FENTON AND FENTON-LIKE AOPs FOR ALUM SLUDGE CONDITIONING: EFFECTIVENESS COMPARISON WITH DIFFERENT Fe2+ AND Fe3+ SALTS

Currently, organic polymers are adopted in alum sludge (aluminum-coagulated drinking water treatment sludge) conditioning. However, there are important concerns regarding the use of these polymers because of the unknown and long-term effects of the potential release of excess polymer to the surrounding environment when the sludge is landfilled. Therefore, as an initial action, this study aimed at investigating alternative chemical conditioning methods and focused mainly on exploiting Fenton (Fe²⁺/H₂O₂) and Fenton-like (Fe³⁺/H₂O₂) reagents as the conditioner. Experiments have been conducted to test the effectiveness of Fenton's reagent (containing the ferrous salts of chloride, sulfate, or oxalate), Fenton-like reagent (containing ferric salts of chloride and sulfate), and the coagulation method using FeCl₃ for alum sludge conditioning at constant hydrogen peroxide and iron salt concentrations of 125 and 20 mg/g DS (dry solids), respectively. The effectiveness on dewaterability of the alum sludge demonstrated that the maximum reduction (%) of SRF (specific resistance to filtration) and CST (capillary suction time) of 74% and 47%, respectively, can be obtained when Fenton's reagent was adopted for sludge conditioning. Such reduction of 64% for SRF and 38% for CST can be achieved when Fenton-like reagents were applied.     

Kinetics and reaction mechanism of fenton's-reagent-initiated graft copolymerization of acrylonitrile onto sodium alginate

The kinetics and mechanism of grafting of acrylonitrile (AN) onto sodium alginate (SA) using Fenton's reagent (Fe²⁺–H₂O₂) has been studied. The experimental results are found to be in good agreement with the proposed kinetic scheme. © 1994 John Wiley & Sons, Inc.     

Post-Treatment of Pulp and Paper Industry Wastewater by Advanced Oxidation Processes

The aim of this study was to investigate the effectiveness of chemical oxidation by applying ozonation, combination of ozone and hydrogen peroxide and Fenton's processes for decolorization and residual chemical oxygen demand (COD) removal of biologically pretreated pulp and paper industry effluents. The batch tests were performed to determine the optimum operating conditions including pH, O₃, H₂O_2, and Fe²⁺ dosages. H₂O₂ addition reduced the reaction times for the same ozone dosages; however combinations of ozone/hydrogen peroxide were only faintly more effective than ozone alone for COD and color removals. In the Fenton‘s oxidation studies, the removal efficiencies of COD, color and ultraviolet absorbance at 254 nm (UV₂₅₄) for biologically treated pulp and paper industry effluents were found to be about 83, 95, and 89%, respectively. Experimental studies indicated that Fenton oxidation was a more effective process for the reduction of COD, color, and UV₂₅₄when compared to ozonation and ozone/hydrogen peroxide combination. Fenton oxidation was found to have less operating cost for color removal from wastewater per cubic meter than the cost for ozone and ozone/hydrogen peroxide applications.     

Removal of diazinon by various advanced oxidation processes

Diazinon is a widely used organophosphorus insecticide that is an important pollutant in aquatic environments. The chemical removal of diazinon has been studied using UV radiation, ozone, Fenton's reagent, UV radiation plus hydrogen peroxide, ozone plus hydrogen peroxide and photo‐Fenton as oxidation processes. In the photodegradation process the observed quantum yields had values ranging between 2.42 × 10^?2 and 6.36 × 10^?2 mol E^?1. Similarly, the ozonation reaction gave values for the rate constant ranging between 0.100 and 0.193 min^?1. In the combined systems UV/H₂O₂ and O₃/H₂O₂ the partial contributions to the global oxidation reaction of the direct and radical pathways were deduced. In the Fenton's reagent and photo‐Fenton systems, the mechanism of reaction has been partially discussed, and the predominant role of the radical pathway pointed out. Additionally, the rate constant for the reaction between diazinon and the hydroxyl radicals was determined, with the value 8.4 × 10⁹ L mol^?1 s^?1 obtained. A comparison of the different oxidation systems tested under the same operating conditions revealed that UV radiation alone had a moderate oxidation efficiency, which is enhanced in the case of ozone, while the most efficient oxidant is the photo‐Fenton system. Copyright © 2007 Society of Chemical Industry     

Kinetics of the Decolorization by Fenton's Reagent

Fenton's reagent was employed in the decolorization of aqueous solutions of one of three dyestuffs (Acid Red 27, Reactive Blue 81, Acid Blue 62). The decolorization with Fenton's reagent was found to be simple and fast. In order to determine the reaction kinetics of the decolorization the stopped-flow technique under pseudo-first order conditions was used. Experiments were carried out at pH=2, at the excess of ferrous salts (FeCl₂·4H₂O or FeSO₄·7H₂O). The rate constants of the decolorization determined by us are in the same order of magnitude: 90 to 100 dm³/(mol-s) for FeSO₄·7H₂O/H₂O₂, and 40 to 50 dm³/(mol-s) for FeCl₂·4H₂O/H₂O₂ systems. The difference between the rate constants for both ferrous salts indicates that the Fenton's reaction may proceed via different mechanisms.     

The mechanism and application of the electro‐Fenton process for azo dye Acid Red 14 degradation using an activated carbon fibre felt cathode

BACKGROUND: The discharge of azo dyes into the environment poses concerns due to their limited biodegradability. The electro‐Fenton process (EF) is a good method to effectively degrade these dyes. The aim of this work was to study the mechanism and the feasibility of the EF reaction using an activated carbon fibre (ACF) cathode. In this study, two methods were used to measure the reactive species generated in anodic oxidation (AO), anodic oxidation with electrogenerated H₂O₂ (AO‐H₂O₂) and the EF process. Acid Red 14 (AR14) was chosen as a model pollutant. The effects of the operational parameters, pH and initial concentrations were investigated. A short‐term biodegradability test was also carried out to evaluate the EF process from a biological point of view. RESULTS: After 2 h EF reaction 118.7 µmol L^?1?OH were produced, which was much higher than that of the AO‐H₂O₂ (63.2 µmol L^?1) process. H₂O₂ is largely generated and Fe³⁺ efficiently reduced on the high surface area of the ACF cathode. The EF process provides more effective degradation of AR14 than the conventional Fenton process, and its current efficiency is significantly affected by the initial pH and the initial AR14 concentration. Following EF treatment, the biodegradability of AR14 is significantly increased. CONCLUSION: The higher formation of ^?OH in the EF process suggests it is an effective method for pollutant removal. This process also leads to increased biodegradability, which is expected to facilitate subsequent biological treatment. Copyright © 2010 Society of Chemical Industry     

An oxidative desulfurization method using ultrasound/Fenton's reagent for obtaining low and/or ultra-low sulfur diesel fuel

The total development trend in the world is towards continuously lower of sulfur content as a quality standard of diesel fuels. Integrating of an oxidative desulfurization unit with a conventional hydrotreating unit can bring benefits to producing low and/or ultra-low sulfur diesel fuels. Using the hydrotreated Middle East diesel fuel as a feedstock, four processes of the oxidative desulfurization have been studied: a hydrogen peroxide–acetic acid system and a Fenton's reagent system both without/with ultrasound. Results showed that the oxidative desulfurization reaction mechanics fitted apparent first-order kinetics. The addition of Fenton's reagent could enhance the oxidative desulfurization efficiency for diesel fuels and sono-oxidation treatment in combination with Fenton's reagent shows a good synergistic effect. Under our best operating condition for the oxidative desulfurization: temperature 313 K, ultrasonic power 200 W, ultrasonic frequency 28 kHz, Fe²⁺/H₂O₂ 0.05 mol/mol, pH 2.10 in aqueous phase and reaction time 15 min, the sulfur content in the diesel fuels was decreased from 568.75 μg/g to 9.50 μg/g.     

Degradation of 2,4-dichlorophenol in aqueous solution by sono-Fenton method

This study presents the results of the Sono-Fenton process for the degradation of 2,4-dichlorophenol (DCP). The influential parameters such as H₂O₂, Fe²⁺ and pH for the Sono-Fenton process were investigated. Sono-Fenton method was found to be the best one for degradation efficiency of DCP when compared with that of the Fenton process. The optimum concentrations for the degradation of DCP using conventional Fenton’s method were found to be 20 mg/L of Fe²⁺ and 580 mg/L of H₂O₂ at pH 2.5. In the case of Sono-Fenton, the optimal concentrations were found to be 10 mg/L of Fe²⁺ and 400 mg/L of H₂O₂ at pH 2.5. Sono-Fenton method resulted in the reduction of required Fe²⁺ concentration (50%) and H₂O₂ concentration (31%). In addition, this method could be applicable even at pH 5.0 and a degradation efficiency of DCP was 77.6%. Kinetic studies for the degradation of DCP proved that the degradation of DCP tends to follow pseudo first order reaction and the rate constant was found to be 7 × 10⁻⁴ min⁻¹.     

Degradation of C.I. Acid Red 88 aqueous solution by combination of Fenton's reagent and ultrasound irradiation

BACKGROUND: Pollution caused by industrial wastewater has become a common problem for many countries. In particular, dye pollutions from industrial effluents disturb human health and ecological equilibrium. The discharge of highly colored synthetic dye effluents is aesthetically displeasing and can damage the receiving water body by impeding penetration of light. Azo dyes can be reduced to more hazardous intermediates on anaerobic conditions. Therefore, an effective and economic treatment of effluents containing a diversity of textile dyes has become a necessity for clean production technology for textile industries. Herein we wish to report the degradation of Acid Red 88 by the combination of Fenton's reagent and ultrasound irradiation. RESULTS: The results show that the combination of ultrasonic irradiation and Fenton's reagent is effective for the degradation of Acid Red 88 aqueous solution. Furthermore, it can achieve better results than either Fenton's reagent or ultrasound alone. The optimum conditions for the degradation of Acid Red 88 aqueous solution were 1.96 mmol L^?1 H₂O₂, 0.108 mmol L^?1 Fe²⁺, pH 3.0, and ultrasonic irradiation frequency of 40 kHz. A degradation efficiency of 98.6% was achieved within 135 min. CONCLUSION: We have provided an efficient and convenient procedure for the degradation of Acid Red 88 aqueous solution. In the present procedure, the azo linkage of Acid Red 88 is broken and some carbonyl compounds are formed, but the complete mineralization of dye cannot be achieved. Copyright © 2008 Society of Chemical Industry     

A novel Electro-Fenton-Like system using PW11O39Fe(III)(H2O) as an electrocatalyst for wastewater treatment

A novel Electro-Fenton-Like (EFL) system was developed using the Keggin-type iron-substituted heteropolytungstate anion PW₁₁O₃₉Fe(III)(H₂O)⁴⁻ to substitute for Fe³⁺ in the conventional Electro-Fenton (EF) system for treatment of water polluted with organic compounds. The EFL system overcomes the drawback of low pH in conventional EF approaches and can be directly applied to neutral water treatment without any pH adjustment. Experimental results for dimethylphthalate (DMP) revealed complete degradation in <80 min in pH 6.86 solution containing 0.1 mM DMP at a potential of −0.5 V and O₂ flow rate of 60 mL min⁻¹. Total organic carbon removal of ∼56% was achieved at 120 min. Comparison with conventional EF oxidation revealed better efficiency of the present system for DMP degradation, suggesting its potential in treatment of water and wastewater with a relaxed pH requirement. The cumulative H₂O₂ concentration generated in situ at the electrode was monitored and the observed degradation rate constants k_obs were determined for different initial DMP concentrations. The ligand exchange reaction of PW₁₁O₃₉Fe(III)(H₂O)⁴⁻ with H₂O₂ and the electron transfer resulting in hydroxyl radicals were examined using HPLC and electrochemical impedance spectroscopy. An electrocatalytic model involving inner-sphere electron transfer and a reaction mechanism for PW₁₁O₃₉Fe(III)(H₂O)⁴⁻ electrocatalytic reduction of H₂O₂ are proposed.     

Sewage sludge treatment using microwave‐enhanced advanced oxidation processes with and without ferrous sulfate addition

BACKGROUND: Microwave‐enhanced advanced oxidation processes with and without the addition of ferrous sulfate (MW/H₂O₂/Fe²⁺‐AOP and MW/H₂O₂‐AOP respectively) were studied for reduction of solids and solubilisation of nutrients from secondary sewage sludge. RESULTS: For the MW/H₂O₂/Fe²⁺‐AOP the yields of solubilisation of orthophosphate and ammonia decreased with increasing temperature. The best results (88.1 mg L^?1 for orthophosphate and 22.7 mg L^?1 for ammonia) were obtained at a treatment temperature of 40 °C. In contrast, the MW/H₂O₂‐AOP had an advantage when it was operated at higher temperatures of 60 and 80 °C. The highest yields of solubilisation were obtained at 60 °C for orthophosphate (81.1 mg L^?1) and at 80 °C for both ammonia (35.0 mg L^?1) and soluble chemical oxygen demand (1954 mg L^?1). Over the temperature range used in this study, the MW/H₂O₂‐AOP gave a better performance than the MW/H₂O₂/Fe²⁺‐AOP. CONCLUSION: For sewage sludge treatment the MW/H₂O₂‐AOP is more effective than the MW/H₂O₂/Fe²⁺‐AOP in terms of solid reduction and nutrient solubilisation. It will also be more cost‐effective, as it does not require iron addition in the process. Copyright © 2008 Society of Chemical Industry     

3D rectangular WO3 hybridized by PrFeO3 nanoparticles with efficient dual charge transfer for enhanced photo-Fenton-like activity

In this work, zero-dimensional (0D) high crystalline PrFeO₃ worm nanocrystals were loaded over a three-dimensional (3D) rectangular WO₃ to construct a 0D/3D PFO/W Z-scheme heterojunction by an in situ ultrasonic synthetic process. This heterojunction exhibited excellent photocatalytic activities towards the degradation of organic pollutants such as rhodamine B (RhB), Methylene blue (MB), and tetracycline hydrochloride (TC) in the presence of small amounts of H₂O₂ under visible-light irradiation. For example, the k value of PFO/W + H₂O₂ was about 67, 107, 45, 27, 11 and 14 times higher than pure H₂O₂, PrFeO₃, WO₃, PFO/W nanocomposite, PrFeO₃+ H₂O₂ and WO₃+H₂O₂ respectively during the degradation of MB. The trapping experiments and ESR measurements identified that the generated ·OH, ·O₂⁻, and h⁺ were the active species involved in the catalysis. Further, the ·OH radical could be continuously generated by Fe³⁺/Fe²⁺ and W⁶⁺/W⁵⁺ conversion and played the dominant role in the degradation of organic pollutants. The superior photocatalytic performance of the PFO/W + H₂O₂ system was derived from the synergistic effect of the Z-scheme heterostructure and dual photo-Fenton-like oxidation (Fe³⁺/Fe²⁺ and W⁶⁺/W⁵⁺). A possible mechanism was postulated based on the results obtained. In summary, this study provided new insights into synthesizing an effectively heterogeneous 0D/3D Z-scheme dual photo-Fenton-like catalyst for water clarification.     

Photo Assisted Fenton in a Batch and a Membrane Reactor for Degradation of Drugs in Water

Abstract

Some advanced oxidation processes (AOP's) such as Fenton H₂O₂/Fe²⁺, photo assisted Fenton UV/H₂O₂/Fe²⁺, UV photolysis, and photo assisted Fenton—like UV/O₂/Fe²⁺ have been tested for the degradation of Gemfibrozil in aqueous solution in a batch system and then in a membrane reactor. A nanofiltration/reverse osmosis type cross‐linked polyamide, UTC‐60 (Toray) membrane (19 cm²) was used. In the batch degradation tests, the gemfibrozil, used at 5 mg/L, was degraded by employing the four AOP's but numerous peaks of intermediates were observed at the HPLC. Indeed DOC analyses showed poor mineralization in the case of photolysis (3.1%) and UV/O₂/Fe (10%), while it was 62% using the photo assisted Fenton and 24% using the Fenton. Thus in the membrane reactor only the Fenton and the photo assisted Fenton were tested. Obtained results showed a drug degradation higher than 92%, a mineralization higher than 55%, and a membrane retention of the catalyst in solution higher than 95%.     

Degradation of the beta-blocker propranolol by electrochemical advanced oxidation processes based on Fenton's reaction chemistry using a boron-doped diamond anode

The electro-Fenton (EF) and photoelectro-Fenton (PEF) degradation of solutions of the beta-blocker propranolol hydrochloride with 0.5 mmol dm⁻³ Fe²⁺ at pH 3.0 has been studied using a single cell with a boron-doped diamond (BDD) anode and an air diffusion cathode (ADE) for H₂O₂ electrogeneration and a combined cell containing the above BDD/ADE pair coupled in parallel to a Pt/carbon felt (CF) cell. This naphthalene derivative can be mineralized by both methods with a BDD anode. Almost overall mineralization is attained for the PEF treatments, more rapidly with the combined system due to the generation of higher amounts of hydroxyl radical from Fenton's reaction by the continuous Fe²⁺ regeneration at the CF cathode, accelerating the oxidation of organics to Fe(III)-carboxylate complexes that are more quickly photolyzed by UVA light. The homologous EF processes are less potent giving partial mineralization. The effect of current density, pH and Fe²⁺ and drug concentrations on the oxidation power of PEF process in combined cell is examined. Propranolol decay follows a pseudo first-order reaction in most cases. Aromatic intermediates such as 1-naphthol and phthalic acid and generated carboxylic acids such as maleic, formic, oxalic and oxamic are detected and quantified by high-performance liquid chromatography. The chloride ions present in the starting solution are slowly oxidized at the BDD anode. In PEF treatments, all initial N of propranolol is completely transformed into inorganic ions, with predominance of NH₄⁺ over NO₃⁻ ion.     

Mercury removal from coal combustion by Fenton reactions – Part A: Bench-scale tests

This series of papers describes the development of technology to convert Hg(0) to Hg(II) in coal-derived flue gas based on the well-known Fenton reactions so that a Hg control strategy can be implemented in a wet scrubber. This effort consists of both bench-scale and pilot-scale work. This first paper reports on the bench-scale tests. The bench-scale results showed that Hg(0) oxidation can be achieved by the Fenton reactions and the oxidation rate is quantitatively dependent on the residence time of the Hg stream in the solution. An average of 75% oxidation of Hg(0) was achieved. Iron-based Fenton-type additives gave much more promising results compared to Cu-based Fenton-like additives for Hg(0) oxidation. The pH value of the sorbent solution also had a significant effect on the oxidation of Hg(0) and a suitable pH window was found to lie between 1.0 and 3.0 for this application. This may be attributed to the chain reaction mechanisms of Fe³⁺/H₂O₂ for Fenton reactions, i.e., the decomposition of H₂O₂ for the production of OOH radicals in the Fe³⁺/H₂O₂ system which is kinetically favoured under a wide range of conditions at pH values of 3 or less. At higher pH values, H₂O₂ is converted to H₂O instead of OOH radicals in the presence of Fe³⁺.     

Oxidation of Esculetin,a Model Pollutant Present in Cork Processing Wastewaters,by Chemical Methods

The ozonation of esculetin (6,7-dihydroxycoumarin), a major pollutant present in the wastewater generated in the cork industry, was accelerated at high pH, with apparent second-order rate constants in the range from 3.3 × 10⁴ L/(mol·s) at pH=2 to 8.4 × 10⁷ L/(mol·s) at pH=9. The acid-base equilibrium of esculetin was studied, resulting in a pK_a value of 7.37. Taking into account this pK_a, the rate constants for the reaction between ozone and the un dissociated and dissociated forms of esculetin were 3.0 × 10⁴ and L/(mol·s) 6.67 × 10⁸ L/(mol·s), respectively. Apparent first-order rate constants for the photolysis by UV irradiation were also evaluated, with values between 0.12 × 10^?2 min^?1 at pH=2 and 1.15 × 10^?2 min^?1 at pH=9, while the quantum yields for this photo-degradation reaction varied from 0.99 × 10^?2 mol/Eins to 11.1 × 10^?2 mol/Eins at these pHs. The Fenton's reagent system was used for the generation of hydroxyl radicals, and the rate constant for the reaction between esculetin and these radicals was determined to be 1.06 × 10¹⁰ L/(mol·s). Finally, several chemical oxidation systems were used in the degradation of this pollutant: single oxidants (ozone, UV irradiation) and advanced oxidation processes (Fenton's reagent, UV/H₂O₂, O₃/H₂O₂, O₃/UV, O₃/H₂O₂ /UV, and photo-Fenton system). The results revealed that the most efficient methods in terms of esculetin removal were ozonation among the single oxidants, and the photo-Fenton system among the combined processes.     

Degradation of the fluoroquinolone enrofloxacin by electrochemical advanced oxidation processes based on hydrogen peroxide electrogeneration

Solutions of the veterinary fluoroquinolone antibiotic enrofloxacin in 0.05 M Na₂SO₄ of pH 3.0 have been comparatively degraded by electrochemical advanced oxidation processes such as anodic oxidation with electrogenerated H₂O₂ (AO-H₂O₂), electro-Fenton (EF), photoelectro-Fenton (PEF) and solar photoelectro-Fenton (SPEF) at constant current density. The study has been performed using an undivided stirred tank reactor of 100 ml and a batch recirculation flow plant of 2.5 l with an undivided filter-press cell coupled to a solar photoreactor, both equipped with a Pt or boron-doped diamond (BDD) anode and a carbon-polytetrafluoroethylene gas diffusion cathode to generate H₂O₂ from O₂ reduction. In EF, PEF and SPEF, hydroxyl radical (OH) is formed from Fenton's reaction between added catalytic Fe²⁺ and generated H₂O₂. Almost total decontamination of enrofloxacin solutions is achieved in the stirred tank reactor by SPEF with BDD. The use of the batch recirculation flow plant showed that this process is the most efficient and can be viable for industrial application, becoming more economic and yielding higher mineralization degree with raising antibiotic content. This is feasible because organics are quickly oxidized with OH formed from Fenton's reaction and at BDD from water oxidation, combined with the fast photolysis of complexes of Fe(III) with generated carboxylic acids under solar irradiation. The lower intensity of UVA irradiation used in PEF with BDD causes a slower degradation. EF with BDD is less efficient since OH cannot destroy the most persistent Fe(III)-oxalate and Fe(III)-oxamate complexes. AO-H₂O₂ with BDD yields the poorest mineralization because pollutants are only removed with OH generated at BDD. All procedures are less potent using Pt as anode due to the lower production of OH at its surface. Enrofloxacin decay always follows a pseudo first-order reaction. Its primary aromatic by-products and short intermediates including polyols, ketones, carboxylic acids and N-derivatives are detected by GC-MS and chromatographic techniques. The evolution of F⁻, NO₃⁻ and NH₄⁺ ions released to the medium during each process is also determined.     

Oxidation of Herbicides in Groundwater by the Fenton Process: A Realistic Alternative for O3/H2O2 Treatment?

Oxidation with O₃/H₂O₂ and Fe²⁺/H₂O₂ are optional for the degradation of herbicides and pesticides in water. The choice of which process will be applied depends upon the degree of degradation of organic micropollutants and the process conditions related to the formation of oxidation by-products, and also on the total costs and the safety and reliability of the process. Under real conditions, atrazine and some phenylureaherbicides were oxidized with O₃/H₂O₂. Comparable experiments under conditions of different pH, iron and DOC content were performed with Fe²⁺/H₂O₂, in order to gain information on the influence of these parameters. The oxidation results of both processes as well as the formation of bromate as one of the oxidation by-products are described. It was found that 80% of atrazine and >99% of some phenylureaherbicides could be degraded with O₃/H₂O₂ at pH 7.8 (H₂O₂/O₃ ratio 3.7 g/g). Under these conditions, bromate was formed up to 5 μg/1. Comparable results were obtained with Fe²⁺/H₂O₂ at a pH value of 5.5, whereas the formation of bromate was kept below 0.2 μg/L.     

Degradation behaviors of perfluorosulfonic acid polymer electrolyte membranes for polymer electrolyte membrane fuel cells under varied acceleration conditions

The degradation of perfluorosulfonic acid (PFSA) membranes (e.g., Nafion membranes) in polymer electrolyte membrane fuel cells has caused wide widespread concern. However, their degradation behaviors, which lead to the damage of fuel cells, need to be investigated under alternative accelerating environments by the simulation of fuel‐cell operating conditions. Nafion membranes showed a homogeneous degradation behavior during hydrogen peroxide (H₂O₂) aging, whereas a nonhomogeneous (or crack‐type) degradation behavior occurs for Nafion membranes aged in an H₂O₂/Fe²⁺ system (Fenton's reagent), where plenty of the typical microcracks appeared. Interestingly, in the case of nonhomogeneous degradation, the membrane presented a lower fluoride emission rate than that with the homogeneous degradation; this indicates a possible selective attack model of free radicals to both CF₂ and the defect end groups in PFSA membranes. In addition, the effects of the different degradation behaviors on the thermal stability and water uptake of membranes were examined by thermogravimetric analyses. H₂ crossover and single‐fuel‐cell tests were carried out to evaluate the influence of the degradation behaviors on the fuel‐cell performance. These showed that the membrane with a nonhomogeneous degradation behavior had a higher hydrogen crossover and was more destructive than that with a homogeneous behavior. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013