Fenton Reaction Research Articles

A Peptide-Copper Self-Assembled Nanoparticle for Enhanced Cuproptosis by Metabolic Reprogramming in Tumor Cells.

Cuproptosis is a type of metabolic cell death and exhibits great potential for cancer treatment. However, currently, most cuproptosis-based therapies are primarily effective in tumor cells reliant on mitochondrial respiration, limiting their broader application. The Warburg effect highlights that many tumors predominantly rely on glycolysis to meet their rapid metabolic demands, but glycolysis-dependent cells are less sensitive to copper ions than their mitochondrial-respiration-dependent counterparts, making it difficult to induce cuproptosis in these cells. Herein, we designed a copper-loaded peptide-based nanoparticle (MHRC@Cu) to enhance cuproptosis by metabolic reprogramming in a wider range of glycolysis-dependent tumor cells. Specifically, triggered by the acidic environment and laser irradiation, MHRC@Cu effectively released Cu2+ inside the cells. Then the peptide-conjugated probe (MHRC) reprogrammed glycolysis-dependent tumor cells, making them more dependent on mitochondrial respiration and increasing their sensitivity to copper ions. Additionally, the H2O2 generated by the photodynamic effect underwent Fenton reaction with Cu2+ in situ, producing highly toxic ·OH, which depleted GSH and disrupted copper efflux protein, thereby exacerbating copper deposition in cells. Through these synergistic mechanisms, MHRC@Cu significantly enhanced cuproptosis in glycolysis-dependent tumor cells, achieving up to 96% inhibition of tumor growth. This copper-loaded peptide-based nanoparticle offers a versatile and potent strategy for enhancing cuproptosis and may inspire the development of advanced self-assembled nanotherapeutic platforms.

Unraveling the Origin of Superior Activity of FeOCl for Photocatalytic Fenton Reaction

Unraveling the Origin of Superior Activity of FeOCl for Photocatalytic Fenton Reaction

X-ray induced in-situ ferroptosis through the Fenton reaction of iron supplements for the cancer therapy

The potential of iron-based therapeutic agents in enhancing radiotherapy efficacy through catalyzing the Fenton reaction has garnered widespread interest. The inherent instability of ferrous ions requires the use of complex ligands for the ligand-dependent reduction from Fe3+ to Fe2+, thereby boosting ferroptosis through inducing the Fenton reaction. However, the reliance on complex redox systems and potential long-term toxicity have seriously limited the clinical application in cancer treatment. In this study, we propose an innovative approach that utilizes the reduction capabilities of hydrated electrons generated by X-ray to directly reduce both ferric ions (Fe3+) and Iron Proteinsuccinylate, a clinically used iron supplement. Our experiments showed that over 20 % of Fe3+, at a concentration of 23 μM, was reduced by X-ray without the need for ligand involvement. Furthermore, both in vitro and in vivo studies confirmed that Iron Proteinsuccinylate exhibited the highest tumor growth inhibition rate through the Fenton reaction and ferroptosis, offering a new and safer method for the in-situ reduction of Fe3+ and enhancing the efficacy of radiotherapy.

Effective mineralization of organic pollutants in real shale gas flowback water via Fenton reactions over CuNiAl LDHs catalysts

Effective mineralization of organic pollutants in real shale gas flowback water via Fenton reactions over CuNiAl LDHs catalysts

A self-sufficient catalytic nanofiber evaporator for solar-driven efficient water purification through in-situ hydrogen peroxide generation

Solar-driven interfacial water evaporation (SDIWE) is an emerging technology for the production of clean water driven by inexhaustible energy source, but its application suffers from volatile organic compounds (VOCs) escaping into condensate water. Herein, a bifunctional SDIWE system integrated with Fenton process was proposed to achieve self-sufficient (not adding any additional chemicals to feed water) high-quality freshwater production from VOCs-contained wastewater through in-situ hydrogen peroxide (H2O2) generation. The hybrid SDIWE system based on AgNPs (Ag nanoparticles)@graphitic carbon nitride (g-C3N4)/beta-iron hydroxide oxide (β-FeOOH)-Polyacrylonitrile (AgG/Fe-PAN) nanofiber membrane exhibited an excellent evaporation performance (1.61 kg m-2h−1) under one sun (1 kW m−2). Significantly, in the absence of external oxidant source, the phenol removal rate in condensate water reached 98.4 ± 0.2 % due to the synergic photocatalysis technology and Fenton reaction, which was 6.1 times that of sole SDIWE (16.2 ± 0.5 %). Mechanism analysis reveals that H2O2 was effectively in-situ generated by AgNPs@g-C3N4 particles (∼18.8 μM at 4 h). Subsequently, the produced H2O2 was further activated to •OH radicals via β-FeOOH that ensures the VOCs decomposition during rapid steam generation. Meanwhile, the hybrid system not only exhibited an excellent phenol removal rate of 91.6 ± 0.6 % in wide pH ranges (1–11), but also ensured a good removal performance for various organic pollutants and excellent antibacterial properties. To sum up, the hybrid system has successfully integrated SDIWE technology with various advanced oxidation processes (AOPs), providing a novel way for the pollution-free production of high-quality clean water during the SDIWE process for water purification.

Zn-MIL53(Fe) as an electro-Fenton catalyst: Application in organic pollutant degradation and pathogen inactivation

In this study, the potential of a bimetallic Metal-Organic Framework Zn-MIL53(Fe) for electro-Fenton catalysis was evaluated. After the material characterisation, its catalytic activity was validated in Fenton reaction to degrade a model organic pollutant: Rhodamine B. After that, the evaluation of Zn-MIL53(Fe) as electro-Fenton catalyst was performed and improved outcomes were reached by electro-Fenton regarding anodic oxidation. Then, electro-Fenton treatment optimisation was carried out using response surface methodology assays considering different catalyst dosages (7.2–43.2 mg), current intensities (5–45 mA) and treatment time (30–90 min) in a volume of 0.1 L. Under optimal conditions, a degradation rate over 90 % for Fluoxetine and Sulfamethoxazole in synthetic wastewater was achieved within 90 min, using graphite sheet as anode and nickel foam as cathode (25 mA), with a catalyst dosage of 43.2 mg in a volume of 0.1 L. Additionally, its application in the pathogen inactivation was evaluated using different gram-negative and gram-positive bacteria. Complete eliminations of both types of bacteria were reached in 5 min using the optimal conditions. In the end, Zn-MIL53(Fe) was proven as a reusable material, capable of performing 3 complete cycles of electro-Fenton treatment for both types of pollutants bacteria and pharmaceuticals, which makes it a promising candidate for more efficient wastewater treatment applications which involve the Fenton reaction.

Rational synthesis of FeWO4 nanozyme with sonopiezoelectric and co-catalytic activity for colorimetric detection of deferiprone

Colorimetric sensing based on nanozyme has been extensively applied in the field of biosensing. The analysis time and detection sensitivity depend on the activity of nanozyme. At present, the methods of traditional regulating the activity of nanozyme mainly include internal and external regulation. However, it is still a challenge for internal and external stimuli to coordinate the regulation of nanozyme activity. Both piezoelectricity and co-catalysis can expedite the rate limiting step (Fe3+/Fe2+cycle) of the Fenton reaction hence facilitating the peroxidase-like (POD-like) activity of nanozyme. In this study, we synthesized FeWO4 nanorod that possess sonopiezoelectric and co-catalytic properties. The Fe3+/Fe2+ cycle of FeWO4 nanorods can be boosted by the internal Fe, W co-catalytic reaction and the external ultrasound stimuli generated e−. Deferiprone (DFP), a small molecule of iron chelating agent, is used clinically to chelate excess iron in thalassemia patients. It can specifically inhibit the POD-like activity of the iron-based nanozyme due to coordination with Fe. Based on the above principles, we constructed a colorimetric sensing platform based on FeWO4 nanozyme for colorimetric detection of DFP in urine of thalassemia patients. The linear range, limit of detection and recovery of the developed colorimetric sensing method based on FeWO4 nanozyme platform are 0.1–5 μM, 0.05 μM and 97.4 % − 105.4 %, respectively. This work not only promotes the development of the method to regulate the activity of nanozyme, but also provides a simple method for the monitoring of DFP.

Rapid and efficient removal of organophosphorus pollutant and recovery of valuable elements: A boosted strategy for eliminating organophosphorus from wastewater

Considering the significant hazards of organophosphorus compounds (OPs) and the potential crisis of phosphorus (P) resource shortage, there is a great necessity to develop economically feasible, highly effective, and sustainable strategies to remove OPs and recover P resources. In this study, low-cost microscale zero-valent iron (mZVI) was used to activate hydrogen peroxide for the rapid and efficient elimination of Tetrakis(hydroxymethyl)phosphonium sulfate (THPS) from the aquatic environment. Compared to the conventional Fenton reaction and commercial mZVI, mZVI/H2O2-based Fenton-like reaction exhibited superior removal performance for THPS. The removal mechanism of the mZVI/H2O2 system for THPS was thoroughly elucidated through the identification of reactive oxygen species, characterization analysis, and theoretical calculation. Furthermore, the valuable components of the degradation products were successfully recovered through thermally induced precipitation of the sample followed by high-temperature calcination. The mZVI/H2O2 system has demonstrated significant advantages in removing organic compounds from various types of actual wastewater and improving the biodegradability of the wastewater. This study presented an environmentally friendly and highly efficient strategy to eliminate OPs pollution and recover P resources. It also provided an easy-to-operate method for remediating actual industrial wastewater.

Exploring the ameliorative potential of rutin against High-Sucrose Diet-induced oxidative stress and reproductive toxicity in Drosophila melanogaster

Sucrose is a vital ingredient in numerous food items consumed regularly. However, exposure to excessive sucrose for a prolonged period can promote health issues. The reproductive system has a delicate physiology that can be targeted by various chemical stressors, including sucrose. Hence, the present in vivo study aims to unveil the impacts of the High-Sucrose Diet (HSD) on the reproductive fitness of Drosophila melanogaster. In addition, the present work has also assessed the protective potential of a bioactive compound, rutin, against it. Here, 1st instar larvae were exposed to HSD (30%) alone and in combination with rutin (100-300µM) till their adult stage. HSD disturbed sex comb morphology in adult males, while fecundity and hatchability of eggs in females. Moreover, HSD triggered gonadal ROS production, oxidative stress, and modulated endogenous antioxidants such as SOD, catalase, and glutathione in both sexes. Nuclear fragmentation and tissue injuries, along with protein and lipid oxidation, were also apparent. Elevated levels of cytosolic Iron suggested an active Fenton reaction in adults. Further, HSD modulated the activities of reproductive and metabolic mediators, including vitellogenin, malate dehydrogenase, glucose-6-phosphate dehydrogenase, and angiotensin-converting enzymes that are critical to overall reproductive fitness. Interestingly, co-treatment with rutin, mainly at 200µM, mitigated these adverse effects and restored reproductive fitness. The protective potential of rutin might be attributed to its ability to normalize redox homeostasis, reduce oxidative stress, and optimize critical enzymes involved in reproductive physiology. These findings suggest that rutin has potential therapeutic implications to counteract the reproductive hazards induced by HSD.

CuS enabled efficient Fenton-like oxidation of phenylarsonic acid and inorganic arsenic immobilization

Herein, copper sulfide (CuS) was introduced to the Fenton-like (Fe(III)/H2O2) system for the efficient removal of phenylarsonic acid (PAA). Results of reactive oxygen and Fe/Cu species showed that CuS preferentially reacted with Fe(III) and H2O2 to generate Cu(I) and superoxide anion (•O2-). These reductive species could efficiently promote the Fe(III)/Fe(II) and Cu(II)/Cu(I) cycles, and are beneficial to the sequential Fenton reaction to generate •OH. The organoic/inorganic arsenic species detected in the CuS/Fe(III)/H2O2 system confirmed that PAA was oxidized by •OH to hydroxylated organoarsenic and phenolic intermediates, which were further mineralized to oxalate and formic acid. Meanwhile, the inorganic As(III)/As(V) released during PAA degradation were efficiently immobilized by CuS. The PAA removal efficiency remained as high as 92.9 % after 5 cycles of the CuS-mediated Fenton-like process. These results demonstrate an innovative method for the treatment of organoarsenic-contaminated water, and provide new insights into the enhanced Fenton-like process utilizing sulfide minerals.

Induced electro-Fenton triggers trace iron utilization for simultaneous organic phosphorous degradation and phosphate recovery

Phosphorus recovery from wastewater has the potential to alleviate both phosphorus scarcity and water pollution. Unlike mineral orthophosphate, organic phosphorus (OP) recovery typically requires multiple steps: oxidation to orthophosphate followed by separation. Electro-Fenton can synchronize these steps in a unified reactor. However, conventional anodic-Fenton (AF) that relies on the direct sacrificial Fe anode, often generates excessive iron sludge. This not only undermines the oxidative capacity but also changes the optimal pH conditions. Herein, we addressed these challenges by developing an induced electro-Fenton (I-EF) system that significantly reduces iron sludge by 94.0 %. The degradation of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC, 5.0 mg P/L) in I-EF reached 76.7 % in 60 min, which is much higher than that (46.0 %) in the conventional AF system. Following PBTC degradation to form PO43-, the I-EF system achieved 88 % PO43- recovery through adsorption onto iron hydroxides. The exceptional performance in simultaneous PBTC degradation and recovery can be attributed to multiple functions of minimal iron utilization in the I-EF system. First, trace iron release can prevent quenching of hydroxyl radicals (·OH) by excessive Fe2+. Second, the absence of strong iron hydrolysis can maintain a stable pH condition (3.0–3.2) for Fenton reaction and avoid PBTC removal through direct coagulation process. The feasibility of I-EF was also successfully demonstrated for other OP forms containing C-P and C-O-P bonds. The degradation efficiency of various OPs was closely related to their bond energy and complexation capacity with iron hydroxides. This study makes use of the I-EF system to innovatively accomplish the degradation of organic phosphorous and simultaneous phosphate recovery.

Preparation of CoS2/Fe/SA hydrogel spheres with Fe2+ slow-release effect to improve Fenton reaction efficiency

Fenton reaction is a traditional advanced oxidation process that has long been used for wastewater treatment. However, the narrow pH range of 2–4, the inefficient utilization of both H2O2 and Fe2+, and the large amount of iron sludge formation limit its application. Here, we prepared sodium alginate composite hydrogel spheres with both Fe2+ and CoS2 loading (denoted as CoS2/Fe/SA hydrogel spheres) to construct a CoS2/Fe/SA + H2O2 reaction system. The degradation efficiency of carbamazepine (CBZ) in the CoS2/Fe/SA + H2O2 system was significantly enhanced with a first-order kinetic reaction constant of 0.1958 min−1, which is 8.9 times higher than that in Fe2++H2O2 system. When the initial solution pH was in the range of 2–8, the removal rate of CBZ at 90 min reaction time ranged from 96.5 % to 99.9 %. The enhanced degradation efficiency even in a slightly alkaline aqueous solution was due to the sustained slow release of Fe2+ from the CoS2/Fe/SA hydrogel spheres that enhances the utilization of Fe2+ and the promotion of Fe3+/Fe2+ cycling via CoS2. Moreover, the release amount of Fe2+ in CoS2/Fe/SA hydrogel spheres could be controlled by tuning the Fe2+ loading amount during preparation, which in turn determines its number of cycling uses.

Engineered Metal–Organic Framework with Stereotactic Anchoring and Spatial Separation of Porphyrins for Amplified Ultrasound‐Mediated Pyroptosis and Cancer Immunotherapy

AbstractUltrasound‐mediated reactive oxygen species (ROS) generation is pivotal in specifically inducing pyroptosis of tumor cells. However, the effectiveness of pyroptosis is generally hindered by the constraints of ROS generation efficiency. Herein, a new porphyrin‐based metal–organic framework (Fe(TCPP)‐MOF) was rationally designed via an innovative dual‐solvent strategy to amplify ROS generation for ultrasound‐controlled pyroptosis. The crystal structure of Fe(TCPP)‐MOF was elucidated by continuous rotation electron diffraction technique, revealing its regular and rigid conformation. The porphyrin molecules were precisely oriented and firmly confined within the scaffold, effectively restricting intramolecular motion. The ample distance of 6.8 Å between two porphyrin molecules, combined with the interaction region indicator visualization, confirmed the absence of π–π stacking interactions in the Fe(TCPP)‐MOF framework, thereby avoiding the aggregation‐caused quenching effect. Furthermore, the permanent porosity and expansive surface area of Fe(TCPP)‐MOF enhanced its interaction with oxygen. These ingenious structural features endowed Fe(TCPP)‐MOF with a unique ability to generate a large amount of singlet oxygen under ultrasound activation. Meanwhile, the impetus of ultrasound also accelerated the rate of the Fenton reaction catalyzed by iron ions, significantly boosting the generation of hydroxyl radicals. Benefiting from the dual amplification of ROS, Fe(TCPP)‐MOF could efficiently induce tumor cells pyroptosis under ultrasound stimulation, thereby intensifying the potency of cancer immunotherapy.

Innovative Synthesis Strategy of a Highly Efficient Amorphous FeS/Heteroatom-Doped Carbon Hybrid Catalyst via the Sulfur Migration and Confinement Effect for an Enhanced Fenton Reaction

Innovative Synthesis Strategy of a Highly Efficient Amorphous FeS/Heteroatom-Doped Carbon Hybrid Catalyst via the Sulfur Migration and Confinement Effect for an Enhanced Fenton Reaction

Cu Anchored Carbon Nitride (Cu/CN) Catalyzes Selective Oxidation of Thiol by Controlling Reactive Oxygen Species Generation.

Production of H2O2 using heterogeneous semiconductor photocatalysts has emerged as an ecofriendly and practical approach across various applications, ranging from environmental detoxification to fuel cells and chemical synthesis. Extensive efforts have been devoted to engineering semiconductors to enhance their catalytic capabilities for H2O2 production. However, in chemical synthesis, the utilization of the potent oxidant H2O2 can present challenges in selectively oxidizing organic compounds. In this study, we introduce copper atoms into carbon nitride (Cu/CN), facilitating the generation of hydroperoxyl radicals (·OOH) as primary reactive oxidants and offering reaction conditions entirely devoid of H2O2 via the Fenton reaction. Cu/CN demonstrates selective oxidation of thiols to disulfides, in contrast to other current heterogeneous photocatalysts that yield undesired overoxidized side products, such as thiosulfinate and thiosulfonate. Cu/CN's controllable capacity for specific ROS generation, broad substrate scopes, and recyclability empower greener and highly selective photooxidation of organic compounds.

Enhanced Fenton-Photocatalytic Degradation of Rhodamine B over Cobalt Ferrite Nanoparticles Synthesized by a Polyvinylpyrrolidone-Assisted Grinding Method.

A simple grinding method using polyvinylpyrrolidone (PVP) as a capping agent is introduced to synthesize CoFe2O4 nanoparticles. The effects of calcination temperature (ranging from 450 to 850 °C) on the structural, morphological, physical, and optical properties of the materials are investigated using various techniques, including thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), N2 adsorption isotherm, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), and vibrating sample magnetometry (VSM). The presence of PVP significantly suppresses the agglomeration of the materials, resulting in a nanocrystalline size of 18 nm for a sample calcined at 650 °C, which is approximately 38% smaller than that of the sample synthesized without PVP. Among the materials studied, the sample calcined at 650 °C exhibits unique properties, including optimal average pore size, specific surface area, and band gap energy, contributing to its superior photocatalytic degradation of rhodamine B via the Fenton reaction. Systematic experiments are performed to investigate the effects of pH, catalyst dosage, dye, and H2O2 concentrations and competitive anions on the rhodamine B degradation. Additionally, the Fenton photodegradation of RhB on CoFe2O4 is well-fitted to the first-order kinetic model. The redox pairs of Co(III)/Co(II) and Fe(III)/Fe(II) in the CoFe2O4 spinel structure might facilitate the formation of Fenton radicals, contributing to the decomposition of RhB through a proposed four-step mechanism. Notably, the material exhibits a strong magnetic response and maintains its excellent performance over five cycles, demonstrating the high potential for reusability as a photocatalyst.

CO2 protects cells from iron-Fenton oxidative DNA damage in Escherichia coli and humans

While hydroxyl radical is commonly named as the Fenton product responsible for DNA and RNA damage in cells, here we demonstrate that the cellular reaction generates carbonate radical anion due to physiological bicarbonate levels. In human and Escherichia coli models, their transcriptomes were analyzed by RNA direct nanopore sequencing of ribosomal RNA and chromatography coupled to electrochemical detection to quantify oxidation products in order to follow the bicarbonate dependency in H2O2-induced oxidation. These transcriptomic studies identified physiologically relevant levels of bicarbonate focused oxidation on the guanine base favorably yielding 8-oxo-7,8-dihydroguanine (OG). In human cells, the bicarbonate-dependent oxidation was further analyzed in the metabolome by mass spectrometry, and a glycosylase-dependent qPCR assay to quantify oxidation sites in telomeres. These analyses further identify guanine as the site of oxidation when bicarbonate is present upon H2O2 exposure. Labile iron as the catalyst for forming carbonate radical anion was demonstrated by repeating the bicarbonate-dependent oxidations in cells experiencing ferroptosis, which had a >fivefold increase in redox-active iron, to find enhanced overall guanine-specific oxidation when bicarbonate was present. The complete profiling of nucleic acid oxidation in the genome, transcriptome, and metabolome supports the conclusion that a cellular Fe(II)-carbonate complex redirects the Fenton reaction to yield carbonate radical anion. Focusing H2O2-induced oxidative modification on one pathway is consistent with the highly evolved base excision repair suite of enzymes to locate G-oxidation sites for repair and gene regulation in response to oxidative stress.

An Enzyme Mimicking Dendritic Platinum–Iron Oxide Catalyzes the Production of Reactive Oxygen Species

Creatine catalase (CAT), superoxide dismutase (SOD), and NADPH oxidase (NOX) are natural enzyme molecules that play a crucial role in regulating reactive oxygen species (ROS) in biological systems. They maintain life activities and eliminate pathogens by catalyzing various biochemical reactions. However, natural enzymes have some drawbacks in ROS control; they may lose activity under certain environmental conditions, such as high temperatures, extreme pH values, or the presence of organic solvents, which affects their stability and reliability in different applications. The construction of artificial nanozymes is an emerging technology that could probably solve the problems existing in natural enzymes. This study introduces a type of dendritic platinum–iron oxide (DPIO) nanozyme. The unique dendritic structure of this DPIO nanozyme provides a high surface area-to-volume ratio, and the addition of a platinum layer on the surface offers stability, thereby effectively enhancing the catalytic efficiency of producing reactive oxygen species (ROS). The combination of iron-based Fenton reactions and platinum-based Fenton-like reactions in this DPIO nanozyme drastically improves ROS catalytic efficiency. This artificial nanozyme has a high level of biosafety and displays no cytotoxicity. The development of DPIO nanozymes marks a significant advancement in the technology of artificial nanozymes.

Amplified Cascade Catalysis for RAFT Polymerization.

We report a conceptually new amplified cascade catalysis that converts oxygen to hydroxyl radical for controlled RAFT polymerization. This catalysis consists of two sequential reactions, deoxygenation catalyzed by glucose oxidase and Fenton reaction catalyzed by ferrocene. The two catalysts can communicate with each other, leading to ferrocene recycling and hence amplification in radical generation. Ferrocene recycling was confirmed by UV-vis spectroscopy, molecular docking simulation, electron paramagnetic resonance spectroscopy, as well as polymerization studies. This catalysis was applied to RAFT polymerization of various monomers, yielding well-defined homopolymers and diblock copolymers with controlled molecular weights and low dispersities. Poly(N,N-dimethyl acrylamide) with molecular weight over 1 million g mol-1 was also successfully synthesized under ambient conditions. Ferrocene-functionalized microspheres were prepared and used as recyclable Fenton catalyst for five consecutive polymerizations with minimal declination in monomer conversion, which further improved the ecofriendly character of this polymerization methodology.

Effect of Fenton-Based Processes on Arsenic Removal in the Presence of Humic Acid

Geogenic arsenic (As) contamination in groundwater poses a significant public health risk in many regions worldwide. Previous studies have reported hydrogen peroxide (H2O2) concentrations ranging from 5.8 to 96 μmol L−1 in rainwater, which may contribute to the oxidation and removal of As. However, the influence of natural organic matter, such as humic acid (HA), on rainwater-borne H2O2-induced Fenton processes for the oxidation and removal of As remains unclear. In this study, the Fenton process was employed to investigate changes in As(V), As(III), and their mixtures, both in the presence and absence of HA. The results showed that low concentrations of HA (0–10 mg/L) promoted the oxidation of As(III) and removal of As(V) when As(V) and As(III) were present individually. However, when As(V) and As(III) coexisted, HA inhibited the Fenton process for As(V) removal. This inhibition was likely due to As(III) competing strongly with HA for hydroxyl radicals in the Fenton reaction system. Additionally, the presence of HA hindered the Fe(III)-driven removal of As(V), a product of the Fenton reaction. These findings further enhance our understanding of the potential role of rainwater-borne H2O2 in the transformation of As species in open water environments.