Modified Fenton Reagent Research Articles

Preparation of Auricularia auricula polysaccharides and their protective effect on acute oxidative stress injury of Caenorhabditis elegans

This research enhanced the extraction procedure for Auricularia auricula crude polysaccharides by utilizing a modified Fenton reagent as a solvent, and obtained A. auricula polysaccharides (AAPs-VH) via alcohol precipitation and deproteinization. The HPLC profile revealed that the purified AAPs-VH using Sepharose 6FF was mainly a heteropolysaccharide, consisting primarily of mannose, glucuronic acid, glucose, and xylose. The Mw and Mn of the purified AAPs-VH were 87.646 kDa and 48.854 kDa, respectively. The FT-IR and NMR spectra revealed that the purified AAPs-VH belonged to pyranose and were mainly formed by (1 → 3)-linked-β-D glucan formation. In vivo experiments conducted with Caenorhabditis elegans, AAPs-VH was found to notably influence the lifespan, improve the antioxidant system, and decrease the level of cell apoptosis. This might be achieved by up-regulating the expression of genes in the IIS and TOR pathways. The study concludes that the modified Fenton reagent can increase Auricularia auricula polysaccharide solubleness and active sites, which may be an essential prompt for future studies.

Zero-Waste Approach: Assessment of Aluminum-Based Waste as a Photocatalyst for Industrial Wastewater Treatment Ecology

Alum sludge (AS) is produced in inevitable amounts from drinking water treatment plants. Also, dye-contaminating wastewater is usually discharged from textile industries that must be treated to meet the environmental authorities; thus, Fenton’s reagent is a suitable candidate. However, reducing the quantity of chemicals used in Fenton reactions can be partly achieved by an industrial ecology approach. This paper is introducing alum sludge waste as a photocatalyst, (termed as AS-Fenton), that is prepared under mild experimental conditions. Thermogravimetric and differential thermogravimetric analyses were conducted to attain full illustrations of the thermal treatment steps. Its chemical composition and morphology is revealed using X-Ray Diffraction and Scanning Electron Microscope. Thus, this research is of great significance for the application of a waste by-product for being a Fenton source for photocatalytic removal of Levafix Blue dye effluent. A new modified Fenton reagent was applied with the addition of 1.0 g/L and 800 mg/L of catalyst and H2O2, respectively, at pH 3.0 shows high potential for the dye removal. The starting concentration of the Levafix Blue CA was halved during the first 5 min under the UV illumination. The most effective operating variables are optimized through Response Surface Methodology. The kinetics of the dye removal was investigated and the reaction following the pseudo-first-order regime with the kinetic constant (KF), ranged in 0.04–0.57 min−1. Thermodynamic parameters reveal that the reaction is a non-spontaneous and endothermic in nature. Hence, toxicity of the dye is significantly reduced via Fenton reaction to non-toxic end products.

Removal of Azo Dye Acid Red 27 from Aqueous Solutions Using Classical and Modified Fenton Reagent with Zero-Valent Iron

The article compares the classic Fenton reagent (Fe2+/H2O2) with its modification with zero-valent iron (ZVI/H2O2) to remove azo dye Acid Red 27 from aqueous solutions at a concentration of 100 mg/L. For both methods, the most favorable parameter values ​​were determined at which visual discoloration of the solutions tested was obtained (for Fe2+/H2O2:pH 3.5, H2O2=60 mg/L, Fe2+/H2O2=0.3, t=15 min, and for ZVI/H2O2: pH 3, H2O2=40 mg/L, ZVI=80 mg/L, t=15 min). Under these conditions, the COD value was reduced by 71.5% and 69.2% for the classic Fenton and its modification, respectively. A reduction in toxicity was also obtained for Vibrio fischeri bacteria to below 25% by using the Microtox test. ZVI digestion at acidic pH for 10 minutes allowed to shorten the reaction time by about four times - from 15 to 4 minutes. BET analysis showed that the specific surface area increases with the digestion time, which significantly accelerates the reaction. The visual discoloration of aqueous solutions was obtained, and the final COD values ​​were very small, ranging from 49-53 mg O2/L. According to the Vibrio fischeri toxicity classification test for water samples, all solutions of dyes tested can be considered as non-toxic (toxicity value <25%). In the study presented, results of decreasing the COD value and concentration of the dye in the ZVI/H2O2 method obtained are slightly worse compared to the Fe2+/H2O2 method. However, taking the decolorisation time as a criterion, a four times faster decolorisation time was obtained in the ZVI/H2O2 method, compared to the Fe2+/H2O2 method.

Effect of various chemical oxidation reagents on soil indigenous microbial diversity in remediation of soil contaminated by PAHs

Chemical oxidation is a promising pretreatment step coupled with bioremediation for removal of polycyclic aromatic hydrocarbons (PAHs). The effectiveness of Fenton, modified Fenton, potassium permanganate and activated persulfate oxidation treatments on the real contaminated soils collected from a coal gas plant (263.6 ± 73.3 mg kg−1 of the Σ16 PAHs) and a coking plant (385.2 ± 39.6 mg kg−1 of the Σ16 PAHs) were evaluated. Microbial analyses showed only a slight impact on indigenous microbial diversity by Fenton treatment, but showed the inhibition of microbial diversity and delayed population recovery by potassium permanganate reagent. After potassium permanganate treatment, the microorganism mainly existed in the soil was Pseudomonas or Pseudomonadaceae. The results showed that total organic carbon (TOC) content in soil was significantly increased by adding modified Fenton reagent (1.4%–2.3%), while decreased by adding potassium permanganate (0.2%–1%), owing to the nonspecific and different oxidative properties of chemical oxidant. The results also demonstrated that the removal efficiency of total PAHs was ordered: permanganate (90.0%–92.4%) > activated persulfate (81.5%–86.54%) > modified Fenton (81.5%–85.4%) > Fenton (54.1%–60.0%). Furthermore, the PAHs removal efficiency was slightly increased on the 7th day after Fenton and modified Fenton treatments, about 14.6%, and 14.4% respectively, and the PAHs removal efficiency only enhanced 4.1% and 1.3% respectively from 1st to 15th day after potassium permanganate and activated persulfate treatments. The oxidants greatly affect the growth of soil indigenous microbes, which cause further influence for PAHs degradation by bioremediation.

Enhanced degradation of polycyclic aromatic hydrocarbons by indigenous microbes combined with chemical oxidation

In this study, the removal efficiency PAHs by chemical oxidation combined with microbe remediation was evaluated in two contaminated soils. The number of indigenous soil microbes decreased after the addition of chemical oxidants and then increased by nutrients addition. The total removal efficiencies of PAHs by chemical oxidation and nutrient addition followed the order: activated persulfate > potassium permanganate > modified Fenton reagent > Fenton reagent. There are 24.29–27.97%, 22.00–23.67%, 10.24–13.74% and 1.9–2.5% contributions separately due to nutrient treatment in Fenton, modified Fenton, activated persulfate and potassium permanganate treatment, which show significantly difference. The different chemical oxidants exhibited 78–90% removal efficiency for 5–6 rings PAHs, while 52–85% removal efficiency for 2–4 rings PAHs. With the addition of nutrients, the growth of indigenous microbes was enhanced significantly, and the contents of 2–4 rings PAHs in the soil were further decreased. Furthermore, the removal efficiencies of NAP and ANY were increased by more than 45%, while the removal efficiencies of ANE, FLE and PHE were about 30% at Fenton system. There was a complementary enhancing effect of microbial remediation for PAHs degradation after chemical oxidation.

Challenges of soil mixing using catalyzed hydrogen peroxide with rotating dual axis blending technology

AbstractAlthough known to be one of the most effective oxidants for treatment of organic contaminants, catalyzed hydrogen peroxide (CHP) is typically not used for soil mixing applications because of health and safety concerns related to vapor generation and very rapid rates of reaction in open excavations. In likely the first large‐scale in situ CHP soil mixing application, an enhanced CHP, modified Fenton's reagent (MFR), was applied during soil mixing at the Kearsarge Metallurgical Superfund Site in New Hampshire. An innovative rotating dual‐axis blender (DAB) technology was used to safely mix the MFR into low‐plasticity silt and clay soils to remediate residual 1,1,1‐trichloroethane (111TCA); 1,1‐dichloroethene (11DCE); and 1,4‐dioxane (14D). It was expected that the aggressive treatment approach using relatively “greener” hydrogen peroxide (HP) chemistry would effectively treat Site contaminants without significant byproduct impacts to groundwater or the adjacent pond. The remediation program was designed to treat approximately 3,000 cubic yards of residual source area soil in situ by aggressively mixing MFR into the soils. The subsurface interval treated was from 7 to 15 feet below ground surface. To accurately track the soil mixing process and MFR addition, the Site was divided into 109 10‐foot square treatment cells that were precisely located, dosed, and mixed using the DAB equipped with an on‐board GPS system. The use of stabilizing agents along with careful calculation of the peroxide dose helped to ensure vapor‐free conditions in the vicinity of the soil mixing operation. Real‐time sampling and monitoring were critical in identifying any posttreatment exceedences of the cleanup goals. This allowed retreatment and supplemental testing to occur without impacting the soil mixing/in situ chemical oxidation (ISCO) schedule. Posttreatment 24‐hr soil samples were collected from 56 random locations after ensuring that the HP had been completely consumed. The posttreatment test results showed that 111TCA and 11DCE concentrations were reduced to nondetect (ND) or below the cleanup goals of 150 μg/kg for 111TCA and 60 μg/kg for 11DCE. Supplemental posttreatment soil samples, collected six months after treatment, showed 100 percent compliance with the soil treatment goals. Groundwater samples collected one year after the MFR soil mixing treatment program showed either ND or low concentrations for 111TCA, 11DCE, and 14D. Successful stabilization and site restoration was performed after overcoming considerable challenges associated with loss of soil structure, high liquid content, and reduced bearing capacity of the blended soils.

Remediation of soil contaminated by NAPLs using modified Fenton reagent: application to gasoline type compounds

AbstractBACKGROUNDA modified Fenton reaction was used for the remediation of a soil polluted with ethylbenzene (EB), a toxic compound in gasoline. Fe(III) and trisodium citrate were used as catalyst and chelating agent, respectively. pH remained near‐neutral during the process. Contaminant, chelating agent, oxidant and iron in solution were monitored at all times. A comparison between slurry (aqueous‐organic and soil phases) and liquid systems (aqueous‐organic phases) was carried out.RESULTSEB conversion increased as H2O2/EB ratios rose, for a given EB concentration. Furthermore, the contaminant conversion was decreased as the EB concentration increased, at a fixed H2O2/EB ratio. This indicates that the reaction takes place in the aqueous phase, with the oxidation rate limited by the EB concentration in this phase. The presence of soil produces a better contact between phases, enhancing EB transport from the organic to the aqueous phase. As EB was oxidized in the aqueous phase, the toxicity of this phase decreased, because non‐toxic oxidation byproducts were obtained. The chelant was oxidized, but not totally mineralized. This chelant oxidation produces precipitation of the catalyst from the aqueous phase.CONCLUSIONSThe results suggest the suitability of modified Fenton reaction to remediate contaminated soils with non‐aqueous phase liquids. © 2014 Society of Chemical Industry

Mobilization of metals during treatment of contaminated soils by modified Fenton's reagent using different chelating agents

Changes in pH and redox conditions and the application of chelating agents when applying in situ chemical oxidation (ISCO) for remediation of contaminated sites can cause mobilization of metals to the groundwater above threshold limit values. The mechanisms causing the mobilization are not fully understood and have only been investigated in few studies. The present work investigated the mobilization of 9 metals from two very different contaminated soils in bench and pilot tests during treatment with modified Fenton's reagent (MFR) and found significant mobilization of Cu and Pb to the water in mg/l levels. Also Fe, As, Mn, Ni, Zn, Mg, and Ca mobilization was observed. These findings were confirmed in a pilot test where concentrations of Cu and Pb up to 52.2 and 33.7 mg/l were observed, respectively. Overall, the chelating agents tested (EDTA, citrate and pyrophosphate) did not seem to increase mobilization of metals compared to treatment with only hydrogen peroxide and iron. The results strongly indicate that the mobilization is caused by hydrogen peroxide and reactive species including oxidants and reductants formed with MFR. Based on these results, the use of chelating agents for ISCO will not cause an increase in metal mobilization.

Inorganic chelated modified-Fenton treatment of polycyclic aromatic hydrocarbon (PAH)-contaminated soils

In this work, the effects of chelating agent (CA) on the removal of phenanthrene (PHE) and fluoranthene (FLUT) from contaminated soil through modified-Fenton (MF) treatment at natural soil pH have been investigated. Chelate enhanced MF treatment resulted in rapid PAH degradation that obeyed pseudo-first-order kinetics with rate constants within the ranges of 9.15 × 10 −2 to 2.30 × 10 −1 min −1 and 7.20 × 10 −2 to 2.34 × 10 −1 min −1 for PHE and FLUT respectively. Inorganic CA sodium pyrophosphate (SP) was demonstrated to be superior to commonly employed organic CAs such as ethylene diamine tetraacetic acid, oxalic acid and sodium citrate, and resulted in PAH removal efficiencies of up to 89.13%. The compatibility of SP was also tested for persulphate enhanced oxidation of PAH-contaminated soil. Remarkable oxidative PAH removals (95.41% and 92.25% for PHE and FLUT respectively) were observed in the persulphate-MF treatment which suggested the feasibility of integrated MF reagent in treating PAH-contaminated soil.

Remediation of Water Contaminated with Herbicide Oxadiazon Using Fenton Reagent

The remediation of water contaminated with herbicide oxadiazon was investigated by applying modified Fenton reagent (Fe3+/H2O2) at unadjusted pH. Experimental conditions in various reactions allowed for the disappearance of oxadiazon. When using Fenton reagent, the maximum degradation rate was obtained under exposure to UV irradiation as compared to dark condition in which the concentrations of ferric ion and hydrogen peroxide were 3 and 100 mM, respectively. After 5 h of photocatalytic treatment with Fenton reagent, 98.4% of the oxadiazon was degraded. The high degradation rate of this herbicide was achieved by hydroxyl radicals (OH.), which were generated by the photocatalytic treatment. UV irradiation accelerated the degradation of oxadiazon in the water system in the presence of Fenton reagent. In addition, the disappearance of oxadiazon was enhanced due to the increased concentrations of ferric ion and/or hydrogen peroxide. For the photo-Fenton reaction, one metabolite (m/z 310) was able to be identified using the GC-MS technique due to dechlorination of oxadiazon. Conclusively, a remediation strategy using Fenton reagent could be applied to degrade oxadiazon from contaminated water.

Oxidation of sulfamethoxazole by UVA radiation and modified Fenton reagent: toxicity and biodegradability of by-products

Improvement of sulfamethoxazole (4-amino-N-(5-methylisoxazol-3-yl)-benzenesulfonamide-SMX) biodegradability using a modified Fenton's reaction has been studied. The modification consists of replacing hydrogen peroxide with atmospheric air and adding copper sulphate as a reaction promoter. Two series of experiments were carried out. The first (Series 1) was conducted using only the catalysts with aeration. In the second series (Series 2), cycles of UVA radiation and aeration were used. During UVA radiation, the removal of sulfamethoxazole proceeds less rapidly than in only aerated solution. After 1.5 h of these two processes, the SMX degradation was 23% in Series 2 and 59% in Series 1. The opposite trend was observed for mineralization and the removal of DOC was about 5% higher in Series 2 than in Series 1. The FTIR spectra of the extracts of reaction products yielded by four organic solvents of varying polarity revealed a wide diversity of functional groups in the post-reaction mixture in comparison to the extracts from sulfamethoxazole solution. Based on FTIR analysis, several oxidation products of sulfamethoxazole are proposed. Apparently, hydroxyl radicals initially attack sulphonamide bonds, resulting in the formation of sulfanilic acid and 3-amino-5-methylisoxazole. Irrespective of the reference organism used in toxicity tests, the post-reaction mixture in the Series 2 was more toxic than the post-reaction mixture in Series 1. In contrast, the biodegradability calculated as BOD(5)/DOC ratio, was higher for post-reaction mixture 2 and amounted to 0.43.

Covalently bound fluorescent probes as reporters for hydroxyl radical penetration into liposomal membranes

The ability of hydroxyl radicals to penetrate into liposomal model membranes (dimyristoylphosphatidylcholine) has been demonstrated. Liposomes were prepared and then characterized by digital fluorescence microscopy and dynamic light scattering after extrusion to determine liposomal lamellarity, size, and shape. Hydroxyl radicals were generated in the surrounding aqueous medium using a modified Fenton reagent (hydrogen peroxide and Fe 2+) with the water-soluble iron chelator EDTA. High and low doses of radical were used, and the low dose was achieved with physiologically relevant iron and peroxide concentrations. Fluorescent probes covalently bound to the membrane phospholipid were used, including two lipophilic pyrenyl probes within the membrane bilayer and one polar probe at the water–membrane interface. Radical reactions with the probes were monitored by following the decrease in fluorescence and by observing oxidation products via matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Differences in the probe position within the membrane were correlated with the reactivity of the probe to assess radical access to the site of the probe. For all probes, reaction rates increased with increasing temperature. Within the membrane bilayer, reaction rates were greater for the probe closest to the membrane–water interface. Cholesterol protected these probes from oxidation. Kinetic models, scavenger studies, and product identification studies indicated that hydroxyl radical reacted directly with the in-membrane probes without the mediation of a secondary radical.

Humic acid modified Fenton reagent for enhancement of the working pH range

The suitability of the Fenton process for the remediation of soil and groundwater is limited by the necessity to acidify the reaction medium. This study examines the applicability of humic acid (HA) as an iron chelator in a modified Fenton system with the aim of extending the optimum pH range for this process towards neutral conditions. Addition of HA at a concentration of 50–100mgL−1 greatly enhances the rate of oxidation of organic compounds in a catalytic Fenton system in the range of pH 5–7. Similar rates at pH 5 in the presence of HA can be achieved as at pH 3 for a typical Fenton process in the absence of HA (k′=9×10−3min−1 for benzene degradation at cH2O2=0.13 M). A comparison of the relative reactivities of various model compounds supported the hypothesis that OH radicals are the main reactive species in the HA-modified Fenton system. In contrast, however, another type of chelated Fe-catalyst (Fe-TAML) proved to be more selective than expected for OH radicals. A long-term study revealed that the HA itself is oxidized and thereby loses its ability to enhance the degradation of the pollutant molecules. Therefore, the HA-modified Fenton system is effective for degrading pollutants which are at least as reactive towards OH radicals as the HA itself, such as BTEX, phenols or PAHs. The results obtained indicate that the HA-modified Fenton system is also applicable for compounds with a high sorption tendency towards HA.

The role of EDTA in malonaldehyde formation from DNA oxidized by Fenton reagent systems.

Calf thymus DNA was oxidized by various Fenton reagent systems [Fe(II)/H(2)O(2)] with or without ethylenediamine tetraacetic acid (EDTA) under different reaction conditions. Calf DNA was also oxidized by a modified Fenton reagent (Fe(III)/H(2)O(2)/ascorbic acid) with EDTA. Malonaldehyde (MA) formed from DNA was derivatized into 1-methyl hydrazine, which was subsequently analyzed by gas chromatography with a nitrogen-phosphorus detector. MA formation increased linearly with an increase of Fe(II) concentration. MA formation reached a plateau at nearly 2 mmol/L of Fe(II) with 0.5 mmol/L of H(2)O(2). Addition of EDTA increased MA formation from DNA nearly 5 times. When DNA was oxidized with various amount of ethanol, MA formation decreased with an increase of ethanol concentration, either with or without EDTA. The rate of inhibition was greater without EDTA than with EDTA. When DNA was oxidized by a modified Fenton reagent, MA formation linearly increased with the increase of DNA. Ascorbic acid alone produced some MA upon oxidation.

Killing of Bacillus subtilis spores by a modified Fenton reagent containing CuCl2 and ascorbic acid.

Bacillus subtilis spores were killed by CuCl(2)-ascorbic acid, chloride ions were essential for killing of spores, and spores with defective coats were killed more rapidly. CuCl(2)-ascorbic acid did not damage spore DNA, and spores killed by this reagent initiated germination. However, spores killed by CuCl(2)-ascorbic acid may have damage to their inner membrane.

Killing of bacillus spores by aqueous dissolved oxygen, ascorbic acid, and copper ions.

An approach to decontamination of biological endospores is discussed. Specifically, the performance of an aqueous modified Fenton reagent is examined. A modified Fenton reagent formulation of cupric chloride, ascorbic acid, and sodium chloride is shown to be an effective sporicide under aerobic conditions. The traditional Fenton reaction involves the conversion of hydrogen peroxide to hydroxyl radical by aqueous ionic catalysts such as the transition metal ions. Our modified Fenton reaction involves the conversion of aqueous dissolved oxygen to hydrogen peroxide by an ionic catalyst (Cu(2+)) and then subsequent conversion to hydroxyl radicals. Results are given for the modified Fenton reagent deactivating spores of Bacillus globigii. A biocidal mechanism is proposed that is consistent with our experimental results and independently derived information found in the literature. This mechanism requires diffusion of relatively benign species into the interior of the spore, where dissolved O(2) is then converted through a series of reactions which ultimately produce hydroxyl radicals that perform the killing action.

Oxidizing 2,4,6-trinitrotoluene with pyrite-H 2O 2 suspensions

A modified Fenton reagent, using solid pyrite in the place of soluble ferrous iron salt, has been used to clean-up pure water spiked with 2,4,6-trinitrotoluene (TNT). Water treatment was conducted at pH 3 with 1.8–28.6 mM Fe (II) (as pyrite) + 0.015-0.029 M of H 2O 2 and compared with Classic Fenton (CF) reaction: 1.8 mM Fe (II) (as ferrous sulfate) + 0.029-0.29 M H 2O 2. All experiments were conducted in the dark and in the light by using an artificial light source of 200-W. The pseudo-first order rate constant, k, of TNT degradation did not significantly increased as a function of peroxide addition like in CF reagent, where all Fe (II) was in solution. When both reagents were used at the concentrations of 1.8 mM Fe (II) + 0.029 M H 2O 2 complete oxidation of TNT with modified Fenton reagent was slower respect to classic Fenton reagent (48 h vs. 24 h). However mineralization of TNT with 1.8 mM Fe(II) from pyrite + 0.029 M H 2O 2 under Dark/Light conditions was of the same order of magnitude ( 42 85 %) as with CF using a 10 times higher concentration of peroxide (0.29 M H 2O 2). Even though reuse of oxidized pyrite after a first oxidation treatment, prolonged the time of TNT disappearance from a second solution (48 h vs 24 h with 5.4 mM Fe 2+ from pyrite + 0.029 M H 2O 2) the extent of mineralization remained unvaried (− 45%).