Residual H2O2 Research Articles

Stability evaluation from hydrogen peroxide spiking studies

The ability to detect traces of hydrogen peroxide (H2O2) in water is an important prerequisite to ensure a safe and reliable use of H2O2 for isolator or cleanroom sanitization. While the residual airborne H2O2 concentration can be easily monitored, detection of trace H2O2 residues in aseptically filled drug products is challenging. In an industrial setting, samples must be pulled, handled, stored, and transported before analysis takes place. Therefore, knowledge about the analyte stability in the relevant matrix is crucial to ensure correct results.The objective of this study was to provide stability data for the analyte at low concentrations and in aqueous solutions. For this, H2O2 was spiked into four different aqueous matrices at two different concentrations and stored up to 60 days at four different storage temperatures. The tested matrices included water, buffer, and an exemplary excipient solution with and without additional protein.A developmental quantitative, fluorometric Amplex UltraRed assay was applied for analysis. The results show clearly, that of the four storage temperatures investigated, only -80 °C resulted in reasonably good recovery of the spiked H2O2 content within two weeks or even up to two months of storage.

Catalytic Decomposition of Residual Hydrogen Peroxide in N-Methylmorpholine-N-oxide by Heteroatom Doping Modified Activated Carbon

N-methyloxymoroline-N-oxide (NMMO) has been used in large quantities for the production of new solvent-treated cellulose. But, excess H2O2 used in the synthesis of NMMO from N-methylmorpholine (NMM) can adversely affect the quality of the product. This study introduces a novel approach using nitrogen and sulfur co-doped activated carbon (N,S co-doped AC) to catalyze the decomposition of residual H2O2 in NMMO products. Characterization techniques including N2 adsorption/desorption, Raman, TEM, FT-IR, and XPS were used to study the surface properties and chemistry of activated carbon doped with heteroatoms. The results revealed that AC800NS800 (800 is the calcinate temperature, NS is denoted by the co-doped of N and S) exhibited superior catalytic performance for H2O2 decomposition compared to singly doped activated carbons. Notably, over 95% of H2O2 in NMMO was decomposed, which the catalytic efficiency of AC800NS800 is no significant loss after ten times reuse. The exceptional catalytic activity of AC800NS800 is attributed to the presence of various functional groups on the surface (graphitic carbon, graphitic nitrogen, and pyrrole nitrogen). EPR tests identified HO• and O2•− as the primary reactive species in the H2O2 decomposition process. This study provides valuable insights into the catalytic decomposition of H2O2 in NMMO solutions and offers a significant reference for the production of high-quality NMMO.

Platinum nanoparticles-based electrochemical H2O2 sensor for rapid antibiotic susceptibility testing

With the increase of antimicrobial resistance, rapid antibiotic susceptibility testing (AST) to guide precise antibiotic administration has become increasingly important. However, current gold standard AST approaches tend to take up to 24–48 h. In this work, based on the nature of catalase-positive bacteria decomposing H2O2, we developed a rapid, portable, straightforward, and cost-effective phenotypic AST approach by detecting residual H2O2 using a Pt nanoparticles-based electrochemical sensor. The pulse current of the sensor exhibited a linear increase with rising H2O2 concentration, demonstrating a high sensitivity of ∼382.2 μA cm−2 mM−1. This approach showed superb diagnostic performance, with an area under the curve of 1 for 24 clinical samples of Escherichia coli and Staphylococcus aureus, with a total detection time of 60 and 45 min, respectively. Furthermore, the performance of the sensor showed no degradation even after 100 detections, promising a substantial reduction in AST costs. Overall, the proposed approach exhibited immense potential for diagnosing bacterial antibiotic resistance.

Toxicity of water treated with Fenton-like ferrite catalyst

Recently, there has been a rapid growth in the use of nanoparticles in water treatment processes. However, an important task is to study the toxicity of the materials used and the reaction products formed. The purpose of this study was to evaluate the impact of the proposed water treatment method on the ecosystem. Algae are excellent model organisms for studying the toxic effects of catalyst nanoparticles. This work investigates the toxicity of cobalt ferrite (CoFe2O4) and hydrogen peroxide (H2O2) on the microalgae Chlorella vulgaris Beij. (C. vulgaris). The growth rate of C. vulgaris depends on the residual concentration of H2O2, indicating a stressful physiological state of the microalgae. Exposure to sintered cobalt ferrite granules does not affect the growth of freshwater algae. At a residual H2O2 concentration of 11.9 mM, algal cells' morphology, membrane integrity, and viability were severely impaired. Hydrogen peroxide is known to cause oxidative stress, as evidenced by a decrease in the growth rate of C. vulgaris and an increase in the number of dead cells. The study showed that the high residual concentration of H2O2 is the main obstacle to the discharge of treated water into the natural ecosystem.

Quenching residual H2O2 from UV/H2O2 with granular activated carbon: A significant impact of bicarbonate

UV/H2O2 has been used as an advanced oxidation process to remove organic micropollutants from drinking water. It is essential to quench residual H2O2 to prevent increased chlorine demand during chlorination/chloramination and within distribution systems. Granular activated carbon (GAC) filter can quench the residual oxidant and eliminate some of the dissolved organic matter. However, knowledge on the kinetics and governing factors of GAC quenching of residual H2O2 from UV/H2O2 and the mechanism underlying the enhancement of the process by HCO3− is limited. Therefore, this study aimed to analyse the kinetics and influential factors, particularly the significant impact of bicarbonate (HCO3−). H2O2 decomposition by GAC followed first-order kinetics, and the rate constants normalised by the GAC dosage (kn) were steady (1.6 × 10−3 L g−1 min−1) with variations in the GAC dosage and initial H2O2 concentration. Alkaline conditions favour H2O2 quenching. The content of basic groups exhibited a stronger correlation with the efficiency of GAC in quenching H₂O₂ than did the acidic groups， with their specific kn values being 8.9 and 2.4 min−1 M−1, respectively. The presence of chloride, sulfate, nitrate, and dissolved organic matter inhibited H2O2 quenching, while HCO3− promoted it. The interfacial hydroxyl radical (HO•) zones were visualised on the GAC surface, and HCO3− addition increased the HO• concentration. HCO3− increased the concentration of persistent free radicals (PFRs) on the GAC surface, which mainly contributed to HO• generation. A significant enhancement of HCO3− on H2O2 quenching by GAC was also verified in real water. This study revealed the synergistic mechanism of HCO3− and GAC on H2O2 quenching and presents the potential applications of residual H2O2 in the H2O2-based oxidation processes.

Mechanical agitation and ultrasound constructed in situ Fenton system: The role of atomic hydrogen for Fe(III) reduction

It has been reported that the ultrasonic agitation coupled system (US/A) has higher oxidation efficiency than the pure ultrasonic system (US), and the atomic hydrogen (H) and hydroxyl radicals (OH) produced by H2O cracking and in situ hydrogen peroxide (H2O2) can be significantly detected. In order to utilize the residual H2O2 and explore the role and fate of H, US/A/Fe(III) as an in situ Fenton oxidation system, was constructed in this study. The experimental results proved that the system can generate H2O2in situ, and adding Fe(III) could significantly promote the oxidation of refractory organic pollutants. Quenching tests, probes experiments and EPR test were performed to successfully monitor the existence of OH. The contribution of H to Fe(III) reduction was speculated and confirmed. In addition, the kinetic model showed the decomposition rate of water molecule and the reduction rate of Fe(III) by H under different ultrasonic power. The effects of the factors (pH, coexisting substance, and actual water environment) on degrading organic pollutants were evaluated. Therefore, this work provides new strategy and mechanistic insight into in situ Fenton technique by coupling ultrasonic agitation and Fe(III) without external oxidants.

Development and Validation of a Customized Amplex UltraRed Assay for Sensitive Hydrogen Peroxide Detection in Pharmaceutical Water.

For clean-room technologies such as isolators and restricted access barrier systems (RABS), decontamination using hydrogen peroxide (H2O2) is increasingly attractive to fulfill regulatory requirements. Several approaches are currently used, ranging from manual wipe disinfection to vapor phase hydrogen peroxide (VPHP) or automated nebulization sanitization. Although the residual airborne H2O2 concentration can be easily monitored, detection of trace H2O2 residues in filled products is rather challenging. To simulate the filling process in a specific clean room, technical runs with water for injection (WfI) are popular. Thus, the ability to detect traces of H2O2 in water is an important prerequisite to ensure a safe and reliable use of H2O2 for isolator or clean room decontamination. The objective of this study was to provide a validated quantitative, fluorometric Amplex UltraRed assay, which satisfies the analytical target profile of quantifying H2O2 in WfI at low nanomolar to low micromolar concentrations (ppb range) with high accuracy and high precision. The Amplex UltraRed technology provides a solid basis for this purpose; however, no commercial assay kit that fulfills these requirements is available. Therefore, a customized Amplex UltraRed assay was developed, optimized, and validated. This approach resulted in an assay that is capable of quantifying H2O2 in WfI selectively, sensitively, accurately, precisely, and robustly. This assay is used in process development and qualification approaches using WfI in H2O2-decontaminated clean rooms and isolators.

Effect of Mn2+ substitution on catalytic properties of Fe3-xMnxO4 nanoparticles synthesized via co-precipitation method

Mn-substituted magnetite samples Fe3-xMnxO4 (x = 0.0; 0.02; 0.05; 0.1; 0.15; 0.2; 0.25) were synthesized using the co-precipitation method. X-ray diffraction patterns confirmed the formation of pure, well-crystallized manganese ferrite with a cubic spinel structure. The crystallites size increases sharply for the minimum degrees of substitution, with a subsequent tendency to decrease with the growth of manganese ions content. The catalytic properties of Fe3-xMnxO4 were investigated for the degradation of oxytetracycline (ОТС) and inactivate E. coli. There is a correlation between particle size and catalytic activity. The Fe2.95Mn0.05O4 sample exhibited the highest catalytic activity in the destruction of OTC. The effect of electromagnetic heating (EMH) on the catalytic properties of iron oxides were investigated. The Fe2.9Mn0.1O4 sample with electromagnetic heating achieved 100 % efficiency in decomposing 5 mg/L of OTC. Fe3-xMnxO4 samples reduce the number of Gram-negative bacteria E. coli at concentrations of 104 and 106 CFU/mL. Electromagnetic heating experiments demonstrated high performance, achieving inactivation of 6 logs of E. coli in the presence of Fe2.98Mn0.02O4 and Fe2.95Mn0.05O4 catalysts within 135 minutes. Studies on ecotoxicity have shown that Daphnia magna is a sensitive bioindicator of residual H2O2 concentration. An increase in the Mn2+ content in the synthesized catalysts resulted in a decrease in the toxicity of purified water. The study suggests that Mn-substituted magnetite catalysts are effective materials for catalytic decomposition of OTC and inactivation of E. coli bacteria.

Multifunctional glucose-powered nanomotors with robust dual enzyme mimic activities

Catalytic micro-/nanomotors (MNMs) that use H2O2 as fuel to generate O2 bubbles for propulsion hold great promise for exciting applications in the biological and environmental fields. However, it is still a challenge to alleviate or avoid the negative impact of H2O2 on the ecological environment of water body. Herein, a novel glucose-driven nanomotor with robust dual enzyme-like activities was prepared by precisely controlling the phase composition and enzyme immobilization to construct a 3D hierarchical structure integrating Fe-MOF, MnO2 and glucose oxidase (GOx) on halloysite nanotube (HNTs) support. Embedding GOx into the framework of Fe-MOF by a simple one-step coprecipitation process allowed the in-situ generation of H2O2 in the presence of glucose. Such H2O2 could be further decomposed to O2 bubbles to drive nanomotors. Meanwhile, O2 bubbles and residual H2O2 could convert to active species superoxide radical (O2•−) and hydroxyl radical (•OH) due to the high peroxidase/oxidase-like activities of Fe-MOF/MnO2 in nanomotors. As a proof of concept, the as-synthesized nanomotors could realize sensitively colorimetric detection of glutathione (GSH) with a detection limit of 9.3 × 10−8 M. In particular, the nanomotors could also rapidly degrade tetracycline hydrochloride (TCH) under neutral conditions without additional H2O2. It is envisioned that the new strategy that combines strong enzyme-like activity with enhanced autonomous motion can promote the nanomotors efficiency for biomolecular sensing and environmental remediation.

Inactivation of Listeria monocytogenes by Hydrogen Peroxide Addition in Commercial Cheese Brines

Commercial cheese brines are used repeatedly over extended periods, potentially for years, and can be a reservoir for salt-tolerant pathogens, such as Listeria monocytogenes. The objective of this study was to determine the inactivation of L. monocytogenes in cheese brines treated with hydrogen peroxide (H2O2) (0, 50, and 100 ppm) at holding temperatures representing manufacturing conditions. In experiment one, four fresh cheese brines were prepared with 10 or 20% salt and pH 4.6 or 5.4 (2x2 design; duplicate trials). Brines were inoculated with L. monocytogenes, treated with H2O2, and stored at 10 and 15.6°C. For experiment two, seven used commercial brines (representing five cheese types, 15–30% NaCl, pH 4.5–5.5; three seasonal trials) were inoculated with L. monocytogenes or S. aureus, treated with H2O2, and stored at 12.8°C (both L. monocytogenes and S. aureus), 7.2 and 0°C (L. monocytogenes only). Each treatment was assayed on Days 0, 1, and 7 for microbial populations and residual H2O2. Data revealed that pathogen populations decreased ≤1 log in cheese brines with no hydrogen peroxide stored for 7 days, regardless of the storage temperature. In fresh brine treated with 50 or 100 ppm of H2O2, populations of L. monocytogenes were reduced to less than the detectable limit by 7 days at 10 and 15.6°C (>4 log reduction). For unfiltered used brines, H2O2 had no effect on L. monocytogenes populations in Brick J (pH 5.4, 15% NaCl) due to rapid inactivation of H2O2, likely by indigenous yeasts (∼3-log CFU/ml). For the remaining brines, the addition of 100 ppm H2O2 killed >4 log L. monocytogenes when stored at 7.2 or 12.8°C for 1 week, but only 3–4 log reduction when stored at 0°C. The addition of 50 ppm H2O2 had similar lethal effects at 12.8°C but was less effective at 7.2 or 0°C. Inactivation rates of S. aureus were similar to that of L. monocytogenes. This study confirmed that high salt, warmer temperature, and 100-ppm H2O2 accelerated the inactivation of L. monocytogenes in cheese brines. Data also suggest that the presence of catalase-positive indigenous microorganisms may neutralize the effect of H2O2.

Fenton oxidation treatment of benzalkonium chlorides to prevent antibiotic resistance development in non-acclimated activated sludge system

Improper discharge of benzalkonium chlorides (BAC) to sewage and wastewater treatment plants can cause acute intoxication and chronic low-dose exposure, which can lead to changes in microbial communities and can promote the development of antibiotic resistance. The aim of this study was to develop a feasible treatment strategy based on the homogeneous Fenton oxidation to minimize the negative impact of BAC-containing wastewater on activated sludge systems. The effect of initial iron and oxidant concentrations was analyzed. After an initial Fenton oxidation stage (180 min), the solution needed to be stored at ambient temperature and in the dark for some time to remove residual oxidizing agents and promote further oxidation. The 0.1 % w/v-BAC solution treated at best operating conditions, i.e., homogeneous Fenton for 180 min at 30 °C, pH0 = 3, stoichiometric oxidant dose, [Fe+2]0:[H2O2]0 = 0.011, and stored during 4 days, led to BAC conversion of 99.9 %, no residual H2O2, no sludge, and DOC conversion of 40.8 %. An increase in metabolic activity was observed when non-acclimated activated sludge was exposed to the treated solution. Treated solution showed biodegradation without increasing resistance to Ampicillin, Cephalexin, or Ciprofloxacin. Evaluation of the effect of water matrix (tap or distilled) showed that the composition of tap water enhanced the oxidation extent, resulting in a 15 % increase in mineralization and a further reduction of COD. This study provides insights into the treatment of wastewater containing BAC and its safe discharge to sewage systems or biological wastewater treatment plants.

Preparation of platinum-free manganese oxide (MnOx) catalyst film for H2O2 decomposition in contact-lens cleaning

A platinum (Pt)-free manganese oxide (MnOx) catalyst film for H2O2 decomposition was prepared on an aluminum (Al) substrate (MnOx/Al) by a hydrothermal impregnation method to decrease the cost of a container used in contact lens cleaning and effectively using Pt materials as other several catalysts. Scanning electron microscopy with energy dispersive X-ray spectroscopy images confirmed that the Al substrate was covered with MnOx. The thickness of the MnOx film was about 300 nm. X-ray diffraction spectra showed that the MnOx film consisted of MnO2 and Mn2O3. The catalytic activity for H2O2 decomposition was estimated by measuring the residual H2O2 concentration, and the target value was ≦100 ppm. The MnOx/Al catalyst was immersed in 35,000 ppm H2O2 solution for 360 min, then the H2O2 concentration decreased to 737 ppm. This result indicated that the MnOx catalyst had a high catalytic activity for H2O2 decomposition but it was not enough for practical use. To improve the catalytic activity, an Al substrate was roughened to increase the specific surface area before preparing an MnOx film. A method with the highest effect of increase in surface roughness was a combination of sandblasting and chemical etching. An MnOx catalyst film was prepared on the roughened Al substrate (MnOx/roughened-Al). When the MnOx/roughened-Al catalyst was immersed in 35,000 ppm H2O2 solution for 360 min, the H2O2 concentration decreased to 38 ppm. When the catalyst was used repeatedly for 10 times, the residual H2O2 concentration was 66 ppm, which indicated that the Pt-free catalyst also had high catalytic durability. These results demonstrated that a roughening was extremely effective in improving both the catalyst activity and durability of a MnOx film catalyst, and a conventional catalyst of a Pt plating film can be replaced with the developed catalyst of the MnOx film on the roughened Al substrate.

Smartphone-assisted colorimetric and near-infrared ratiometric fluorescent sensor for on-spot detection of H2O2 in food samples

Hydrogen peroxide (H2O2) is closely involved in the fields of food industry. Excessive residual H2O2 in food samples will exert adverse effects on the nutritional value of foods and pose great threat to the health of consumer. Development of a reliable analytical method for on-spot quantitative detection of H2O2 levels in food is of urgent necessity. Here, we presented a colorimetric and near-infrared (NIR) ratiometric fluorescent sensor for on-spot quantitative detection of H2O2 in various food samples. The sensor displayed colorimetric and NIR ratiometric fluorescence dual-signal response to H2O2 with high selectivity and sensitivity. The limits of detection (LOD) was measured to be 23.08 nM (S / N = 3). The sensor has been applied for detecting exogenous and endogenous H2O2 in living cells by fluorescence imaging. Also, the changes of H2O2 level in potato tissue infected by phytophthora infestans has been monitored. Particularly, to achieve on-spot quantitative detection of H2O2 in food samples, a portable and field deployable detection device was rationally developed. The sensor, together with portable detection devices and smartphones, performed on-spot quantitative detection of H2O2 in chicken wings and milk through dual signal outputs of colorimetry and fluorescence. We anticipate that the analytical method developed here could be served as convenient tool for on-spot quantitative detection of H2O2 in different foods in near future.

Iodide-Mediated Etching of Gold Nanostar for the Multicolor Visual Detection of Hydrogen Peroxide.

A multicolor visual method for the detection of hydrogen peroxide (H2O2) was reported based on the iodide-mediated surface etching of gold nanostar (AuNS). First, AuNS was prepared by a seed-mediated method in a HEPES buffer. AuNS shows two different LSPR absorbance bands at 736 nm and 550 nm, respectively. Multicolor was generated by iodide-mediated surface etching of AuNS in the presence of H2O2. Under the optimized conditions, the absorption peak Δλ had a good linear relationship with the concentration of H2O2 with a linear range from 0.67~66.67 μmol L-1, and the detection limit is 0.44 μmol L-1. It can be used to detect residual H2O2 in tap water samples. This method offered a promising visual method for point-of-care testing of H2O2-related biomarkers.

Design and Characterization of Non-Erosive Polymeric Tooth-Whitening Compositions

We investigated the physical properties and tooth-whitening effect of polymeric tooth-whitening compositions based on orally acceptable polymers, polyvinyl acetate (PVAc), ethyl cellulose (EC), and polyvinyl pyrrolidone. The tooth-whitening composition was prepared with hydrogen peroxide (H2O2) as a tooth-bleaching agent and an orally acceptable polymer through simple mixing and stirring in ethyl alcohol. PVAc and EC polymers showed non-erosive features and sustainable polymeric matrices in a similar oral environment. In particular, non-erosive PVAc polymer exhibited excellent adhesive and flexible film matrix on bovine teeth. PVAc-H2O2 tooth-whitening composition presented a residual H2O2 and an overall color change value (ΔE*) of 26.5% and 16.54%, respectively. The non-erosive polymeric composition is expected to improve tooth-whitening efficacy in various oral products.

An innovative approach to the application of electrochemical processes based on the in-situ generation of H2O2 for water treatment

This study presents an innovative strategy for the implementation of electrochemical treatment systems based on the in-situ generation of H2O2 targeted at the removal of organic contaminants in aqueous matrices. Unlike the studies based on the continuous application of electric current, in the present work, the electric power supply was interrupted once desired concentrations of H2O2 were accumulated in solutions previously spiked with the contaminant. The accumulated H2O2 was then activated by illuminating the solution with UVC light, which gave rise to the process called UVC/¢-H2O2. The application of current densities of 10 and 25 mA cm−2 for only 10 min led to the efficient production of H2O2 in concentrations ranging from ∼48 to 112 mg L−1, which resulted in the complete degradation of the antibiotic norfloxacin (NOR; 60 μmol L−1) and high mineralization rates in the UVC/¢-H2O2@10 mA cm−2 and UVC/¢-H2O2@25 mA cm−2 processes. Moreover, no residual H2O2 was detected within 90 min of treatment in both conditions. Although similar results in terms of NOR degradation/mineralization were obtained from the application of the UVC/c-H2O2@25 mA cm−2 process (i.e., based on the continuous application of 25 mA cm−2), a significant residual concentration of H2O2 (∼100 mg L−1) was detected after treatment. Noticeably, the application of the UVC/¢-H2O2@25 mA cm−2 method led to ∼26% reduction in overall energy consumed in the mineralization process compared to the conventional system using the continuous application of electric current.

Lactate oxidase/catalase-displaying nanoparticles efficiently consume lactate in the tumor microenvironment to effectively suppress tumor growth

The aggressive proliferation of tumor cells often requires increased glucose uptake and excessive anaerobic glycolysis, leading to the massive production and secretion of lactate to form a unique tumor microenvironment (TME). Therefore, regulating appropriate lactate levels in the TME would be a promising approach to control tumor cell proliferation and immune suppression. To effectively consume lactate in the TME, lactate oxidase (LOX) and catalase (CAT) were displayed onto Aquifex aeolicus lumazine synthase protein nanoparticles (AaLS) to form either AaLS/LOX or AaLS/LOX/CAT. These complexes successfully consumed lactate produced by CT26 murine colon carcinoma cells under both normoxic and hypoxic conditions. Specifically, AaLS/LOX generated a large amount of H2O2 with complete lactate consumption to induce drastic necrotic cell death regardless of culture condition. However, AaLS/LOX/CAT generated residual H2O2, leading to necrotic cell death only under hypoxic condition similar to the TME. While the local administration of AaLS/LOX to the tumor site resulted in mice death, that of AaLS/LOX/CAT significantly suppressed tumor growth without any severe side effects. AaLS/LOX/CAT effectively consumed lactate to produce adequate amounts of H2O2 which sufficiently suppress tumor growth and adequately modulate the TME, transforming environments that are favorable to tumor suppressive neutrophils but adverse to tumor-supportive tumor-associated macrophages. Collectively, these findings showed that the modular functionalization of protein nanoparticles with multiple metabolic enzymes may offer the opportunity to develop new enzyme complex-based therapeutic tools that can modulate the TME by controlling cancer metabolism.Graphical

Stoichiometric excesses of H2O2 as dosimetry strategy: proof of concept for UVC-H2O2, dark-Fenton, and UVC-Fenton.

Hydrochlorothiazide (HCT) is a pharmaceuticalmicropollutant highly toxic to the environment, being absolutely necessary to oxidize it completely to CO2. Here, the variables stoichiometric H2O2 excess for (a) degradation and (b) mineralization are defined and used as metric to quantify the dosimetry of the H2O2. So that, dose of H2O2 qualifies being under- and over-dose respectively for values below and above such standards. In this work, these concepts have been elucidated across AOPs regarding the H2O2 degradation excess, whereas only UVC-Fenton was used regarding the H2O2 mineralization excess. At a H2O2 mineralization excess of 0.68 (equivalent to degradation excess of 36.74), oxidation via UVC-H2O2 enables absolute (100%) HCT degradation within 60min; however, the mineralization of HCT demonstrated limited optimization for all AOPs employed in the beaker-like reactor of this work, being the underlying reasons investigated hereby. At best, 26.70% HCT mineralization was observed within 60min of UVC photo-Fenton using an initial 2.00 H2O2 mineralization excess. Such mineralization of 26.7% is unexpectedly low considering that, in addition, the residual H2O2 concentration almost fully depletes within 30min of UVC-Fenton oxidation. Taken all that together, the loss of H2O2 due its decomposition induced by the risen temperature from 28 to 70ºC very likely were the underlying reason preventing better mineralization performance. We successfully demonstrated 18% of mean efficiency of radical •OH consumption signals that the overheating is indeed a designer problem with the photo-reactor since a well-refrigerated photo-reactor shows a mean efficiency of 38% for the same H2O2 excess.

High-performance liquid chromatography using diode array detector and fluorescence detector for hydrogen peroxide analysis in processed fishery foods.

Hydrogen peroxide (H2O2) is a food additive for bleaching and sterilization, owing to its strong oxidizing effect. The current study aimed to develop analytical methods to detect trace amounts of residual H2O2 in diverse foods using high-performance liquid chromatography (HPLC) equipped with diode array detector (DAD) or fluorescence detector (FLD). The vanadium(V)-peroxo complex, derived from the reaction of H2O2 with ammonium metavanadate, was used for the detection of H2O2 with DAD. H2O2 was indirectly analyzed using FLD via the detection of 7-hydroxycoumarin, derived by Fenton reaction, followed by verification using liquid chromatography with tandem mass spectrometry analysis. Both the detection methods showed good linearity with R2 > 0.997. Limit of detection and limit of quantification were 0.30 and 0.91mg/L (8.82 and 26.76μM) with HPLC-DAD and 0.001 and 0.003mg/L (0.03 and 0.09μM) with HPLC-FLD, respectively. Applicability of both the methods was successively tested through sample analysis.

Interactions between H2O2 and dissolved organic matter during granular activated carbon-based residual H2O2 quenching from the upstream UV/H2O2 process

Granular activated carbon (GAC) filtration can be employed to synchronously quench residual H2O2 from the upstream UV/H2O2 process and further degrade dissolved organic matter (DOM). In this study, rapid small-scale column tests (RSSCTs) were performed to clarify the mechanisms underlying the interactions between H2O2 and DOM during the GAC-based H2O2 quenching process. It was observed that GAC can catalytically decompose H2O2, with a long-lasting high efficiency (>80% for approximately 50,000 empty-bed volumes). DOM inhibited GAC-based H2O2 quenching via a pore-blocking effect, especially at high concentrations (10 mg/L), with the adsorbed DOM molecules being oxidized by the continuously generated ·OH; this further deteriorated the H2O2 quenching efficiency. In batch experiments, H2O2 could enhance DOM adsorption by GAC; however, in RSSCTs, it deteriorated DOM removal. This observation could be attributed to the different ·OH exposure in these two systems. It was also observed that aging with H2O2 and DOM altered the morphology, specific surface area, pore volume, and the surface functional groups of GAC, owing to the oxidation effect of H2O2 and ·OH on the GAC surface as well as the effect of DOM. Additionally, the changes in the content of persistent free radicals in the GAC samples were insignificant following different aging processes. This work contributes to enhancing understanding regarding the UV/H2O2-GAC filtration scheme, and promoting the application in drinking water treatment.