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In recent years, researchers have increasingly focused on flow electrode capacitive deionization (FCDI) for heavy metal removal. However, the practical application of FCDI has been limited because of its low removal efficiency at low voltages. To address this limitation, we investigated Cr(VI) removal using FCDI in high-voltage mode (≥1.23 V). We aimed to clarify the mechanism and capabilities of high-voltage FCDI, including the removal energy efficiency, ion valence changes, migration process, and practical applications. Our findings demonstrate that even at high voltages (≤1.6 V), FCDI maintains efficient Cr(VI) removal and charge efficiency. This success was attributed to the significant IR drop in the FCDI system. Additionally, Cr (VI) removal by high-voltage FCDI results from a synergistic effect combining electroporation and electroreduction. The higher the applied voltage, the stronger was the electroporation capacity and the reduction ratio. Under the voltage condition of 2.2 V, the maximum electroporation capacity reached 172.82 mg g−1. However, excessively high-voltage can also lead to a more pronounced side reaction, resulting in a slow improvement in the removal efficiency. We further optimized the process parameters of the FCDI using response surface methodology (RSM). The optimized conditions yielded impressive results, a 99.96 % removal efficiency and low energy consumption (0.104 kWh/m3) in actual Cr(VI)-containing wastewater. Additionally, even in the 19th cycle of continuous operation, Cr(VI) removal by FCDI exceeded 90 %. This study unveils the efficacy and mechanism of Cr(VI) removal by high-pressure FCDI, which is expected to advance industrial applications of FCDI for treating heavy metal-containing wastewater. [Display omitted] • Electro-absorption can effectively increase the adsorption capacity of activated carbon. • Reduction of Cr(VI) to Cr(III) on activated carbon during the FCDI process. • High-voltage FCDI can effectively treat actual chromium-containing electroplating wastewater. • RSM-optimised FCDI removes 99.96 % of Cr(VI) from real electroplating wastewater. • Study reveals new insights into FCDI-based treatment. [ABSTRACT FROM AUTHOR]

To simultaneously promote the generation of H 2 O 2 and the cycling of Fe3+/Fe2+, and improve the electrical Fenton performance, we propose a strategy of preparing PEDOT/GF cathode for efficient generation of H 2 O 2 and reduction of Fe3+ in electro-Fenton (EF) process without additional reducing agent. The accumulated concentration of H 2 O 2 on the PEDOT/GF-100 cathode reached 67.2 mg L–1 in 1 h, with a current efficiency of 70.6 %, which is much higher than that of the raw GF. Moreover, the H 2 O 2 concentration by PEDOT/GF-100 could reach 49.3–67.2 mg L−1 in a wide pH range (3–9). With 2,4-DCP as main target pollutant, the EF process of PEDOT/GF-100 cathode accelerated the degradation of 2,4-DCP. In addition to the improvement of H 2 O 2 production, the reduction rate of Fe3+ in the EF process of PEDOT/GF-100 cathode system was also increased compared to the raw GF, while the total iron remained stable. The quenching experiment confirmed the dominant role of • OH in the degradation of 2,4-DCP. The PEDOT/GF-100 cathode can synergistically promote the electrosynthesis of H 2 O 2 and iron interconversion, thereby accelerating the production of •OH. The utilization of PEDOT/GF cathode can simultaneously solve the problems of low Fe3+/Fe2+cycling efficiency and low H 2 O 2 production in the EF process, promoting its application in practical wastewater treatment. [Display omitted] • The PEDOT modified graphite felt cathode was prepared. • The accumulated concentration of H 2 O 2 reach 49.3–67.2 mg L−1 in a wide pH range. • The reduction rate of Fe3+ was greatly increased in EF process. • Degradation efficiencies of 2,4-DCP achieve 99 % in 15 min. [ABSTRACT FROM AUTHOR]

Influence of granular size and groundwater flow rate on transport of Pseudomonas migulae AN-1 in saturated porous media was non-invasively and visually investigated with a novel imaging technique based on our previously established green fluorescent protein-tagging approach. AN-1 was transported faster than water was. The finer the media were, the greater the enhancement of bacterial velocity was. Mass recovery ( MR ) increased, while deposition rate coefficient ( K c ) decreased, with increasing granular size. Similar and linear trends of MR and K c , respectively, were quantitatively observed with increasing water flow rate. The images revealed that the initial shape of bacterial plume after injection was a narrow strip along the injection well and an ellipsoid in the lower part of the injection well in medium and coarse sand, respectively. Bacterial plume migrated horizontally in medium sand, but shifted slightly downward in coarse sand. Under similar conditions, the fluorescent area carrying AN-1 in medium sand was larger than that carrying AN-1 in coarse sand during the same period. The visualisation method of this study captured both the movement of free-state and retained bacteria that adhered to sediments. A continuous biological zone composed of planktonic and retained AN-1 was observed. These findings are significant for actual bioremediation. [ABSTRACT FROM AUTHOR]

An advanced reduction process (ARP) was established for the highly reductive radical CO 2 − produced by thermally activated persulfate (TAP) system in the presence of formate anions (FA). A series of control tests suggested that FA converted a strong oxidative condition into a reductive one, with CO 2 − as the predominant radical for Cr(VI) reduction initiated by SO 4 − in the presence of FA. This mechanism was confirmed by electron spin resonance experiment. The ability of the system to reduce Cr(VI) mainly depended on the dosage ratio of FA and persulfate (PS), and the system maintained a strong reductive condition at ratios of FA to PS equal to or higher than one. Moreover, the rate of reaction increased with increasing PS dosage and reaction temperature, but decreased with increasing pH. The reduction efficiency of Cr(VI) reached more than 99% within 240 min for an initial Cr(VI) concentration of 50 mg·L −1 under the condition of [FA] 0 = 30 mM, [PS] 0 = 30 mM, T = 70 °C, and unadjusted pH. [ABSTRACT FROM AUTHOR]

Rhizoremediation is acknowledged as a green technology for removing polychlorinated biphenyls (PCBs) in soil. However, rhizoremediation is limited because most soil microorganisms enter into a viable but non-culturable (VBNC) state under PCBs stress. This work was to study the effect of resuscitation-promoting factor (Rpf) on rhizoremediation efficiency of PCBs in alfalfa and rhizosphere microbiological communities. Results suggested that Rpf promoted alfalfa growth in PCB-contaminated soil by improving antioxidant enzymes and detoxification metabolites in alfalfa. After 40 d Rpf treatment, removal rate for five selected PCBs significantly increased by 0.5–2.2 times. Rpf enhanced relative abundances of bphA and bphC responsible for degrading PCBs, and enzymatic activities of metabolizing exogenous compounds in rhizosphere soil. High-throughput sequencing showed that Rpf did not change the dominant microbial population at phyla and genera levels, but caused variation of the bacterial community structures. The promoting function of Rpf was linked to the shift of various key populations having different functions depending on Rpf concentrations. Pseudomonas and Rhizobium spp. enrichment might stimulate PCB degradation and Streptomyces and Bacillus spp. primarily contributed to alfalfa growth. Predicted functions in rhizosphere soil bacterial community indicated Rpf facilitated soil nutrient cycling and environmental adaptation. This study indicated that Rpf was an active additive for strengthening rhizoremediation efficiency of PCB-contaminated soil and enhancing their in-situ remediation. [Display omitted] • Rpf enhanced the efficiency of PCBs degradation in rhizosphere soil. • Rpf promoted alfalfa growth by increasing PGPB growth and plant metabolism. • Rpf modulated various beneficial microbial populations in rhizosphere soil. [ABSTRACT FROM AUTHOR]

Chlorophenols (CPs) are common environmental pollutants. As such, different treatments have been assessed to facilitate their removal. In this study, 2,4-dichlorophenol (2,4-DCP) hydroxylase was used to systematically investigate the activity and removal ability of 19CP congeners at 25 and 0 °C. Results demonstrated that 2,4-DCP hydroxylase exhibited a broad substrate specificity to CPs. The activities of 2,4-DCP hydroxylase against specific CP congeners, including 3-CP, 2,3,6-trichlorophenol, 2-CP, and 2,3-DCP, were higher than those against 2,4-DCP, which is the preferred substrate of previously reported 2,4-DCP hydroxylase. To verify whether cofactors are necessary to promote hydroxylase activity against CP congeners, we added FAD and found that the added FAD induced a 1.33-fold to 5.13-fold significant increase in hydroxylase activity against different CP congeners. The metabolic pathways of the CP degradation in the enzymatic hydroxylation step were preliminarily proposed on the basis of the analyses of the enzymatic activities against 19CP congeners. We found that the high activity and removal rate of 2,4-DCP hydroxylase against CPs at 0 °C enhance the low-temperature-adaptability of this enzyme to the CP congeners; as such, the proposed removal process may be applied to biochemical, bioremediation, and industrial processes, particularly in cold environments. [ABSTRACT FROM AUTHOR]

This work demonstrated a novel N , N -bis(carboxymethyl)glutamic acid (GLDA) modified visible (vis) light assisted Fenton–like system which could effectively removal ciprofloxacin (CIP) at neutral pH. The removal rate of CIP in the GLDA/Fe(III)/H 2 O 2 /vis system was 97.9% within 120 min and was approximately twice as high as that in the Fe(III)/H 2 O 2 /vis system. GLDA could significantly accelerate the Fe(III)/Fe(II) cycle under visible light irradiation. Radical scavenging experiments demonstrated that 74.2% of the Fe(II) in the GLDA/Fe(III)/H 2 O 2 /vis system originated from the ligand–to–metal charge transfer reaction between Fe(III) and GLDA. The hydroxyl radical was the dominant species for CIP degradation. H 2 O 2 utilization kinetic modeling exhibited that 90.1% of H 2 O 2 was used for CIP mineralization. The effects of experimental parameters and coexisting substances on the removal of CIP in the Fe(III)/GLDA/H 2 O 2 /vis system were investigated in detail. The intermediate products of CIP were explored via the high–performance liquid chromatography-mass spectrometry. [Display omitted] • GLDA/Fe(III)/H 2 O 2 /vis process could effectively removal CIP at neutral pH. • GLDA–Fe(III) complex facilitated the cycle of Fe(III)/Fe(II) under visible light. • ·OH was the dominant reactive species for CIP degradation. • The H 2 O 2 utilization efficiency in the GLDA/Fe(III)/H 2 O 2 /CIP/vis process was 90.1%. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is a hazardous contaminant when dispersed into soil. It is toxic to plants and further decreases the efficiency of phytoremediation. To improve plant tolerance to Cd, applying plant-associated bacteria is an effective way. This work aimed to determine the effect of a plant growth promoting bacterium Pseudomonas monteilii strain PN1 on alfalfa (Medicago sativa L.) growth, Cd phytoextraction, and bacterial communities in rhizosphere. A pot trail was performed with alfalfa planted in soil containing Cd at various concentrations and drenched with PN1 suspension. Plants and soil were sampled for biochemical and microbial analyses. Results showed that alfalfa growth was negatively correlated with Cd concentration. However, PN1 inoculation enhanced the growth of alfalfa, and augmented the capacity of Cd phytoextraction. Phytohormone (indole-3-acetic acid) production and antioxidant enzymatic activities (guaiacol peroxidase, superoxide dismutase, and catalase), and 1-aminocyclopropane-1-carboxylic acid deaminase activities of alfalfa were enhanced, which indicated PN1 might mitigate Cd stress. There was a negative impact of Cd on the rhizosphere bacterial communities. However, PN1 can restore the bacterial community in Cd contaminated soil to a certain level. Relative abundance of beneficial bacteria in soil increased and their interactions were strengthened in the presence of PN1 under Cd stress, which was indicated by increased alfalfa growth. All the activities on alfalfa and bacteria in soil facilitated the adaptability of plant-bacteria systems to Cd stress. Thus, the association of alfalfa with PN1 can be a potential biological system for in-situ remediating Cd-contaminated soil. [Display omitted] • PN1 enhanced alfalfa growth by elevating enzymatic activities and IAA production. • PN1 augmented the capacity of Cd phytoextraction from soils. • PN1 resulted in heavy-metal-tolerant bacteria and PGPB enriched in soils. • The association of alfalfa with PN1 can be a potential candidate for in situ remediation of Cd-contaminated soil. [ABSTRACT FROM AUTHOR]

In this study, we reported that the presence of rosemary acid (RA) could strongly enhance the Fe(III)-mediated Fenton oxidation of 2,4-DCP as the model contaminant at near neutral pH. This enhancement was verified by the strong chelating and reducing ability of RA, which could prevent ion precipitation and accelerate the Fe3+/Fe2+ cycle. Radical quenching experiments and electron paramagnetic resonance confirmed the existence and roles of hydroxyl radicals in the Fe3+/RA/H 2 O 2 system. Lot size optimized experiments were executed to achieve efficient 2,4-DCP degradation (99.93%) under the optimum conditions of 100 μmol/L Fe3+, 100 μmol l/L RA and 8 mmol/L H 2 O 2 within 60 min. In addition, co-existing metal ions, inorganic anions and natural organic matters were proved that they could inhibit removal efficiency and rate at varying degrees. Total organic carbon and chloride ion measurements were employed to probe the mineralization of organic matters (including RA and 2,4-DCP). This study provides a new modified Fenton system to enhance the oxidation removal of refractory organics in water and will enrich the understanding on effective H 2 O 2 activation at neutral pH. Unlabelled Image • A novel Fe3+/RA/H 2 O 2 process was proposed to oxidize organic pollutant at near neutral pH. • RA can prevent iron precipitation and accelerate Fe3+/Fe2+ cycle. • Generation of hydroxyl radical was verified in the Fe3+/RA/H 2 O 2 system. • RA and 2,4-DCP were mineralized simultaneously in the Fe3+/RA/H 2 O 2 system. [ABSTRACT FROM AUTHOR]

The gradient distribution of microbial communities has been detected in profiles along many natural environments. In a mangrove seedlings inhabited mudflat, the microbes drive a variety of biogeochemical processes and are associated with a dramatically changed environment across the tidal zones of mudflat. A better understanding of microbial composition, diversity and associated functional profiles in relation to physicochemical influences could provide more insights into the ecological functions of microbes in a coastal mangrove ecosystem. In this study, the variation of microbial community along successive tidal flats inhabited by mangrove seedlings were characterized based on the 16S rDNA gene sequences, and then the factors that shape the bacterial and archaeal communities were determined. Results showed that the tidal cycles strongly influence the distribution of bacterial and archaeal communities. Dissimilarity and gradient distribution of microbial communities were found among high tidal flat, mid-low tidal flat and seawater. Discrepancies were also as well observed from the surface to subsurface layers specifically in the high tidal flat. For example, Alphaproteobacteria displayed an increasing trend from low tidal to high tidal flat and vice versa for Deltaproteobacteria; Cyanobacteria and Thaumarchaeota were more dominant in the surface layer than the subsurface. In addition, by classifying the microorganisms into metabolic functional groups, we were able to identify the biogeochemical pathway that was dominant in each zone. The (oxygenic) photoautotrophy and nitrate reduction were enhanced in the mangrove inhabited mid tidal flat. It revealed the ability of xenobiotic metabolism microbes to degrade, transform, or accumulate environmental hydrocarbon pollutants in seawater, increasing sulfur-related respiration from high tidal to low tidal flat. An opposite distribution was found for major nitrogen cycling processes. The shift of both composition and function of microbial communities were significantly related to light, oxygen availability and total dissolved nitrogen instead of sediment types or salinity. [ABSTRACT FROM AUTHOR]

Magnetic spinel FeCo 2 O 4 nanoparticles (NPs) were synthesized and proposed as a catalyst of peroxymonosulfate (PMS) for the degradation of 2,4-dichlorophenol (2,4-DCP). The catalyst was characterized by XRD, TEM, XPS, nitrogen adsorption–desorption isotherms, and magnetization curve. In addition, the effects of parameters, such as initial pH, PMS dosage, FeCo 2 O 4 addition, and initial concentration of 2,4-DCP were studied. The results showed that FeCo 2 O 4 NPs exhibit good properties for the degradation and mineralization of 2,4-DCP, achieving 95.8% and 44.7% removal of 2,4-DCP and TOC, respectively, within 90 min under reaction conditions of 4 mM PMS, 0.06 g L −1 FeCo 2 O 4 , 100 mg L −1 2,4-DCP, pH = 7.0, and T = 30 °C. Furthermore, SO 4 − and HO were main radical species in the reaction system was explored. The 2,4-DCP degradation efficiency could reach 91.8% even after FeCo 2 O 4 NPs were used for the fifth run. Moreover, the degradation efficiencies of metronidazole (MNZ), methylene blue (MB), and rhodamine B (RhB) could reach 74.8%, 86.7%, and 96.1% under the same reaction conditions, respectively. Results revealed that the FeCo 2 O 4 /PMS system shows potential for degrading contaminants in the environment. [ABSTRACT FROM AUTHOR]

A novel alkylpolyglycoside (APG)-modified MnFe 2 O 4 nanocomposite (APG@MnFe 2 O 4) enriched with oxygen vacancies (VOs) was developed via co-precipitation and characterized as a peroxymonosulfate (PMS) activator to degrade 2,4-dichlorophenol (2,4-DCP) as the model contaminant. The APG effectively promoted the in situ formation of VOs on MnFe 2 O 4 and subsequently enhanced the production of singlet oxygen (1O 2). Furthermore, the APG@MnFe 2 O 4 initialized an even more efficient non-radical pathway and dominated the degradation of 2,4-DCP. The constructed APG@MnFe 2 O 4 exhibited a much higher reaction rate constant (0.0522) by ~12.73 times of that of the bare MnFe 2 O 4 (0.0041). The degradation efficiency of 2,4-DCP in the APG@MnFe 2 O 4 /PMS system approached 93% within 90 min, a rate significantly higher than that in the MnFe 2 O 4 /PMS system (32%) given the same condition. The reasonable catalytic mechanism can be attributed to the Fe/Mn/VOs species. The APG@MnFe 2 O 4 also exhibits universally high removal activity for various pollutants and excellent cyclic stability. Thus, the APG@MnFe 2 O 4 is a promising PMS activator, and its utilization offers a useful strategy for developing VOs-enriched MnFe 2 O 4 catalysts as a means of eliminating organic pollutants from wastewater. • A novel APG modified MnFe 2 O 4 was developed as a PMS activator. • The APG in the synthesis process enriched VOs in MnFe 2 O 4。. • The enhanced 1O 2 dominated the degradation of 2,4-DCP. • A strategy for developing VOs-enriched MnFe 2 O 4 catalysts was provided. [ABSTRACT FROM AUTHOR]