•Algae can promote biogenic oxidation of Mn(II) by accelerated O2− production.•The inhibited Fe-S cluster activity of QJX-1 by algae can induce electron leakage.•Decomposition of H2O2 can benefit the ...transformation of intermediate Mn(III) ions.•The phenomenon can be found with many prevalent algae species in algae blooms.
Microbial manganese (Mn) oxidation, predominantly occurs within the anaerobic-aerobic interfaces, plays an important role in environmental pollution remediation. The anaerobic-aerobic transition zones, notably riparian and lakeside zones, are hotspots for algae-bacteria interactions. Here, we adopted a Mn(II)-oxidizing bacterium Pseudomonas sp. QJX-1 to investigate the impact of algae on microbial Mn(II) oxidation and verify the underlying mechanisms. Interestingly, we achieved a remarkable enhancement in bacterial Mn(II)-oxidizing activity within the algae-bacteria co-culture, despite the inability to oxidize Mn(II) for the algae used in this study. In addition, the bacterial density almost remains constant in the presence of algal cells. Therefore, the increased Mn(II) oxidation by QJX-1 in the presence of algae cannot be due to the increased biomass. Within this co-culture system, the Mn(II) oxidation rate surged to an impressive 0.23 mg/L/h, in stark contrast to 0.02 mg/L/h recorded within pure QJX-1 system. The presence of algae could inhibit the Fe-S cluster activity of QJX-1 by the produced active substance in co-culture, and result in the acceleration of extracellular superoxide production due to the impairment of electron transfer functions located in QJX-1 cell membranes. Moreover, elevated peroxidase gene expression and heightened extracellular catalase activity not only expedited Mn(II) ions oxidation but also facilitated conversion of intermediate Mn(III) ions into microbial Mn oxides, achieved through the degradation of hydrogen peroxide. Therefore, the acceleration of extracellular superoxide production and the decomposition of hydrogen peroxide are identified as the principal mechanisms behind the observed enhancement in Mn(II) oxidation within algae-bacteria co-cultures. Our findings highlight the need to consider the effect of algae on microbial Mn(II) oxidation, which plays an important role in the environmental pollution remediation.
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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−.
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•Mn(II) can be effectively oxidized by oxygen in the presence of sulfite.•Sulfite-promoted Mn(II) removal is dependent on pH and sulfite concentration.•HSO5− is generated in this process and contribute to Mn(II) oxidation.•SO4.•- is the key radical responsible for Mn(II) oxidation by HSO5−.•Fe(II) can enhance sulfite-induced Mn(II) removal.
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•A novel Mn-oxidizing bacterium of Aeromonas hydrophila strain DS02 was isolated.•The maximum of Mn(II) removal (89.6%) and oxidation (45.6%) was obtain in the initial Mn(II) ...concentration of 10 mM.•Mn(IV)-oxide was the major component (82.0%) of the flake-shaped BioMnOx.•99.5% 2,4-DMA was degraded by BioMnOx/PMS system in 80 min.
The extensive applications of biogenic manganese oxides (BioMnOx) generated by manganese oxidizing bacteria (MOB) have attracted considerable attentions. In this study, we report on a novel MOB that has been isolated from sediments and identified as Aeromonas hydrophila strain DS02. The Mn(II) oxidation activity of strain DS02 under Mn(II) stress and the application of the associated BioMnOx products were investigated. Nearly 90.0% (495 mg L−1) of the soluble Mn(II) were removed and 45.6% (240 mg L−1) was converted to Mn(III/IV). Fitting the XPS data showed that Mn(IV)-oxide is the major component (82.0%) of the flake-shaped BioMnOx, corresponding to an average Mn oxidation number of 3.71. When the BioMnOx were coupled with the PMS activation, a 99.5% catalytic degradation of 2,4-dimethylaniline was observed after 80 min, revealing a high degradation efficiency.
Manganese and its compounds have been extensively studied because of their far-reaching roles in a wide range of biogeochemical processes in natural systems. The (ad)sorption behavior of Mn(II), ...however, is poorly understood despite its important role as the primary reaction step for surface-catalyzed Mn(II) oxidation that is the principal abiotic process forming various Mn (oxyhydr)oxides in nature. Here, we systematically examined Mn(II) (ad)sorption to one of the most common natural sorbents, goethite, in oxygen- and carbonate-free systems. Traditional sorption edge and isotherm experiments were conducted by varying sorbate-to-sorbent ratio (0.027–15 μmol∙m−2) and solution pH (pH 5.0–9.0). The effects of dissolved carbonates on Mn(II) sorption were also assessed in a range of naturally prevalent concentrations (0.5–10 mM NaHCO3). The Mn(II) uptake on goethite followed a typical Langmuir isotherm in the absence of dissolved carbonates, with increasing maximum adsorption capacities (Γmax) from 0.19 at pH 6.5 to 3.4 μmol∙m−2 at pH 9.0. The presence of dissolved carbonates raised the extent of Mn(II) adsorption, which appeared to be directly correspondent to that of the adsorption of dissolved carbonates. Extended X-ray absorption fine structure (EXAFS) analysis indicated that Mn(II) predominantly formed inner-sphere binuclear bidentate surface complexes. Mn(II) uptake became deviated from the Langmuir model and showed a clear indication of surface precipitation when the Mn(II) sorption density (Γ) exceeded a threshold value in a given solution composition. This secondary Mn(II) phase was identified as rhodochrosite using X-ray diffraction (XRD) and transmission electron microscope (TEM). Additionally, it would be plausible that a minor fraction of adsorbed Mn(II) coexisted with the secondary rhodochrosite according to a linear combination fitting (LCF) of the X-ray absorption near edge structure (XANES) spectra of Mn reference and samples. These systematic investigations of the macroscopic and microscopic behaviors of Mn(II) (ad)sorption to goethite provide a critical avenue for disentangling surface-catalytic Mn(II) oxidation processes, which ultimately lead to the formation of diverse Mn (oxyhydr)oxides in the environment.
Mn(II) adsorption-oxidation on iron (Fe) oxides (e.g., ferrihydrite) occurs in various soils and sediments, significantly affecting the toxicities and bioavailabilities of Mn and other associated ...elements. However, the detailed processes of Mn(II) adsorption-oxidation on ferrihydrite remain elusive. In this study, the Mn(II) (2 mM) adsorption-oxidation kinetics on different masses of ferrihydrite (0.25, 0.50, 1.00, and 1.25 g) at pH 7 were determined using batch kinetic studies combined with X-ray diffraction, transmission electron microscopy, and wet chemistry analyses. The results indicated that the low-concentration Mn(II) adsorption-oxidation on ferrihydrite occurred in two steps. First, Mn(II) was adsorbed onto ferrihydrite, where it was partially oxidized by the catalytic effect of ferrihydrite, within ~0–60 min; subsequently, the remaining Mn(II) underwent autocatalytic oxidation on the previously generated Mn (oxyhydr)oxides. The initial adsorption-oxidation behaviors of Mn(II) on the ferrihydrite surface determined the kinetics of Mn(II) removal and oxidation, and therefore the amounts and types of Mn (oxyhydr)oxides formed. Furthermore, the specific characteristics of Mn(II) adsorption-oxidation on ferrihydrite showed a strong dependence on the Fe/Mn molar ratio. When this ratio was below 16.35, the initial process was dominated by Mn(II) adsorption onto ferrihydrite, with slight oxidation generating hausmannite (~0–60 min), followed by the catalytic oxidation of Mn(II) on the formed hausmannite, generating manganite or groutite. Conversely, when the Fe/Mn molar ratio was above 32.7, the reactions primarily involved Mn(II) adsorption onto ferrihydrite with minor oxidation to form Mn(III/IV) (oxyhydr)oxides (~0–60 min), followed by the autocatalytic oxidation of Mn(II) on the freshly-generated Mn(III/IV) (oxyhydr)oxides, forming Mn(III) (oxyhydr)oxides, i.e., feitknechtite. These results provide further insight into the interaction between Fe and Mn, Mn(II) removal, and Mn (oxyhydr)oxide formation in the environment.
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•We explored the adsorption-oxidation characteristics of Mn(II) on ferrihydrite.•Mn(II) adsorption-oxidation processes on ferrihydrite occurred in two steps.•Mn(II) adsorption-oxidation showed strong dependence on the Fe/Mn mole ratio.•Different initial reactions of Mn(II) on ferrihydrite determined Mn(II) removal and oxidation.
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•BioMnOx removes Mn(II) through adsorption and catalytic oxidation.•The chemical catalysis by BioMnOx makes a major contribution in Mn(II) removal.•Long-term Mn(II) removal by BioMnOx ...depends on MnOB.•MnOB can sustain BioMnOx in a high valence state.
Biogenic manganese oxides (BioMnOx) can effectively remove Mn(II) from drinking water. In the gravity-driven membrane (GDM) system for Mn(II)-containing water treatment, both BioMnOx and Mn(II)-oxidizing bacteria (MnOB) present in the cake layer, and their role in Mn(II) oxidation is still controversial. To address this issue, in this study, we naturally formed a cake layer containing BioMnOx and MnOB using the GDM process and identified the different roles of BioMnOx and MnOB in the removal of Mn(II). The experimental results showed that the BioMnOx accounted for a major proportion of the cake layer of GDM, and it played a principal role in the removal of Mn(II) through the combination of adsorption and catalytic oxidation. However, this removal efficiency would be continuously reduced in the absence of MnOB, while stabilized in the presence of MnOB. XPS analysis revealed that the proportion of Mn(III) and Mn(IV) in BioMnOx with MnOB reached 64.1% and 35.8%, respectively, while BioMnOx without MnOB did not contain Mn(IV). These findings suggest that BioMnOx may be the primary catalyst for Mn(II) oxidation, but its long-term activity is dependent on MnOB, which can maintain the catalytic activity by 1) producing new BioMnOx and 2) sustaining the high valence state of MnOx.
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•3D-sized catalyst is constructed for facial recovery after degradation process.•Mn-MoS2@AABs is firstly proposed as a PMS catalyst for TC degradation.•PMS can be activated ...effectively by Mn-MoS2@AABs under visible light.•The regulation of doped Mn enhances the catalytic performance of Mn-MoS2@AABs.
In this work, Mn (II) was doped into MoS2 structure and then anchored on activated alumina beads to construct 3D-sized composites (Mn-MoS2@AABs). This component material was used as PMS activator for tetracycline (TC) degradation under light irradiation. According to experiment results, Mn-MoS2@AABs exhibited well degradation performance to TC, which ascribed to excellent photo-response property of Mn-MoS2 and activation of Mn. Importantly, the 3D-sized structure made it facilely be recycled from solution, which catered to the demand for the practical application. Therefore, the novel strategy of designing Mn-MoS2@AABs had great significance for environmental restoration.
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•Comparison of nitrate removal efficiency in IBR under different electron donor.•A novel material Fe3O4@Cu/PVA as an adsorbent and bacterial immobilized carrier.•Analyzation of ...microbial community structures in IBR under different electron donor.•The IBR could removal nitrate and oxidize Mn(II) simultaneously.
An immobilized biofilm reactor (IBR) was established to treat nitrate using different electron donors. A novel material, Fe3O4@Cu/PVA, was synthesized as an adsorbent and bacterial immobilized carrier in the reactor. The optimum condition of nitrate removal were pH 7.0, hydraulic retention time (HRT) of 10 h under autotrophic and mixotrophic conditions. Strain H-117 in the mixotrophic reactor had better adaptability to changes in the initial pH. The metabolism in the mixotrophic reactor was more vigorous than that in autotrophic reactor. The microbial communities and structures were evaluated to determine the nitrate removal mechanisms in this system. Microbial analyses demonstrated that different electron donor could influence the bacterial abundance and species in the IBR system. Proteobacteria was the most dominant phylum in all IBRs and accounted for more than 50% of the total phyla. Pseudomonas and Rhizobium were the dominant contributor to the effective removal of nitrate in the IBRs.
•New CPs Mn(H2L)n (1) and Mn(H2L)(H2O)2n (2) were synthesized.•1 is a 3D network with the point symbol of {48·67}.•2 is a 4-connected 2D grid framework.•TGA, PXRD, magnetic properties of 1–2 were ...studied.
Two new coordination polymers (CPs), Mn(H2L)n (1) and Mn(H2L)(H2O)2n (2) (H4L= 5,5′-(ethene-1,2-diyl)diisophthalic acid), have been synthesized under different temperature. 1 is a 3D (6,6)-connected framework built by infinite O-Mn-O-C-O-Mn- chains and H2L2− linkers. 2 has a 2D (4,4)-connected network structure formed by metal-chain. 2 obtained at higher temperature than of 1, which will induce a 3D architecture. The results indicated that the hydrothermal reaction temperature may affect on the structure of the CPs 1 and 2 in this system. The magnetic behaviors of the complexes have been investigated in detail in CPs 1 and 2.
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