Reaction Of H2O2 Research Articles

Heterogeneous electro-Fenton treatment of chemotherapeutic drug busulfan using magnetic nanocomposites as catalyst

The rapid and efficient mineralization of the chemotherapeutic drug busulfan (BSF) as the target pollutant has been investigated for the first time by three different heterogeneous EF systems that were constructed to ensure the continuous electro-generation of H2O2 and •OH consisting of: i) a multifunctional carbon felt (CF) based cathode composed of reduced graphene oxide (rGO), iron oxide nanoparticles and carbon black (CB) (rGO-Fe3O4/CB@CF), ii) rGO modified cathode (rGO/CB@CF) and rGO supported Fe3O4 (rGO-Fe3O4) catalyst and iii) rGO modified cathode (rGO/CB@CF) and multi walled carbon nanotube supported Fe3O4 (MWCNT-Fe3O4) catalyst. The effects of main variables, including the catalyst amount, applied current and initial pH were investigated. Based on the results, H2O2 was produced by oxygen reduction reaction (ORR) on the liquid-solid interface of both fabricated cathodes. •OH was generated by the reaction of H2O2 with the active site of ≡FeII on the surface of the multifunctional cathode and heterogeneous EF catalysts. Utilizing carbon materials with high conductivity, the redox cycling between ≡FeII and ≡FeIII was effectively facilitated and therefore promoted the performance of the process. The results demonstrated almost complete mineralization of BSF through the heterogeneous systems over a wide applicable pH range. According to the reusability and stability tests, multifunctional cathode exhibited outstanding performance after five consecutive cycles which is promising for the efficient mineralization of refractory organic pollutants. Moreover, intermediates products of BSF oxidation were identified and a plausible oxidation pathway was proposed. Therefore, this study demonstrates efficient and stable cathodes and catalysts for the efficient treatment of an anticancer active substance.

Predicting chlorine demand by peracetic acid in drinking water treatment.

Peracetic acid (PAA) may be used in drinking water treatment for pre-oxidation and mussel control at the intake. PAA may exert a downstream chlorine demand, but full details of this reaction have not been reported. There are three possible mechanisms of this demand: (1) PAA may react directly with chlorine; (2) PAA exists in equilibrium with hydrogen peroxide, which is known to react with chlorine; and (3) as H2O2 reacts with chlorine, PAA will hydrolyze to form more H2O2 to re-establish PAA/H2O2 equilibrium, thereby serving as an indirect reservoir of chlorine demand. While the H2O2 reaction with chlorine is well known, the other mechanisms of possible PAA-induced chlorine demand have not previously been investigated. The observed molar stoichiometric ratio of PAA to free chlorine (n) for the presumed direct PAA+free chlorine reaction was determined to be approximately 2, and the corresponding observed reaction rate coefficients at pH 6, 7, 8, and 9 were 2.76, 3.14, 1.61, 10.1 M-n·s-1, respectively (at 25°C). With these estimated values, a kinetic model was built to predict the chlorine demand by PAA. The results suggest that chlorine demand from PAA is likely to be negligible over the course of several days (e.g., < 20% chlorine loss) for most conditions except for high pH (e.g., >8) and high PAA:Cl2 molar ratios (e.g., >2:1).

Detached eddy simulation of the heat release characteristics of H2-O2 reacting flow in supercritical water

The mild H2-O2 reaction is critical for coal-gasification-based polygeneration of power and heat in supercritical water. Time-averaged methods turbulence studies cannot accurately predict the flow, reaction, and heat release during the start-up of the H2-O2 reaction, which was crucial for the start-up and safe operation of supercritical water environment oxidation reactors (SCOR). In contrast, ordinary time-accurate method studies require a tremendous computational effort. Detached eddy simulation (DES), a hybrid model, could balance numerical simulation's computational accuracy and speed. Consequently, this paper has conducted a DES investigation on the start-up process of H2-O2 reaction in SCW with detailed kinetics. Through this article, the spatio-temporal distribution and reaction structure of the H2-O2 reaction start-up process had been unveiled. The process could be divided into the transition and the steady stage, with H2 mass fraction (XH2) and inlet temperature significantly affecting the H2-O2 reaction start-up process. Moreover, the stability of the H2-O2 reaction start-up process was heavily influenced by the XH2. This numerical study could guide the design, scale-up and optimization of SCOR.

Enhanced performance of heterogeneous fenton-like Co-Cu catalysts for metronidazole degradation: Ethylene glycol as a superior fabrication solvent

This study addresses the gap in understanding of fabrication solvent influence on Cu-Co catalyst performance for MNZ degradation. By synthesizing recyclable Cu-Co catalysts using the co-precipitation method, the study investigates the impact of ethylene glycol (EG) solvent compared to conventional water (H2O) solvent. The optimized operational parameters resulted in stable and high MNZ degradation efficiency (above 90 % removal) with twice-feeding of 1600 ppm H2O2, pH ∼7.15, and 50 °C. The use of EG solvent enhances catalyst surface area, exposing more active sites with higher Cu+ and Cu2+ content, which incorporated in CoO6 environment with promoted redox property to facilitate H2O2 reaction and •OH production. This research contributes valuable insights into catalyst design and optimization, highlighting the potential of EG solvent for industrial application in antibiotic organic pollutant remediation.

Formulation of DOX-dimer with bi-functionalized chitooligosaccharide for tumor-specific self-boosted drug release and synergistic chemo/chemodynamic therapy

The toxic side effects and possible drug resistance of the chemotherapeutics hinder their antitumor efficacy. Here, a pH/reactive oxygen species (ROS) dual-triggered nanodrug was developed for the tumor-specific self-boosted drug release and synergistic chemo/chemodynamic therapy, by formulating ROS-cleavable doxorubicin (DOX)-based dimer (DOX-TK-DOX) with bi-functionalized chitooligosaccharide (COS-Fc-TK) with ferrocenecarboxylic acid (Fc) and thioketal (TK). The resultant DOX-TK-DOX/COS-Fc-TK nanoparticles with a high DOX content of 39.70 % showed tumor-specific self-boosted drug release, which was triggered by highly toxic OH generated via Fc-catalyzed Fenton reaction of the endogenous H2O2 in tumor intracellular microenvironment. As a result, a synergistic chemo/chemodynamic therapy with combination index (CI) of 0.94 was achieved for selective treatment of tumors.

Highly Efficient Photo-Fenton Ag/Fe2O3/BiOI Z-Scheme Heterojunction for the Promoted Degradation of Tetracycline.

Novel Ag/Fe2O3/BiOI Z-scheme heterostructures are first fabricated through a facile hydrothermal method. The composition and properties of as-synthesized Ag/Fe2O3/BiOI nanocomposites are characterized by powder X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, UV-Vis diffuse reflectance spectra, etc. The Ag/Fe2O3/BiOI systems exhibit remarkable degradation performance for tetracycline (TC). In particular, the composite (Ag/Fe2O3/BiOI-2) shows the highest efficiency when the contents of Ag and α-Fe2O3 are 2 wt% and 15%, respectively. The effects of operating parameters, including the solution pH, H2O2 concentration, TC concentration, and catalyst concentration, on the degradation efficiency are investigated. The photo-Fenton mechanism is studied, and the results indicated that •O2- is the main active specie for TC degradation. The enhanced performance of Ag/Fe2O3/BiOI heterostructures may be ascribed to the synergic effect between photocatalysis and the Fenton reaction. The formation of Ag/Fe2O3/BiOI heterojunction is beneficial to the transfer and separation of charge carriers. The photo-generated electrons accelerate the Fe2+/Fe3+ cycle and create the reductive reaction of H2O2. This research reveals that the Ag/Fe2O3/BiOI composite possesses great potential in wastewater treatment.

Environment-friendly epoxidation of limonene using tungsten-based polyoxometalate catalyst

Terpene epoxides play a vital role as chemical intermediates in industries such as flavourings, fragrances, paints, and polymers manufacturing. However, current methods for limonene epoxidation suffer from low selectivity and environmental concerns. To address these limitations, we aimed to develop a highly selective and environmentally benign process for limonene epoxidation. Our approach involved employing hydrogen peroxide (H2O2) as an oxidant in the presence of tungsten-based polyoxometalates as catalysts. A novel catalyst was synthesized using sodium tungstate dihydrate (Na2WO4·2H2O), phosphoric acid (H3PO4), sulfuric acid (H2SO4), and sodium sulfate (Na2SO4) as an inorganic salt. We investigated the influence of various process variables, including the limonene:H2O2 molar ratio, reaction time, temperature, and solvent type, to optimize the epoxidation process. Through systematic screening, we achieved remarkable results, attaining 96% limonene conversion, 80% selectivity to limonene-1,2-epoxide, and 19% selectivity to limonene bis-epoxide within a short reaction time of 15 min. Notably, this high performance was accomplished by introducing H2O2 in a single step. To mitigate the hydrolysis of the epoxide, we employed sodium sulphate (Na2SO4) to saturate the reaction mixture. Furthermore, we proposed a comprehensive mechanism for the limonene epoxidation process using tungsten-based polyoxometalates as catalysts. Our kinetic study revealed a first-order reaction with respect to both limonene and the catalyst. Importantly, the decomposition of H2O2 was negligible under the investigated operating conditions, confirming the stability and efficiency of our approach. Our findings present eco-friendly, scalable, and catalytic epoxidation methods as valuable synthetic tools for converting inexpensive bio-renewable terpene feedstocks into essential chemical building blocks. The implications of our work extend to the synthesis of useful chemical products in a biorefinery setting, promoting a more sustainable and efficient utilization of terpenes.

A Novel Fluorescent Probe for the Detection of Hydrogen Peroxide.

Hydrogen peroxide (H2O2) is one of the important reactive oxygen species (ROS), which is closely related to many pathological and physiological processes in living organisms. Excessive H2O2 can lead to cancer, diabetes, cardiovascular diseases, and other diseases, so it is necessary to detect H2O2 in living cells. Since this work designed a novel fluorescent probe to detect the concentration of H2O2, the H2O2 reaction group arylboric acid was attached to the fluorescein 3-Acetyl-7-hydroxycoumarin as a specific recognition group for the selective detection of hydrogen peroxide. The experimental results show that the probe can effectively detect H2O2 with high selectivity and measure cellular ROS levels. Therefore, this novel fluorescent probe provides a potential monitoring tool for a variety of diseases caused by H2O2 excess.

Treatment of Pharmaceutical Industry Wastewater by PhotoelectroFenton Oxidation

The use of Photoelectro-Fenton oxidation to treat real pharmaceutical effluent is an attractiveoption for the elimination of complex and persistent organic contaminants. This advanced oxidation processcombines the electrochemical generation of highly reactive hydroxyl radicals (OH•) with the photochemicaldegradation of by-products, resulting in the efficient removal of pharmaceutical compounds fromwastewater. In the Photoelectro-Fenton process, an appropriate anode material, such as BDD or DSA, isused to generate OH•radicals through the electrochemical oxidation of Fe2+ ions. The addition of a smallamount of Fe2+ and H2O2 facilitates the Fenton reaction, leading to the production of additional OH•radicalsin the solution. The presence of these OH•radicals ensures the effective oxidation of pharmaceuticalpollutants, which are often resistant to conventional wastewater treatment methods. The use of UV orsunlight irradiation further enhances the Photoelectro-Fenton process by promoting thephotodecomposition of intermediate by-products formed during the oxidation process. This simultaneouselectrochemical and photochemical degradation mechanism provides synergistic effects, resulting inenhanced degradation and mineralization of pharmaceutical compounds. Studies have demonstrated thesuccessful application of Photoelectro-Fenton oxidation for the treatment of real pharmaceuticalwastewater, showing significant removal efficiencies for a wide range of pharmaceutical compounds,including antibiotics, analgesics, and hormones. Additionally, the process has been shown to effectivelydegrade recalcitrant by-products and reduce the overall toxicity of the wastewater. However, it is importantto consider factors such as optimal pH, Fe2+ and H2O2 dosages, irradiation intensity, and reaction time toachieve optimal treatment efficiency. Furthermore, the cost-effectiveness and scalability of thePhotoelectro-Fenton process need to be evaluated for its potential implementation in large-scale wastewatertreatment facilities.

New Measurements and Calculations on the Kinetics of an Old Reaction: OH + HO2 → H2O + O2.

Literature rate coefficients for the prototypical radical-radical reaction at 298 K vary by close to an order of magnitude; such variations challenge our understanding of fundamental reaction kinetics. We have studied the title reaction at room temperature via the use of laser flash photolysis to generate OH and HO2 radicals, monitoring OH by laser-induced fluorescence using two different approaches, looking at the direct reaction and also the perturbation of the slow OH + H2O2 reaction with radical concentration, and over a wide range of pressures. Both approaches give a consistent measurement of k1,298K ∼1 × 10-11 cm3 molecule-1 s-1, at the lowest limit of previous determinations. We observe, experimentally, for the first time, a significant enhancement in the rate coefficient in the presence of water, k1,H2O,298K = (2.17 ± 0.09) × 10-28 cm6 molecule-2 s-1, where the error is statistical at the 1σ level. This result is consistent with previous theoretical calculations, and the effect goes some way to explaining some, but not all, of the variation in previous determinations of k1,298K. Supporting master equation calculations, using calculated potential energy surfaces at the RCCSD(T)-F12b/CBS//RCCSD/aug-cc-pVTZ and UCCSD(T)/CBS//UCCSD/aug-cc-pVTZ levels, are in agreement with our experimental observations. However, realistic variations in barrier heights and transition state frequencies give a wide range of calculated rate coefficients showing that the current precision and accuracy of calculations are insufficient to resolve the experimental discrepancies. The lower value of k1,298K is consistent with experimental observations of the rate coefficient of the related reaction, Cl + HO2 → HCl + O2. The implications of these results in atmospheric models are discussed.

The removal of NO from flue gas by Fe/NaOH/H2O2 system

NO emitted from coal combustion was harmful to the environment. For most current wet denitrification technologies, obtaining the desired removal efficiency was always dependent on the contact time of NO with the reaction solution. In this paper, a novel Fe/NaOH/H2O2 technology was proposed to remove NO, which could obtain 90% NO removal efficiency when the flue gas residence time in solution was 3 s. The mechanism of H2O2 decomposition and NO removal were analyzed. Results demonstrated that Fe and NaOH together catalyzed H2O2 to produce radicals, and ⋅O2− radicals took the main responsibility in the process of NO removal. NO3− and NO2− were the final forms of NO. In addition, the effects of several common experimental parameters were investigated on the NO removal performance. The increase of H2O2 concentration, Fe concentration, solution pH and reaction temperature all had a positive effect on NO removal, but this process was also accompanied by an intensification of the useless decomposition of H2O2 (consumption of H2O2 in the form of O2). The addition of SO2 to the flue gas had a slight effect on the NO removal and the useless decomposition of H2O2.

Selectivity Control of Oxygen Reduction Reaction over Mesoporous Transition Metal Oxide Catalysts for Electrified Purification Technologies

Direct electrification of oxygen-associated reactions contributes to large-scale electrical storage and the launch of the green hydrogen economy. The design of the involved catalysts can mitigate the electrical energy losses and improve the control of the reaction products. We evaluate the effect of the interface composition of electrocatalysts on the efficiency and productivity of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), both mechanistically and at device levels. The ORR and OER were benchmarked on mesoporous nickel(II) oxide and nickel cobaltite (NiO and NiCo2O4, respectively) obtained by a facile template-free hydrothermal synthesis. Physicochemical characterization showed that both NiO and NiCo2O4 are mesoporous and have a cubic crystal structure with abundant surface hydroxyl species. NiCo2O4 showed higher electrocatalytic activity in OER and selectivity to water as the terminal product of ORR. On the contrary, ORR over NiO yielded hydroxyl radicals as products of a Fenton-like reaction of H2O2. The product selectivity in ORR was used to construct two electrolyzers for electrified purification of oxygen and generation of hydroxyl radicals.

MoS2/α-FeOOH heterojunction composites with enhanced photo-Fenton performance

As-synthesized MoS2/α-FeOOH heterojunction exhibits efficient reactivities for Fenton and photo-Fenton degradation of acid orange 7 (AO7) and sulfamethoxazole. Work functions investigated by DFT method suggest a spontaneous electron transfer from MoS2 to α-FeOOH by constructing a type II heterojunction. The electron transfer across the heterojunction was further confirmed by XPS observation. The carrier transfer can be maintained and intensified by surface redox reaction of H2O2 with the accumulated carriers, which amplifies the role of heterojunction. The reaction rate constant for photo-Fenton degradation of AO7 with MoS2/α-FeOOH-10 is 6.6 times higher than that of α-FeOOH. Notably, although α-FeOOH cannot absorb the 660 nm irradiation, a much-enhanced photo-Fenton degradation of AO7 with MoS2/α-FeOOH-10 under 660 nm irradiation further verifies the occurrence of electron transfer from MoS2 to α-FeOOH. This work provides an in-depth observation on the role of type II heterojunction in promoting the photo-Fenton reactivity for organic degradation.

Degradation of organic pollutants accompanied by the ultrasonic separation of the spent lithium-ion battery cathode materials.

Since the majority of valuable components in spent lithium-ion batteries, such as lithium, exists in the electrode materials, common studies focused on the treatment of the cathode materials, which ignored the harm of residual electrolyte. The cavitation and thermal effects produced by ultrasonic can not only be used for the separation of electrode materials, but also have a wide range of applications in the field of sewage pollutant degradation. This work used ultrasonic to treat simulated electrolyte (propylene carbonate (PC)) solution of spent lithium-ion batteries, explored the effect of ultrasonic power, the addition amount of H2O2 solution (30 wt%) and reaction temperature on the degradation of electrolyte, and analysed the ultrasonic degradation reaction from the perspective of reaction kinetics. And the synchronous experiment of cathode material separation and electrolyte degradation was conducted under the optimal conditions. The results showed that the highest degradation efficiency of PC in the electrolyte was 83.08% under the condition of ultrasonic power of 900 W, the addition of H2O2 solution (30 wt%) of 10.2 mL, reaction temperature of 120°C and reaction time of 120 minutes, and the separation efficiency was 100%. This work reduced the environmental and health risks in the cathode material separation process and was conducive to the green development of spent lithium-ion battery recycling technology.

Control of N-nitrosodimethylamine (NDMA) formation from N,N-dimethylhydrazine compounds by ozone-based advanced oxidation processes

N-nitrosodimethylamine (NDMA) is formed during ozonation of model compounds with dimethylhydrazine groups, such as daminozide (DMZ) and 2-furaldehyde 2,2-dimethylhydrazone (2-F-DMH) at pH 7 with yields of 100 % and 87 %, respectively. In this study, ozone/hydrogen peroxide (O3/H2O2) and ozone/peroxymonosulfate (O3/PMS) were investigated to control NDMA formation, and O3/PMS (50–65 %) was more effective than O3/H2O2 (10–25 %) with a ratio of H2O2 or PMS to O3 of 8:1. The reaction of PMS or H2O2 to decompose ozone could not compete with the ozonation of model compound because of the high second-order rate constants of the ozonation of DMZ (5 ×105 M−1 s−1) or 2-F-DMH (1.6 ×107 M−1 s−1). The Rct value of the sulfate radical (SO4•−) showed a linear relationship with NDMA formation, indicating that SO4•− significantly contributed to its control. NDMA formation could be further controlled by injecting small quantities of ozone numerous times to minimize the dissolved ozone concentration. The effects of tannic acid, bromide and bicarbonate on NDMA formation were also investigated during ozonation, O3/H2O2, and O3/PMS processes. Bromate formation was more pronounced in the O3/PMS process than in the O3/H2O2 process. Therefore, in practical applications of O3/H2O2 or O3/PMS processes, the generation of NDMA and bromate should be detected.

2D carbon network arranged into high-order 3D nanotube arrays on a flexible microelectrode: integration into electrochemical microbiosensor devices for cancer detection

In this work, we develop a new type of mesoporous 2D N, B, and P codoped carbon network (NBP-CNW) arranged into high-order 3D nanotube arrays (NTAs), which are wrapped onto a flexible carbon fiber microelectrode, and this microelectrode is employed as a high-performance carbon-based nanocatalyst for electrochemical biosensing. The NBP-CNW-NTAs synthesized by a facile, controllable, ecofriendly and sustainable template strategy using ionic liquids as precursors possess a high structural stability, large surface area, abundant active sites, and effective charge transport pathways, which dramatically improve their electrocatalytic activity and durability in the redox reaction of cancer biomarker H2O2. Benefiting from these unique structural merits, superb electrochemical activity and good biocompatibility, the NBP-CNW-NTAs-modified microelectrode demonstrates excellent sensing performance toward H2O2 and is embedded in a homemade microfluidic electrochemical biosensor chip for the real-time tracking of H2O2 secreted from different live cancer cells with or without radiotherapy treatment, which provides a new strategy for distinguishing the types of cancer cells and evaluating the radiotherapeutic efficacy of cancer cells. Furthermore, the functional microelectrode is integrated into an implantable probe for the in situ detection of surgically resected human specimens to distinguish cancer tissues from normal tissues. These will be of vital significance for cancer diagnoses and therapy in clinical practice.

Effect of Redox Potential on Diiron-Mediated Disproportionation of Hydrogen Peroxide.

Heme and nonheme dimanganese catalases are widely distributed in living organisms to participate in antioxidant defenses that protect biological systems from oxidative stress. The key step in these processes is the disproportionation of H2O2 to O2 and water, which can be interpreted via two different mechanisms, namely via the formation of high-valent oxoiron(IV) and peroxodimanganese(III) or diiron(III) intermediates. In order to better understand the mechanism of this important process, we have chosen such synthetic model compounds that can be used to map the nature of the catalytically active species and the factors influencing their activities. Our previously reported μ-1,2-peroxo-diiron(III)-containing biomimics are good candidates, as both proposed reactive intermediates (FeIVO and FeIII2(μ-O2)) can be derived from them. Based on this, we have investigated and compared five heterobidentate-ligand-containing model systems including the previously reported and fully characterized [FeII(L1-4)3]2+ (L1 = 2-(2'-pyridyl)-1H-benzimidazole, L2 = 2-(2'-pyridyl)-N-methyl-benzimidazole, L3 = 2-(4-thiazolyl)-1H-benzimidazole and L4 = 2-(4'-methyl-2'-pyridyl)-1H-benzimidazole) and the novel [FeII(L5)3]2+ (L5 = 2-(1H-1,2,4-triazol-3-yl)-pyridine) precursor complexes with their spectroscopically characterized μ-1,2-peroxo-diiron(III) intermediates. Based on the reaction kinetic measurements and previous computational studies, it can be said that the disproportionation reaction of H2O2 can be interpreted through the formation of an electrophilic oxoiron(IV) intermediate that can be derived from the homolysis of the O-O bond of the forming μ-1,2-peroxo-diiron(III) complexes. We also found that the disproportionation rate of the H2O2 shows a linear correlation with the FeIII/FeII redox potential (in the range of 804 mV-1039 mV vs. SCE) of the catalysts controlled by the modification of the ligand environment. Furthermore, it is important to note that the two most active catalysts with L3 and L5 ligands have a high-spin electronic configuration.

Generation mechanism of singlet oxygen from the interaction of peroxymonosulfate and chloride in aqueous systems

Peroxymonosulfate (PMS, HSO5−) is a widely-used disinfectant and oxidant in environmental remediation. It was deemed that PMS reacted with chloride (Cl−) to form free chlorine during water purification. Here, we demonstrated that singlet oxygen (1O2) was efficiently generated from PMS and Cl− interaction. Mechanism of 1O2 formation was uniquely verified by the reaction of HSO5− and chlorine molecule (Cl2) and the oxygen atoms in 1O2 deriving from the peroxide group of HSO5− were revealed. Density functional theory calculations determined that the reaction of HSO5− and Cl2 was thermodynamically favorable and exergonic at 37.8 kcal/mol. Quite intriguingly, 1O2 was generated at a higher yield (1.5 × 105 M − 1 s − 1) than in the well-known reaction of H2O2 with Cl2 (35 M − 1 s − 1). Besides chlorine, 1O2 formed in PMS-Cl− interaction dominated the degradation of micropollutants, also it substantially enhanced the damage of deoxynucleoside in DNA, which were beneficial to micropollutant oxidation and pathogen disinfection. The contribution of 1O2 for carbamazepine degradation was enhanced at higher Cl− level and lower pH, and reached 96.3% at pH 4.1 and 5 min. Natural organic matter (NOM) was a sink for chlorine, thereby impeding 1O2 formation to retard carbamazepine degradation. 1O2 also played important roles (48.3 − 63.5%) on the abatement of deoxyguanosine and deoxythymidine at pH 4.1 and 10 min in PMS/Cl−. On the other hand, this discovery also alerted the harm of 1O2 for human health as it can be formed during the interaction of residual PMS in drinking water/swimming pools and the high-level Cl− in human bodies.

Coagulation Combined with Electro-Fe0/H2O2 Reaction for Effective Treatment of Landfill Leachate Effluent of Membrane Bioreactor

In this study, coagulation combined with the electro-Fe0/H2O2 reaction was developed to treat refractory organics in the landfill leachate effluent of a membrane bioreactor (MBR), and the change in biodegradability was investigated. The results showed that polymerized ferric sulfate (PFS) was the best coagulant, with removal efficiencies of chemical oxygen demand (COD) and chromaticity of 74.18% and 72.22%, respectively, when the dosage was 2 g/L and the initial pH (pH0) was 6. Under the optimal conditions of pH0 of 3, current density of 5 mA/cm2, Fe0 dosage of 3 g/L, and H2O2 dosage of 0.059 M, the electro-Fe0/H2O2 reaction showed the removal efficiencies of COD and chromaticity for coagulated effluent were 76.68% and 74%, respectively. UV-vis and 3D-EEM spectral analysis showed that humic and fulvic acids were effectively degraded, and the effluent was mostly small molecules of aromatic protein-like substances. The whole process increased the BOD5/COD from 0.049 to 0.46, indicating that the biodegradability was substantially improved. This is due to the conjunction of the Fe0/H2O2 reaction with electrochemistry, which accelerated the reduction of Fe3+ to Fe2+ on the Fe0 surface and cathode and improved the efficiency of hydroxyl radical (•OH) generation, thus promoting the removal of pollutants. The operating cost was only 4.18 $/m3, with the benefits of less Fe0 loss and no pH adjustment. In summary, coagulation combined with the electro-Fe0/H2O2 reaction is a cost-effective method for treating refractory organics in leachate and enhancing biodegradability.

A novel Schiff base ligand and its metal complexes: Synthesis, characterization, theoretical calculations, catalase-like and catecholase-like enzymatic activities

In this study, a new Schiff base (H2L), which has not been recorded in the literature, and its metal complexes with general formula [ML].(H2O) [M: Cu(II) and Mn(II)] were synthesized and their structures were elucidated. Techniques such as 1H- and 13C-NMR, FT-IR, UV–vis, TG-DTG, molar conductivity, magnetic susceptibility, ICP-OES, and elemental analysis were used to characterize the structures of the Schiff base and metal complexes. According to the analysis's findings, the complexes' metal:ligand ratio was 1:1. Additionally, the 6-311G(d,p) and LANL2DZ basis sets of the DFT/B3LYP method were used to calculate the optimized molecular geometries of the H2L and its metal complexes, respectively. Additionally, the synthesized compounds' molecular electrostatic potential (MEP) diagrams, frontier molecular orbitals (HOMO-LUMO), chemical shift values for the 1H- and 13C-NMR, vibrational frequencies, and wavelengths of electronic transitions were all determined. Experimentally obtained results were verified with theoretical data that matched well. [CuL].(H2O) and [MnL].(H2O) were examined for their catalase-like and catecholase-like enzymatic activities using volumetric and spectrophotometric techniques, respectively. For this objective, the catalytic activities of the synthesized molecules in the disproporsion reaction of H2O2 in the presence of 1-methylimidazole and the oxidation reaction of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone in aerobic medium were investigated. According to the enzyme-like studies, [MnL].(H2O) was more catalytically active than [CuL].(H2O) in both of the mentioned reactions.