Bioremediation using mercury (Hg)-volatilizing and immobilizing bacteria is an eco-friendly and cost-effective strategy for Hg-polluted farmland. However, the mechanisms controlling the ...transformation of and resistance to Hg(II) by these bacteria remain unknown. In this study, a plant-associated Pseudomonas sp. strain, AN-B15 was isolated and determined to effectively remove Hg(II) under both nutrient-poor and nutrient-rich conditions via volatilization by transforming Hg(II) to Hg(0) and immobilization by transforming Hg(II) to mercury sulfide and Hg-sulfhydryl. Genome and transcriptome analyses revealed that the molecular mechanisms involved in Hg(II) resistance in AN-B15 were a collaborative process involving multiple metabolic systems at the transcriptional level. Under Hg(II) stress, AN-B15 upregulated genes involved in the mer operon and producing the reducing power to rapidly volatilize Hg(II), thereby decreasing its toxicity. Hydroponic culture experiments also revealed that inoculation with strain AN-B15 alleviated Hg-induced toxicity and reduced the uptake of Hg(II) in the roots of wheat seedlings, as explained by the volatilization and immobilization of Hg(II) and plant growth-promoting traits of AN-B15. Overall, the results from the in vitro assays provided vital information that are essential for understanding the mechanism of Hg(II) resistance in plant-associated bacteria, which can also be applied for the bioremediation of Hg-contamination in future.
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•Strain AN-B15 immobilize Hg(II) by transforming Hg(II) to mercury sulfide and Hg-sulfhydryl.•Strain AN-B15 volatilize Hg(II) by transforming Hg(II) to Hg(0).•Strain AN-B15 reduced Hg accumulation and phytotoxicity for wheat seedlings.•Hg resistance in AN-B15 is a collaborative process involving multiple metabolic systems at the transcriptional level.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Over-potential membrane capacitive deionization (OP-MCDI) improves desalination.•The OP-MCDI system shows 8 times higher salt capacity than a typical CDI system.•OP-MCDI with ...reversed polarity (OP-MCDI-RP) works well for high salinity water.•OP-MCDI-RP enhances desalination with either mesoporous carbon or carbon aerogel.•The OP-MCDI-RP technology can desalinate natural seawater into freshwater.
The salt removal capacity (SRC) of the carbon electrodes in membrane capacitive deionization (MCDI) is limited by the applied potential (<1.6 V). Thus, enhancement of the SRC is essential before applying MCDI to seawater desalination. This study aims at developing a novel MCDI system for seawater desalination by applying over-potential (OP) to enhance ion-adsorption capacity and kinetics, and by reversing the polarity (RP) of electrodes to improve ion-desorption kinetics (hereafter named OP-MCDI-RP) for seawater desalination. At 2.4 V, the OP-MCDI system with mesoporous carbon demonstrated a SRC value of 64.7 mg g−1 when desalting 0.5 M NaCl solution, while the OP-CDI system could only remove 8.2 mg g−1 under identical conditions. Similarly, an OP-MCDI cell using carbon aerogel demonstrated a greater SRC value of 43.4 mg g−1 in comparison with 12.5 mg g−1 achieved in OP-CDI. These results indicate that the OP-MCDI system can directly desalt high salinity water regardless of the electrode material. In contrast to the OP-MCDI system, the OP-MCDI-RP system yields a higher regeneration efficiency by applying a reversed low-voltage. It is shown that, under appropriate operating conditions, the OP-MCDI-RP system reduced the electrical conductivity of a seawater sample of 37 practical salinity units by 99.9%, suggesting that the OP-MCDI-RP system can be employed for seawater desalination. Due to the dramatic increase in energy demand and insufficient long-term stability caused by high potential and high salt concentration, however, the OP-MCDI-RP process should be further investigated for potential practical applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Flow electrode capacitive deionization (FCDI) has attracted growing attention for the treatment of high-concentration saline water and continuous operation, but the mechanism responsible for the ...separation of ions has so far received minimal attention. In this study, an asymmetric FCDI (AFCDI) was assembled with nickel hexacyanoferrate (NiHCF) as cathode and activated carbon (AC) as anode. Its desalination performance and distribution of the removed ions were investigated and compared with FCDI using AC as both cathode and anode. Results showed better desalination performance for AFCDI than FCDI at high applied voltages of 2.4 and 2.8 V. The removed ions were adsorbed by active materials (capacitance contribution) and existed in the electrode electrolyte (charge neutralization contribution). However, the contribution of capacitance and charge neutralization was significantly different between NiHCF electrode and AC electrode. When NiHCF was used as electrode, capacitance contribution dominated the removal of sodium and more than 80% sodium was adsorbed by NiHCF at applied voltages of 1.2–2.8 V. On the contrary, the removed ions mainly existed in electrode solution when AC was used as electrode and charge neutralization contributed to about 80% of removed ions at 2.8 V. These results clarify the mechanism of ions removal in FCDI.
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•AFCDI was assembled with NiHCF as cathode and AC as anode.•AFCDI showed better desalination performance than FCDI under higher voltage.•Both charge neutralization and capacitance contributed to the removal of ions.•Capacitance contribution dominated the removal of sodium in AFCDI.•Removed ions mainly existed in electrode solution in FCDI.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Reducing Hg contamination in soil using eco-friendly approaches has attracted increasing attention in recent years. In this study, a novel multi-metal-resistant Hg-volatilizing fungus belonging to ...Lecythophora sp., DC-F1, was isolated from multi-metal-polluted mining-area soil, and its performance in reducing Hg bioavailability in soil when used in combination with biochar was investigated. The isolate displayed a minimum inhibitory concentration of 84.5mg·L−1 for Hg(II) and volatilized >86% of Hg(II) from LB liquid medium with an initial concentration of 7.0mg·L−1 within 16h. Hg(II) contents in soils and grown lettuce shoots decreased by 13.3–26.1% and 49.5–67.7%, respectively, with DC-F1 and/or biochar addition compared with a control over 56days of incubation. Moreover, treatment with both bioagents achieved the lowest Hg content in lettuce shoots. Hg presence and DC-F1 addition significantly decreased the number of fungal ITS gene copies in soils. High-throughput sequencing showed that the soil fungal community compositions were more largely influenced by DC-F1 addition than by biochar addition, with the proportion of Mortierella increasing and those of Penicillium and Thielavia decreasing with DC-F1 addition. Developing the coupling of Lecythophora sp. DC-F1 with biochar into a feasible approach for the recovery of Hg-contaminated soils is promising.
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•A novel metal-resistant Hg(II)-volatilizing fungus, Lecythophora sp. DC-F1, was isolated.•DC-F1 and biochar both effectively reduced Hg(II) contents in soil and plants.•The soil with both bioagents exhibited the lowest Hg uptake in lettuce shoots.•Soil fungal abundance and community structure were influenced to a greater degree by DC-F1 addition than by biochar addition.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Biogenic carbon emissions, including carbon dioxide (CO2) and methane (CH4), have emerged as a major concern during organic pollutant degradation within constructed wetlands (CWs). Since these ...organic compounds primarily originate from the photosynthetic fixation of atmospheric CO2, it potentially introduces uncertainty when assessing the greenhouse effect of biogenic carbon emissions in CWs based on direct field observations. To objectively assessing this effect, this study proposed a new strategy by quantifying CO2-equivalent (CO2-eq) changes as carbon passes through CWs and tested it in various types of CWs based on 64 literature records. The findings reveal that CWs can contribute to CO2-eq additions, yet are only responsible for 15.6% derived from direct field observations. The type of CWs plays a crucial role in these CO2-eq additions, with vertical flow CWs causing the lowest levels (6.8%), followed by surface flow CWs (14.2%). In contrast, horizontal flow CWs are associated with the strongest CO2-eq addition (25.7%). The findings provide new insights for the objective assessment of the greenhouse effect of biogenic carbon emissions in CWs, which will be beneficial for future life cycle assessment.
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•A new strategy was proposed to assess the greenhouse effect of CW carbon emissions.•CWs contribute to CO2-eq addition by recycling organic carbon into CH4.•CWs are only responsible for 15.6% of current estimates.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Sediment phosphorus (P) is the main source of endogenous P for lake eutrophication. An in-situ combined technology for determination the removal effect of sediment P in all fractions was first ...developed using the novel modified maifanite (MMF) and submerged macrophytes in this study. MMF was synthesized using an acidification process (2.5 mol/L H2SO4) and then a calcination (400 °C) method. The morphology and structure of MMF were characterized by XRD, SEM, XPS, and BET. We tested the removal effects of sediment P by MMF and submerged macrophytes in combination and separately. The results demonstrated that the synergistic removal capacity of sediment P using MMF coupled with submerged macrophytes was higher than the sum of them applied separately. MMF could promote the submerged macrophytes growth and enhance the adsorption of extra P on MMF through root oxygenation and nutrient allocation. The microcosm experiment results showed that sediment from fMMF+V. spiralis exhibited the most microbial diversity and abundance among the sediment. The combination of MMF and submerged macrophytes increased the Firmicutes abundance and decreased the Bacteroidetes. These results indicated that adsorption-biological technology can be regarded as a novel and competitive technology to the endogenous pollution control in eutrophic shallow lakes.
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•MMF (acidification-calcination modification) was prepared and characterized.•MMF promotes the growth of submerged macrophytes.•MMF and submerged macrophytes enhanced the microbial diversity and abundance.•MMF and submerged macrophytes exhibited a higher synergistic removal capacity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Novel nanofibers-covered hollow fiber membrane (N-HFM), combining the advantages of both electrospun nanofibers film and hollow fiber membrane was fabricated via electrospinning with non-rotational ...collectors. The key parameters of electrospinning including positive voltage, negative voltage, polymer concentration and working distance were optimized to examine their effects on the morphology and structure of N-HFM. Meanwhile, a solvent vapor welding post-treatment was firstly applied to enhance the mechanical strength of hollow fiber membranes. The welding can improve the mechanical property and water repellency as well as maintain the high porosity, by fusing the nanofibers just at junctions. After a 40 min welding, the Young's modulus, strain at break and tensile strength of the welded N-HFM increased by 117%, 79% and 90% respectively, compared to the pristine N-HFM. Furthermore, the welded N-HFM was able to present a high flux of 13.2 L m−2 h−1 and a stable salt rejection of over 99.9% during the 5 h of direct contact membrane distillation (DCMD) test, suggesting the competency of the welded N-HFM for MD applications.
•A novel nanofibers-covered hollow fiber membrane was prepared.•Solvent vapor welding was firstly applied to hollow fiber membrane.•Welding can reinforce the mechanical property and water repellency.•Flux of 13.2 L m−2 h−1 and stable salt rejection more than 99.9% were obtained.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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•Asymmetric MCDI with only anion-exchange membrane (AMCDI-AEM) is proposed.•AMCDI-AEM shows better performance compared with CDI.•AEM with high IEC and low resistance and water uptake ...favors desalination.•AEM plays a stronger role than CEM in membrane-assisted CDI application.
Membrane capacitive deionization (MCDI) usually contains both anion and cation exchange membranes (AEM, CEM) to restrict the ion desorption during charging and re-adsorption during discharging in capacitive deionization (CDI). In this study, different from conventional MCDI, an asymmetric membrane capacitive deionization (AMCDI) device packing an AEM only (AMCDI-AEM) was constructed, where the AEM was lab-synthesized from poly (2, 6-dimethyl-1, 4-phenylene oxide). The effect of the AEM properties, such as ion exchange capacity, water uptake and membrane resistance on the desalination performance of AMCDI-AEM was systematically discussed. The results indicate that an AEM with high ion exchange capacity, low membrane resistance and low water uptake is beneficial for AMCDI-AEM. Furthermore, AMCDI packed with a commercial cation exchange membrane only (AMCDI-CEM) and a conventional MCDI device were also assembled to stress the importance of AEM application. Although the charge efficiency of AMCDI-AEM is lower than a full MCDI cell (54.7 vs 95.0%) due to the unprotected cathode, AMCDI-AEM device shows comparable salt adsorption capacity to MCDI (7.4 vs 7.2 mg g−1), and is much better than that of CDI (2.3 mg g−1) and AMCDI-CEM (1.5 mg g−1), suggesting that AEM plays a stronger role than CEM for membrane-assisted CDI application. By using a single AEM and commercial activated carbon electrode, this work provides an opportunity to reduce membrane cost for the industrialization of MCDI technology.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Heavy metal contamination of agricultural lands may give rise to health risks by cultivation and consumption of food crops from such lands, as well as result in economic loss. Phytoremediation is an ...eco-friendly and cost-effective approach to restore contaminated soil. However, the restoration process is slow and its sustainability is difficult to maintain. Bioenergy crops may provide alternative economic benefits to agriculture sector and reduce the risks associated with transfering heavy metals into food webs. In this study, a field experiment was carried out to determine the level of reclamation that would be attained in severely heavy metal-contaminated land by planting cassava (Manihot esculenta), a bioenergy crop. The results showed that cassava could grow well on the derelict land, with a fresh tuber yield of 23.13-26.22 t ha
−1
in one growing season, which could potentially produce 3680-4160 L ha
−1
bioethanol. The economic income of the cassava was estimated to be 11.6-13.1 × 10
3
CNY ha
−1
. Among the cassava tissues, metal concentrations were lowest in the tuber. The soil fertility and acidity were ameliorated after cassava plantation, and the mobile and bioavailable metal fractions in the soils were decreased. The cultivation of cassava as a renewable energy crop appears applicable for sustainable utilization and reclamation of heavy metal-contaminated land.
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BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Hg contamination is a critical environmental problem, and its remediation using cost-effective and environmentally friendly methods is highly desirable. In this study, a multi-metal-resistant ...bacterium showing strong Hg(II) volatilization ability, Pseudomonas sp. DC-B1, was isolated from heavy metal-contaminated soils. DC-B1 volatilized 81.1%, 79.2% and 74.3% of the initial Hg2+ from culture solutions with initial Hg2+ concentrations of 5.1, 10.4, and 15.7 mg/L, respectively, within 24 h. Microcosm experiments were performed to investigate the remediation of Hg(II)-spiked soils inoculated with DC-B1 coupled with sawdust biochar amendment. The efficiency of Hg removal from two types of soil samples with different properties and an initial Hg(II) content of approximately 100 mg/kg was enhanced 5.7–13.1% by bio-augmentation with inoculation of the bacterial strain DC-B1, 5.4–10.7% by amendment of 4% (w/w) biochar, and 10.7–23.2% by the combination of DC-B1 and biochar amendments over an incubation period of 24 d over the efficiency in the control treatment under flooded conditions. Longer root lengths were observed in lettuce grown in the treated soils than in lettuce from the control soil, confirming the bioremediation efficacy of the two bioagents for soil Hg contamination.
•A multi-metal-resistant Pseudomonas sp. strain showing strong Hg(II) volatilization ability, DC-B1, was isolated.•Hg content in flooded soils was reduced spontaneously, which was further enhanced by DC-B1 inoculation.•Amendment with sawdust biochar facilitated the microbial remediation of Hg(II) in the soil.•Bacterium-mediated Hg(II) volatilization coupled with biochar amendment has high potential for soil Hg remediation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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