Keywords: electrochemical oxidation, nickel oxyhydroxide, metal-organic framework, ammonium, nitrate

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Authors: Ali Bahri Lubis

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Tryptophan oxidation by Heme-dioxygenase enzyme is initial important stepTryptophan oxidation by Heme-dioxygenase enzyme is initial important step in kynurenine pathway implicating to several severe diseases such as Parkinson’s Disease, Huntington Disease, poliomyelitis and cataract. It is crucial to comprehend the oxidation mechanism with the hope to find decent treatment upon abovementioned diseases. The mechanism has been debatable since no one has been yet proved the mechanism obviously. In this research we have attempted to prove mechanistic steps of tryptophan oxidation via human indoleamine dioxygenase (h-IDO) using various substrates: L-tryptophan, L-tryptophan (indole-ring-2-13C), L-fully-labelled13C-tryptophan, L-N-methyl-tryptophan, L-tryptophan and 2-amino-3-(benzo(b)thiophene-3-yl) propanoic acid. All enzyme assay experiments were measured using a UV-Vis spectrophotometer, LC-MS, 1H-NMR, and HSQC. We also successfully synthesized enzyme products as our control in NMR measurements. The result exhibited that the distinct substrates produced N-formyl kynurenine (NFK) and hydroxypyrrolloindoleamine carboxylate acid (HPIC) in different concentrations and isomers, correlated to the proposal of considered mechanism reaction in kynurenine pathway implicating to several severe diseases such as Parkinson’s Disease, Huntington Disease, poliomyelitis and cataract. It is crucial to comprehend the oxidation mechanism with the hope to find decent treatment for the abovementioned diseases. The mechanism has been debatable since no one has yet proven the mechanism obviously. In this research we have attempted to prove mechanistic steps of tryptophan oxidation via human indoleamine dioxygenase (h-IDO) using various substrates: L-tryptophan, L-tryptophan (indole-ring-2-13C), L-fully-labelled13C-tryptophan, L-N-methyl-tryptophan, L-tryptophan and 2-amino-3-(benzo(b)thiophene-3-yl) propanoic acid. All enzyme assay experiments were measured using a UV-Vis spectrophotometer, LC-MS, 1H-NMR and HSQC. We also successfully synthesized enzyme products as our control in NMR measurements. The result exhibited that the distinct substrates produced N-formyl kynurenine (NFK) and hydroxypyrrolloindoleamine carboxylate acid (HPIC) in different concentrations and isomers, correlated to the proposal of considered mechanism reaction.

Keywords: heme-dioxygenase enzyme, tryptophan oxidation, kynurenine pathway, n-formyl kynurenine

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Authors: Mohammed Nasir Kajama, Ngozi Claribelle Nwogu, Edward Gobina

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Pt/γ-Al2O3 membrane catalysts were prepared via an evaporative-crystallization deposition method. The obtained Pt/γ-Al2O3 catalyst activity was tested after characterization (SEM-EDAX observation, BET measurement, permeability assessment) in the catalytic oxidation of selected volatile organic compound (VOC) i.e. propane, fed in mixture of oxygen. The VOC conversion (nearly 90%) obtained by varying the operating temperature showed that flow-through membrane reactor might do better in the abatement of VOCs.

Keywords: VOC combustion, flow-through membrane reactor, platinum supported alumina catalysts

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Authors: Nuray Güy, Mahmut Özacar

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Semiconductor nanoparticles such as TiO₂ and ZnO as photocatalysts are very efficient catalysts for wastewater treatment by the chemical utilization of light energy, which is capable of converting the toxic and nonbiodegradable organic compounds into carbon dioxide and mineral acids. ZnO semiconductor has a wide bandgap energy of 3.37 eV and a relatively large exciton binding Energy (60 meV), thus can absorb only UV light with the wavelength equal to or less than 385 nm. It exhibits low efficiency under visible light illumination due to its wide band gap energy. In order to improve photocatalytic activity of ZnO under visible light, band gap of ZnO may be narrowed by doping such as N, C, S nonmetal ions and coupled two separate semiconductors possessing different energy levels for their corresponding conduction and valence bands. ZnS has a wider band gap (Eg=3.7 eV) than ZnO and generates electron–hole pairs by photoexcitation rapidly. In the present work, N doped ZnO/ZnS nano photocatalysts with visible-light response were synthesized by microwave-hydrothermal method using thiourea as N source. The prepared photocatalysts were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV–visible (UV–vis). The photocatalytic activities samples and undoped ZnO have been studied for the degradation of dye, and have also been compared with together.

Keywords: photocatalyst, synthesis, visible light, ZnO/ZnS

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Authors: Siyang Wang, Yujin Hu, Xuelin Wang, Wenqian Zhang

Abstract:

Austenitic stainless steels are widely used in nuclear industry to manufacture critical components owing to their excellent corrosion resistance at high temperatures. Almost all the components used in nuclear power plants are produced by surface finishing (surface cold work) such as milling, grinding and so on. The change of surface states induced by machining has great influence on the corrosion behavior. In the present study, long time oxidation behavior of machined 316 austenitic stainless steel exposed to simulated pressure water reactor environment was investigated considering different surface states. Four surface finishes were produced by electro-polishing (P), grinding (G), and two milling (M and M1) processes respectively. Before oxidation, the surface Vickers micro-hardness, surface roughness of each type of sample was measured. Corrosion behavior of four types of sample was studied by using oxidation weight gain method for six oxidation periods. The oxidation time of each period was 120h, 216h, 336h, 504h, 672h and 1344h, respectively. SEM was used to observe the surface morphology of oxide film in several period. The results showed that oxide film on austenitic stainless steel has a duplex-layer structure. The inner oxide film is continuous and compact, while the outer layer is composed of oxide particles. The oxide particle consisted of large particles (nearly micron size) and small particles (dozens of nanometers to a few hundred nanometers). The formation of oxide particle could be significantly affected by the machined surface states. The large particle on cold worked samples (grinding and milling) appeared earlier than electro-polished one, and the milled sample has the largest particle size followed by ground one and electro-polished one. For machined samples, the large particles were almost distributed along the direction of machining marks. Severe exfoliation was observed on one milled surface (M) which had the most heavily cold worked layer, while rare local exfoliation occurred on the ground sample (G) and the other milled sample (M1). The electro-polished sample (P) entirely did not exfoliate.

Keywords: austenitic stainless steel, oxidation, machining, SEM

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Authors: Ali Bahri Lubis

Abstract:

The study of dioxygenase enzymatic mechanism on tryptophan oxidation has been a wide interest since the reaction is rate-limiting step of kynurenine pathway. In this research, observation of tryptophan oxidation through h-IDO enzyme along with synthesis of enzyme products was conducted in order to comprehend how the enzyme works on distinct substrates. UV-vis spectrophotometry, LC-MS, H-NMR and HSQC measurement were carried out to characterise enzyme product. It is found that while tryptophan was oxidised to form Nformylkynurenine (NFK) as a major product and hydroxypyrroloindole amine carboxylic acid (HPIC) in cis and trans confirmed in HSQC, N-methyl tryptophan substrate was converted to NFK and trans HPIC only. Other intriguing results showed that 5-hydroxy- tryptophan and Stryptophan was degraded to become NFK and epoxide cyclic respectively. The formation of NFK was considered through dioxygenation pathway, however HPIC was formed via monooxygenation. The epoxide cyclic—considered as intermediate compound in the mechanism— from S-tryptophan was not able to cleave the epoxide ring since bond energy of epoxide was probably much stronger. This validates the enzymatic mechanism where the intermediate compound in the enzymatic mechanism is epoxide cyclic.

Keywords: tryptophan oxidation, heme-dioxygenases, N-formylkynurenine, hydroxypyrrroloindoleamine, monooxidation

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Authors: Xiaoling Ren, Guidong Yang

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As one of the largest industrial synthetic chemicals in the world, ammonia has the advantages of high energy density, easy liquefaction, and easy transportation, which is widely used in agriculture, chemical industry, energy storage, and other fields. The industrial Haber-Bosch method process for ammonia synthesis is generally conducted under severe conditions. It is essential to develop a green, sustainable strategy for ammonia production to meet the growing demand. In this direction, photocatalytic nitrogen reduction has huge advantages over the traditional, well-established Haber-Bosch process, such as the utilization of natural sun light as the energy source and significantly lower pressure and temperature to affect the reaction process. However, the high activation energy of nitrogen and the low efficiency of photo-generated electron-hole separation in the photocatalyst result in low ammonia production yield. Many researchers focus on improving the catalyst. In addition to modifying the catalyst, improving the dispersion of the catalyst and making full use of active sites are also means to improve the overall catalytic activity. Few studies have been carried out on this, which is the aim of this work. In this work, by making full use of the nitrogen activation ability of WO3-x with defective sites, small size WO3-x photocatalyst with high dispersibility was constructed, while the growth of WO3-x was restricted by using a high specific surface area mesoporous SBA-15 molecular sieve with the regular pore structure as a template. The morphology of pure SBA-15 and WO3-x/SBA-15 was characterized byscanning electron microscopy (SEM). Compared with pure SBA-15, some small particles can be found in the WO3-x/SBA-15 material, which means that WO3-x grows into small particles under the limitation of SBA-15, which is conducive to the exposure of catalytically active sites. To elucidate the chemical nature of the material, the X-ray diffraction (XRD) analysis was conducted. The observed diffraction pattern inWO3-xis in good agreement with that of the JCPDS file no.71-2450. Compared with WO3-x, no new peaks appeared in WO3-x/SBA-15.It can be concluded that WO3-x/SBA-15 was synthesized successfully. In order to provide more active sites, the mass content of WO3-x was optimized. Then the photocatalytic nitrogen reduction performances of above samples were performed with methanol as a hole scavenger. The results show that the overall ammonia production performance of WO3-x/SBA-15 is improved than pure bulk WO3-x. The above results prove that making full use of active sites is also a means to improve overall catalytic activity.This work provides material basis for the design of high-efficiency photocatalytic nitrogen reduction catalysts.

Keywords: ammonia, photocatalytic, nitrogen reduction, WO3-x, high dispersibility

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Authors: Ts. Lazarova, V. Tumbalev, S. Atanacova-Vladimirova, G. Ivanov, A. Naydenov, D. Kovacheva

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Methane is a major Greenhouse Gas (GHG) that accounts for 14% of the world’s total amount of GHG emissions, originating mainly from agriculture, Coal mines, land fields, wastewater and oil and gas facilities. Nowadays the problem caused by the methane emissions has been a subject of an increased concern. One of the methods for neutralization of the methane emissions is it's complete catalytic oxidation. The efforts of the researchers are focused on the development of new types of catalysts and optimizing the existing catalytic systems in order to prevent the sintering of the palladium, providing at the same time a sufficient activity at temperatures below 500oC. The aim of the present work is to prepare mixed Cu-Ag-Pd oxide catalysts supported on alumina and to test them for methane complete catalytic oxidation. Cu-Ag-Pd/Al2O3 were prepared on a γ-Al2O3 (BET surface area = 220 m2/g) by the incipient wetness method using the corresponding metal nitrates (Cu:Ag = 90:10, Cu:Pd =97:3, Cu:Ag:Pd= 87:10:3) as precursors. A second set of samples were prepared with addition of urea to the metal nitrate solutions with the above mentioned ratios assuming increased dispersivity of the catalysts. The catalyst samples were dried at 100°C for 3 hours and calcined at 550°C for 30 minutes. Catalysts samples were characterized using X-ray diffraction (XRD), low temperature adsorption of nitrogen (BET) and scanning electron microscopy (SEM). The catalytic activity tests were carried out in a continuous flow type of reactor at atmospheric pressure. The effect of catalyst aging at 500 oC for 120 h on the methane combustion activity was also investigated. The results clearly indicate the synergetic effect of Ag and Pd on the catalytic activity.

Keywords: catalysts, XRD, BET, SEM, catalytic oxidation

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Authors: E. Kolvari, N. Koukabi, A. Sabet, A. Fakhraee, M. Ramezanpour

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A green and efficient method for oxidation of thiols to the corresponding disulfides is reported using free nano-iron oxide in the H2O2 and methanol as solvent at room tempereture. H2O2 is anoxidant for S-S coupling variety aromatic of thiols to corresponding disulfide in the presence of supported iron oxide as recoverable catalyst. This reaction is clean, fast, mild and easy work-up with no side reaction.

Keywords: thiol, disulfide, free nano-iron oxide, H2O2, oxidation, coupling

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Authors: Sonya Barzgar, J. Patrick, A. Hettiaratchi

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Methane (CH4) is reputed as the second largest contributor to greenhouse effect with a global warming potential (GWP) of 34 related to carbon dioxide (CO2) over the 100-year horizon, so there is a growing interest in reducing the emissions of this gas. Methane biofiltration (MBF) is a cost effective technology for reducing low volume point source emissions of methane. In this technique, microbial oxidation of methane is carried out by methane-oxidizing bacteria (methanotrophs) which use methane as carbon and energy source. MBF uses a granular medium, such as soil or compost, to support the growth of methanotrophic bacteria responsible for converting methane to carbon dioxide (CO₂) and water (H₂O). Even though the biofiltration technique has been shown to be an efficient, practical and viable technology, the design and operational parameters, as well as the relevant microbial processes have not been investigated in depth. In particular, limited research has been done on the effects of sulphur on methane bio-oxidation. Since bacteria require a variety of nutrients for growth, to improve the performance of methane biofiltration, it is important to establish the input quantities of nutrients to be provided to the biofilter to ensure that nutrients are available to sustain the process. The study described in this paper was conducted with the aim of determining the influence of sulphur on methane elimination in a biofilter. In this study, a set of experimental measurements has been carried out to explore how the conversion of elemental sulphur could affect methane oxidation in terms of methanotrophs growth and system pH. Batch experiments with different concentrations of sulphur were performed while keeping the other parameters i.e. moisture content, methane concentration, oxygen level and also compost at their optimum level. The study revealed the tolerable limit of sulphur without any interference to the methane oxidation as well as the particular sulphur concentration leading to the greatest methane elimination capacity. Due to the sulphur oxidation, pH varies in a transient way which affects the microbial growth behavior. All methanotrophs are incapable of growth at pH values below 5.0 and thus apparently are unable to oxidize methane. Herein, the certain pH for the optimal growth of methanotrophic bacteria is obtained. Finally, monitoring methane concentration over time in the presence of sulphur is also presented for laboratory scale biofilters.

Keywords: global warming, methane biofiltration (MBF), methane oxidation, methanotrophs, pH, sulphur

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Authors: Feny Mentang, Roike Iwan Montolalu, Henny Adeleida Dien, Kristhina P. Rahael, Tomy Moga, Ayub Meko, Siegfried Berhimpon

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Smoked fish is one of the famous fish products in North Sulawesi, Indonesia. Research in producing smoked fish using smoke liquid, and the use of that product as main taste for a new “natural condiment” have been done, including a series of researches to find materials for sachet. Research aims are to determine the effectiveness of smoked edible sachets, in preventing oxidation of natural condiment, stored in ambient temperature. Two kinds of natural condiment flavors were used, i.e. smoked Skipjack flavor, and Sea Food flavor. Three variables of edible sachets were used for the natural condiments, i.e. non-sachet, edible sachet without smoke liquid, and edible sachet with smoke liquid. The natural condiments were then stored in ambient temperature, for 0, 10, 20, and 30 days. To determine the effectiveness of edible sachets in preventing oxidation, analysis of TBA, water content, and pH were conducted. The results shown that natural condiment with smoked seafood taste had TBA values higher than that of smoked Skipjack. Edible sachet gave a highly significant effect (P > 0.01) on TBA. Natural condiment in smoked edible sachet has a lower TBA than natural condiment non-sachet, and with sachet without smoke liquid. The longer storing time, the higher TBA, especially for non-sachet and with sachet without smoke liquid. There were no significant effect (P > 0.05) of edible sachet on water content and pH.

Keywords: edible sachet, smoke liquid, natural condiment, oxidation

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Authors: Saeed Ghali, Azza Ahmed, Taha Mattar

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Solid Oxide Fuel Cell (SOFC) is a promising solution for the energy resources leakage. Ferritic stainless steel becomes a suitable candidate for the SOFCs interconnects due to the recent advancements. Different steel alloys were designed to satisfy the needed characteristics in SOFCs interconnect as conductivity, thermal expansion and corrosion resistance. Refractory elements were used as alloying elements to satisfy the needed properties. The oxidation behaviour of the developed alloys was studied where the samples were heated for long time period at the maximum operating temperature to simulate the real working conditions. The formed scale and oxidized surface were investigated by SEM. Microstructure examination was carried out for some selected steel grades. The effect of alloying elements on the behaviour of the proposed interconnects material and the performance during the working conditions of the cells are explored and discussed. Refractory metals alloying of chromium steel seems to satisfy the needed characteristics in metallic interconnects.

Keywords: SOFCs, Cr-steel, interconnects, oxidation

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