The profound review of Fenton process: What's the next step?

Fenton and Fenton-like processes, which could produce highly reactive species to degrade organic contaminants, have been widely used in the field of wastewater treatment. Therein, the chemistry of Fenton process including the nature of active oxidants, the complicated reactions involved, and the behind reason for its strongly pH-dependent performance, is the basis for the application of Fenton and Fenton-like processes in wastewater treatment. Nevertheless, the conflicting views still exist about the mechanism of the Fenton process.

Degradation of iopamidol in the permanganate/sulfite process: Evolution of iodine species and effect on the subsequent formation of disinfection by-products.

Permanganate/sulfite (Mn(VII)/S(IV)) process is a promising pre-oxidation technology for sequestering the emerging organic contaminants in drinking water treatment plant. Iopamidol (IPM), a representative of iodinated X-ray contrast media, has been widely detected in water sources and has the risk of forming iodinated disinfection byproducts (I-DBPs) in water treatment system. In this study, we investigated the evolution of iodine species during the IPM degradation by the Mn(VII)/S(IV) process and its effect on the subsequent formation of I-DBPs during chlorination at pH 7.

Green polyaspartic acid as a novel permanganate activator for enhanced degradation of organic contaminants: Role of reactive Mn(III) species.

Attention has been long focused on enhancing permanganate (Mn(VII)) oxidation capacity for eliminating organic contaminants via generating active manganese intermediates (AMnIs). Nevertheless, limited consideration has been given to the unnecessary consumption of Mn(VII) due to the spontaneous disproportionation of AMnIs during their formation. In this work, we innovatively introduced green polyaspartic acid (PASP) as both reducing and chelating agents to activate Mn(VII) to enhance the oxidation capacity and utilization efficiency of Mn(VII).

Naproxen as a Turn-On Chemiluminescent Probe for Real-Time Quantification of Sulfate Radicals.

Current techniques for identifying and quantifying sulfate radicals (SO) in SO-based advanced oxidation processes (SR-AOPs) are unsatisfactory due to their low selectivity, poor reliability, and limited feasibility for real-time quantification. In this study, naproxen (NAP) was employed as a turn-on luminescent probe for real-time quantification of SO in SR-AOPs. The chemiluminescence(CL) yield (Φ) of the reaction of NAP with SO was first determined to be 1.

Roles of MnO Colloids and Mn(III) during the Oxidation of Organic Contaminants by Permanganate.

Although intermediate manganese species can be generated during the reactions of permanganate (Mn(VII)) with organic pollutants in water, the role of the in situ generated MnO colloids in the Mn(VII) oxidation process remained controversial and the contribution of Mn(III) was largely neglected. This study showed that the apparent second-order rate constants () of Mn(VII) oxidation of methyl phenyl sulfoxide and carbamazepine remained constant with time. However, the degradation of four selected phenolic contaminants by Mn(VII) exhibited an autoaccelerating trend and a linear trend at pH 3.

Mechanistic Insights into the Markedly Decreased Oxidation Capacity of the Fe(II)/SO Process with Increasing pH.

The poor oxidation capacity of the Fe(II)/SO [Fe(II)/PDS] system at pH > 3.0 has limited its wide application in water treatment. To unravel the underlying mechanism, this study systematically evaluated the possible influencing factors over the pH range of 1.

[Investigation of the Performance of Organic Contaminant Degradation by Fe/PDS Under Environmentally Relevant pH Conditions].

Peroxydisulfate (PDS) activation by Fe has proven to be a promising method to abate emerging organic contaminants by generating reactive oxidation species. Nevertheless, this process may only achieve good decontamination performance under acidic conditions, which has markedly limited its application in real practice. To address this issue, we comprehensively investigated the performance of the Fe/PDS process toward some probe contaminants at different pH levels and explored the potential change in reactive oxidative species and the influence of oxygen.

Simultaneous Sequestration of Humic Acid-Complexed Pb(II), Zn(II), Cd(II), and As(V) by Sulfidated Zero-Valent Iron: Performance and Stability of Sequestration Products.

Heavy metal(loid)s (HMs) such as Pb(II), Zn(II), Cd(II), and As(V) are ubiquitously present in co-contaminated soil and shallow groundwater, where the humic acid (HA)-rich environments can significantly influence their sequestration. In this study, sulfidated zero-valent iron (S-ZVI) was found to be able to simultaneously sequestrate these HA-complexed HMs. Specially, the HA-complexed Pb(II), Zn(II), Cd(II), and As(V) could be completely removed by S-ZVI within 60 min, while only 35-50% of them could be sequestrated within 72 h by unsulfidated ZVI.

Abiotic reductive removal of organic contaminants catalyzed by carbon materials: A short review.

Since the observation that carbon materials can facilitate electron transfer between reactants, there is growing literature on the abiotic reductive removal of organic contaminants catalyzed by them. Most of the interest in these processes arises from the participation of carbon materials in the natural transformation of contaminants and the possibility of developing new strategies for environmental treatment and remediation. The combinations of various carbon materials and reductants have been investigated for the reduction of nitro-organic compounds, halogenated organics, and azo dyes.

Enhanced Oxidation of Organic Contaminants by Mn(VII)/CaSO Under Environmentally Relevant Conditions: Performance and Mechanisms.

Although permanganate activation by sodium sulfite (Mn(VII)/NaSO) has shown great potential for rapid abatement of organic contaminants, the limited reactivity under alkaline conditions and undesirable Mn residual may prevent its widespread application. To solve these challenges, calcium sulfite (CaSO) was employed as a slow-release source of SO/HSO (S(IV)) to activate Mn(VII) in this study. It was found that the application of CaSO solid could extend the effective working pH range of Mn(VII)/S(IV) from ≤7.

Enhanced trichloroethylene dechlorination by carbon-modified zero-valent iron: Revisiting the role of carbon additives.

Given that there are still some debates on the influence of carbon modification on zerovalent iron (ZVI) decontamination process, the roles of carbon on trichloroethylene (TCE) reduction by ZVI were re-investigated in this work. Compared to activated carbons (AC) with high adsorption ability, carbon fibers (CF) with good electronic conductivity performed much better in enhancing ZVI performance in terms of both reactivity and selectivity. Moreover, it was interesting to observe that a low carbon loading is sufficient to effectively improve TCE reduction and this promoting effect would decline with further increasing the carbon amounts from 1.

Influence of [sulfite]/[Fe(VI)] molar ratio on the active oxidants generation in Fe(VI)/sulfite process.

Although several groups have made efforts to study micropollutants degradation by Fe(VI)/sulfite process, the mechanism is far from clear and warrants further investigation. Herein, the degradation kinetics and mechanism of selected micropollutants by sulfite (SO)-activated Fe(VI) oxidation were systematically investigated. The oxidation rates of enrofloxacin (ENR) and phenol in Fe(VI)/sulfite process ranged from 0.

Influence of Pyrophosphate on the Generation of Soluble Mn(III) from Reactions Involving Mn Oxides and Mn(VII).

The detection of soluble Mn(III) is typically accomplished using strong complexing agents to trap Mn(III), but the generation of soluble Mn(III) induced by strong complexing agents has seldom been considered. In this study, pyrophosphate (PP), a nonredox active ligand, was chosen as a typical Mn(III) chelating reagent to study the influence of ligands on soluble Mn(III) formation in reactions involving Mn oxides and Mn(VII). The presence of excess PP induced the generation of soluble Mn(III)-PP from α- and δ-MnO and led to the conproportionation reaction of α-, β-, δ-, or colloidal MnO with Mn(II) at pH 7.

Can multiple harvests of plants improve nitrogen removal from the point-bar soil of lake?

Point bar areas around lakes can provide ecological service functions. For example, plants growing on point bars absorb and remove nutrients from the soil and water. However, if the point-bar plants are unregulated, in the fall and winter, plant debris will decompose, releasing nutrients that then enter the water body and cause eutrophication.

Selenate removal by Fe coupled with ferrous iron, hydrogen peroxide, sulfidation, and weak magnetic field: A comparative study.

Dosing ferrous ions (ZVI/Fe), combining with oxidants (e.g., HO) (ZVI/HO), sulfidation treatment (S-ZVI), and introducing a weak magnetic field (ZVI/WMF) have been widely used to enhance the performance of zerovalent iron (ZVI) for reductive removal of contaminants.

Enhanced immobilization of chromium(VI) in soil using sulfidated zero-valent iron.

Batch tests were conducted in this study to evaluate the influence of sulfidation on the remediation of Cr(VI) in soil by zero-valent iron (ZVI). It was demonstrated that sulfidated ZVI synthesized by ball-milling with elemental sulfur (S-ZVI) could reduce and immobilize Cr(VI) in soil more rapidly and efficiently than unamended ZVI (ZVI). Specifically, with the optimal S/Fe molar ratio of 0.

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

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 MnO 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 MnO and, secondarily, to the adsorption of Mn(II) on generated MnO.

Removal of Anabaena spiroides by potassium permanganate pre-oxidation: effect on photosynthetic capacity and molecular weight distribution.

Bench scale tests were conducted to investigate the effect of potassium permanganate pre-oxidation on the photosynthetic activity and molecular weight distribution of Anabaena spiroides. Different concentrations of potassium permanganate were added into the suspension of Anabaena spiroides, one of the dominant algae in water bloom, and after pre-oxidation of permanganate for 1 h, the results show that the removal rate significantly increases by 33.99~36.

Enhanced removal of heavy metals by zerovalent iron in designed magnetic reactors.

A magnetic propeller agitator and a magnetic reactor were designed to enhance the removal of heavy metals by zerovalent iron (ZVI) in comparison with the non-magnetic reactor. The weak magnetic field (WMF) applied significantly improved the CuII-EDTA removal by ZVI from 10% without WMF to 98% with WMF within 2.5 h at pHini 6.

Flocculation of low algae concentration water using polydiallyldimethylammonium chloride coupled with polysilicate aluminum ferrite.

The combined application of polydiallyldimethylammonium chloride (PDADMAC) and polysilicate aluminum ferrite (PSFA) was investigated to treat low algae density water samples, in which Microcystis aeruginosa is one of the dominant species. coagulation performance of M. aeruginosa was studied with regard to algal removal, Algal density was evaluated by determining the change in the optical density of the algal culture suspension at 680 nm and chlorophyll a.

Multi-wavelength spectrophotometric determination of Cr(VI) in water with ABTS.

A new method for Cr(VI) (0.025-8.00 mg/L) determination based on the reaction of Cr(VI) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) in aqueous solutions was developed.

Decomplexation and subsequent reductive removal of EDTA-chelated Cu II by zero-valent iron coupled with a weak magnetic field: Performances and mechanisms.

The feasibility of EDTA-chelated Cu(II) (Cu(II)-EDTA) removal by zero-valent iron (Fe(0)) in the presence of a weak magnetic field (WMF) and the involved mechanisms were systematically investigated. Fe(0) combined with WMF (Fe(0)/WMF) was very effective for removing Cu(II)-EDTA at pH 4.0-6.