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•A novel nanofibers-covered hollow fiber membrane was prepared.•An efficiency technique of electrospinning with non-rotational collectors.•High porosity of 83.5% and distillate flux ...of 17Lh−1m−2 in MD were obtained.
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 1mlL−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 17kgm−2h−1 was obtained while the feed and permeate temperatures were fixed at 333K and 293K, 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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Acid mine drainage (AMD) can cause severe risks to the surrounding environment and ecosystems because of its high metal content and acidity and thus should be disposed of properly. In this study, a ...novel constructed wetland (CW) model system was established by packing a mixture of walnut shell (WS) and its biochar product as substrates to treat AMD with a pH of 4.0. Sucrose and plant straw broth (PSB) were successively supplemented as external carbon sources to fuel the bacterial sulfate reduction (BSR) process. Heavy metals in the AMD were efficiently removed in the CW column (Cu > 99 %, Cd > 97 %, Zn > 94 %, Cr > 93 % and Fe > 76 %), and the pH increased from 4.0 to 6.5 despite an unsatisfactory sulfate removal efficiency (<40 %). Among the substrates, biochar exhibited a notably higher metal retention capacity, followed by WS. The relative abundance of sulfate-reducing bacteria (SRB) in the biochar substrate was the highest, followed by that in the WS. The cooperation of organic-degrading bacteria mainly consisting of Cellulomonas, Clostridium and Bacteroides and SRB consortia was responsible for biotic AMD treatment in the CW. A mixture of organic solid waste and biochar is a preferable filler candidate for CW systems treating AMD although further evaluation of its capacity under varying conditions is required.
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•Walnut shell (WS) and its biochar product were filled in a CW model for AMD treatment.•Heavy metals were effectively eliminated predominantly by substrate retention.•Biochar substrate performed best in metal retention and supporting SRB growth.•Syntrophy of organic-degrading bacteria and SRB was responsible for AMD biotreatment in the CW.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The strength of cellulose/chitosan cryogels could be improved by adding ZIFs.•The structure and pore size of carbon cryogels could be tunable by adding ZIFs.•Forming sandwich and bead structure ...could efficiently improve the capacitance performance of carbon cryogels.•Ratios of pyrrolic-N and graphitic-N to total N content were improved after adding ZIF-7.•ZIF-7 was better than other ZIFs to enhance the electrochemical performance of carbon cryogel.
In order to promote sustainable development, green and renewable clean energy technologies continue to be developed to meet the growing demand for energy, such as supercapacitor, fuel cells and lithium-ion battery. It is urgent to develop appropriate nanomaterials for these energy technologies to reduce the volume of the device, improve the efficiency of energy conversion and enlarge the energy storage capacity. Here, chitosan/cellulose carbon cryogel (CCS/CCL) were designed and synthesized. Through the introduction of zeolite imidazole frameworks (ZIFs) into the chitosan/cellulose cryogels, the obtained materials showed a microstructure of ZIF-7 (a kind of ZIFs) coated chitosan/cellulose fibers (CS/CL). After carbonizing, the as-prepared carbonized ZIF-7@cellulose cryogel (NC@CCL, NC is carbonized ZIF-7) and carbonized ZIF-7@chitosan cryogel (NC@CCS) exhibited suitable microspore contents of 34.37% and 30%, respectively, and they both showed an internal resistance lower than 2Ω. Thereby, NC@CCL and NC@CCS exhibited a high specific capacitance of 150.4Fg−1 and 173.1Fg−1, respectively, which were much higher than those of the original materials. This approach offers a facile method for improving the strength and electronic conductivity of carbon cryogel derived from nature polymers, and also efficiently inhibits the agglomeration of cryogel during carbonization in high temperature, which opens a novel avenue for the development of carbon cryogel materials for application in energy conversion systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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•NR could accelerate electron transfer efficiency in MEC for sulfate removal.•Graphite felt triggered a better synergy with NR to facilitate electron transfer.•GF morphology was ...conducive to biofilm formation and bioelectrocatalytic activity.•Optimized MEC features higher sulfate removal and electron utilization efficiency.•Improved MEC enhanced the population dominant of SRB and metabolic activity.
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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Dilution by importing external clean water and restoration of aquatic vegetation are widely applied strategies for improving water quality of eutrophic lakes, while the influence of dilution or ...aquatic plant litter decomposition on dissolved organic matter (DOM) properties, which is closely associated with the health of aquatic ecosystems, is rarely known. In this study, the temporal variations of DOM properties in the overlying water of a eutrophic lake (Yilong lake in Yunnan, southwest China) under water dilution and aquatic plant litter decomposition were comparatively investigated via a simulated microcosm study using in situ samples. The results showed that water dilution reduced DOM concentration and bioavailability in the overlying water in a short term (about 45 d), and increased DOM humification, but such effect diminished over time. DOM concentration increased substantially during aquatic plant litter decomposition, and reed litter released much more amounts of DOM than that of cattail litter, which dominated by protein-like substances and characterized by high bioavailability and low humification degree. Nutrient (available phosphorus (AP), NH4+-N and TN) contents in the sediment indirectly affected DOM properties by remarkably influencing microbial community compositions and enzyme activities. The strong correlations between the relative abundances of dominant genera Bacillus and Clostridium and concentrations of DOM components implied the important roles of these taxa in DOM transformations. Our findings highlighted the effects and potential mechanisms of dilution and aquatic plant litter decomposition on DOM properties in eutrophic water bodies, and the necessity of proper water diversion and plant litter harvest to reduce endogenous organic pollution in lakes.
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•Dilution and plant litter decomposition can notably affect DOM properties in a eutrophic lake.•Water dilution increased DOM humification degree and reduced DOM content in 30 d.•DOM affected by plant litter was characterized by dominant tyrosine-like substances and low humification degree.•More DOM with distinct compositions was released from reed litter compared to that from cattail litter.•Environmental variables drove DOM conversions by affecting structure and functions of microbiota.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The effective remediation of groundwater contaminated by multiple pollutants via cost-effective and sustainable approaches is a major challenge. In this study, constructed wetland (CW) microcosms ...filled with a mixture of iron scraps (IS) and biochar were employed to remediate groundwater containing nitrate, phosphate and Cr(VI) (2.0 and 10.0 mg L−1 Cr in operation phases I and II, respectively), and a walnut shell or pyrite substrate was added to enhance remediation performance. The results showed that the iron‑carbon (FeC)-filled CWs performed notably better in terms of simultaneous nitrate (30.3–46.0 %), phosphate (58.9–59.5 %) and Cr(VI) removal (88.6–90.6 %) than the control CWs filled with only biochar (8.4–13.0 % for nitrate, 22.6–23.8 % for TP and 32.7–44.9 % for Cr(VI)) did. This was because FeC microelectrolysis effectively drove chemical and microbial nitrate and Cr(VI) reduction and bound phosphate and the production of Cr(III) as precipitates inside the CWs. The enhancing effect of walnut shells on remediation performance was significant because they drove mixotrophic denitrification and Cr(VI) reduction, achieving removal efficiencies of 57.0–67.3 % for nitrate, 65.4–69.7 % for TP and 92.8–95.3 % for Cr(VI). Nitrogen removal in the CWs was adversely impacted by the increase in the influent Cr concentration. The characterization of deposits on the IS surface verified the essential role of ISs and supplementary electron donors in pollutant removal. IS amendment caused a decrease in microbial diversity, while some genera related to nitrate and Cr(VI) reduction were enriched. The proportions of Simplicispira and Vibrio were enhanced by the addition of walnut shells or pyrite, which might be crucial for pollutant removal in the intensified CWs. The developed novel FeC-filled CWs with organic solid amendments present highly promising application prospects for the remediation of groundwater contaminated by multiple pollutants.
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•Iron-carbon constructed wetlands (FeC CWs) effectively removed N, P and Cr(VI) in groundwater.•Walnut shell or pyrite amendment enhanced pollutant removal in FeC CWs.•High Cr removal (>88.6 % at 10.0 mg L−1) was achieved in FeC-filled CWs.•Simplicispira and Vibrio were significant in the intensified CWs for groundwater remediation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Straws of four ornamental flowers (carnation, rose, lily, and violet) were added into denitrification biofilters using gravel as matrix through vertically installed perforated polyvinylchloride pipes ...to provide organic carbon for the treatment of nitrate-contaminated wastewater operating in batch mode. Removal efficiencies of nitrate and phosphate, as well as temporal variations of nitrogen and carbon during batches 10 and 19, were investigated and assessed. Nitrate removal was efficiently enhanced by the addition of flower straws, but decreased gradually as the organic substances were consumed. Phosphate removal was also improved, although this very limited. High nitrate removal rates were achieved during the initial 12 h in the two batches each lasting for 3 days, along with the depletion of influent dissolved oxygen due to aerobic degradation of the organic compounds. NO2(-)-N of 0.01-2.83 mg/L and NH4(+)-N of 0.02-1.69 mg/L were formed and both positively correlated to the nitrate reduced. Inorganic carbon (IC) concentrations increased during the batches and varied conversely with the nitrate contents, and could be indicative of nitrate removal due to the highly significant positive correlation between NO3(-)-N removed and IC concentration (r(2) = 0.881, p < 0.0001). It is feasible and economical to use the denitrification biofilter to treat nitrate-contaminated wastewater, although further optimization of carbon source addition is still required.
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