Weak magnetic field and coexisting ions accelerate phenol removal by ZVI/H2O2 system: Their efficiency and mechanism

Human activity and industrial production have led to phenol becoming a significant risk factor. The proper treatment of phenol in wastewater is essential. In this study, the utilization of weak magnetic field (WMF) and zero-valent iron (ZVI) was proposed to activate H2O2 to degrade phenol contaminant. The results show that the weak magnetic field has greatly enhanced the reaction rate of ZVI/H2O2 removal of phenol. The removal rates of phenol by ZVI/H2O2/WMF generally decreased with increasing initial pH and phenol concentrations, and firstly increase and then decrease with increasing Fe0 or H2O2 dosage. When the initial pH is 5.0, ZVI concentration of 0.2 g L-1, H2O2 concentration of 6 mM, and phenol concentration of 100 mg L-1 were used, complete removal of phenol can be achieved within 180 min at 25 °C. The degradation process was consistent with the pseudo-first-order kinetic model when the experimental data was fitted. The ZVI/H2O2/WMF process exhibited a 1.05-2.66-fold enhancement in the removal rate of phenol under various conditions, surpassing its counterpart lacking WMF. It was noticed that the presence of 1-5 mM of Ca2+, Mg2+, Cl-, SO42- ions can significantly enhance the kinetics of phenol removal by ZVI/H2O2 system with or without WMF to 2.22-10.40-fold, but NO3-, CO32-, PO43- inhibited the reaction significantly in the following order: PO43- > CO32- > NO3-. Moreover, pre-magnetization for 3 min could enhance the ZVI/H2O2 process which was valuable in treatment of real wastewater. The hydroxyl radical has been identified as the primary radical species responsible for phenol degradation. The presence of WMF accelerates the corrosion rate of ZVI, thereby promoting the release of Fe2+ ions, which in turn induces an increased production of hydroxyl radicals and facilitates phenol degradation. The compounds hydroquinone, benzoquinone, catechol, maleic acid, and CO2 were identified using GC-MS, and degradation pathways were proposed. Employing WMF in combination with various ions like Ca2+, Mg2+, Cl-, SO42- is a novel method, which can enhance oxidation capacity of ZVI/H2O2 and may lead to economic benefit.

Austenitic Stainless Steel as a Catalyst Material for Photo-Fenton Degradation of Organic Dyes

In this paper, a typical austenitic stainless steel was used as a catalyst in the visible photo-Fenton degradation process of two model dyes, methylene blue and methylorange, in the presence of hydrogen peroxide and potassium persulfate as free radical-generating species. The concentration intervals for both peroxide and persulfate were in the range of 333–1667 μg/L. Very high photodecoloration efficiencies have been achieved using peroxide (>93%), while moderate ones have been achieved using persulfate (>75%) at a pH value of 6.5. For methylene blue, the maximum mineralization yield of 74.5% was achieved using 1665 μg/L of hydrogen peroxide, while methylorange was better mineralized using 999 μg/L of persulfate. The photodegradation of the dye occurred in two distinct steps, which were successfully modeled by the Langmuir–Hinshelwood pseudo-first-order kinetic model. Reaction rate constants k between 0.1 and 4.05 h−1 were observed, comparable to those presented in the reference literature at lower pH values and higher concentrations of total iron from the aqueous media.

Preparation, characterization, and applications of Fe-based catalysts in advanced oxidation processes for organics removal: A review

Fe-based catalysts as low-cost, high-efficiency, and non-toxic materials display superior catalytic performances in activating hydrogen peroxide, persulfate (PS), peracetic acid (PAA), percarbonate (PC), and ozone to degrade organic contaminants in aqueous solutions. They mainly include ferrous salts, zero-valent iron, iron-metal composites, iron sulfides, iron oxyhydroxides, iron oxides, and supported iron-based catalysts, which have been widely applied in advanced oxidation processes (AOPs). However, there is lack of a comprehensive review systematically reporting their synthesis, characterization, and applications. It is imperative to evaluate the catalytic performances of various Fe-based catalysts in diverse AOPs systems and reveal the activation mechanisms of different oxidants by Fe-based catalysts. This work detailedly summarizes the synthesis methods and characterization technologies of Fe-based catalysts. This paper critically evaluates the catalytic performances of Fe-based catalysts in diverse AOPs systems. The effects of solution pH, reaction temperature, coexisting ions, oxidant concentration, catalyst dosage, and external energy on the degradation of organic contaminants in the Fe-based catalyst/oxidant systems and the stability of Fe-based catalysts are also discussed. The activation mechanisms of various oxidants and the degradation pathways of organic contaminants in the Fe-based catalyst/oxidant systems are revealed by a series of novel detection methods and characterization technologies. Future research prospects on the potential preparation means of Fe-based catalysts, practical applications, assistive technologies, and impact in AOPs are proposed.

A review of the new multifunctional nano zero-valent iron composites for wastewater treatment: Emergence, preparation, optimization and mechanism

Nano zero-valent iron (NZVI) with high chemical reactivity and environmental friendliness had recently become one of the most efficient technologies for wastewater restoration. However, the unitary NZVI system had not met practical requirements for wastewater treatments. Expectantly, the development of NZVI would prefer multifunctional NZVI-based composites, which could be prepared and optimized by the combined methods and technologies. Consequently, a systematic and comprehensive summary from the perspective of multifunctional NZVI-composite had been conducted. The results demonstrated that the advantages of various systems were integrated by multifunctional NZVI-composite systems with a more significant performance of pollutant removal than those of the bare NZVI and its composites. Simultaneously, characteristics of the product prepared by the incorporation of numerous methods were superior to those by a simple method, resulting in the increase of the entirety efficiency. By comparison with other preparation methods, the ball milling method with higher production and field application potential was worthy of attention. After combining multiple technologies, the effect of NZVI and its composite systems could be dramatically strengthened. Preparation technology parameters and treatment effect of contaminants could be further optimized using more comprehensive experimental designs and mathematical models. The mechanism of the multifunctional NZVI system for contaminants treatment was primarily focused on adsorption, oxidation, reduction and co-precipitation. Multiple techniques were combined to enhance the dispersion, alleviating passivation, accelerating electron transfer efficiency or mass transfer action for optimizing the effect of NZVI composites.

Role of weak magnetic field for enhanced oxidation of orange G by magnetic Fenton

The role of weak magnetic field (WMF) on the degradation of a common textile azo-dye, orange G (OG), by magnetic Fenton system was investigated in detail. The results showed that the presence of WMF can provide better performance of the Fe₃O₄/H₂O₂ system for OG degradation. The optimized reaction conditions were contained at 1 mM Fe₃O₄ as Fe, 20 mT of magnetic field intensity, 20 mM H₂O₂, and initial pH of 3.0. The removal efficiency of OG by Fe₃O₄/H₂O₂ coupling with WMF increased largely from 56.3 to 82.3% compared with Fe₃O₄/H₂O₂ process. Both the electron paramagnetic resonance (EPR) analysis and the quenching effect of tert-butyl alcohol (TBA) confirmed that hydroxyl radical (•OH) was the primary reactive oxygen species in WMF-Fe₃O₄/H₂O₂ system. The improving effect of WMF was explained by the magnetoconvection theory. The presence of WMF could accelerate the corrosion rate of Fe₃O₄ and thus promoted the release of Fe(II), which led to the increased production of •OH and enhanced the degradation of OG. Moreover, it was surprising to observe that the WMF induced improvement in OG degradation by heterogeneous Fenton involving the iron sludge, namely FeOOH and Fe₂O₃, as catalysts. These results indicated that WMF could be utilized as an efficient and cost-effective strategy to improve the removal of organic pollutants by iron oxide-based Fenton process.

Nano zero-valent iron on activated carbon cloth support as Fenton-like catalyst for efficient color and COD removal from melanoidin wastewater

To reduce undesired iron leaching in Fenton reaction and to realize reusability of catalyst, chitosan-coated activated carbon cloth support loaded with nano zero-valent iron (ACC-CH-nZVI) was applied as a heterogeneous Fenton catalyst to treat melanoidin wastewater. Chitosan coating on ACC by chemical crosslinking results in 6% chitosan on ACC subsequently loading 3.5% iron. At optimum conditions, ACC-CH-nZVI leads to 88.4% and 76.2% of color and chemical oxygen demand (COD) removal, respectively, upon treating synthetic melanoidin wastewater of 8000 mg/l COD. The corresponding weight ratio of consumed H₂O₂ to COD is 1.02, far below the stoichiometric ratio 2.125, indicating the economic value of this catalyst. Reusability of ACC-CH-nZVI is demonstrated for five cycles of treatment with minimal iron leaching (<2%). The high removal efficiency and very low levels of iron leaching suggests that ACC-CH-nZVI is a highly efficient and cost-effective catalyst for Fenton-like oxidation of non-biodegradable organic wastes in water.

Removal of reactive brilliant red X-3B by a weak magnetic field enhanced Fenton-like system with zero-valent iron

The effect of a weak magnetic field (WMF) on the removal of reactive brilliant red X-3B (X-3B) by zero-valent iron (ZVI)/H₂O₂ was studied. The optimum conditions for the removal of X-3B by the ZVI/H₂O₂/WMF system were as follows: pH = 4.0, X-3B was 50 mg L⁻¹, H₂O₂ was 8 mM, and ZVI with particle size of 20 μm was 0.5 g L⁻¹. The X-3B decolorization rate could reach 99.41% in 10 minutes. The superposed WMF increased the working pH of ZVI from 3.0 to 4.0. The main part of ZVI/H₂O₂ removal kinetics of X-3B followed the zero order rate law. In this study, the removal effect of X-3B by pre-magnetization ZVI was not as good as that of real-time magnetization, but it was better than the removal of X-3B by the ZVI/H₂O₂ system. The ZVI/H₂O₂/WMF system still had the ability to remove X-3B after 4 consecutive cycles. The use of WMF improved the removal of X-3B by ZVI/H₂O₂ mainly due to the corrosion of ZVI. Under acidic conditions, WMF enhanced the activity of ZVI, which promoted the efficiency of the Fenton reaction. The use of WMF to enhance the ZVI/H₂O₂ removal X-3B was a promising and environmental friendly process because it did not require additional energy and expensive reagents and did not cause secondary pollution.

The effect of a weak magnetic field (WMF) on the removal of reactive brilliant red X-3B (X-3B) by zero-valent iron (ZVI)/H₂O₂ was studied.

Efficiency and mechanisms of rhodamine B degradation in Fenton-like systems based on zero-valent iron

Based on the Fe0/H2O2 heterogeneous Fenton system, the degradation of rhodamine B (RhB, an organic dye pollutant) was researched in this paper. The effects of initial pH value, concentration of H2O2, dosage of zero-valent iron (ZVI), and initial RhB concentration on RhB degradation by Fe0/H2O2 were studied. The results showed that when the initial pH = 4, dosage of ZVI was 9 mM, and concentrations of H2O2 and RhB were 8 mM and 0.1 mM, respectively, the color of RhB could be completely faded within 30 min, and the total organic carbon (TOC) removal percentage was about 63% after 120 min. The dissolved oxygen (DO) content and oxidation-reduction potential (ORP) were monitored during the reaction. Quenching experiments with methanol confirmed that the degradation of the dye was mainly due to oxidation by the ˙OH radical. Besides, the results from UV-Vis spectroscopy showed that the degradation of RhB was mainly due to the destruction of the conjugated oxygen hetero-anthracene in the RhB molecule. The solid-phase characterization of the ZVI samples after reaction confirmed that the original regular and slippery ZVI samples finally were corroded into rough and irregular lepidocrocite and magnetite. Two possible competitive reaction pathways for the degradation of RhB by Fe0/H2O2 were proposed by GC-MS analysis, which were attributed to the dissociation of ethyl radicals and the degradation of chromophore radicals.

Enhanced polarization of electron-poor/rich micro-centers over nZVCu-Cu(II)-rGO for pollutant removal with H2O2

Nanoscale zero-valent copper combined with Cu(II)-doped reduced graphene oxide hybrid (nZVC-Cu(II)-rGO) is synthesized through an annealing reduction process, and it shows very high activity and efficiency for removing refractory organic compounds with H₂O₂. The conversion rate for the organic pollutant in this system is ∼77 and ∼13 times higher than that in the graphene oxide (GO) and reduced graphene oxide (rGO) systems, respectively. The characterization shows that nanoscale Cu(0) and Cu(II) are generated on the rGO surface during the annealing process and they are accompanied by the COCu bonding formation between the rGO substrate and the Cu(II) species in nZVC-Cu(II)-rGO, which induces cation-π interactions on the surface, resulting in the reinforced electron-rich micro-centers formation around the nZVC-enhanced Cu(II) species and electron-poor micro-centers on rGO-aromatic rings. The generation of nanoscale Cu(0) consolidates the polarization of the dual reaction micro-centers and greatly accelerates the electron transfer of the system, thus promoting H₂O₂ reduction to OH in the electron-rich micro-centers. Pollutants can obviously replace H₂O₂ as the electron donors of the system and are efficiently oxidized and degraded in the electron-poor micro-centers, with their own electron energy being fully utilized in the nZVC-Cu(II)-rGO Fenton-like system.

Comparative time-based intermediates study of ozone oxidation of 4-chloro- and 4-nitrophenols followed by LCMS-TOF

Greater insights on the degradation pathways and intermediates formed during the oxidation of organics can be achieved by more suitable and compatible instrumentation. In our research, we sought to explore the relative advantages of the liquid chromatography coupled to a time of flight mass spectrometer (LCMS-TOF) technique for the comparative time-based degradation intermediates and pathways of 4-chlorophenol (4CP) and 4-nitrophenol (4NP). The ozonation of the analytes solution (100 mL of 2 x 10^-3 M) was done in a sintered glass reactor, with an ozone dose of 0.14 mg min^-1 (O₂/O₃ 10 mL/min). The comparative oxidation results revealed that the 4-chloro- and 4-nitrocatechol pathways via hydroxylation were the major degradation route for 4CP and 4NP. Catechol intermediate was present as a primary breakdown product for the two analytes. Hydroquinone was observed as transient degradation intermediate for 4CP, but was absent for 4NP. Rather, a novel ozonation intermediate 2, 4-dinitrophenol was identified which was further oxidized to 3,6-dinitrocatechol. Several dimer products were identified in the oxidation processes, favored by alkaline conditions with more versatility shown by 4CP. The study provided a great insight into the ozone degradation intermediates and pathways, with some intermediates scarce in literature identified.

Activation of oxygen with sulfite for enhanced Removal of Mn(II): The involvement of SO4•

Taking advantage of the active oxidants generated in the process of Mn(II)-catalyzed sulfite oxidation by oxygen, this study sought to enhance Mn(II) removal from water by activating oxygen with sulfite. The results revealed that Mn(II) can be effectively oxidized by oxygen to MnO₂ with the addition of sulfite under environmentally relevant conditions, and the performance of this process is dependent on the dosage of sulfite and the initial pH. Mn K-edge XANES analysis indicates that Mn(II) removal is primarily due to the transformation of Mn(II) to MnO₂ and, secondarily, to the adsorption of Mn(II) on generated MnO₂. Co-existing NaCl and CaCl₂ negatively affect Mn(II) removal, while the presence of Fe(II) considerably enhances Mn(II) removal by improving both Mn(II) oxidation and Mn(II) adsorption on the generated solids. Consequently, Mn(II) removal is as high as 98% in the presence of 1.0 mg/L of Fe(II) and both the residual Mn (<0.1 mg/L Mn) and Fe (<0.3 mg/L Fe) can meet China's drinking water standard. The experiments with real water samples also demonstrate the effectiveness of the sulfite-promoted Mn(II) removal process, especially in the presence of Fe(II). The enhancing effect of sulfite on Mn(II) oxidation by oxygen is mainly associated with the generation of HSO₅^-, and the critical step for generating HSO₅^- is the rapid oxidation of SO₃^•- by oxygen. EPR and radical scavenging studies demonstrate that SO₄^•- radical is the key reactive oxygen species responsible for Mn(II) oxidation by HSO₅^-.

Efficient Fenton-like Process Induced by Fortified Electron-Rich O Microcenter on the Reduction State Cu-Doped CNO Polymer

The discharge of organic pollutants threatens the environment and health and is also a waste of organic energy. Here, the reduction state Cu (RSC) species-doped carbon-nitrogen-oxygen polymer (RSC-CNOP) is synthesized from high-temperature polymerization of a Cu-polyimide precursor, which is used as a Fenton-like catalyst and exhibits excellent performance for pollutant degradation, accompanied by the utilization of the electron energy of the pollutants. Experiments and theoretical calculations reveal the promotion mechanism. The formed Cu(RSC)-O-C(π) electron-transfer bridges in RSC-CNOP induce the bidirectional electron transfers from RSC to O and from C(π) to O (RSC → O ← π), forming the polarized reaction micro-areas (reinforced electron-rich O microcenters and electron-poor C(π) microcenters). The free electrons in electron-rich centers of RSC-CNOP are as many as ∼8 times that of the pure CNOP sample from the electron paramagnetic resonance measurement. Pollutants are oxidized by supplying electrons to electron-poor microcenters, and H₂O₂ can be selectively reduced to ^•OH (also destruct pollutants) in the electron-rich microcenter over RSC-CNOP. This work reveals that the energy and electrons of pollutants can be efficiently utilized in the Fenton-like system through constructing and reinforcing the polarized dual reaction microcenters.

Hydroxyl radical dominated degradation of aquatic sulfamethoxazole by Fe0/bisulfite/O2: Kinetics, mechanisms, and pathways

In this study, batch experiments were carried out to investigate the key factors on sulfamethoxazole (SMX) removal kinetics in a new AOPs based on the combination of zero valent iron (Fe⁰) and bisulfite (S(IV)). With the increase of Fe⁰ from 0.25 mM to 5 mM, the removal rate of SMX was linearly increased in the Fe⁰/S(IV)/O₂ system by accelerating the activation of S(IV) and Fe⁰ corrosion to accelerate. In the first 10 min of reaction, the increasing concentration of S(IV) inhibited SMX removal after since the high S(IV) concentration quenched reactive oxidative species (ROS). Then SMX removal rate was accelerated with the increase of S(IV) concentration after S(IV) were consumed up. The optimal ratio of S(IV) concentrations to Fe⁰ concentration for SMX removal in the Fe⁰/S(IV)/O₂ system was 1:1. With SMX concentrations increasing from 1 to 50 μM, SMX removal rate was inhibited for the limitation of ROS yields. Although the presence of SO₄^- and OH was confirmed by electron paramagnetic resonance (EPR) spectrum, OH was identified as the dominant ROS in the Fe⁰/S(IV)/O₂ system by chemical quenching experiments. Besides, strong inhibitive effects of 1,10-phenanthroline on SMX degradation kinetics by Fe⁰/S(IV)/O₂ proved that the generation of ROS was rely on the release of Fe(II) and Fe(III). The generation of SO₄^- was ascribed to the activation of S(IV) by Fe(II)/Fe(III) recycling and the activation of HSO₅^- by Fe(II). And OH was simultaneously transformed from SO₄^- and generated by Fe⁰/O₂. Density functional theory (DFT) calculation was conducted to reveal special reactive sites on SMX for radicals attacking and predicted intermediates. Finally, four possible SMX degradation pathways were accordingly proposed in the Fe⁰/S(IV)/O₂ system based on experimental methods and DFT calculation.

Combined Effect of Weak Magnetic Fields and Anions on Arsenite Sequestration by Zerovalent Iron: Kinetics and Mechanisms

In this study, the effects of major anions (e.g., ClO₄^-, NO₃^-, Cl^-, and SO₄^2-) in water on the reactivity of zerovalent iron (ZVI) toward As(III) sequestration were evaluated with and without a weak magnetic field (WMF). Without WMF, ClO₄^- and NO₃^- had negligible influence on As(III) removal by ZVI, but Cl^- and SO₄^2- could improve As(III) sequestration by ZVI. Moreover, the WMF-enhancing effect on As(III) removal by ZVI was minor in ultrapure water. A synergetic effect of WMF and individual anion on improving As(III) removal by ZVI was observed for each of the investigated anion, which became more pronounced as the concentration of anion increased. Based on the extent of enhancing effects, these anions were ranked in the order of SO₄^2- > Cl^- > NO₃^- ≈ ClO₄^- (from most- to least-enhanced). Furthermore, the inhibitory effect of HSiO₃^-, HCO₃^-, and H₂PO₄^- on ZVI corrosion could be alleviated taking advantage of the combined effect of WMF and SO₄^2-. The coupled influence of anions and WMF was associated with the simultaneous movement of anions with paramagnetic Fe²⁺ to keep local electroneutrality in solution. Our findings suggest that the presence of anions is quite essential to maintaining or stimulating the WMF effect.

Factors affecting p-nitrophenol removal by microscale zero-valent iron coupling with weak magnetic field (WMF)

The effect of WMF on the kinetics of p-nitrophenol (PNP) removal by six commercial zero-valent iron (ZVI) samples from different origins were studied at pH 4.0.

Degradation of aquatic sulfadiazine by Fe0/persulfate: kinetics, mechanisms, and degradation pathway

Degradative mechanisms of aquatic sulfadiazine by Fe⁰/persulfate.

Nanoscale zero-valent metals: a review of synthesis, characterization, and applications to environmental remediation

Engineered nanoscale zero-valent metals (NZVMs) representing the forefront of technologies have been considered as promising materials for environmental remediation and antimicrobial effect, due to their high reducibility and strong adsorption capability. This review is focused on the methodology for synthesis of bare NZVMs, supported NZVMs, modified NZVMs, and bimetallic systems with both traditional and green methods. Recent studies have demonstrated that self-assembly methods can play an important role for obtaining ordered, controllable, and tunable NZVMs. In addition to common characterization methods, the state-of-the-art methods have been developed to obtain the properties of NZVMs (e.g., granularity, size distribution, specific surface area, shape, crystal form, and chemical bond) with the resolution down to subnanometer scale. These methods include spherical aberration corrected scanning transmission electron microscopy (Cs-corrected STEM), electron energy-loss spectroscopy (EELS), and near edge X-ray absorption fine structure (NEXAFS). A growing body of experimental data has proven that nanoscale zero-valent iron (NZVI) is highly effective and versatile. This article discusses the applications of NZVMs to treatment of heavy metals, halogenated organic compounds, polycyclic aromatic hydrocarbons, nutrients, radioelements, and microorganisms, using both ex situ and in situ methods. Furthermore, this paper briefly describes the ecotoxicological effects for NZVMs and the research prospects related to their synthesis, modification, characterization, and applications.

Effects of oxygen and weak magnetic field on Fe(0)/bisulfite system: performance and mechanisms

The performance and mechanisms of 4-nitrophenol (4-NP) degradation by the Fe(0)/bisulfite system were systematically investigated for the first time. The evidences presented in this study verified that O2 was a crucial factor that affected the mechanism of Fe(0)/bisulfite-driven 4-NP degradation. In the Fe(0)/bisulfite/O2 system, Fe(0) acted as a supplier of Fe(2+) to catalyze bisulfite oxidation that induced a chain reaction to produce reactive radicals for 4-NP degradation. While under N2 purging condition, bisulfite worked as a specified reductant that facilitated the transformation of Fe(3+) to nascent Fe(2+) ions, which principally accounted for the reductive removal of 4-NP. The application of a weak magnetic field (WMF) efficiently improved the removal rate of 4-NP and did not alter the mechanisms in both Fe(0)/bisulfite/O2 and Fe(0)/bisulfite/N2 processes. The secondary radicals, HO(·), SO4 (·-), and SO5 (·-), were considered as the most possible active oxidants contributing to the oxidative removal of 4-NP and even partial mineralization under an oxic condition. Compared with anoxic conditions, the performance removal of 4-NP by the WMF-Fe(0)/bisulfite/O2 system showed less pHini dependence. To facilitate the application of WMF-Fe(0)/bisulfite/O2 technology in real practice, premagnetization of Fe(0) was employed to combine with bisulfite/O2 and proved to be an effective and applicable method for 4-NP removal.

Modeling the Kinetics of Contaminants Oxidation and the Generation of Manganese(III) in the Permanganate/Bisulfite Process

Permanganate can be activated by bisulfite to generate soluble Mn(III) (noncomplexed with ligands other than H2O and OH(-)) which oxidizes organic contaminants at extraordinarily high rates. However, the generation of Mn(III) in the permanganate/bisulfite (PM/BS) process and the reactivity of Mn(III) toward emerging contaminants have never been quantified. In this work, Mn(III) generated in the PM/BS process was shown to absorb at 230-290 nm for the first time and disproportionated more easily at higher pH, and thus, the utilization rate of Mn(III) for decomposing organic contaminant was low under alkaline conditions. A Mn(III) generation and utilization model was developed to get the second-order reaction rate parameters of benzene oxidation by soluble Mn(III), and then, benzene was chosen as the reference probe to build a competition kinetics method, which was employed to obtain the second-order rate constants of organic contaminants oxidation by soluble Mn(III). The results revealed that the second-order rate constants of aniline and bisphenol A oxidation by soluble Mn(III) were in the range of 10(5)-10(6) M(-1) s(-1). With the presence of soluble Mn(III) at micromolar concentration, contaminants could be oxidized with the observed rates several orders of magnitude higher than those by common oxidation processes, implying the great potential application of the PM/BS process in water and wastewater treatment.