Persulfate Decomposition Research Articles

Unraveling the catalyzing behaviors of different iron species (Fe2+ vs. Fe0) in activating persulfate-based oxidation process with implications to waste activated sludge dewaterability

Dewatering of waste activated sludge (WAS) is of major interest in its volume reduction, transportation and ultimate disposal. Persulfate-based oxidation process is a newly developed option for enhancing WAS dewaterability through the generation of powerful sulfate radicals (SO4−·). However, the enhancement in WAS dewaterability by persulfate differs with the species of iron catalysts used. In this study, two types of iron catalysts (i.e. Fe2+ vs. Fe0) were employed to initiate the persulfate (S2O82−), and the catalyzing behaviors and the underlying principles in enhancing WAS dewaterability were investigated and compared. The Fe2+ exhibited the high effectiveness in catalyzing the decomposition of persulfate to sulfate radicals (SO4−·), inducing the greater improvement in WAS dewatering. The WAS dewaterability (indicated by dry solids content after filtration) increased with the added S2O82−/Fe2+ dosages, with the dry solids content reaching up to 5.1 ± 0.8 wt% at S2O82−/Fe2+ dosages of 1.2/1.5 mmol/g-VS after only 30 s’ filtration, roughly 1.8-fold increase than raw WAS (1.8 ± 0.1 wt%). In contrast, the influence of the persulfate oxidation when activated with Fe0 on WAS dewaterability was statistically insignificant. The WAS dewaterability remained nearly unchanged (i.e. dry solids content of 2.0 ± 0.0 wt%), irrespective of the employed S2O82−/Fe0 dosages. Further analysis demonstrated that the WAS dewaterability negatively corresponded to loosely bound extracellular polymeric substances (LB-EPS) and tightly bound EPS (TB-EPS). The abundant SO4−· from S2O82−/Fe2+ system could effectively disrupt the gel-like EPS matrix, break apart the cells and subsequently arouse the release of the water inside EPS and cells, facilitating water-solid separation. In the case of S2O82−/Fe0, the dissolution of Fe0 particles was the rate-limiting step, due to the formation of oxide iron layer near Fe0 metallic surface, which resulted in the slow SO4−· production and thus hardly promoted WAS dewaterability. The pH adjustment could accelerate Fe0 dissolution and enhance the dewatering performance of S2O82−/Fe0 process to a certain degree, but the effect was unsatisfactory. Additionally, the observations regarding the dissolved organic matters and ammonium collectively revealed that except for enhancing WAS dewatering, S2O82−/Fe2+ oxidation could concurrently degrade COD and ammonia from WAS filtrate, lighten the burden of the subsequent sewage treatment facilities and reduce operational expense. Hence, from an environmental and economic perspective, the S2O82−/Fe2+ system possesses much greater promise for WAS dewatering.

Sludge biochar-based catalysts for improved pollutant degradation by activating peroxymonosulfate

Sludge-based biochar was able to catalyse persulfate decomposition to produce singlet oxygen for pollutant degradation.

Mackinawite (FeS) activation of persulfate for the degradation of p-chloroaniline: Surface reaction mechanism and sulfur-mediated cycling of iron species

Among the numerous iron-based materials for persulfate (PS) activation, mackinawite (FeS) particles have gained considerable interest as a ubiquitous natural mineral due to their high reactivity. However, the iron and sulfur co-mediated reaction mechanism of PS activation by FeS remains ambiguous. In this study, FeS was applied as a catalyst to activate PS for p-chloroaniline (PCA) degradation and mineralization over a wide initial pH range (3.0–11.0). The reaction was found to follow pseudo-first-order kinetics, with rate constants ranging from 0.0044 to 0.0144min−1. The reaction mechanism was elucidated by electron spin resonance (ESR) and quenching studies. A heterogeneous activation mechanism, in which surface Fe(II) species activated PS to produce OHads and SO4−ads, controlled by surface reaction and diffusion was proposed, whereas OHfree and SO4−free diffusing from the FeS surface were mainly responsible for PCA degradation. The sulfur-mediated cycling of iron species was investigated by comparing PS activation by zero-valent iron (ZVI) and FeS, exogenous Fe(III) addition and X-ray photoelectron spectroscopy (XPS). The results suggested that Fe(II) and S(-II) experienced independent oxidations and that S(-II) species could regenerate Fe(II) from Fe(III) at the FeS surface. Therefore, the S(-II)-promoted Fe(II)/Fe(III) cycle resulted in less PS decomposition but a higher PCA mineralization efficiency. The findings of this study elucidated the novel surface activation mechanism of PS by FeS and provided useful information for utilizing FeS to remediate contaminated water.

UV-LED/ilmenite/persulfate for azo dye mineralization: The role of sulfate in the catalyst deactivation

This work investigates the effect of UV-LED on the persulfate (PS) activation with natural ilmenite (FeTiO3) in the oxidation of azo dye Disperse Blue 3 (DB3). The high induction period and the scarce ability of this mineral to activate PS can be overcome by using UV irradiation to increase the SO4− generation via photoreduction of Fe(III) to Fe(II) on the ilmenite surface, main responsible of SO4− formation in iron-based catalysis. The effect of several operating conditions such as persulfate dose (20–100% of the theoretical stoichiometric amount), reaction temperature (30–70°C) and mineral concentration 320mgL−1 has been studied. Under optimum conditions (320mgL−1of ilmenite, pH0: 3, using 100% of stoichiometric amount of PS at 70°C under UV-LED radiation) more than 95% TOC reduction and 92% PS decomposition were reached after 180min. The progressive deactivation of FeTiO3 through successive experiments can be explained, according to density functional theory (DFT) calculations, by the formation of a passivation layer due to adsorption of SO42− on the FeTiO3 surface.

Naphthenic acids removal from high TDS produced water by persulfate mediated iron oxide functionalized catalytic membrane, and by nanofiltration

Oil industries generate large amounts of produced water containing organic contaminants, such as naphthenic acids (NA) and very high concentrations of inorganic salts. Recovery of potable water from produced water can be highly energy intensive in some cases due to its high salt concentration, and safe discharge is more suitable. Here, we explored catalytic properties of iron oxide (FexOy nanoparticles) functionalized membranes in oxidizing NA from water containing high concentrations of total dissolved solids (TDS) using persulfate as an oxidizing agent. Catalytic decomposition of persulfate by FexOy functionalized membranes followed pseudo-first order kinetics with an apparent activation energy of 18kcal/mol. FexOy functionalized membranes were capable of lowering the NA concentrations to less than discharge limits of 10ppm at 40°C. Oxidation state of iron during reaction was quantified. Membrane performance was investigated for extended period of time. A coupled process of advanced oxidation catalyzed by membrane and nanofiltration was also evaluated. Commercially available nanofiltration membranes were found capable of retaining NA from water containing high concentrations of dissolved salts. Commercial NF membranes, Dow NF270 (Dow), and NF8 (Nanostone) had NA rejection of 79% and 82%, respectively. Retentate from the nanofiltration was further treated with advanced oxidation catalyzed by FexOy functionalized membrane for removal of NA.

Morphology evolution of poly(glycidyl methacrylate) colloids in the 1,1-diphenylethene controlled soap-free emulsion polymerization

This work reports for the first time that milky poly(glycidyl methacrylate) (PGMA) colloids produced in the early stage of 1, 1-diphenylethene (DPE) controlled soap-free emulsion polymerization of GMA evolved into transparent polymer solution 90min after the polymerization was initiated. Qualitative and quantitative analysis confirmed that during the polymerization, large amount of hydrophilic hydroxyls and flexible aliphatic ethers were generated by the ring-opening reactions of epoxy groups catalyzed by H+ which is a byproduct of the decomposition of potassium persulfate. As a control agent, DPE could dramatically decrease the polymerization degree of PGMA, resulting in much shorter hydrophobic main chains comparing with PGMA produced in the absence of DPE. The hydrophilic hydroxyls by ring-opening reaction and the shorter hydrophobic main chains by DPE controlled polymerization would facilitate water swelling into the polymers. The swelled polymers along with the aliphatic ethers and shorter main chains endowed the particles with flexible and proteiform, forming structures similar to transparent polymer solution rather than milky colloidal suspensions.

Mechanisms on the Impacts of Alkalinity, pH, and Chloride on Persulfate-Based Groundwater Remediation.

Persulfate (S2O82-)-based in situ chemical oxidation (ISCO) has gained more attention in recent years due to the generation of highly reactive and selective sulfate radical (SO4•-). This study examined the effects of important groundwater chemical parameters, i.e., alkalinity, pH, and chloride on benzene degradation via heterogeneous persulfate activation by three Fe(III)- and Mn(IV)-containing aquifer minerals: ferrihydrite, goethite, and pyrolusite. A comprehensive kinetic model was established to elucidate the mechanisms of radical generation and mineral surface complexation. Results showed that an increase of alkalinity up to 10 meq/L decreased the rates of persulfate decomposition and benzene degradation, which was associated with the formation of unreactive surface carbonato complexes. An increase in pH generally accelerated persulfate decomposition due to enhanced formation of reactive surface hydroxo complexation. A change in the chloride level up to 5 mM had a negligibly effect on the reaction kinetics. Kinetics modeling also suggested that SO4•- was transformed to hydroxyl radical (HO•) and carbonate radical (CO3•-) at higher pHs. Furthermore, the yields of two major products of benzene oxidation, i.e., phenol and aldehyde, were positively correlated with the branching ratio of SO4•- reacting with benzene, but inversely correlated with that of HO• or CO3•-, indicating that SO4•- preferentially oxidized benzene via pathways involving fewer hydroxylation steps compared to HO• or CO3•-.

Photochemical oxidation of persistent cyanide-related compounds

Kinetic regularities of the photolysis of thiocyanate solutions using of mono- and polychromatic UV radiation sources with different spectral ranges are studied. Comparative experiments aimed at investigating the role of photochemical action during the oxidation of thiocyanates with persulfates and additional catalytic activation with iron(III) ions are performed. The rate of conversion and the initial rate of thiocyanate oxidation are found to change in the order UV < UV/S2O 8 2− < S2O 8 2− /Fe3+ < UV/S2O 8 2− /Fe3+. A synergistic effect is detected when using the combined catalytic method for the destruction of thiocyanates by the UV/S2O 8 2− /Fe3+ oxidation system. This effect is due to the formation of reactive oxygen species, as a result of both the decomposition of persulfate and the reduction of inactive Fe3+ intermediates into Fe3+.

Accelerated degradation of iopamidol in iron activated persulfate systems: Roles of complexing agents

As an environment-friendly activator, iron ions (Fe(II) and Fe(III)) have been extensively studied in homogeneous activation of persulfate (PS) to remove organic pollutants from water. However, the slow reduction of Fe(III) to Fe(II) and the subsequent low activation efficiency limit the wide applications of PS/Fe(II) or PS/Fe(III). In this study, the roles of four complexing agents, including gallic acid (GA), ethylene diamine tetraacetic acid, (S,S)-ethylenediamine-N,N′-disuccinic acid trisodium salt and citric acid in the activation of PS/Fe(III) were comparatively investigated with iopamidol (IPM) used as a model organic pollutant. Results indicate that GA was the most effective with an increase in the observed pseudo-first-order rate constant (kobs) by 9.2 folds for IPM degradation by PS/Fe(III). Through radical scavenger (ethanol and tert-butanol) tests and electron paramagnetic resonance analysis, HO and SO4− were identified to be responsible for the accelerated degradation of IPM, and HO played a more important role. Intrinsically, the promoted Fe(III) reduction and PS decomposition accelerated the degradation of IPM. The transformation by-products of IPM in the PS/Fe(III)/GA system were identified and potential degradation pathways were proposed. Besides, the accelerated degradation of other three organic pollutants (methyl orange, congo red, and diclofenac) further demonstrated the applicability of the PS/Fe(III)/GA system to water treatment.

Oxidative degradation of benzoic acid using Fe0- and sulfidized Fe0-activated persulfate: A comparative study

Implications of sulfidized Fe0 (nFe/FeS) for the abatement of pollutants of various categories are widely established. In this study, degradation of one of the major organic pollutants, benzoic acid (BA), has been performed using persulfate activated with nFe/FeS. Complete degradation of BA and its transformed product, hydroxybenzoic acid, was observed within 6min. When the degradation was performed at alkaline pH, the degradation decreased to 8% in the case of Fe0, but nFe/FeS still showed 100% degradation after 60min. Iron dissolution and persulfate decomposition in the presence of scavengers showed that both sulfate and hydroxyl radicals were involved in the Fe0-persulfate system and that the hydroxyl radicals were the major species in the nFe/FeS-persulfate system. The major degradation pathway of benzoic acid was hydroxylation followed by complete mineralization, as supported by the practical removal of total organic carbons (more than 75% within 15min). The observed results are promising in using persulfate activated by nFe/FeS for the remediation of various micro-pollutants from a multitude of water sources.

Insight into reactive oxygen species in persulfate activation with copper oxide: Activated persulfate and trace radicals

Activated persulfate along with trace sulfate and hydroxyl radicals were found to be reactive oxygen species in copper oxide activated persulfate system in this study. Persulfate decomposition study revealed that activated persulfate was predominant instead of sulfate and hydroxyl radicals. The radical scavenger investigation supported this point and led to the surface activation mechanism of persulfate. The p-chloroaniline (PCA) degradation in copper oxide activated persulfate system in neutral and acidic condition provided the evidence of prime heterogeneous persulfate activation and minor homogeneous persulfate activation caused by dissolved copper ion. Electron Paramagnetic Resonance study indicated the generation of sulfate and hydroxyl radicals. Integrating all the experiment facts, it is proposed that activated persulfate was main reactive oxygen species generated on copper oxide surface, along with minor sulfate and hydroxyl radicals produced. Chloride ions showed no effect on PCA degradation in copper oxide activated persulfate system. While bicarbonate ions improved PCA degradation without pH adjustment (initial pH is about 3) and performed an inhibition effect when the initial pH was adjusted to neutral. These findings indicated the potential applicability of copper oxide for in situ chemical oxidation for two reasons: (1) ubiquitous chloride and bicarbonate ions showed no negative effect and (2) the slight radical generation avoid the persulfate consumption by non-pollutant reductive materials.

Activation of persulfate with vanadium species for PCBs degradation: A mechanistic study

In the present study, the activation of persulfate (PS) with vanadium (V) species for PCBs (2,4,4′-trichlorobiphenyl [PCB28]) degradation was investigated for the first time. It was found that V2O3 exhibited high catalytic activity toward PS decomposition for PCB28 degradation. Even under near neutral pH (7.4), PCB28 was efficiently degraded in V2O3/PS. Sulfate radical anions (SO4−) and hydroxyl radicals (OH) were produced from PS activation with V2O3 for PCB28 degradation, and were characterized with electron paramagnetic resonance (EPR) technique. Free radical quenching studies showed that ethanol inhibited PCB28 degradation, while tert-butyl alcohol enhanced PCB28 degradation via reductive dechlorination with alcohol radicals. The pathway of PCB28 degradation was proposed on the basis of GC–MS analysis of intermediates of PCB28 degradation in V2O3/PS. The mechanisms of PS activation are elucidated. It was found that V(III) in V2O3 activated PS to form SO4− and V(IV) (VO2) via electron transfer process, and the formed V(IV) further transferred an electron to PS to generate SO4− and V(V) (V6O13), which were supported with XRD analysis. Furthermore, both VO2 and V2O5 can activate PS for PCB28 degradation, indicating that V(IV) would be regenerated from the reduction of V(V) by persulfate ions (S2O82−) on the surface of V2O5 particles. These findings would help to better understand the interactions between naturally occurring V minerals and PS, and provide a novel activator for PS activation to degrade contaminants.

Persulfate-enhanced sonochemical degradation of naphthol blue black in water: Evidence of sulfate radical formation

This work explores the effect of persulfate (PS) on the sonochemical degradation of organic pollutants taking naphthol blue black (NBB), an anionic diazo dye, as a substrate model. The sonolytic experiments were conducted in the absence and presence of PS under various experimental conditions including acoustic power (10−80W), frequency (20 and 585kHz) and saturating gas (argon, air and nitrogen). Experimental results showed that PS decomposition into sulfate radical (SO4−) takes place by sonolysis and increasing PS concentration up to 1g/L would result in an increase in the NBB degradation rate. It was found that the PS-enhanced effect was strongly operating parameters dependent. The positive effect of PS decreased with increasing power and the best enhancing effect was obtained for the lowest acoustic power. Correspondingly, the PS-enhanced effect was more remarkable at low frequency (20kHz) than that observed at high frequency ultrasound (585kHz). Nitrogen saturating gas gave the best enhanced effect of PS than argon and air atmospheres. Theoretical (computer simulation of bubble collapse) and experimental measurements of the yields of free radical generation under the different experimental conditions have been made for interpreting the obtained effects of PS on the sonochemical degradation of the dye pollutant. The experimental findings were attributed to the fact that radical-radical recombination reactions occur at faster rate than the radical-organic reaction when the concentration of free radicals is too high (at higher sonochemical conditions).

Chemisorption of Perfluorooctanoic Acid on Powdered Activated Carbon Initiated by Persulfate in Aqueous Solution.

Perfluorooctanoic acid (PFOA) is a perfluorocarboxylic acid that is difficult to treat by most conventional methods. As a result, it is often removed from solution by adsorption on powdered activated carbon (PAC), followed by incineration of the spent carbon. To provide a new approach for treatment, PFOA was exposed to sulfate radicals (SO4(-•)) produced by thermolysis of persulfate (S2O8(2-)) in the presence of PAC. Under acidic conditions, thermal activation of persulfate resulted in transformation of PFOA to shorter-chain-length perfluorinated compounds, as previously reported. However, when thermolysis of persulfate occurred under circumneutral pH conditions in the presence of PAC, a new removal pathway for PFOA was observed. Under these conditions, the removal of PFOA was attributable to chemisorption, a process in which PAC catalyzed persulfate decomposition and reacted with the transformation products to produce covalently bound PFOA. At PAC concentrations between 200 and 1000 mg/L and an initial PFOA concentration of 0.5 μM, covalent bonding resulted in removal of 10-40% of the PFOA. Under these conditions, the process resulted in removal of more than half of a more hydrophilic perfluoroalkyl acid (i.e., perfluorobutanoic acid, PFBA), which was greater than the amount of PFBA removed by physical adsorption on PAC. Although the high reaction temperatures (i.e., 80 °C) and relatively high doses of PAC used in this study may be impractical for drinking water treatment, this process may be applied to the treatment of these recalcitrant compounds in industrial wastewater, reverse osmosis concentrate, and other waters that contain high concentrations of PFOA and other perfluorocarboxylic acids.

Bentonite-supported nanoscale zero-valent iron/persulfate system for the simultaneous removal of Cr(VI) and phenol from aqueous solutions

In this study, bentonite-supported nanoscale zero-valent iron (B-nZVI) was used as a catalyst to activate persulfate (PS) for the simultaneous removal of Cr(VI) and phenol from aqueous solutions. Experimental results indicated that the presence of bentonite could decrease the aggregation of nZVI and increase its reactivity. The removal rates of Cr(VI) and phenol by B-nZVI system were 99.90% and 6.50%, respectively. Whereas the corresponding values by B-nZVI/PS system were 99.30% and 71.50%, respectively. The presence of persulfate could not significantly decline B-nZVI reactivity toward Cr(VI) reduction but remarkably promote phenol oxidation. The addition of Cr(VI) did positively affect the oxidation rate of phenol, a significant synergistic effect between Cr(VI) reduction and phenol oxidation was achieved in B-nZVI/PS system. A positive correlation between persulfate decomposition and dissolved Fe2+ was found. Cr(III) species such as Cr2O3, Cr(OH)3 were identified in Cr(VI) reduction process, whereas the oxidation products such as catechol, 1,4-benzoquinone, propionic acid and formic acid were identified in phenol oxidation process. The reusability experiments of B-nZVI demonstrated that the structure of B-nZVI was relatively stable after four cycles of reuse. This is the first report for the feasibility of B-nZVI as a catalyst to activate persulfate for the simultaneous removal of heavy metal and organic pollutant.

Simultaneous removal of Cr(VI) and phenol by persulfate activated with bentonite-supported nanoscale zero-valent iron: Reactivity and mechanism

The applicability of bentonite-supported nanoscale zero-valent iron (B-nZVI) as a catalyst to activate persulfate (PS) for the simultaneous removal of Cr(VI) and phenol was systematically investigated in this study. Experimental results demonstrated that phenol degradation was significantly enhanced under acidic condition and with oxygen supply, whereas the Cr(VI) reduction was not obviously declined. The removal efficiencies of Cr(VI) and phenol in B-nZVI/PS combined system were 99.8 and 72.3%, respectively. Cr(VI) reduction and phenol oxidation was simultaneously achieved in B-nZVI/PS combined system, which provided a promising environmental treatment for industrial wastewater containing metal ions and organic compounds. An acidic condition was more favorable to the decomposition of persulfate for the production of sulfate radicals. Radical scavenging tests revealed that the predominant reactive oxygen species for phenol degradation was SO4−, neither HO nor O2−. A reaction mechanism, which involves the Cr(VI) removal mainly by the reduction of nZVI and the degradation of phenol mainly by the SO4− from the decomposition of persulfate, was proposed. These findings revealed that B-nZVI/PS combined system has a potential in the environmental remediation polluted jointly by organic compounds and/or heavy metals.

Oxidation of 2,4-dichlorophenol by non-radical mechanism using persulfate activated by Fe/S modified carbon nanotubes

The aim of this study was to develop a new approach for the activation of persulfate (PS) based on carbon nanotubes (CNTs). Fe/S modified carbon nanotubes (Fe/S-CNTs) were synthesized via impregnation–precipitation in the aqueous-phase synthesis method. The morphologies and chemical states of the catalysts were characterized and 2,4-dichlorophenol (2,4-DCP) was selected to investigate the degradation performance using Fe/S-CNTs with PS. The results reveal that the Fe/S-CNTs catalysts can significantly accelerate the removal of 2,4-DCP compared to single PS or PS/CNTs. The catalytic capacity is also enhanced by S modification and is affected by the solution pH. The iron loading content, PS concentration and catalyst dosage could play important roles in the degradation. A non-radical process of 2,4-DCP degradation is demonstrated for the first time in the results of the radical scavengers and chloride ionic, as well as persulfate decomposition. It is suggested that PS is first bonded with the sp2-hybridized system and activated by iron oxide particles and iron-sulfur complexes, then it reacts rapidly with the adsorbed 2,4-DCP.

Kinetic features of ammonium persulfate decomposition in aqueous medium

Decomposition of ammonium persulfate in an aqueous medium (353–368 K) is limited by decomposition of persulfate ions with a rate constant logk2 = (15±3)–(52±8)•103 J mol–1/(2.3RT). The apparent rate constant for decomposition of persulfate ammonium kapp = = k2γ depends on the decomposition rate constant and the activity coefficient of persulfate ions, the temperature, and the ionic strength of solution.

Electrokinetic delivery of persulfate to remediate PCBs polluted soils: Effect of different activation methods.

Persulfate-based in-situ chemical oxidation (ISCO) for the remediation of organic polluted soils has gained much interest in last decade. However, the transportation of persulfate in low-permeability soil is very low, which limits its efficiency in degrading soil pollutants. Additionally, the oxidation-reduction process of persulfate with organic contaminants takes place slowly, while, the reaction will be greatly accelerated by the production of more powerful radicals once it is activated. Electrokinetic remediation (EK) is a good way for transporting persulfate in low-permeability soil. In this study, different activation methods, using zero-valent iron, citric acid chelated Fe(2+), iron electrode, alkaline pH and peroxide, were evaluated to enhance the activity of persulfate delivered by EK. All the activators and the persulfate were added in the anolyte. The results indicated that zero-valent iron, alkaline, and peroxide enhanced the transportation of persulfate at the first stage of EK test, and the longest delivery distance reached sections S4 or S5 (near the cathode) on the 6th day. The addition of activators accelerated decomposition of persulfate, which resulted in the decreasing soil pH. The mass of persulfate delivered into the soil declined with the continuous decomposition of persulfate by activation. The removal efficiency of PCBs in soil followed the order of alkaline activation > peroxide activation > citric acid chelated Fe(2+) activation > zero-valent iron activation > without activation > iron electrode activation, and the values were 40.5%, 35.6%, 34.1%, 32.4%, 30.8% and 30.5%, respectively. The activation effect was highly dependent on the ratio of activator and persulfate.

In-situ activation of persulfate by iron filings and degradation of 1,4-dioxane

Activation of persulfate by iron filings and subsequent degradation of 1,4-dioxane (dioxane) was studied in both batch-reactor and column systems to evaluate the potential of a persulfate-enhanced permeable reactive barrier (PRB) system for combined oxidative-reductive removal of organic contaminants from groundwater. In batch experiments, decomposition of persulfate to sulfate and degradation of dioxane both occurred rapidly in the presence of iron filings. Conversely, dioxane degradation by persulfate was considerably slower in the absence of iron filings. For the column experiments, decomposition and retardation of persulfate was observed for transport in the columns packed with iron filings, whereas no decomposition or retardation was observed for transport in columns packed with a reference quartz sand. Both sulfate production and dioxane degradation were observed for the iron-filings columns, but not for the sand column. The pH of the column effluent increased temporarily before persulfate breakthrough, and significant increases in both ferrous and ferric iron coincided with persulfate breakthrough. Multiple species of free radicals were produced from persulfate activation as determined by electron paramagnetic resonance (EPR) spectroscopy. The impact of the oxidation process on solution composition and iron-filings surface chemistry was examined using ICP-MS, SEM-EDS, and XRD analyses. A two-stage reaction mechanism is proposed to describe the oxidation process, consisting of a first stage of rapid, solution-based, radical-driven decomposition of dioxane and a second stage governed by rate-limited surface reaction. The results of this study show successful persulfate activation using iron filings, and the potential to apply an enhanced PRB method for improving in-situ removal of organic contaminants from groundwater.