High Rate Constants Research Articles

Nanomolar detection of organic pollutant -tartrazine in food samples using zinc-metal organic framework/carbon nano fiber - composite modified screen-printed electrode

In this study, we achieved a significant breakthrough by applying a binder-free Zn-MOF@CNF composite as a modifier on a screen-printed electrode (SPE) to achieve highly sensitive and selective detection of tartrazine (TRZ). This composite, with its unique rod-like structure for Zn-MOF and a curl thread-like morphology for carbon nanofibers (CNF), demonstrated a remarkable threefold increase in the sensing current of TRZ at a lower anodic oxidation potential (0.92 V) compared to the bare SPE. The Zn-MOF@CNF/SPE also exhibited a reduced charge transfer resistance of 61.9 Ω, elevated electrochemical active surface area of 0.416 cm2, and high heterogeneous electron transfer rate constant (k0) of 9.77×10−5 cm s−1. Furthermore, it displayed a broad linear range from 0.2 μM to 1000 μM with a remarkable sensitivity of 0.136 µAµM−1cm−2 and an impressive detection limit of 54 nM. Ultimately, the developed Zn-MOF@CNF/SPE sensor demonstrated excellent selectivity amidst various structurally similar overlapping species, outstanding repeatability, reproducibility, and stability in TRZ detection. The practical applicability of Zn-MOF@CNF/SPE was validated through 97 – 100.9 % recovery results in food samples such as jelly, ice cream, soft drinks, and candies.

A Comparative Study of Encapsulation of β-Carotene via Spray-Drying and Freeze-Drying Techniques Using Pullulan and Whey Protein Isolate as Wall Material.

The encapsulation of β-carotene was investigated using pullulan and whey protein isolate (WPI) as a composite matrix at a weight ratio of 20:80, employing both spray-drying and freeze-drying techniques. The influence of processing parameters such as the concentration of wall material, flow rate, and inlet temperature for SP encapsulants, as well as wall-material concentration for FZ encapsulants, was examined in terms of encapsulation efficiency (EE). The morphology, structural characterization, moisture sorption isotherms, and thermal properties of the resulting encapsulants at optimum conditions were determined. Their stability was investigated under various levels of water activity, temperature conditions, and exposure to UV-Vis irradiation. β-carotene was efficiently encapsulated within SP and FZ structures, resulting in EE of approximately 85% and 70%, respectively. The degradation kinetics of β-carotene in both structures followed a first-order reaction model, with the highest rate constants (0.0128 day-1 for SP and 0.165 day-1 for FZ) occurring at an intermediate water-activity level (aw = 0.53) across all storage temperatures. The photostability tests showed that SP encapsulants extended β-carotene's half-life to 336.02 h, compared with 102.44 h for FZ encapsulants, under UV-Vis irradiation. These findings highlight the potential of SP encapsulants for applications in functional foods, pharmaceuticals, and carotenoid supplements.

Removal of Bisphenol S (BPS) by Adsorption on Activated Carbons Commercialized in Brazil.

This study assessed three powdered activated carbons (BETM, COCO, and SIAL) commercialized in Brazil at the bench scale in agitated reactors, analyzing their kinetic behavior and adsorptive capacity for BPS and BPA in ultrapure water. BETM exhibited the highest adsorption capacities (Q0max) for BPS and BPA at 260.62 and 264.64 mg/g, respectively, followed by SIAL, with a Q0max of 248.25 mg/g for BPS and for 231.20 mg/g BPA, and COCO, with a Q0max of 136.51 mg/g for BPS and 150.03 mg/g for BPA. The Langmuir isotherm model can describe the processes well. A pseudo-second-order model can describe the adsorption kinetics, and SIAL carbon had the highest rate constants (7.45 × 10-3 mg/g/min for BPS and 2.84 × 10-3 mg/g/min for BPA). The Weber-Morris intraparticle diffusion model suggests intraparticle diffusion as the rate-limiting step of all adsorption processes. Boyd's model confirmed more than the mechanism actuating in the bisphenol adsorption. The results suggest that adsorbents with basic surfaces, high specific surface areas, and high mesopore volumes tend to remove BPS and BPA efficiently. Therefore, activated carbons can effectively complement the existing treatment in Brazilian water treatment plants (WTPs).

Proton-Coupled Electron Transfer and Hydrogen Tunneling in Olive Oil Phenol Reactions.

Olive oil phenols are recognized as molecules with numerous positive health effects, many of which rely on their antioxidative activity, i.e., the ability to transfer hydrogen to radicals. Proton-coupled electron transfer reactions and hydrogen tunneling are ubiquitous in biological systems. Reactions of olive oil phenols, hydroxytyrosol, tyrosol, oleuropein, oleacein, oleocanthal, homovanillyl alcohol, vanillin, and a few phenolic acids with a DPPH• (2,2-diphenyl-1-picrylhydrazyl) radical in a 1,4-dioxane:water = 95:5 or 99:1 v/v solvent mixture were studied through an experimental kinetic analysis and computational chemistry calculations. The highest rate constants corresponding to the highest antioxidative activity are obtained for the ortho-diphenols hydroxytyrosol, oleuropein, and oleacein. The experimentally determined kinetic isotope effects (KIEs) for hydroxytyrosol, homovanillyl alcohol, and caffeic acid reactions are 16.0, 15.4, and 16.7, respectively. Based on these KIEs, thermodynamic activation parameters, and an intrinsic bond orbital (IBO) analysis along the IRC path calculations, we propose a proton-coupled electron transfer mechanism. The average local ionization energy and electron donor Fukui function obtained for the phenolic compounds show that the most reactive electron-donating sites are associated with π electrons above and below the aromatic ring, in support of the IBO analysis and proposed PCET reaction mechanism. Large KIEs and isotopic values of Arrhenius pre-exponential factor AH/AD determined for the hydroxytyrosol, homovanillyl alcohol, and caffeic acid reactions of 0.6, 1.3, and 0.3, respectively, reveal the involvement of hydrogen tunneling in the process.

TiO2 nanoparticle photoactivation and oxidation reactions in freshwater and marine systems: The role of radical scavengers

Titanium dioxide nanoparticles (TiO2-NP) present in wastewater effluent are discharged into freshwater and saltwater (i.e., marine) systems. TiO2-NP can be solar-driven photoactivated by ultraviolet (UV)-light producing reactive oxygen species including hydroxyl radicals (·OH). ·OH are non-selective and react with a broad range of species in water. In other studies, photoactivation of TiO2-NP has been correlated with oxidative stress and ecotoxicological impacts on plant and animal biota. This study examined the photoactivation of TiO2-NP in freshwater and saltwater systems, and contrasted the oxidation potential in both systems using methylene blue (MB) as a reaction probe. Maximum MB loss (51.9%, n = 4; 95% confidence interval 49.4–54.5) was measured in salt-free, deionized water where ·OH scavenging was negligible; minimum MB loss (1%) was measured in saltwater due to significant ·OH scavenging, indicating the inverse correlation between MB loss and radical scavenging. A kinetic analysis of scavenging by seawater constituents indicated Cl− had the greatest impact due to high concentration and high reaction rate constant. Significant loss of MB occurred in the presence of Br− relative to other less aggressive scavengers present in seawater (i.e., HCO3−, HSO4−). This result is consistent with the formation of Bromate, a strong oxidant that subsequently reacts with MB. In freshwater samples collected from different water bodies in Oklahoma (n = 12), the average MB loss was 13.4%. Greater MB loss in freshwater systems relative to marine systems was due to lower ·OH scavenging by various water quality parameters. Overall, TiO2-NP photoactivation in freshwater systems has the potential to cause greater oxidative stress and ecotoxicological impacts than in marine systems where ·OH scavenging is a dominant reaction.

Simultaneously enhancing toluene adsorption and regeneration process by hierarchical pore in activated coke: a combined experimental and adsorption kinetic modeling study.

Activated coke is a type of commonly used adsorbent for benzene series VOCs such as toluene, but traditional microporous activated coke usually faces the challenge of poor regeneration performance. Herein, based on self-made activated cokes with typical pore configuration, we found that adsorption and regeneration of toluene can be simultaneously enhanced by constructing hierarchical pore in activated coke. Correlations of pore configuration with toluene adsorption capacity and regeneration efficiency reveal that micropore contributes for strong toluene adsorption; meso-macropore provides mass transfer channel for toluene desorption and regeneration process. Hierarchical porous activated coke prepared from Zhundong subbituminous coal not only achieves the highest toluene adsorption capacity of 340.92mg·g-1, but also can retain more than 90% of initial adsorption capacity after five adsorption-regeneration cycles. By contrast, micropore-dominant activated cokes can only retain 70% of initial adsorption capacity. Adsorption kinetic modelling on adsorption breakthrough curves shows that hierarchical porous activated coke prepared from Zhundong subbituminous coal exhibits high adsorption and diffusion rate constants of 14.39 and 33.45min-1, respectively, much higher than those of micropore-dominant activated cokes. Due to the accelerated surface adsorption and diffusion processes induced by meso-macropore, toluene adsorption and regeneration behavior can be simultaneously improved. Results from this work validated the role of pore hierarchy in toluene adsorption-regeneration process, providing guidance for designing high-performance activated coke with synergistically improved toluene adsorption capacity and regeneration performance.

Significantly optimized piezoelectric catalytic properties of surface functionalized Nano-BaTiO3

In piezoelectric catalysis, the interaction between reaction molecules and the catalyst surface is of great significance for designing highly selective reaction processes. In this study, chemically functionalized BaTiO3 nanoparticles were fabricated using the hydrothermal method, and the piezoelectric catalytic activity was evaluated for degradation dye reactants by ultrasonic vibration. Due to surface modification of BaTiO3 nanoparticles, the carboxyl groups will be applied on the surface of BaTiO3 nanoparticles, resulting in the reduction in particle size and an increase in specific surface area. The adsorption of the carboxyl groups on the surface can also improve the ability of the BaTiO3 nanoparticles to capture the organic dyes. A high piezoelectric catalytic reaction rate constant of 0.0716 min−1, together with a degradation efficiency of >90 % was achieved within 30 min under 60 kHz and 100 W ultrasonic conditions. These results show that the surface modification of BaTiO3 nanoparticles brought excellent performance of piezoelectric catalysis by controlling the precursor and hydrothermal parameters. This study provides a new method for the preparation of chemically functionalized piezoelectric catalysts and design of other new highly selective catalysts.

Nano-architected titania/gold@GO nanosheets for sonocatalytic degradation of azo dyes in textile wastewater

Environmental pollution is creating serious risks to both human health and the atmosphere which has been a major threat on a global scale. Therefore, it is necessary to focus on the evolution of the environment and trace contaminants for effective and reliable detection and degradation methods. Photochemical methods such as Surface-Enhanced Raman Scattering (SERS) and sono-catalytic degradation can be used to accelerate the detection and degradation of toxic dyes. In the present work, a Gold/Titania/Graphene oxide nanocomposite (ATG) was investigated as a capable dual substrate for SERS sensing and sono-catalytic degradation of pollutants. The nanosize distribution (6–12 nm) of ATG was synthesized by a solvothermal route. X-ray diffraction pattern illustrates the anatase phase of the titanium dioxide. Sonocatalytic degradation was aided using Raman spectroscopy. The effectiveness of ATG as a sono-catalytic substrate and SERS sensor was first evaluated using commercial dyes, such as malachite green and Bismarck brown. Furthermore, research has been conducted on the harmful elements in textile effluents (TE). The NN and C-N bands found in the SERS spectra of TE indicates the presence of carcinogenic azo-dye impurities. The enhancement factor was observed to be 5.77×1012 with the limit of detection (LOD) as 6.0×10−12M. Additionally, the sono-catalysis of ATG was evaluated for the elimination of these dye pollutants in TE. Following sono-catalysis by ATG, a high degradation rate constant of approximately 8.44 ×10−3/min was noted in TE with 89 % of degradation efficiency. The enhanced SERS detection, sono-catalytic degradation of synthetic dyes and effluent stem from the combined action of’ plasmonic characteristics of Au NPs, anatase TiO2, and the π-π stacking characteristic of GO.

Cu/N co-doped biochar activating PMS for selective degrading paracetamol via a non-radical pathway dominated by singlet oxygen and electron transfer

The non-free radical oxidation pathway (PMS-NOPs) of peroxymonosulfate (PMS) holds significant promise for practical wastewater treatment applications, owing to its low oxidation potential, high PMS utilization rate, and robust anti-interference capability in the degradation of pollutants. A novel activator copper nitrogen co-doped porous biochar (Cu-N-BC) with rich defect edges and functional groups was obtained by adding Cu and N to the biochar matrix generated by sodium alginate through pyrolysis in this study. Under the condition of 1 mM PMS, 30 mg/L activator was used to activate PMS and achieve efficient degradation of 10 mg/L paracetamol (PCT) within 15 min, with a high reaction rate constants (kobs) of 0.391 min−1. The activation mechanism of the Cu-N-BC/PMS/PCT system was a non-radical activation pathway with the dominance of singlet oxygen (1O2) and the presence of catalyst-mediated electron transfer. The graphite nitrogen, pyridine nitrogen, and Cu–N coordination introduced by Cu/N co-doping, as well as the carbon skeleton and CO functional group of biochar, were considered active sites that promote the 1O2 generation. The Cu-N-BC/PMS system exhibits strong stability, eco-friendliness, effective mineralization, and interference resistance across diverse pH levels (3–11) and interfering ions, including Cl−, H2PO4−, NO3−, SO42−, and humic acid. Remarkably, it efficiently degrades PCT in tap and lake water, achieving a notable 63.73% TOC mineralization rate, with leached copper ions below 0.02 mg/L. This research introduces a novel method for obtaining metal nitrogen carbon activators and enhances understanding of PMS non-radical activation pathways and active sites.

Low-cost ternary composite photocatalysts consisting of TiO2, kaolinite and cement for an efficient organic waste decontamination in water

The present study demonstrates the fabrication of heterogeneous ternary composite photocatalyst consisting of TiO2, kaolinite and cement (TKCe), which is essential to overcome the practical barriers that are inherent to currently available photocatalysts. TKCe is prepared via a cost-effective method, which involved the mechanical compression and thermal activation as a major fabrication steps. Clay-cement ratio primarily determines TKCe mechanical strength and photocatalytic efficiency where TKCe with the optimum clay-cement ratio, which is 1:1 results in uniform matrix with fewer surface defects. The composites that have clay-cement ratio below or above the optimum ratio account for comparatively low mechanical strength and photocatalytic activity due to inhomogeneous surface with more defects, including particle agglomeration and cracks. The TKCe mechanical strength is mainly from clay-TiO2 interactions and TiO2-cement interactions. TiO2-cement interactions result in CaTiO3 formation, which significantly increases matrix interactions; however, the maximum composite performance is observed at the optimum titanate level; anything above or below this level deteriorates composite performance. Over 90% degradation rates are characteristic to all TKCe, which follow pseudo first order kinetics in methylene blue decontamination. The highest rate constant is observed with TKCe 1-1, which is 1.57 h−1 and being the highest among all the binary composite photocatalyst that were fabricated previously. The TKCe 1-1 accounts for the highest mechanical strength, which is 6.97 MPa, while the lowest is observed with TKCe 3-1, indicating that clay-cement ratio has direct relation to composite strength. TKCe is a potential photocatalyst, which can be obtained in variable sizes and shapes, complying with real industrial wastewater treatment requirements.

Green preparation of fiberboard waste derived N–doped carbon catalysts with tailored properties for efficient hydrogenation reduction of nitroaromatics

Biomass–derived carbon materials doped with diverse heteroatoms have demonstrated huge potentials for environment and energy applications, thanks to the availability, preferable porous and channel structures, and excellent conductivity and stability. In this work, fiberboard waste containing resin–based adhesive was selected for the green fabrication of N–doped carbon catalysts without using extra N–sources. A facile two–step calcination strategy with sequential carbonization and activation was proposed for generation and exposure of indispensable active sites, realizing the controllable regulation of textural and morphological characteristics. The resulting N–doped fiberboard derived carbon (NFC) samples possessed unique hierarchically porous structures with a significantly enlarged surface area, plentiful activity–dependent N species (e.g., graphitic N and pyridinic N), as well as suitable graphitization degree and surface hydrophilicity. As a result, a favorable adsorption procedure and an enhanced accessibility of active sites synergistically boosted the catalytic performance towards hydrogenation reduction of nitroaromatics. Taking the NFC–hh sample as paradigm, an excellent performance was demonstrated for 4–nitrophenol (4–NP) reduction, achieving a high apparent rate constant of 0.40 min−1 and an impressive turnover frequency of ∼0.20 mmol g−1 min−1. Besides, the continuous–flowing catalytic test exhibited an excellent conversion efficiency > 99.50% with a long–term stability over 100 h, showing an attractive prospect for industrial application. This work presents a new approach for high value–added utilization of biomass waste, and provides a low–cost and high–active catalyst for environmental remediation.

Insight into the role of reactive species on catalyst surface underlying peroxymonosulfate activation by P–Fe2MnO4 loaded on bentonite for trichloroethylene degradation

In this study, bentonite supporting phosphorus-doped Fe2MnO4 (BPF) was synthesized and applied for PMS activation to degrade TCE. Morphology and structure characterization results indicated the successfully synthesized of BPF, and the BPF/PMS system not only featured high TCE removal (97.4%) but also high reaction rate constant (kobs = 0.0554 min−1) and PMS utilization (70.4%, kobs = 0.0228 min−1). According to the results of various experiments, massive oxygen vacancies on P–Fe2MnO4 alter its charge balance and facilitate the electron transfer process named adjacent transfer (direct electron capture by adsorbed PMS from adjacent TCE). Mn(III) is the main adsorption site for PMS, and the hydroxyl groups on the catalyst (Fe sites of P–Fe2MnO4, Si and Al sites of bentonite) can also offer binding sites for PMS. The hydrogen-bonded PMS on Fe(III) and Mn(III) sites will subsequently accept the discharged electrons to generate free radicals and high-valent metal species. Meanwhile, electron loss of HSO5− that chemically bonded to hydroxyl groups on bentonite will generate SO5•−, which will further produce 1O2 through self-bonding. the active species on the catalyst surface contribute 65% of TCE degradation in the heterogeneous catalytic oxidation system.

The Effect of Composition on the Properties and Application of CuO-NiO Nanocomposites Synthesized Using a Saponin-Green/Microwave-Assisted Hydrothermal Method.

In this study, we explored the formation of CuO nanoparticles, NiO nanoflakes, and CuO-NiO nanocomposites using saponin extract and a microwave-assisted hydrothermal method. Five green synthetic samples were prepared using aqueous saponin extract and a microwave-assisted hydrothermal procedure at 200 °C for 30 min. The samples were pristine copper oxide (100C), 75% copper oxide-25% nickel oxide (75C25N), 50% copper oxide-50% nickel oxide (50C50N), 25% copper oxide-75% nickel oxide (25C75N), and pristine nickel oxide (100N). The samples were characterized using FT-IR, XRD, XPS, SEM, and TEM. The XRD results showed that copper oxide and nickel oxide formed monoclinic and cubic phases, respectively. The morphology of the samples was useful and consisted of copper oxide nanoparticles and nickel oxide nanoflakes. XPS confirmed the +2 oxidation state of both the copper and nickel ions. Moreover, the optical bandgaps of copper oxide and nickel oxide were determined to be in the range of 1.29-1.6 eV and 3.36-3.63 eV, respectively, and the magnetic property studies showed that the synthesized samples exhibited ferromagnetic and superparamagnetic properties. In addition, the catalytic activity was tested against para-nitrophenol, demonstrating that the catalyst efficiency gradually improved in the presence of CuO. The highest rate constants were obtained for the 100C and 75C25N samples, with catalytic efficiencies of 98.7% and 78.2%, respectively, after 45 min.

Degradation Profiles of MgO@Graphene Nanocomposite Photocatalyst for Organic and Antibiotic Pollutants: Novel Approaches

Streptomycin was chosen as the test species, and MgO@graphene nanocomposites were created and assessed for their catalytic activity towards the breakdown of 4-NP. As a new catalyst with strong catalytic activity and good stability, MgO@graphene was used. It was discovered that this catalyst’s catalytic activity was much increased in an acidic environment. It is suggested that the degradation mechanism is caused by MgO@graphene nanocomposites reacting with dissolved oxygen. This further demonstrates the obvious significance of graphene in serving as the MgO nanocatalyst’s support. XRD results indicated that the majority of G species in MgO@ (0.25 g) G more strongly interacted with the MgO surface. The doped catalyst MgO@ (0.25 g) G reached its steady state activity faster than the other catalysts. The degree of MgO@G interaction decreased in the following S4 > S[Formula: see text] > S[Formula: see text] > S[Formula: see text] > S[Formula: see text] > S5 > S[Formula: see text] > S[Formula: see text]. High degradation rate constants were found, and the amounts of streptomycin and 4-nitrophenol vary exponentially over time. It was demonstrated that, in most situations, the pseudo-first- order equation fits the degradation kinetics. Hence, in degrading systems, MgO NPs@Graphene nanostructures are thought to be a very effective and promising catalyst.

Distinguishable photorecycling of PVDF nanocomposites membrane for reactive yellow 145 dye and real industrial wastewater treatment by different photocatalytic processes

This paper investigates the photocatalytic performance and recyclability of PVDF-MWCNTs-TiO2 nanocomposite membranes for the treatment of textile wastewater under sunlight irradiation. The nanocomposites were fabricated by incorporating varying weight ratios of MWCNTs-TiO2 (1 %, 3 %, 6 %, and 9 %) into PVDF matrices using a solvent casting method. Optimal loading of MWCNTs-TiO2 at 9 wt% resulted in nanocomposites with enhanced surface area (94.15 m2/g), reduced band gap (2.38 eV), uniform dispersion of nanoparticles, and abundant surface hydroxyl groups. Under Xenon lamp irradiation, the optimized PVDF-9 %(MWCNTs-9 %TiO2) nanocomposite achieved a high apparent reaction rate constant (kapp) of 9.92 × 10−3 s−1 for photocatalytic degradation of the model dye Reactive Yellow 145. Significantly, when tested on-site at a Saudi Arabian textile facility over 6 months, this nanocomposite effectively reduced the chemical oxygen demand (COD) of real wastewater samples to regulatory limits of 1000 ppm under natural sunlight irradiation. The COD values were lowered from an initial 5050–6200 ppm to a final range of 785–945 ppm using the PVDF-9 %(MWCNTs-9 %TiO2) membrane. Furthermore, the optimized nanocomposite exhibited good recyclability, retaining around 87 % of its initial activity after 8 reuse cycles for industrial wastewater treatment. The excellent photocatalytic efficiency and reusability of the MWCNTs-TiO2 modified PVDF nanocomposite under solar irradiation highlight its promise as a sustainable membrane technology for environmental remediation.

Facile Fabrication of ZnO Nanorods with Extremely Strong Photocatalytic Performance and Antibacterial Activity

Development of nanomaterials with strong antibacterial action and highly enhanced photocatalytic activity for water purification is of immense interest. ZnO nanorods, with extremely enhanced solar-driven photocatalytic performance and good antibacterial activity, have been fabricated by facile chemical route. The structural properties of the nanomaterial were thoroughly characterized by SEM, TEM, EDX, HRTEM, STEM-HAADF, elemental profiling, XRD and Raman spectroscopy, while the optical and photocatalytic properties were studied by UV-vis absorption spectroscopy. TEM and FESEM showed nanorods with average width and length as 80[Formula: see text]nm and 178[Formula: see text]nm. XRD showed wurtzite ZnO with 27[Formula: see text]nm crystallite size. PL analysis of ZnO nanorods showed peaks at 415[Formula: see text]nm, 439[Formula: see text]nm, 499[Formula: see text]nm and 561[Formula: see text]nm. The fabricated ZnO nanorods exhibited extremely enhanced photocatalytic performance with very high rate constant of 0.201[Formula: see text]min[Formula: see text] for degradation of organic pollutant MB in water under only 15[Formula: see text]min of solar exposure. ZnO nanorods completely inhibited growth of Bacillus oceanisediminis and Escherichia coli at 500[Formula: see text][Formula: see text]g/mL and 700[Formula: see text][Formula: see text]g/mL, respectively. The origin of antibacterial behavior of ZnO nanorods against B. oceanisediminis and E. coli has been investigated using histidine for scavenging ROS, morphological change by SEM and agarose gel electrophoresis. Our results showed that ROS-induced oxidative stress damages cell wall, evident from SEM, and leads to fragmentation of DNA both of which contribute to the antibacterial action of ZnO nanorods. The tentative mechanism of extremely strong photodegradation performance of ZnO nanorods has also been proposed.

Catalytic Reductive Degradation of 4-Nitrophenol and Methyl orange by Novel Cobalt Oxide Nanocomposites

Cobalt oxide nanocomposites were synthesized and used for the catalytic degradation of 4-nitrophenol (4-NP) and methyl orange (MO). Cobalt oxide nanocomposites PyroHAB9 was prepared by heating cobalt acetylacetonate complex HAB9 at 300 °C, while PyroHAB19 was prepared by heating cobalt acetylacetonate–carboxymethyl cellulose complex at 300 °C. FTIR indicated the presence of Co3O4 species, while Raman spectrum indicated the presence of graphite in PyroHAB19. The SEM morphology of nanocomposites exhibited irregular spherical shape nanoparticles with sizes ranging between 20 to 60 nm. Additionally, nanowires were also seen in HAB19. Also, 2Ɵ peaks in PXRD revealed the formation of Co3O4 in HAB19. Cyclic voltammetry indicated enhanced electrochemical redox activity of HAB19. The structures of the nanocomposites were related to their catalytic activities. The turnover frequency (TOF) values of the catalytic reduction of p-nitrophenol (P-NP) and methyl orange (MO) were greater for HAB19 compared to HAB9 nano-catalysts. Also, the TOF values of the catalytic reduction of MO were greater than that of P-NP by both nano-catalysts. It is obvious that the rate constants of catalytic reductions for MO by metal oxide nanocomposites were greater than the corresponding rate constants for PNP. The highest rate constant was found for PyroHAB19 in MO reduction.

Electron Redistribution in Iridium-Iron Dual-Metal-Atom Active Sites Enables Synergistic Enhancement for H2O2 Decomposition.

Developing efficient heterogeneous H2O2 decomposition catalysts under neutral conditions is of great importance in many fields such as clinical therapy, sewage treatment, and semiconductor manufacturing but still suffers from low intrinsic activity and ambiguous mechanism understanding. Herein, we constructed activated carbon supported with an Ir-Fe dual-metal-atom active sites catalyst (IrFe-AC) by using a facile method based on a pulsed laser. The electron redistribution in Ir-Fe dual-metal-atom active sites leads to the formation of double reductive metal active sites, which can strengthen the metal-H2O2 interaction and boost the H2O2 decomposition performance of Ir-Fe dual-metal-atom active sites. Ir-Fe dual-metal-atom active sites show a high second-order reaction rate constant of 3.53 × 106 M-1·min-1, which is ∼106 times higher than that of Fe3O4. IrFe-AC is effective in removing excess intracellular reactive oxygen species, protecting DNA, and reducing inflammation under oxidative stress, indicating its therapeutic potential against oxidative stress-related diseases. This study could advance the mechanism understanding of H2O2 decomposition by heterogeneous catalysts and provide guidance for the rational design of high-performance catalysts for H2O2 decomposition.

Pillar‐Layered Metal‐Organic Framework decorated onto TiO2: An Efficient Photocatalyst for Mineralization of Nonsteroidal Anti‐Inflammatory Drugs (NSAIDs)

AbstractHeterostructures of metal‐organic frameworks (MOFs) and metal oxide nanostructured are extensively explored as promising photocatalysts owing to their combined advantages of the highly porous and molecular sieving characteristics of MOFs and the effectual features of encapsulated metal oxide nanostructures. Herein, we reported for the first time two novice hybrid materials abbreviated as PMOF‐55@TiO2 and PMOF‐56@TiO2 constructed by incorporation of Zn4(TRZ)4(2,6‐NDC)2.2DMFand Zn4(TRZ)4(2,4‐BDC)2. 2DMF (TRZ=1,2,4‐triazole, 2,6‐NDC=2,6‐naphthalene dicarboxylic acids, and BDC=terephthalic acid) into the TiO2 nanostructure. The resultant heterostructures were explore for the photodegradation of three Nonsteroidal Anti‐Inflammatory Drugs (ibuprofen, salicylic acid, and aspirin). The successful fabrication of heterostructures was authenticated by various spectroscopic and microscopic techniques. The surface morphological studies revealed the highly dense coating of MOFs nanoparticles on the surface of TiO2. The maximum % degradation i. e. (87.5 %, 88 %) IBU, (81.3 %, 86.5 %) SAL, (80 %, 85.5 %) ASP was achieved using PMOF‐55@TiO2 and PMOF‐56@TiO2 heterostructures with (catalyst dose‐0.6 g/L, and drug concentration‐5 mg/L) under UV light irradiation within 105 min. PMOF‐56@TiO2 is superior photocatalyst compare to PMOF‐55@TiO2 as confirmed by high rate constant (k) and lower half‐life time (t1/2) values of PMOF‐56@TiO2. Moreover, they also maintain a good recyclability performance.

Removal of sulfonamide antibiotics by non-free radical dominated peroxymonosulfate oxidation catalyzed by cobalt-doped sulfur-containing biochar from sludge

The reuse of activated sludge as a solid waste is severely underutilized due to the limitations of traditional treatment and disposal methods. Given that, the sulfur-containing activated sludge catalyst doped with cobalt (SK-Co(1.0)) was successfully prepared by one-step pyrolysis and calcinated at 850 ℃. The generation of CoSx was successfully characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), indicating that the sulfur inside the sludge was the anchoring site for the externally doped cobalt. Cobalt (Ⅱ) (Co2+), as the main adsorption site for peroxymonosulfate(PMS), formed a complex (SK-Co(1.0)-PMS* ) and created the conditions for the generation of surface radicals. The SK-Co(1.0)/PMS system showed high degradation efficiency and apparent rate constants for Sulfamethoxazole (SMX) (91.56% and 0.187 min−1) and Sulfadiazine (SDZ) (90.73% and 0.047 min−1) within 10 min and 30 min, respectively. Three sites of generation of 1O2, which played a dominant role in the degradation of SMX and SDZ in the SK-Co(1.0)/PMS system, were summarized as：sulfur vacancies (SVs), the Co3+/Co2+ cycles promoted by sulfur(S) species, oxygen-containing functional groups (C-O). The degradation mechanisms and pathways had been thoroughly investigated using DFT calculations. In view of this, a new idea for the resource utilization of activated sludge solid waste was provided and a new strategy for wastewater remediation was proposed.