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1.
J Environ Manage ; 270: 110870, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32721314

RESUMO

In this study, elsmoreite/tungsten oxide is used to form a heterojunction with ZnS-containing industrial waste. The effect of the elsmoreite/tungsten oxide content on photocatalytic activity of ZnS using the different ratios of ZnS:Na2WO4 in the synthesis solution is estimated. The initial ZnS:Na2WO4 ratio leads to the formation of hexagonal WO3∙0.33H2O on the surface of ZnS. A further increase in the ZnS:Na2WO4 ratio results in the domination of cubic WO3∙0.5H2O over hexagonal WO3. The ultraviolet-visible (UV-Vis) diffuse reflectance spectra of elsmoreite/tungsten oxide@ZnS composite photocatalysts show that the absorption onset shifts monotonously towards lower wavelengths from 450 nm to 400 nm. The microrods of hexagonal WO3 and {111}-truncated submicron-sized crystals of WO3∙0.5H2O are grown on the ZnS surface. The transmission electron microscopy (TEM) results confirm the formation of a heterojunction between elsmoreite/tungsten oxide and ZnS. The photocatalytic activities of elsmoreite/tungsten oxide@ZnS composite photocatalysts are evaluated for the degradation of selected pharmaceuticals and personal care products (PPCPs): metoprolol - Mt, triclosan - TCS, and caffeine - CAF both in single and in mixture solutions. The elsmoreite/tungsten oxide@ZnS photocatalysts degrade 50% of Mt, 70% TCS, and 60% CAF in single solution and 35% of Mt, 20% of CAF, and 20% of TCS in mixture solution. Hydrated Mt and TCS are preferably adsorbed on the surface of WO3∙0.5H2O (111), and CAF has better affinity to the surface of WO3. The elsmoreite/tungsten oxide@ZnS photocatalysts show a good reusability. Hydroxyl radicals (•OH) and photogenerated holes (h+) are involved in the photocatalytic removal of Mt, while only h+ is involved in the photocatalytic removal of TCS. Interestingly, none of the above-mentioned species is involved in the photocatalytic removal of CAF. Also, nontoxic CAF is mainly degraded into intermediates with higher toxicity. The toxicity of the photocatalytically treated model wastewater in the mixture solution, tested with Vibrio fischeri, is much lower than that in the single solution.


Assuntos
Cosméticos , Tungstênio , Catálise , Óxidos , Sulfetos , Compostos de Zinco
2.
Water Sci Technol ; 81(9): 1951-1960, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32666948

RESUMO

Two bioreactors were investigated as an alternative for the post-treatment of effluent from an upflow anaerobic sludge blanket (UASB) reactor treating domestic sewage, aiming at dissolved sulfide and methane removal. The bioreactors (R-control and R-air) were operated at different hydraulic retention times (HRT; 6 and 3 h) with or without aeration. Large sulfide and methane removal efficiencies were achieved by the microaerated reactor at HRT of 6 h. At this HRT, sulfide removal efficiencies were equal to 61% and 79%, and methane removal efficiencies were 31% and 55% for R-control and R-air, respectively. At an HRT of 3 h, sulfide removal efficiencies were 22% (R-control) and 33% (R-air) and methane removal did not occur. The complete oxidation of sulfide, with sulfate formation, prevailed in both phases and bioreactors. However, elemental sulfur formation was more predominant at an HRT of 6 h than at an HRT of 3 h. Taken together, the results show that post-treatment improved the anaerobic effluent quality in terms of chemical oxygen demand and solids removal. However, ammoniacal nitrogen was not removed due to either the low concentration of air provided or the absence of microorganisms involved in the nitrogen cycle.


Assuntos
Metano , Esgotos , Anaerobiose , Reatores Biológicos , Sulfetos , Eliminação de Resíduos Líquidos
3.
Sci Total Environ ; 736: 139641, 2020 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-32474268

RESUMO

Portmán Bay is one of the most contaminated and chronically impacted coastal marine areas of the world. Here, from the 1957 to 1990, about 60 million tons of mine tailings from the processing of sulfide ores were dumped directly at the shoreline. The resulting deposit provides a unique opportunity to assess the impact of mine tailings on coastal marine ecosystems after ca 30 years since the discharge has ceased. We investigated meiofaunal abundance, biomass and biodiversity along a gradient of metal concentration that overlaps with a bathymetric gradient from 30 to 60 m depth. Despite the localized presence of extremely high concentration of metals, the bay was not a biological desert, but, nevertheless, was characterized by evident signs of impact on benthic diversity. Meiofaunal variables increased significantly with decreasing metal contamination, eventually reaching values comparable to other uncontaminated coastal sediments. Our results show that mine tailings influenced the spatial distribution of meiofaunal taxa and nematode species composition. In particular, we report here that the bay was characterized by the dominance of nematode opportunistic species tolerant to high metal concentration. The effects of mine tailing discharge on meiofaunal biodiversity and composition were still evident ca 30 years after the end of the mining activities. Overall, this study provides new insights on the potential impact of mine tailings disposal and metal contamination in coastal sediments, and, can also contribute to predict the potential long-term consequences of ever-expanding deep-sea mining industry on benthic environments.


Assuntos
Ecossistema , Sedimentos Geológicos , Baías , Mar Mediterrâneo , Sulfetos
4.
Mar Pollut Bull ; 152: 110940, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32479301

RESUMO

Distributions and variations of biogenic sulfur compounds including dimethylsulfide (DMS), dissolved and total dimethylsulfoniopropionate (DMSPd and DMSPt) and acrylic acid (AA) were investigated in coastal waters off Qingdao, China during the late-bloom and after-bloom periods of the Ulva prolifera bloom of 2015. DMSPd, DMS and AA concentrations after the bloom were significantly higher than during the late-bloom, but DMSPt concentrations in surface waters began to decrease. High concentrations of these compounds in the surface layer were associated with the bloom, with the exception of increased concentrations of DMSPt in the middle layer as decaying U. prolifera debris settled. The sea-to-air fluxes of DMS were estimated to be 18.08 and 24.24 µmol m-2 d-1 during the late-bloom and after-bloom, and about three times higher than the reported average fluxes of the Yellow Sea, which highlighted the impacts of U. prolifera blooms on DMS emissions.


Assuntos
Ulva , China , Eutrofização , Sulfetos/análise , Compostos de Enxofre
5.
Environ Pollut ; 264: 114804, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32559864

RESUMO

A large amounts of arable land is facing a high risk of hexavalent chromium (Cr(VI)) pollution, which requires remediation using a low toxic agent. In this study, the remediation effect of amorphous iron pyrite (FeS2(am)) on Cr(VI) in Cr(VI)-contaminated soil was evaluated by systematically analyzing the variation of the leachability, bioaccessibility, phytotoxicity, and long-term stability of the remediated soil. The effectiveness of FeS2(am) on the leachability was assessed by alkaline digestion and the toxicity characteristic leaching procedure (TCLP); the effect on the bioaccessibility was evaluated via the physiologically based extraction test (PBET) and the Tessier sequential extraction; the effect on the phytotoxicity was assessed via phytotoxicity bioassay (seed germination experiments) based on rape (Brassica napus L.) and cucumber (Cucumis Sativus L.), and the long-term stability of the Cr(VI)-remediated soil was appraised using column tests with groundwater and acid rain as the influents. The results show that FeS2(am), with a stoichiometry of 4× exhibited a high efficiency in the remediation of Cr(VI) and decreased its leachability and bioaccessibility during the 30-day remediation period. In addition, seed germination rate, accumulation and translocation of Cr, and root and shoot elongation of rape and cucumber of remediated soil are not significantly different from those of clean soil, illustrating that FeS2(am) is suitable for remediating Cr(VI) contaminated arable soil. The stabilization of Cr(VI) in contaminated soil using FeS2(am) was maintained for 1575 days. The long-term effectiveness was further confirmed by the increasing amount of free Fe and Mn in the effluent and the decreasing redox potential. In summary, FeS2(am) has an excellent efficiency for the remediation of Cr(VI), demonstrating it is a very promising alternative for use in the contaminated arable soil.


Assuntos
Recuperação e Remediação Ambiental , Poluentes do Solo/análise , Cromo/análise , Ferro , Solo , Sulfetos
6.
Chemosphere ; 257: 127181, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32485515

RESUMO

Cadmium (Cd) and lead (Pb) are two typical heavy metals of the Jialing River, and their threat to the river has been considered by the government in recent years. In this study, the diffusive gradient in thin films (DGT) technique and sequential extraction were employed together to analyse the remobilization and fraction of Cd and Pb in the sediments. The total concentration of Cd and Pb in four sampling sites both followed the order S3>S4>S2>S1. The sequential extraction results indicated that large amounts of Cd and Pb (over 50% of the total concentration) were bound to the exchangeable and reducible fraction. The DGT results showed that both Cd and Pb presented a significant increasing trend at the bottom of the DGT probe (-10 cm to -12 cm) and that the two metals had a significant positive correlation (r = 0.831, p < 0.01). The apparent diffusive flux result indicated that Cd and Pb had a potential risk of release from surface sediments. A significant correlation was observed between the DGT-labile fraction and sequential extraction at the surface sediments. A further correlation analysis found that the concentration of labile Cd/Pb measured by DGT (CDGT-Cd and CDGT-Pb) had a strong negative correlation with CDGT-Fe, and this process was mainly mitigated by the iron oxides in the sediments. In addition, the correspondence of a "dark area" of AgI gel with corresponding "hotspots" of Chelex gel also proved that the release of Cd and Pb may regulate the dissolved sulfide in the sediments.


Assuntos
Cádmio/análise , Monitoramento Ambiental , Chumbo/análise , Poluentes Químicos da Água/análise , Difusão , Sedimentos Geológicos/análise , Metais Pesados/análise , Rios , Sulfetos/análise
7.
J Environ Manage ; 270: 110835, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32501237

RESUMO

The degradation of the antibiotic thiamphenicol has been studied by photoelectro-Fenton (PEF) process with UVA light using pyrite particles as catalyst source. Pyrite is a sulfide mineral that naturally acidifies the reaction medium and releases Fe2+, thus promoting the effective generation of OH from Fenton's reaction. The assays were made in an IrO2/air-diffusion cell, which yielded similar results to a boron-doped diamond (BDD)/air-diffusion one at a lower cost. In dark conditions, electro-Fenton (EF) process showed an analogous ability for drug removal, but mineralization was much poorer because of the large persistence of highly stable by-products. Their photolysis explained the higher performance of PEF. Conventional homogeneous PEF directly using dissolved Fe2+ exhibited a lower mineralization power. This suggests the occurrence of heterogeneous Fenton's reaction over the pyrite surface. The effect of current density and drug content on pyrite-catalyzed PEF performance was examined. The drug heteroatoms were gradually converted into SO42-, Cl- and NO3- ions. Nine aromatic derivatives and two dichloroaliphatic amines were identified by GC-MS, and five short-chain carboxylic acids were detected by ion-exclusion HPLC. A reaction route for thiamphenicol mineralization by PEF process with continuous H2O2 and Fe2+ supply on site is proposed.


Assuntos
Tianfenicol , Poluentes Químicos da Água , Catálise , Técnicas Eletroquímicas , Eletrodos , Peróxido de Hidrogênio , Ferro , Oxirredução , Sulfetos
8.
J Environ Manage ; 269: 110772, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32560993

RESUMO

In this research, the effect of curing temperature on the metalloid (As) leachability of cemented paste backfill (CPB; a mix of tailings, cement and water) is studied. ASTM C 1308 leaching protocol is used to determine the leachability of CPB samples subjected to different curing temperatures (2, 20 and 35 °C). In addition, the effect of curing temperature on the microstructure of CPB is assessed to determine if the temperature dependence of the leaching characteristics of CPB is related to variations in the microstructure of the cement matrix. The microstructural techniques used include, powder x-ray diffraction, mercury intrusion porosimetry, and scanning electron microscopy techniques. The results obtained indicate that the curing temperature has a significant effect on the leachability of CPB. It is found that as curing temperature increased from 2 °C to 35 °C the performance of the CPB for arsenic immobilization decreased. The magnitude of this temperature-induced change in As-leachability of CPB depends on the curing temperature range (low (≤20 °C) or elevated (35 °C) temperatures). This curing temperature dependency of the leachability of CPB is attributable to the temperature-induced changes in the pore structure of CPB, formation/development of hydration products and pH in the CPBs during the curing process. The results also indicate that diffusion dominates as the leaching mechanism through the studied temperature range and is independent of curing temperature. However, curing temperature does control the availability for arsenic to leach. The new findings presented in this paper will contribute to design more environmental-friendly cemented paste backfill materials and structures, which is vital for sustainable mining.


Assuntos
Arsênico , Materiais de Construção , Mineração , Sulfetos , Temperatura
9.
Water Sci Technol ; 81(4): 845-852, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32460287

RESUMO

Food waste (FW) management has become an important issue worldwide. Diverting FW into the sewer system is considered promising to tackle the FW issue. However, the transformation of FW in sewers and its impact on the sewer process have not received adequate attention due to the overlooked sewer networks. In this study, a laboratory-scale sewer reactor system was established to investigate the transformation of FW and the production of sulfide and methane under anaerobic conditions. The transformation of FW in the sewer reactor could result in an increase in the substrate level through hydrolyzing and converting biodegradable substances into preferred substrates. Moreover, the generated substrates from the addition of FW were preferable for the metabolism of key microbes in sewer biofilms. As a result, methane production from the sewer reactor could be enhanced from the addition of FW, whereas sulfide production was not affected at a low sulfate concentration. The findings of this study suggest that the diversion of FW may exert an adverse impact on sewers and the environment in terms of greenhouse gas emission. Hence, more research is necessary to clarify the detailed impacts on FW management and wastewater treatment.


Assuntos
Eliminação de Resíduos , Esgotos , Alimentos , Metano , Sulfetos
10.
Water Res ; 179: 115914, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32413614

RESUMO

Iron sulphides, mainly in the form of mackinawite (FeS), pyrrhotite (Fe1-xS, x = 0-0.125) and pyrite (FeS2), are the most abundant sulphide minerals and can be oxidized under anoxic and circumneutral pH conditions by chemoautotrophic denitrifying bacteria to reduce nitrate to N2. Iron sulphides mediated autotrophic denitrification (ISAD) represents an important natural attenuation process of nitrate pollution and plays a pivotal role in linking nitrogen, sulphur and iron cycles in a variety of anoxic environments. Recently, it has emerged as a promising bioprocess for nutrient removal from various organic-deficient water and wastewater, due to its specific advantages including high denitrification capacity, simultaneous nitrogen and phosphorus removal, self-buffering properties, and fewer by-products generation (sulphate, waste sludge, N2O, NH4+, etc.). This paper provides a critical overview of fundamental and engineering aspects of ISAD, including the theoretical knowledge (biochemistry, and microbial diversity), its natural occurrence and engineering applications. Its potential and limitations are elucidated by summarizing the key influencing factors including availability of iron sulphides, low denitrification rates, sulphate emission and leaching heavy metals. This review also put forward two key questions in the mechanism of anoxic iron sulphides oxidation, i.e. dissolution of iron sulphides and direct substrates for denitrifiers. Finally, its prospects for future sustainable wastewater treatment are highlighted. An iron sulphides-based biotechnology towards next-generation wastewater treatment (NEO-GREEN) is proposed, which can potentially harness bioenergy in wastewater, incorporate resources (P and Fe) recovery, achieve simultaneous nutrient and emerging contaminants removal, and minimize waste sludge production.


Assuntos
Desnitrificação , Águas Residuárias , Processos Autotróficos , Reatores Biológicos , Compostos Ferrosos , Ferro , Nitratos , Nitrogênio , Sulfetos , Eliminação de Resíduos Líquidos
11.
Mar Pollut Bull ; 156: 111215, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32366365

RESUMO

The objective of this study was to evaluate the bioavailability of the metals cadmium, copper, lead, nickel, and zinc from sediment samples collected in the Paraguaçu river between the cities of Cachoeira and São Félix in the state of Bahia in Brazil. The method used was the acid extraction of volatile sulfides and metals extracted simultaneously (AVS-SEM) as described in the literature. For the extraction of sulfide, an argon drag system was used after acidification of the samples with HCl, releasing the volatile sulfides collected in the basic solution. Its determination was made by molecular absorption spectrophotometry using the methylene blue method. For quantification of the metals, the sediment with acid was filtered and the residual solution was analyzed by inductively coupled plasma mass spectrometry (ICP MS) in which the elements that were associated with the sulfide were released in solution. The bioavailability evaluation was done by the relation between the sum of the concentrations of the metals in solution (SEM) and the concentration of sulfide in each sample (AVS). When the ∑SEM/AVS ratio is >1, the medium is considered contaminated by the high bioavailability of the metals to other environmental compartments. In the samples collected in the Paraguaçu river in two campaigns, with an ∑SEM/AVS ratio of 0.007 to 1.082, the last value being the only critical>1, while the other quantities in the metallic phase were not available for a biota. By comparing the metal concentration data with the internationally established tolerance limits, all the values found were below the critical values, presenting no toxic risks to the surrounding ecosystem.


Assuntos
Metais Pesados/análise , Poluentes Químicos da Água/análise , Disponibilidade Biológica , Brasil , Ecossistema , Monitoramento Ambiental , Sedimentos Geológicos , Rios , Sulfetos/análise
12.
Environ Sci Pollut Res Int ; 27(21): 26810-26816, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32378109

RESUMO

Synthesis of highly efficient photocatalysts for energy and environment catalysis is still a big challenge in the materials field. Cadmium sulfide (CdS) is a promising visible light-driven photocatalyst, which can be composited with co-catalysts to increase its photo-activity and stability. In this study, a kind of graphene material with abundant structure defects (D-rGO) is synthesized by a two-step annealing process with nitrogen-doped rGO (N-rGO) as an intermediate. The high-temperature annealing could remove the doped heteroatoms to form structure defects with five or seven carbon atoms. The D-rGO is then used as co-catalyst for the modification of CdS nanoparticles, and enhanced photocatalytic activities could be obtained. A large hydrogen evolution rate of 102.7 µmol h-1 g-1 is achieved, which is also effective for 4-nitrophenol reduction with a rate constant of 0.168 min-1. The novel CdS/D-rGO composite contains no noble metals and could be used as multi-functional photocatalysts, thus should has great potential in the photocatalysis field.


Assuntos
Compostos de Cádmio , Grafite , Catálise , Sulfetos
13.
J Environ Sci (China) ; 93: 120-128, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32446447

RESUMO

The potential environmental implications of a Pb (Lead)-Zn (Zinc) sulfide tailing impoundment were found to be dependent on its geochemical characteristics. One typical lead-zinc sulfide tailing impoundment was studied. Ten boreholes were set with the grid method and 36 tailings were sampled and tested. According to the results of metal content analysis, the tailing samples contained considerably high contents of heavy metals, ranging from 6.99 to 89.0 mg/kg for Cd, 75.3 to 602 mg/kg for Cu, 0.53% to 2.63% for Pb and 0.30% to 2.54% for Zn. Most of the heavy metals in the sample matrix showed a uniform concentration distribution, except Cd. Cd, Pb, Zn, and Mn were associated with each other, and were considered to be the dominant contributors based on hierarchical cluster analysis. XRD, SEM and XPS were employed for evaluation of the tailing weathering characteristics, confirming that the tailings had undergone intensive weathering. The maximum potential acidity of the tailings reached 244 kg H2SO4/ton; furthermore, the bioavailability of heavy metals like Pb, Cd, Cr, Cu, and Zn was 37.8%, 12.9%, 12.2%, 5.95%, and 5.46% respectively. These metals would be potentially released into drainage by the weathering process. Analysis of a gastrointestinal model showed that Pb, Cr, Ni and Cu contained in the tailings were high-risk metals. Thus, control of the heavy metals' migration and their environmental risks should be planned from the perspective of geochemistry.


Assuntos
Metais Pesados/análise , Poluentes do Solo/análise , China , Monitoramento Ambiental , Chumbo , Sulfetos , Zinco/análise , Compostos de Zinco
14.
Water Res ; 178: 115848, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32361288

RESUMO

Micro-aerobic enhancement technology has been developed as an effective tool to enhance simultaneous removal of sulfide, nitrate and organic carbon during the integrated autotrophic-heterotrophic denitrification (IAHD) process under high loading; however, its mechanism of enhancement for functional bacteria remains ambiguous. In this study, we discovered that heterotrophic sulfide-oxidizing nitrate-reducing bacteria (h-soNRB) are responsible for enhancing IAHD performance under micro-aerobic conditions with high sulfide loading. In a continuous IAHD bioreactor, aeration rate of 2.6 mL min-1·L-1 promoted 2 to 4 times higher removal efficiencies of sulfide, nitrate and acetate with an influent sulfide concentration of 18.75 mmol/L. Metagenomic analysis revealed that trace oxygen stimulated the abundance of genes responsible for sulfide oxidation (sqr, glpE, pdo, sox and cysK), which were upregulated by 15.2%-129.9%, and the genes encoding nitrate reductase were up-regulated by 67.4%. The increased acetate removal efficiency was attributed to upregulation of ack, pta and TCA cycle related genes. The h-NRB Pseudomonas, Azoarcus, Thauera and Halomonas were detected and regarded as h-soNRB in our bioreactor. According to Illumina MiSeq sequencing, these genera were absolutely dominant in the micro-aerobic microbial community at relative abundances ranging from 82.72% to 90.84%. The sulfide, nitrate and acetate removal rates of Pseudomonas C27, a typical h-soNRB, were at least 10 times higher under micro-aerobic conditions than under anaerobic conditions. Besides, the sulfur, nitrogen and carbon metabolic network was constructed based on the Pseudomonas C27 genome. The pdo and cysK genes found in this strain may be the most advantageous for autotrophic sulfide oxidizing nitrate reducing bacteria (a-soNRB), which are closely related to the high-efficiency sulfide, nitrate and acetate removal performance under high sulfide concentrations and a limited oxygen supply. In addition, after micro-aerobic cultivation, the anaerobic sulfide loading tolerance of the IAHD bioreactor increased from 18.75 to 37.5 mmol/L with sulfide, nitrate and acetate removal efficiencies increasing 1.5 to 3 times, which suggests that intermittent micro-aeration might be a more economical and efficient regime for high-sulfide IAHD regulation.


Assuntos
Processos Autotróficos , Desnitrificação , Bactérias , Reatores Biológicos , Nitratos , Oxirredução , Sulfetos
15.
Bioresour Technol ; 309: 123451, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32361619

RESUMO

Micro-aeration is an effective tool that helps integrated autotrophic and heterotrophic denitrification process to withstand high sulfide concentration by making heterotrophic sulfide-oxidizing nitrate-reducing bacteria (h-soNRB) prevail. For further understanding of the dominance of h-soNRB, Pseudomonas C27 was selected as the typical bacterium and its metabolic characteristics responding to sulfide and oxygen stimulation were studied. Under high sulfide concentration condition, addition of trace oxygen led to a two-stage sulfide oxidation process, and sulfide oxidation rate in the first stage was 1.4 times more than that under anaerobic condition. According to transcriptome analysis, the pdo gene significantly up-regulated 2.36 and 2.57 times with and without oxygen under stimulation of high sulfide concentration. Additionally, two possible enhanced sulfide removal pathways coping with high sulfide concentration, namely sqr-cysI-gpx-gor-glpE and cysK-gshA-gshB-pdo-glpE, caused by oxygen were proposed in Pseudomonas C27. These findings provide a theoretical basis for locating high-efficiency sulfur oxidase in h-soNRB.


Assuntos
Oxigênio , Pseudomonas , Bactérias , Reatores Biológicos , Desnitrificação , Nitratos , Oxirredução , Sulfetos
16.
Sci Total Environ ; 722: 137830, 2020 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-32349200

RESUMO

Anodic mixotrophic denitrification microbial fuel cell (MFC) was developed for pollutants removal and electricity generation in treatment of low C/N domestic wastewater. The experimental results show that the MFC achieved up to 100% of acetate, 100% of sulfide, and more than 91% of nitrate removal efficiency in all the MFCs. Particularly, thiosulfate was generated as the main intermediate of sulfide oxidation, and the sulfate generation ratio ranged from 66.93% to 73.76%. Those electrons produced during the acetate and sulfide oxidation were mainly used for denitrification and electricity generation. The microbial community analysis revealed that heterotrophic denitrifying bacteria (HDB) and sulfide-based autotrophic denitrifying bacteria (SADB) were the dominant bacteria for pollutants removal, and those facultative autotrophic bacterium (FAB) were key functional genera for high sulfate generation under both low and high sulfide concentrations. Meanwhile, the microbial functional prediction revealed that sulfide oxidation gene of Sqr and Sox were highly expressed. Moreover, a preliminary sulfide-based autotrophic denitrification (SAD) potential estimation indicated that the sulfide generated in the WWTPs had great potential for denitrification.


Assuntos
Microbiota , Fontes de Energia Bioelétrica , Reatores Biológicos , Desnitrificação , Elétrons , Nitratos , Sulfetos , Águas Residuárias
17.
Environ Sci Pollut Res Int ; 27(24): 30571-30582, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32468370

RESUMO

Odor emissions from sewer systems and wastewater treatment plants have attracted much attention due to the potential negative effects on human health. A single-chamber membrane-free microbial electrolysis cell was proposed for the removal of sulfides in a sewer system. The feasibility of the use of volatile sulfur compounds and their removal efficiency in liquid and headspace gas phases were investigated using synthetic wastewater with real sewer sediment and Ru/Ir-coated titanium electrodes. The results indicate that hydrogen sulfide and volatile organic sulfur compounds were effectively inhibited in the liquid phase upon electrochemical treatment at current densities of 1.55, 2.06, and 2.58 mA/cm2, and their removal rates reached up to 86.2-100%, except for dimethyl trisulfide, the amount of which increased greatly at 1.55 mA/cm2. In addition, the amount of volatile sulfur compounds in the headspace decreased greatly; however, the total theoretical odor concentration was still high, and methanethiol and ethanethiol greatly contributed to the total strength of the odor concentration due to their low odor threshold concentrations. The major pathway for sulfide removal in the single-chamber membrane-free microbial electrolysis cell is biotic oxidation, the removal rate of which was 0.4-0.5 mg/min, 4-5 times that of indirect electrochemical oxidation.


Assuntos
Compostos de Enxofre , Compostos Orgânicos Voláteis , Eletrólise , Odorantes , Sulfetos , Enxofre
18.
Chemosphere ; 256: 127101, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32450355

RESUMO

Previous studies of the dynamics of sulfate-reducing bacteria (SRB) and sulfur-oxidizing bacteria (SOB) have focused on deep stratified lakes. The objective of this study is to present an in-depth investigation of the structure and dynamics of sulfur bacteria (including SRB and SOB) in the water column of shallow freshwater lakes. A cyanobacterial bloom biomass (CBB)-amended mesocosm experiment was conducted in this study, in which water was taken from a shallow eutrophic lake with sulfate levels near 40 mg L-1. Illumina sequencing was used to investigate SRB and SOB species involved in CBB decomposition and the effects of the increases in sulfate input on the water column microbial community structure. The accumulation of dissolved sulfide (∑H2S) produced by SRB during CBB decomposition stimulated the growth of SOB, and ∑H2S was then oxidized back to sulfate by SOB in the water column. Chlorobaculum sequences (the main SOB species in the study) were significantly influenced by increases in sulfate input, with relative abundance increasing approximately four-fold in treatments amended with 40 mg L-1 sulfate (referred to as 40S) when compared to the treatment without additional sulfate addition (referred to as CU). Additionally, an increase in SOB number was observed from day 26-37, concurrent with the decrease in SRB number, indicating the succession of sulfur bacteria. These findings suggest that biological sulfur oxidation and succession of sulfur bacteria occur in the water column during CBB decomposition in shallow freshwater ecosystems, and the increases in sulfate input stimulate microbial sulfur oxidation.


Assuntos
Cianobactérias/crescimento & desenvolvimento , Lagos/microbiologia , Biomassa , Chlorobi , Ecossistema , Oxirredução , Sulfatos , Sulfetos , Enxofre/química
19.
Ecotoxicol Environ Saf ; 200: 110744, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32460050

RESUMO

Hematite nanoparticles (α-Fe2O3 NPs) were successfully synthesized by a low-cost solvent-free reaction using Ferrous sulfate waste (FeSO4·7H2O) and pyrite (FeS2) as raw materials and employed for the decolorization of Methyl Orange by the photo-Fenton system. The properties of α-Fe2O3 NPs before and after photo-Fenton reaction were characterized by X-ray powder diffraction (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectrum and X-ray photoelectron spectroscopy (XPS), and the optical properties of α-Fe2O3 NPs were analyzed by UV-vis diffuse reflectance spectra (UV-vis DRS) and Photoluminescence (PL) spectra. The analytic results showed that the as-formed samples having an average diameter of ~50 nm exhibit pure phase hematite with sphere structure. Besides, little differences were found by comparing the characterization data of the particles before and after the photo-Fenton reaction, indicating that the photo-Fenton reaction was carried out in solution rather than on the surface of α-Fe2O3 NPs. A 24 central composite design (CCD) coupled with response surface methodology (RSM) was applied to evaluate and optimize the important variables. A significant quadratic model (P-value<0.0001, R2 = 0.9664) was derived using an analysis of variance (ANOVA), which was adequate to perform the process variables optimization. The optimal process conditions were performed to be 395 nm of the light wavelength, pH 3.0, 5 mmol/L H2O2 and 1 g/L α-Fe2O3, and the decolorization efficiency of methyl orange was 99.55% at 4 min.


Assuntos
Compostos Azo/química , Corantes/química , Compostos Férricos/química , Nanopartículas Metálicas/química , Catálise , Compostos Férricos/síntese química , Compostos Ferrosos/química , Ferro/química , Solventes , Sulfetos/química
20.
Life Sci ; 255: 117834, 2020 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-32454158

RESUMO

AIMS: Hydrogen sulfide (H2S) is shown in ocular tissues and suggested to involve in the regulation of retinal circulation. However, the mechanism of H2S-induced relaxation on retinal artery is not clarified yet. Herein, we aimed to evaluate the role of several calcium (Ca2+) signaling and Ca2+ sensitization mechanisms in the relaxing effect of H2S donor, NaHS, on retinal arteries. MATERIALS AND METHODS: Relaxing effects of NaHS (10-5-3 × 10-3M) were determined on precontracted retinal arteries in Ca2+ free medium as well as in the presence of the inhibitors of Ca2+ signaling and Ca2+ sensitization mechanisms. Additively, Ca2+ sensitivity of the contractile apparatus were evaluated by CaCl2-induced contractions in the presence of NaHS (3 × 10-3M). Functional experiments were furtherly assessed by protein and/or mRNA expressions, as appropriate. KEY FINDINGS: The relaxations to NaHS were preserved in Ca2+ free medium while NaHS pretreatment decreased the responsiveness to CaCl2. The inhibitors of plasmalemmal Ca2+-ATPase, sarcoplasmic-endoplasmic reticulum Ca2+-ATPase, Na+-Ca2+ ion-exchanger and myosin light chain kinase (MLCK) unchanged the relaxations to NaHS. Likewise, Ca2+ sensitization mechanisms including, rho kinase, protein kinase C and tyrosine kinase were unlikely to mediate the relaxation to NaHS in retinal artery. Whereas, a marked reduction was determined in NaHS-induced relaxations in the presence of MLCP inhibitor, calyculin A. Supportively, NaHS pretreatment significantly reduced phosphorylation of MYPT1-subunit of MLCP. SIGNIFICANCE: The relaxing effect of NaHS in retinal artery is likely to be related to the activation of MLCP and partly, to decrement in Ca2+ sensitivity of contractile apparatus.


Assuntos
Cálcio/metabolismo , Sulfeto de Hidrogênio/metabolismo , Fosfatase de Miosina-de-Cadeia-Leve/metabolismo , Artéria Retiniana/metabolismo , Animais , Cloreto de Cálcio/administração & dosagem , Sinalização do Cálcio/fisiologia , Bovinos , Membrana Celular/metabolismo , Retículo Endoplasmático/metabolismo , Feminino , Masculino , Fosforilação/fisiologia , Sulfetos/administração & dosagem , Sulfetos/farmacologia
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