Search

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 a...

Effective removal of mercury (Hg) pollutants from contaminated water/wastewater to prevent severe environmental pollution is of great significance due to the extremely high toxicity of Hg. In this study, granular biochar and gravel (control) were packed into intermittently aerated constructed wetland (CW) microcosms to treat Hg(Ⅱ)-containing wastewater over 100 d. The results showed that the biochar-filled CWs exhibited notably better Hg(Ⅱ) removal than the gravel systems by facilitating chemical and microbial Hg(Ⅱ) reduction and volatilization and promoting plant growth and Hg assimilation. More than ten times more Hg was absorbed by the plants (L. salicaria) in biochar CWs than in the gravel systems, with the roots acting as the major sink. In contrast, substrate binding in a predominantly oxidizable fraction was the dominant pathway for Hg removal in the gravel CWs. Biochar substrates also exhibited higher levels of COD, N and P removal, and Hg(Ⅱ) import impacted the removal of these pollutants only slightly. Filling material played a more crucial role than Hg input in shaping the microbial communities in the CWs. The proportions of some dominant genera, including Arenimonas, Lysobacter, Micropruina and Hydrogenophaga, increased in the presence of Hg, implying their tolerance to Hg toxicity and potential roles in Hg detoxification in the CWs. Granular biochar-based CW has high potential for treating Hg(Ⅱ)-contaminated wastewater.

In this work, electrochemical impedance spectroscopy (EIS) was utilized to probe interfacial structures of antifouling anion exchange membranes (AEMs) with different modifying architectures fabrica...

Non-carbon materials in capacitive deionization (CDI) can help to enhance the capacity of removed ions. Here, we report for the first time the removal of chloride ions (Cl−) with a bismuth (Bi) anode when coupled with an activated carbon (AC) cathode in CDI. The effects of carbon black in the Bi electrode, applied voltage, electrode mass loading and initial concentration on Cl− removal are investigated. Moreover, its cycle performance is also tested. Results show that addition of carbon black to a Bi electrode (Bi@CB) significantly improves Cl− removal. The declining trend of Cl− concentration and appearance of peaks assigned to products of bismuth oxychloride (BiOCl) in XRD patterns confirm Cl− storage by the Bi electrode, which is enhanced with an increase in voltage. When coupled with AC in a fixed mass, increasing the Bi mass does not contribute to more Cl− removal. Although the cycle performance is not excellent (the attenuation rate is 74% after 10 cycles), its chloride removal capacity is ∼2–3 times the value of AC (e.g. 0.95 vs. 0.32 mmol gBi−1 at 1.2 V in 500 mg L−1 NaCl solution). Besides, the Bi–AC electrode pair in CDI is more suitable to remove Cl− from a solution with a Cl− concentration of below 600 mg L−1.

Polytetrafluoroethylene (PTFE) is an attractive membrane material due to its superior chemical resistance, thermal stability and strong hydrophobicity. However, PTFE hollow fiber membranes are challenging to produce by conventional technique due to the high solvent resistance and high melt viscosity of PTFE. In this study, novel PTFE hollow fiber membranes composed of pure PTFE nanofibers were firstly fabricated via a scalable and environment-friendly method based on emulsion electrospinning with a non-rotating collector and followed by a high-temperature sintering process. The effects of PTFE/PEO mass ratio and sintering temperature on the morphologies and properties of the resulting membranes were investigated. The prepared PTFE hollow fiber membrane shows the excellent characteristics combining the advantages of both electrospun nanofibers membrane and hollow fiber membrane, such as high porosity (more than 82%), self-supporting and superhydrophobicity. The membrane sintered at 380 °C present the highest mechanical strength, which shows the tensile strength, Young's modulus, strain at break of 30.5 Mpa, 53 Mpa, and 315%, respectively. The permeate flux of the prepared PTFE hollow fiber membrane is about 4.6–8.8 times as that of the commercial PTFE hollow fiber membranes, as well as is approximately 3.2–11.6 times higher than the date of the reported PTFE hollow fiber membranes. Additionally, the prepared membrane shows high and stable flux in long-term and rising salinity experiments, indicating it is very promising for membrane distillation (MD) application and even for the treatment of hyper-saline wastewater.

Microbial methods are promising and environmentally friendly methods for remediating heavy metal contamination. In this study, a Cr(VI)-resistant bacterial strain, DC-B3, which was identified as Pseudomonas sp. by 16S rDNA gene sequencing, was isolated from heavy metal-contaminated mine soil, and its performance in Cr(VI) removal from wastewater in terms of Cr(VI) reduction and total Cr adsorption was assessed. This strain exhibited a high capability to reduce Cr(VI) to less toxic Cr(III) without the addition of an external electron donor at low pH (2.0). The Cr(VI) reduction capacity and rate both increased linearly with increasing Cr(VI) concentration, with a reduction capacity of 32.0 mg Cr(VI)·g−1 achieved at an initial concentration of 135.0 mg L−1 over 75 h. In addition, 41.0% of the total Cr was removed from the solution by biosorption, and equilibrium was reached within approximately 5 h. The total Cr sorption process was well described by the pseudo-second-order kinetic and Langmuir isotherm models. Desorption assays indicated that NaOH was the most efficient agent for total Cr desorption, and Cr(VI) and generated Cr(III) were both loaded on the DC-B3 biomass. The bacterial cells after Cr treatment were characterized by scanning electron microscopy-energy dispersive X-ray spectrometer and Fourier transform infrared spectroscopy analyses. Strain DC-B3 showed high potential for possible application in the remediation of Cr(VI) contamination in mine areas.

Excessive ammonia nitrogen in wastewater seriously endangers ecological environment, so high-flux and selectivity membrane is urgently needed for ammonia removal using membrane absorption (MA). In this paper, a high-performance electrospun hollow fiber membrane was fabricated and solvent vapor welding treatment was adopted to enhance mechanical strength. The post-treatment membrane showed 103.8% higher in the Young’s modulus than the pristine membrane. High mechanical strength, porosity and hydrophobicity of the membrane make it superior in mass transfer and selectivity. The effects of membrane thickness, pH and temperature of feed solution on experimental overall mass transfer coefficient (KOE) and selectivity coefficient (SNH3/H2O (g)) were intensively investigated to examine the membrane performance in MA application. The results show KOE is 1.35 * 10−5 m s−1 and SNH3/H2O (g) is 7.58 when pH is 11, which are higher than that of commercial membrane. Moreover, the selectivity can be improved greatly from 6.91 to 9.74 by increasing the thickness of the hollow fiber membrane from 55 ± 5 μm to 115 ± 5 μm. The welded electrospun hollow fiber membrane demonstrates great potential for ammonia removal in MA application.

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 84.5 mg·L−1 for Hg(II) and volatilized >86% of Hg(II) from LB liquid medium with an initial concentration of 7.0 mg·L−1 within 16 h. 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 56 days 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.

Water electrolysis can hinder the operation of capacitive deionization (CDI) and membrane CDI (MCDI). This study is aimed at investigating the overpotential limits of CDI and MCDI (OP-MCDI) for wat...

In this study, biofilters (BFs) packed with inorganic (ceramsite and lava rock) and organic (fibrous carrier and biological ball) materials were applied in a tide-flow mode at three flooded/drained (F/D) time ratios (16/8 h, 12/12 h and 8/16 h) to treat heavily polluted river water. The results showed that higher ammonium and phosphorus removals were achieved with BFs filled with ceramsite (95–97% and 76–77%) and lava rock (87–92% and 84–94%), while fibrous carrier-packed BFs obtained better total nitrogen removal (37–44%). Moreover, the F/D time ratio of 16/8 h was slightly preferable for pollutant removal. High-throughput sequencing analysis illustrated that the relative abundance of potential denitrifiers that developed on organic media was much higher than those on inorganic substrates. The results indicated that the combination of inorganic materials and fibrous carriers as substrates could be an effective strategy for enhancing overall pollutant removal in BFs.

Ecological restoration is one of the hot technologies for the reconstruction of eutrophic lake ecosystems in which the restoration and propagation of submerged plants is the key and difficult step. In this paper, the effect of vermiculite on the growth process of Vallisneria spiralis and sediment microenvironment were investigated, aiming to provide a theoretical basis for the application of vermiculite in aquatic ecological restoration. Results of growth indexes demonstrated that 5% and 10% vermiculite treatment groups statistically promote the growth of Vallisneria spiralis compared to the control. Meanwhile, the results of ecophysiological indexes showed that photosynthetic pigment, soluble sugar content, superoxide dismutase (SOD), and catalase (CAT) activity of 5% and 10% group were increased compared with the control while the malondialdehyde (MDA) content exhibited the opposite result (p 0.05), which illustrated that vermiculite can improve the resistance of plants and delay the aging process of Vallisneria spiralis. In addition, result of PCA (Principal Component Analysis) demonstrated 5% and 10% group has improved the sediment physical conditions and create more ecological niche for microorganisms directly, and then promoted the growth of plants. The dissolution results showed that vermiculite can dissolve the constant and trace elements needed for plant growth. Furthermore, the addition of vermiculite increased the diversity of microorganisms in the sediments, and promoted the increase of plant growth-promoting bacteria and phosphorus-degrading bacteria. This study could provide a technique reference for the further application of vermiculite in the field of ecological restoration.

The interactions between sediment microbial assemblages and submerged macrophytes in aquatic ecosystems can be potentially regulated by benthic macrofauna, and the regulation effect may be closely related to macrophyte species with distinct properties; however, little information on this is available. An aquarium experiment was designed to evaluate the role of snail Bellamya aeruginosa (Reeve) in regulating sediment bacterial communities associated with two common types of submerged macrophytes, Ceratophyllum demersum (L.) and Hydrilla verticillata (L. f.) Royle. The results showed that the effect of B. aeruginosa on sediment bacterial diversity and richness was plant species-specific; the presence of B. aeruginosa increased the bacterial diversity and richness in C. demersum systems while slightly decreased them in H. verticillata systems. Similar variations in the predicted microbial functions related to matter cycle in these systems were observed. Bacterial community composition patterns were also modified by B. aeruginosa; in its presence, the discrepancy between systems harbouring two different plants diminished, although the effect was limited. Application of the linear discriminant analysis effect size (LEfSe) method showed that the presence of B. aeruginosa resulted in appearance of significantly different bacterial taxa mainly in the C. demersum systems. Redundancy analysis showed that available phosphorus and NH4+ were significantly related to the observed variations in bacterial community compositions across the samples. Overall, a plant species-specific role of B. aeruginosa in modifying sediment bacterial communities and functions was found.

The salt removal capacity (SRC) of the carbon electrodes in membrane capacitive deionization (MCDI) is limited by the applied potential (

The production of lithium-ion battery is around 9100 million sets in 2016 and is believed to further increase consecutively. This fact triggers the generation of spent cathode materials which contain metals of both valuable and hazardous. Their recycling corresponding to life cycle sustainability of lithium-ion battery has attracted significant attention. However, most technologies for recycling waste lithium-ion batteries are dependent on metallurgical based processes where secondary pollution is inevitable. This research demonstrates a process to directly regenerate LiNi1−x−yCoxMnyO2 cathode material by incorporating methods of mechanochemical activation and solid-state sintering, which can restore the layered structure and improve the lithium ion diffusion without introducing extra impurities. By understanding the effects of sintering temperature, the optimal conditions for direct regeneration of cathode materials with obvious improvement on electrochemical performance can be obtained. As a result, this research proves the possibility of direct regeneration of nickel-containing waste cathode materials with minimized chemical consumption.

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 (

BACKGROUND: Mercury (Hg) contamination is a major global environmental problem, and its remediation using environmentally friendly biotechnologies has attracted increasing attention. In this study, an Hg(II)‐resistant bacterial strain, Bacillus sp. DC‐B2, was isolated from a metal‐contaminated site, and its ability to remediate five types of Hg‐contaminated soils was investigated. RESULTS: The isolate DC‐B2 showed strong resistance to multiple metals and volatilized 91.6% of the Hg(II) in a culture with an initial Hg(II) concentration of 10 mg L⁻¹ within 8 h. Microcosm experiments showed that the addition of DC‐B2 culture improved Hg(II) removal by 11.7–17.2% from four artificially Hg(II)‐spiked soil samples with initial Hg contents of approximately 100 mg kg⁻¹ after incubating for 30 days under flooded conditions compared to the control treatment. For the field‐contaminated farmland soil containing 2.50 mg Hg kg⁻¹, an Hg(II) elimination rate of 82.1% was achieved within 30 days with the DC‐B2 inoculation, relative to the 34.1% elimination rate observed for the uninoculated control. The amendment of peptone broth slightly inhibited Hg removal (2.2–8.7%). The remediation effectiveness was verified by observations of longer root and shoot lengths of lettuce plants grown in treated soils compared to those grown in the control soil. CONCLUSION: The isolate Bacillus sp. DC‐B2 shows great potential to be developed as a bioagent for effective bioremediation of Hg‐contaminated soils. © 2018 Society of Chemical Industry

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.

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.

Growth patterns of aquatic macrophytes have been shown to vary in response to hydrological properties; however, such properties are typically characterized by water level fluctuation, flow velocity, flooding season, and sedimentation, but not by water exchange rate (WER). Herein, we experimentally investigated how WER (three levels: exchange 0%, 20%, and 40% of total water per day) affects water and sediment properties, and the consequences that these variations have on the individual responses of two submerged macrophytes, Hydrilla verticillata and Myriophyllum aquaticum which were planted in two different sediment types (sand and clay). In the experiment without ramets, it was found that turbidity, pH value, and dissolved carbon dioxide concentration of the system water were statistically unaffected by WER, while water dissolved oxygen (DO) concentration and sediment oxidation–reduction potential (ORP, in both sediments) consistently increased with increasing WER, regardless of experimental time. In the experiment containing ramets, biomass accumulation and relative growth rate (RGR) of both species gradually increased with increasing WER regardless of sediment type. The mechanisms were related to (a) increased oxygen availability, as indicated by gradually increased water DO concentration and sediment ORP; and (b) enhanced phosphorus (P) and nitrogen (N) absorbing abilities associated with stimulated root growth, reflected in increased mean root length, specific root length, and the root/above‐ground biomass ratio, with increasing WER. Additionally, in the experiments containing ramets, significant linear relationships were consistently detected between sediment ORP and root parameters, root parameters and plant nutrients (N and P), and plant nutrients and plant growth conditions (biomass accumulation and RGR). These results demonstrate that WER plays an important role in determining oxygen availability and thus impacts the growth of submerged macrophytes by altering the ability of roots to absorb nutrients, indicating that ecosystem functions are more sensitive to WER than previously recognized.

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 novel omniphobic nanofiber membrane for membrane distillation (MD) was successfully fabricated by one-step electrospinning of PVDF-HFP and fluorinated-decyl polyhedraloligomeric silsesquioxane (F-POSS) colloidal suspension solution. The fabricated F-POSS/PVDF-HFP membrane possessed uniform fiber structures and had extreme high F-POSS concentration on the surface. This F-POSS based membrane exhibited excellent omniphobicity, as indicated by its wetting resistance to different low surface tension liquids, including ethanol with a contact angle of 128.2°. Membrane distillation (MD) experiments showed that the water flux and water quality were stably maintained in highly saline feed solutions containing low surface tension substances, which successfully demonstrated its potential application for desalination of challenging industrial wastewater.

A Cu- and Cd-resistant bacterial strain, DC-B3, was isolated from heavy metal-contaminated soils in a Cu mine, was identified as belonging to Pseudomonas sp. and biosorbed Cu2+ and Cd2+ from aqueous solution in the present study. Its biosorption properties as a function of environmental parameters such as contact time, initial concentration, pH, temperature and bacterial dosage were investigated through batch experiments, and the removal capacity peaked at pH 6.0, 40 °C and 0.5 g biomass L−1 at an initial concentration of 105 mg L−1. Sorption occurred extremely rapidly at the beginning, equilibrium was reached after approximately 1 h and 4 h for Cu2+ and Cd2+, respectively, and the biosorption kinetic data for both metals were well fitted by the pseudo-second-order model (r2 > 0.99). Sorption isotherms showed that the adsorptions of both metals were highly favourable, and equilibrium data were better described by the Langmuir model (r2 > 0.98 for Cu2+ and 0.99 for Cd2+), with the estimated maximum sorption capacities of 12.6 and 26.5 mg g−1 for Cu2+ and Cd2+, respectively. Desorption assays suggested that biosorption was a chemical process and that a fraction of the metal ions might have entered the bacterial cells. Fourier transform infrared spectroscopy analysis revealed that hydroxyl, amino, carboxyl and phosphate functional groups on the bacterial cell walls might be mainly responsible for the biosorption, although their contributions to the binding of Cu2+ and Cd2+ were different. This result implied that the strain DC-B3 can be used as a potentially eco-friendly and efficient biosorbent for the remediation of Cu(II) and Cd(II) contaminants.

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 new class of sea-buckthorn-like composite material, MnO2/TNTs (TNT = titanate nanotube), was developed and used for 17β-estradiol (E2) degradation in this study. The new material was characterized as amorphous MnO2 nanoparticles decorated on titanate nanotubes, with chemical formula 0.4MnO2·Na1.1H0.9Ti3O7. The MnO2 fraction can preactivate E2 through one-electron oxidation, while the TNT skeleton is the primary photocatalysis center. Unlike the traditional weak oxidation and photocatalytic degradation, the synergetic effect of these two processes leads to efficient E2 removal by MnO2/TNTs under simulated solar light. The apparent first-order rate constant (k1) was determined to be 0.198 min–1, which was ∼28 times that for MnO2/TNTs direct oxidation without light and ∼15 times of that for calcined TNTs photocatalysis with light. Moreover, the higher TOC elimination rate (82.6% at 1 h) was also obtained compared to that in the pure MnO2 system. Dual-enhanced mechanisms are proposed to interpret the high E...

The identification of active sites and the establishment of structure-reactivity relationship at atomic scale is important for designing efficient catalysts and understanding the reaction mechanism. Here, single atom catalysts (SACs) of Fe anchored on g-C3N4 were synthesized. The catalysts have larger surface area, more photo-generated electrons with stronger reduction ability and faster charge carrier migration than g-C3N4, thereby exhibited dramatically enhanced activity and stability in electron reduction of ozone (O3) under visible light. However, lower catalytic performance was observed when Fe nanoparticles coexisted, which regulated more photoelectrons to reduce O2 to OH via two or three-electron reduction pathways rather than one-electron reduction of O3. Mossbauer spectrum and X-ray adsorption spectroscopy indicated that the presence of Fe nanoparticles led to higher proportion of Fe(II)Nx, which played more significant role in the adsorption and reduction of O2. The insight on the contribution of different Fe sites with well-defined local coordination structure is beneficial for rational design of efficient catalysts in photocatalytic ozonation.

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.

We developed a kind of macropore- and micropore-dominated carbon (HPAC) derived from poly(vinyl alcohol) and polyvinylpyrrolidone for electric double-layer capacitive (EDLC) applications, e.g., supercapacitors and capacitive deionization (CDI). By comparing the EDLC performance of HPAC with those of ordered mesoporous carbon (OMC) and commercial activated carbon (AC), we evaluated the pore size effects. Cyclic voltammetry (CV) was employed for static and flowing CDI processes to identify the disparities between supercapacitors and CDI. HPAC exhibits a specific capacitance of 309 F g–1 at a specific current of 0.5 A g–1 (6 M KOH) in a three-electrode half-cell and has a salt removal capacity of 16.3 mg g–1 (1.2 V, 500 mg L–1 NaCl), which is better than those of AC and OMC. Cycling tests of HPAC in supercapacitors and CDI show excellent stability. The properties of HPAC, fine, hydrophilic, macroporous, and microporous, endow HPAC with the promising possibility of use in supercapacitors and capacitive deioni...

The recent thrust in utilizing microbial electrolysis cell (MEC) has led to accelerated attention in environmental decontamination. One key factor that governs this process is electron transfer efficiency. In this study, neutral red (NR) is involved as electron transfer mediator to investigate whether it could contribute to MEC performance. Afterwards, influence of electrode material selection on NR addition system was also studied. The results indicate MEC with NR shows better electrochemistry activity, which means sulfate-reducing bacteria (SRB) can response to electron transfer mediator NR. Further study reveals graphite felt triggers a better synergy with NR to facilitate electron utilization efficiency of the system subsequently maintains bacteria metabolic activity for a longer time. Sulfate removal in this reactor reaches 79.0% with electron utilization efficiency of 54.2%. To explore the mechanism, electrode bioelectrochemical property, microorganism activity and community were investigated. Electrode morphology analysis confirms graphite felt affords abundant space for the growth of electroactive microorganisms especially SRB and promotes electron exchange through cooperating with NR, which fits in with electrochemical impedance spectroscopy (EIS) analysis. High-throughput sequencing analysis confirms improved reactor can fortify the population dominant of SRB in the community which greatly raises electron utilization efficiency of SRB.

A novel nanofibers-covered hollow fiber membrane (N-HFM) with high porosity (83.5%) was prepared via employing electrospinning to deposit nanofibers onto a porous supporting tube. Electrospun nanofibers covered on a porous supporting tube serve as the outer layer of the N-HFM. The supporting tube fixed on the soft electrode serves as the collector as well as the inner layer of the N-HFM. When the feeding rate was 1 ml L −1 , it was possible to continuously fabricate N-HFM with a non-rotational collector. The prepared N-HFM was used for desalination by direct contact membrane distillation (DCMD), and a high distillate flux of 17 kg m −2 h −1 was obtained while the feed and permeate temperatures were fixed at 333 K and 293 K, respectively. It is expected that the novel hollow fiber membranes with high porosity fabricated by this continuous electrospinning technique may be attractive in various separation and purification processes.

The practical applications of membrane distillation (MD) are hindered by the absence of effective membranes with high porosity, sufficient strength, and durable wetting repellency for long term operation. In this study, we developed a facile method to construct composite membranes with high MD performance via one-step electrospinning of PVDF solutions blended with hydrophobic silica nanoparticles (NPs). The characterizations reveal that the incorporation of silica NPs have altered the membrane surface morphology and endowed the composite membrane with hierarchical structure on both surface and bulk layers (three-dimensional (3D) superhydrophobic membrane). The hydrophobicity of the membranes can be easily tailored by the dosage of silica NPs, and the water contact angle (WCA) of the membranes can be optimized to be 157 ± 1°, which was close to that of the lotus leaf (160°). Furthermore, the incorporation of silica NPs have promoted the mechanical strength, salt rejection, and water permeation flux of the membranes. The composite membrane containing 7.47 wt% silica NPs (designated as SIL40) can achieve a high MD performance with a water flux of 25.73 kg m −2 h −1 and a permeate conductivity below 5.0 μS cm −1 during a 100 h test-period. The SIL40 also shows a tensile strength and a Young’s modulus of 3.18 and 12.8 MPa, respectively; the values surpassed those of the pristine PVDF membrane (1.5 and 5.4 MPa, respectively). In addition, the MD test indicates that the 3D superhydrophobic membrane exhibits a more durable wetting resistance and a more stable MD performance than the surface-modified superhydrophobic membranes.

Bioremediation of Hg-contaminated soil using microbe-based strategies is a promising and efficient method as it is inexpensive and not harmful to the environment. In this study, a novel Hg(II)-volatilizing fungus Penicillium spp., DC-F11 was isolated and showed bioremediation potential for reducing Hg(II) phytotoxicity, total Hg, and exchangeable Hg in Hg(II)-polluted soil. Subsequently, the mechanisms of Hg(II) volatilization and resistance involved were investigated using multiple complementary techniques. The fungal cells could detoxify Hg(II) by extracellular sequestration via adsorption and precipitation. Moreover, a comparative transcriptome analysis uncovered the primary intracellular adaptive responses of the DC-F11 to Hg(II) stress, including mer-mediated detoxification system, thiol compound metabolism, and oxidative stress defense and damage repair metabolism. These results showed that the resistance of DC-F11 to Hg(II) was generally a multisystem collaborative process. Here, we report, for the first time, that the mer-mediated detoxification system was responsible for Hg(II) volatilization in fungus. These findings provide a better understanding of the mechanisms involved in Hg(II) volatilization and resistance that occur in fungi and also provide a strong theoretical basis for the future application of fungi in the bioremediation of Hg-polluted environments.

Granular biochar made from walnut shells was layered into sand-based constructed wetlands (CWs) to treat simulated mining-impacted water (MIW). The results showed that the biochar media exhibited markedly high capacities for metal binding and acidity neutralization, supported notably better plant growth and mitigated metal transfer from the plant roots to the shoots. The addition of organic liquid wastes (domestic sewage and plant straw hydrolysation broth) stimulated biogenic sulfate reduction after 40 d of adaptation to effectively remove multiple heavy metals in the MIW. The microbial community compositions were prominently regulated by organic carbon, with desirable communities dominated by Cellulomonas and Desulfobulbus formed in the CWs for MIW biotreatment. The role of macrophytes in the CWs in MIW treatment was insignificant and was dependent on operation conditions and metal species. A biochar-packed CW system with liquid organic waste supplementation was effective in metal removal and acidity neutralization of MIW.

Constructed wetlands (CWs) are well recognized as a cost-effective and environmentally friendly eco-technology for contaminated water remediation, especially in decentralized communities and rural areas. As a critical component in CWs, the substrate determines the wastewater treatment performance and ecological effects of CW systems. Biochar, a versatile and green carbonaceous biomaterial produced by carbonization of various biomasses, has recently been amended into CWs or biofilters (BFs) as a novel alternative substrate for wastewater treatment. In this paper, the performance of biochar amendment in CWs/biofilters with respect to the removal of nitrogen, phosphorus, organic contaminants, heavy metals and pathogens and its concurrent ecological benefits in improving macrophyte growth and mitigating greenhouse gas (GHG) emissions are summarized and evaluated. Furthermore, the mechanisms involved in these benefits, which are considerably different from those in batch tests, are analysed and elucidated, especially highlighting the roles of microorganisms. The high potential for recycling spent biochar media in CWs/BFs as a soil ameliorant/remediator is proposed. Collectively, it is highly promising to apply biochar as a substrate in CW/BF treatment systems, and more relevant research and practical applications of biochar substrates in CWs/BFs, especially the durability, recycling and possible negative effects of biochar, are required in the future.

The start-up of the anaerobic ammonium oxidation (anammox) process in three up-flow column reactors seeded with common mixed activated sludge and added with three materials, sponge (R1), sponge + volcanic rock (R2) and sponge + charcoal (R3), as carriers for biofilm formation were comparatively investigated in this study. The supplement of volcanic rock and charcoal could significantly shorten the start-up time of the anammox process, which primarily occurred in the activity-enhanced phase, with ammonium and nitrite removal efficiencies stabilized above 92.5% and 93.4% after an operation period of 145, 105 and 121 d for R1, R2 and R3, respectively. After the successful anammox start-up, R2 performed significantly better in TN removal (p −3 d−1 compared to R1 of 88.4% and 172.1 g N m−3 d−1, and R3 of 89.9% and 180.1 g N m−3 d−1 in the steady running phase. The ratios of consumed and generated /consumed after anammox start-up were lower than the theoretical values, probably suggesting the simultaneous existences of anammox, denitrification as well as nitrification processes in the reactors. A reddish brown biofilm was wrapped on the carriers and morphological detection of biofilm displayed the presentations of thick and compact floc aggregates and some filamentous bacteria on the sponge, and spherical-, ovoid- and shortrod-shaped microorganisms on the volcanic rock and charcoal. Using porous material as carrier for biofilm development is an effective strategy for practical application of the anammox reactor.

Four laboratory-scale baffled subsurface-flow constructed wetlands (BSCWs) were established for the treatment of greenhouse wastewater containing high levels of nitrate and sulfate in the present study. Each BSCW microcosm involved a treatment zone and another post-treatment zone with a surface area ratio of 2:1. Evenly mixed straws of carnation and rose (w/w: 1/1), two common ornamental flowers, were supplemented as an organic carbon source into the treatment zone through a hydrolysis zone (CW 1), decentralized vertically installed perforated pipes (CW 2), and centralized pipes (CW 3 in the figures), except the blank system. Removals and transformations of nitrogen and sulfate as well as carbon release in the BSCWs were investigated and comparatively assessed. Results showed that the supplements of flower straws could greatly enhance both the nitrate and sulfate removals, and good performance was achieved during the beginning operation period of 30 days, followed by decline due to insufficient organic carbon supply. Nitrate removal efficiency was significantly higher and more stable compared to sulfate. The highest removal rates of nitrate and sulfate were achieved in the CW 3, with a mean value of 4.33 g NO3 −-N·m−2 d−1 and 2.74 g SO4 2−-S·m−2 d−1, respectively, although the differences among the experimental microcosms were not statistically significant. However, almost the same TN removal rate (3.40–3.47 g N·m−2 d−1) was obtained due to the productions of NO2 −-N and NH4 +-N and leaching of organic N from the straws. High contents of organic carbon and colored substance were leached from the straws during the initial 10 days, but dropped rapidly to low levels, and could hardly determined after 30 days operation. The post-treatment zone could further eliminate various contaminants, but the capability was limited. Inorganic carbon (IC) concentration was detected to be a highly good indicator for the estimation of nitrate and sulfate removal efficiencies of the BSCWs, particularly for nitrate.

The feasibility of adding straws of ornamental flowers as carbon source into gravel-based biofilters to enhance removals of nitrate and sulfate simultaneously, and the concomitant adverse effects were evaluated in this study. The straws were added into a perforated PVC pipe vertically inserted into each biofilter. Results showed that compared to the control biofilter with almost no removal capacity, the experimental systems effectively co-eliminated nitrate and sulfate from the wastewater, with a mean removal rate of 1.29–2.11 g NO 3 − -N m −3 d −1 and 1.03–2.16 g SO 4 2− m −3 d −1 , and higher efficiencies achieved for carnation and lily straws than rose and violet. A significant positive correlation was detected between nitrate and sulfate removal efficiency, with the nitrate removal notably more efficient. Nitrate and sulfate removal rates both decreased gradually with the operation time due to the declining carbon supply, and could be augmented again by fresh straw addition even in winter season. The phosphorous removal capacity of the biofilter was low and just influenced limitedly by the straw addition. High contents of organic carbon and colored matter were determined in the effluent after the straw addition but sharp drops to low levels were followed, resulting in insufficient carbon source for the removals of nitrate and sulfate. Mild accumulations of nitrite and ammonium occurred, averaging 0.39–1.30 mg L −1 and 0.46–0.93 mg L −1 in the effluent, while the content of dissolved sulfide was low. The biofilter added with rose straw showed the lowest relative adverse effects despite of its low removal capacities, and good performance with moderate adverse effects were obtained when adding with the carnation straw. The biofilter can be potentially applied to co-alleviate nitrate and sulfate pollutions although further optimization of straw addition is still required.

Gravel-based subsurface-flow constructed wetlands (CWs) amended with a walnut shell (WS) substrate were established to treat synthetic acid mine drainage (AMD) in this study, and artificial domestic wastewater (DW) and plant litter broth (PLB) were supplemented to enhance the performance. The CW media rapidly reached adsorption saturation with respect to metals (except Fe and Cr) without an external carbon source, while the addition of DW and PLB stimulated sulfate reduction activity and achieved efficient biogenic metal removal, primarily by the formation of hydroxide and sulfide precipitates and concomitant co-precipitation. The WS-amended CWs performed notably better than the control systems, not only in sequestering more metals and rapidly establishing favourable environments for biogenic metal abatement but also in supporting better growth of plants and functional microbes. The external organic carbon input greatly shaped the bacterial community compositions in the CWs, with substantial increases in the proportions of core functional populations involved in AMD biotreatment. Cooperation among Cellulomonas, Propioniciclava and sulfate-reducing bacteria (SRB), dominated by Desulfobulbus and Desulfatirhabdium, was the primary biogenic mechanism of AMD remediation in the CWs. Cellulosic waste-amended CWs with DW and PLB addition offer a promising eco-technology for AMD remediation.

Biochar substrates and tidal flow (TF) and intermittent aeration (IA) operation modes have recently been applied to improve the treatment performance of constructed wetlands (CWs), but their roles in regulating greenhouse gas (GHG) emissions from CWs are still unclear. In this preliminary study, CO2, CH4 and N2O fluxes and associated microbial characteristics in four groups of subsurface-flow CWs, i.e., ceramsite CWs (C-CWs), biochar-amended CWs (B-CWs), intermittently aerated B-CWs (AB-CWs) and tide-flow B-CWs (TB-CWs), were comparatively investigated. The results showed that biochar amendment significantly mitigated CH4 and N2O fluxes from the CWs by supporting higher abundances of mcrA and nosZ genes and higher ratios of pmoA/mcrA and nosZ/(nirK + nirS), thus reducing global warming potential (GWP, a decrease of 55.8%), in addition to promoting total nitrogen (TN) removal by 41.3%, mainly by increasing the abundances and activities of nitrifiers and denitrifiers. The TF mode efficiently improved nitrogen removal, but it greatly increased GHG fluxes since large amounts of GHGs escaped from the empty CW matrix after water draining. IA abated GHG emissions from the CWs, mainly after aeration. TF and IA decreased the abundances of functional bacteria and archaea related to C and N transformation, except nitrifiers, and shaped the microbial community structures. The application of a biochar substrate and IA mode can facilitate the design and operation of CWs in a more ecologically sustainable way.

The biotic enzymatic reduction of mercury II [Hg(II)] to elemental Hg [Hg(0)] is an important pathway for Hg detoxification in natural ecosystems. However, the mechanisms of Hg(II) volatilization and resistance in fungi have not been understood completely. In the present study, we investigated the mechanisms of Hg(II) volatilization and resistance in the fungus Lecythophora sp. DC-F1. Hg(II) volatilization occurred during the investigation via the reduction of Hg(II) to Hg(0) in DC-F1. Comparative transcriptome analyses of DC-F1 revealed 3439 differentially expressed genes under 10 mg/L Hg(II) stress, among which 2770 were up-regulated and 669 were down-regulated. Functional enrichment analyses of genes and pathways further suggested that the Hg(II) resistance of DC-F1 is a multisystem collaborative process with three important transcriptional responses to Hg(II) stress: a mer-mediated Hg detoxification system, a thiol compound metabolism, and a cell reactive oxygen species stress response system. The phylogenetic analysis of merA protein homologs suggests that the Hg(II) reduction by merA is widely distributed in fungi. Overall, this study provides evidence for the reduction of Hg(II) to Hg(0) in fungi via the mer-mediated Hg detoxification system and offers a comprehensive explanation for its role within Hg biogeochemical cycling. These findings offer a strong theoretical basis for the application of fungi in the bioremediation of Hg-contaminated envionments.

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.

Common methods in capacitive deionization (CDI) for selective removal are derived from membrane separation mechanism or size-based intercalation mechanism. In this study, based on the electrochemical activity of bismuth (Bi) material to chloride ions (Cl−) and inertness to sulfate ions (SO42−), Bi electrode is used as anode in CDI to selectively remove Cl− ions from mixed NaCl and Na2SO4 solution. Through the reaction with Bi, Cl− ions are stored in bismuth oxychloride (BiOCl). Results show that Bi electrode exhibits selectivity for Cl− over SO42− with a selectivity coefficient of more than 1.5 in solutions with mole ratio of Cl− to SO42− larger than 1. The selectivity coefficient is greatly dependent on the mole ratio of Cl− to SO42− and increases when the ratio rises. In solution with a fixed Cl−/SO42− mole ratio, higher applied voltage and prolonged time result in higher Cl− ion removal capacity, but not necessarily better selectivity. The highest selectivity coefficient of 4.5 is achieved in 8.5 mM NaCl and 1.1 mM Na2SO4 mixed solution at voltage of 1.6 and 2.0 V after charging for 1 h. These results demonstrate that Bi electrode can selectively remove Cl− ions from mixed solution with a relatively lower concentration of SO42− ions, which provides new insights into ion separation and selective removal by CDI.