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1.
Food Funct ; 11(9): 7415-7420, 2020 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-32966484

RESUMO

Coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread around the world at an unprecedented rate. In the present study, 4 marine sulfated polysaccharides were screened for their inhibitory activity against SARS-CoV-2, including sea cucumber sulfated polysaccharide (SCSP), fucoidan from brown algae, iota-carrageenan from red algae, and chondroitin sulfate C from sharks (CS). Of them, SCSP, fucoidan, and carrageenan showed significant antiviral activities at concentrations of 3.90-500 µg mL-1. SCSP exhibited the strongest inhibitory activity with IC50 of 9.10 µg mL-1. Furthermore, a test using pseudotype virus with S glycoprotein confirmed that SCSP could bind to the S glycoprotein to prevent SARS-CoV-2 host cell entry. The three antiviral polysaccharides could be employed to treat and prevent COVID-19.


Assuntos
Antivirais/farmacologia , Betacoronavirus/efeitos dos fármacos , Feófitas/química , Polissacarídeos/farmacologia , Rodófitas/química , Pepinos-do-Mar/química , Animais , Antivirais/química , Betacoronavirus/fisiologia , Infecções por Coronavirus/virologia , Humanos , Pandemias , Pneumonia Viral/virologia , Polissacarídeos/química , Tubarões , Sulfatos/química , Internalização do Vírus/efeitos dos fármacos
2.
Chemosphere ; 254: 126899, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957294

RESUMO

In this study, the reduction of iron-carbon internal electrolysis was reinforced by persulfate for p-nitrophenol removal. The effects of persulfate dosage, initial pH and iron-carbon mass ratio were comprehensively studied in batch experiments. In the system of iron-carbon internal electrolysis coupled with persulfate, the iron-carbon internal electrolysis and persulfate had a significant mutual influence, exhibiting a wide range of pH in the treatment process. Moreover, the coupled system also showed the remarkable removal and degradation efficiency of p-nitrophenol according to the contrast experiments. The satisfactory results should be attributed to the potential reduction of iron-carbon internal electrolysis, which was stimulated by persulfate to transform the nitro group to the amine group, accompanying the subsequent oxidation. Furthermore, persulfate possessed the ability that the dynamically destructive effect on external and internal of Fe0 and the scavenging action on activated carbon, effectively strengthening the potential energy for release and transfer of reductive substances. Both HO• and SO4•- as the main free radicals were formed to mineralize the intermediates in the coupled system. These findings indicate that the system of iron-carbon internal electrolysis coupled with persulfate can be a promising strategy for the treatment of the toxic and refractory wastewater.


Assuntos
Carvão Vegetal/química , Eletrólise/métodos , Ferro/química , Nitrofenóis/análise , Sulfatos/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Modelos Teóricos , Nitrofenóis/química , Oxirredução , Águas Residuárias/química , Poluentes Químicos da Água/química
3.
Chemosphere ; 258: 127288, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32947659

RESUMO

The discharge of toxic elements from tailings soils in the aquatic environments occurs chiefly in the presence of indigenous bacteria. The biotic components may interact in the opposite direction, leading to the formation of a passivation layer, which can inhibit the solubility of the elements. In this work, the influence of jarosite on the bio-immobilization of toxic elements was studied by native bacteria. In batch experiments, the bio-immobilization of heavy metals by an inhibitory layer was examined in the different aquatic media using pure cultures of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. A variety of analyses also investigated the mechanisms of metals bio-immobilization. Among different tests, the highest metal solubility yielded 99% Mn, 91% Cr, 95% Fe, and 78% Cu using A. ferrooxidans in 9KFe medium after ten days. After 22 days, these percentages decreased down to 30% Mn and about 20% Cr, Fe, and Cu, likely due to metal immobilization by biogenic jarosite. The formation of jarosite was confirmed by an electron probe micro-analyzer (EPMA), X-ray diffraction (XRD), and scanning electron microscope (SEM). The mechanisms of metal bio-immobilization by biogenic jarosite from tailings soil confirmed three main steps: 1) the dissolution of metal sulfides in the presence of Acidithiobacillus bacteria; 2) the nucleation of jarosite on the surface of sulfide minerals; 3) the co-precipitation of dissolved elements with jarosite during the bio-immobilization process, demonstrated by a structural study for jarosite. Covering the surface of soils by the jarosite provided a stable compound in the acidic environment of mine-waste.


Assuntos
Compostos Férricos/química , Substâncias Perigosas/análise , Sulfatos/química , Acidithiobacillus , Acidithiobacillus thiooxidans , Bactérias , Substâncias Perigosas/toxicidade , Metais Pesados , Minerais , Solubilidade , Sulfetos/química , Difração de Raios X
4.
Ecotoxicol Environ Saf ; 202: 110921, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32800256

RESUMO

Jarosite is one of the iron oxyhydroxysulfate minerals that are commonly found in acid mine drainage (AMD) systems. In natural environments, phosphate and sulfate reducing bacteria (SRB) may be coupled to jarosite reduction and transformation. In this research, the effect of phosphate on jarosite reduction by SRB and the associated secondary mineral formation was studied using batch experiments. The results indicated that Fe3+ is mainly reduced by biogenic S2- in this experiment. The effect of PO43- on jarosite reduction by SRB involved not only a physico-chemical factor but also a microbial factor. Phosphate is an essential nutrient, which can support the activity of SRB. In the low PO43- treatment, the production of total Fe2+ was found to be slightly larger than that in the zero PO43- treatment. Sorption of PO43- effectively elevated jarosite stability via the formation of inner sphere complexes, which, therefore, inhibited the reductive dissolution of jarosite. At the end of the experiment, the amounts of total Fe2+ accumulation were determined to be 4.54 ± 0.17a mM, 4.66 ± 0.22a mM, 3.91 ± 0.04b mM and 2.51 ± 0.10c mM (p < 0.05) in the zero, low, medium and high PO43- treatments, respectively, following the order of low PO43- treatment > zero PO43- treatment > medium PO43- treatment > high PO43- treatment. PO43- loading modified the transformation pathways for the jarosite mineral, as well. In the zero PO43- treatment, the jarosite diffraction lines disappeared, and mackinawite dominated at the end of the experiment. Compared to PO43--free conditions, vivianite was found to become increasingly important at higher PO43- loading conditions. These findings indicate that PO43- loading can influence the broader biogeochemical functioning of AMD systems by impacting the reactivity and mineralization of jarosite mineral.


Assuntos
Bactérias/metabolismo , Compostos Férricos/química , Fosfatos/química , Sulfatos/química , Adsorção , Biodegradação Ambiental , Compostos Ferrosos , Ferro/química , Compostos de Ferro/química , Minerais , Mineração , Oxirredução
5.
Ecotoxicol Environ Saf ; 204: 110977, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32739673

RESUMO

Indirect oxidation induced by reactive free radicals, such as hydroxyl radical (HO), sulfate radical (SO4-) and carbonate radical (CO3-), plays an important or even crucial role in the degradation of micropollutants. Thus, the coadjutant degradation of phenacetin (PNT) by HO, SO4- and CO3-, as well as the synergistic effect of O2 on HO and HO2 were studied through mechanism, kinetics and toxicity evaluation. The results showed that the degradation of PNT was mainly caused by radical adduct formation (RAF) reaction (69% for Г, the same as below) and H atom transfer (HAT) reaction (31%) of HO. For the two inorganic anionic radicals, SO4- initiated PNT degradation by sequential radical addition-elimination (SRAE; 55%), HAT (28%) and single electron transfer (SET; 17%) reactions, while only by HAT reaction for CO3-. The total initial reaction rate constants of PNT by three radicals were in the order: SO4- > HO > CO3-. The kinetics of PNT degradation simulated by Kintecus program showed that UV/persulfate could degrade target compound more effectively than UV/H2O2 in ultrapure water. In the subsequent reaction of PNT with O2, HO and HO2, the formation of mono/di/tri-hydroxyl substitutions and unsaturated aldehydes/ketones/alcohols were confirmed. The results of toxicity assessment showed that the acute and chronic toxicity of most products to fish increased and to daphnia decreased, and acute toxicity to green algae decreased while chronic toxicity increased.


Assuntos
Carbonatos/toxicidade , Peróxido de Hidrogênio/toxicidade , Fenacetina/toxicidade , Sulfatos/toxicidade , Testes de Toxicidade Aguda , Testes de Toxicidade Crônica , Animais , Carbonatos/química , Clorófitas/efeitos dos fármacos , Daphnia/efeitos dos fármacos , Peixes , Peróxido de Hidrogênio/química , Íons/química , Íons/toxicidade , Cinética , Modelos Químicos , Oxigênio/química , Fenacetina/química , Sulfatos/química , Água/química
6.
Ecotoxicol Environ Saf ; 202: 110893, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32615495

RESUMO

Leaching of the hazardous electric arc furnace (EAF) dust containing mainly zinc ferrite and zinc oxide, accompanied by minor concentrations of arsenic compounds, was investigated using sulfuric acid. In order to reach the maximum recovery of zinc, the leaching solution was adjusted to recover both iron and zinc at their maximum possible values. To obtain a high recovery value of zinc and iron, analyzed by AAS, the optimum leaching condition was found to be the temperature of 90 °C, the sulfuric acid concentration of 3 M, the particle size of 75 µm, the S/L ratio of 1:10 g/mL and the leaching time of 2 h. The percentages of the zinc and iron recovery under the optimum condition were ca. 98.6% and 99.1% respectively, which were verified by a confirmation test and were very close to the predicted values of 100% based on the optimized model, obtained through the software. From the thermodynamics' point of view, it has been found that Zn2+ is the predominant species (90%) under the leaching condition applied. Moreover, the predominant species of iron are FeSO4+, FeHSO42+, Fe(SO4)2- and Fe3+ in the magnitudes of 65.8%, 25.6%, 4.4% and 4.0%, respectively. According to the kinetic results, the controlling step in the leaching was the chemical reaction at the most of the operating temperatures and times. In order to purify the zinc solution for electrowinning, iron and arsenic were removed through the jarosite formation process as confirmed by the XRD results. The speciation of arsenic in the precipitated jarosite was explored by XPS. Finally, the low concentrations of arsenic (less than 0.1 ppm) and iron (less than 50 ppm) were determined by the ICP analysis.


Assuntos
Compostos Férricos/química , Metalurgia/métodos , Reciclagem , Sulfatos/química , Zinco/análise , Poeira/análise , Eletricidade , Ferro/química , Tamanho da Partícula , Ácidos Sulfúricos , Temperatura , Óxido de Zinco
7.
Chemosphere ; 256: 127092, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32559887

RESUMO

Although nitrogen removal from wastewater is essential to prevent eutrophication, the biological processes employed to this end are characterized by several disadvantages, including high energy consumption and the production of large quantities of sludge. Thus, in this study, the organic matter and nitrogen removal efficiencies of the new sulfate reduction, denitrification/anammox and partial nitrification (SRDAPN) process were examined using an anaerobic-anoxic-oxic biofilter reactor. The results showed that the organic matter removal efficiency of the new process at loading rate 1.0 kg COD/m3 per day was 97%. With a circulation flow from the oxic to the anoxic column that was 3 times influent, the nitrogen removal efficiency of the sulfur denitrification and nitrification (SRDN) process without anammox, was 66%, while that of the SRDAPN process with anammox was 76%. Additionally, nitrogen consumption by the anammox reaction in the anoxic column was 13.8% for nitrite-nitrogen and 10.5% for ammonium-nitrogen, and the withdrawal of excess sludge was not required throughout the 170 days of operation. Microbial community analysis showed that acetogenic sulfate reducing bacteria and acetoclastic methanogens coexisted in the anaerobic column, and in the anoxic column, the total relative abundance of anammox bacteria, including Candidatus Brocadia, which coexisted with heterotrophic denitrifying bacteria and sulfur denitrifying bacteria, was 17-18%. Thus, this study established the SRDAPN process as an energy saving and high removal efficiency process.


Assuntos
Sulfatos/química , Eliminação de Resíduos Líquidos/métodos , Compostos de Amônio , Bactérias , Reatores Biológicos/microbiologia , Desnitrificação , Nitrificação , Nitritos , Nitrogênio , Oxirredução , Esgotos/microbiologia , Enxofre , Águas Residuárias/química , Águas Residuárias/microbiologia
8.
Chemosphere ; 257: 127294, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32535362

RESUMO

Sulfonamide antibiotics (SAs) are widely used in veterinary medicine but are poorly metabolized in biological systems; thus, they can cause a selective pressure to promote the proliferation of antibiotic resistant pathogens and threaten human health. Persulfate (PS)-based advanced oxidation processes (AOPs) have been applied for SA degradation, but using transition metal ions as PS activators is relatively limited. In this study, sulfamethazine (SMZ) was used as a model SA to evaluate the performance of a Cu2+ -activated PS system. Cu2+-PS exhibited better SMZ removal than other metal ions, and 25 mg/L SMZ can be degraded in the presence of 0.2 mM Cu2+ and 2.5 g L-1 PS within 120 min. Various anions inhibited SMZ degradation to different degrees except HCO3-. Among the cations, Fe3+ significantly inhibited SMZ removal, while Ni2+ increased the removal rate. High concentrations of humic acid and protein also increased the degradation rate of SMZ. Radical and singlet oxygen quenching experiments, together with the results of electron spin-resonance spectroscopy (ESR), showed that the main active species generated from Cu2+-PS are SO4·- and ·OH. The degradation pathway of SMZ was identified through HPLC-HRMS. Direct SO4·- and ·OH oxidation products of SMZ were not found, suggesting that the complex formed between Cu2+ and SMZ may affect the fate of SMZ. On the other hand, the efficiency and selectivity of Cu2+-PS against different SAs were confirmed. Overall, this study provides a facile and effective method for SMZ and other SA removal.


Assuntos
Cobre/química , Sulfametazina/química , Sulfatos/química , Poluentes Químicos da Água/química , Antibacterianos , Humanos , Substâncias Húmicas , Oxirredução , Poluentes Químicos da Água/análise
9.
Chemosphere ; 257: 127215, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32505950

RESUMO

Red mud, as industrial solid waste, causes severe environmental problems such as soil alkalization and groundwater pollution. In this work, we researched and developed the red mud as a selective catalytic reduction catalyst for NOx removal with NH3 (NH3-SCR). After selective dissolution and specific heat treatment, different Ce precursors were used to modifying its physical and chemical properties. The results showed that Ce(NO3)3 and Ce(NH4)2(NO3)6 modified red mud (RMcn and RMcan) had excellent SCR performance below 300 °C. Ce(SO4)2 modified red mud (RMcs) showed relatively low NOx conversions at 200-300 °C. The redox property was improved with the Ce(NO3)3 and Ce(NH4)2(NO3)6, while depressed with the Ce(SO4)2. Agglomerates generated on the RMcs and blocked the accumulated pores due to the formation of Ce2(SO4)3. The surface acidity of RMcs enhanced with increased adsorption for ammonia. However, these new adsorbed ammonia species, highly related to the sulfate from the Ce2(SO4)3, were inert and did not react with the adsorbed or gaseous NO species at 200-300 °C. The abundant surface lattice oxygen from CeO2 microcrystals improved the catalytic oxidation capacity of the RMcn and RMcan.


Assuntos
Cério/química , Adsorção , Amônia/química , Catálise , Óxidos de Nitrogênio , Oxirredução , Óxidos/química , Oxigênio , Sulfatos/química , Propriedades de Superfície
10.
Chemosphere ; 258: 127275, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32535445

RESUMO

Clay minerals are widely used to treat sewage containing heavy metals such as zinc and cadmium. In this study, the chemical reactivity of natural serpentine was signally improved through mechanochemical activation, achieving the efficient separation of Zn(Ⅱ) and Cd(Ⅱ) ions in a mixed solution. The activated serpentine would release a large amount of Mg2+ and OH- and thereby selectively precipitate Zn(Ⅱ) ions as an uncommon metamorphic zinc mineral, bechererite, in the presence of SO42-. By adjusting the parameters including grinding intensity, reaction temperature, serpentine dosage and salt species, the optimum conditions were determined and a 92% separation rate of Zn(Ⅱ) and Cd(Ⅱ) ions was achieved. The mechanochemical activation of natural clay minerals expresses a great potential for purification of heavy metal contaminated sewage, as well as the simultaneous separation and recovery of multi-metal secondary resources.


Assuntos
Asbestos Serpentinas/química , Cádmio/isolamento & purificação , Zinco/isolamento & purificação , Precipitação Química , Esgotos/química , Soluções , Sulfatos/química
11.
Chemosphere ; 259: 127400, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32593002

RESUMO

Granular activated carbon (GAC) was used as catalyst for the activation of peroxydisulfate (PDS) to decolorize and degrade Acid Orange 7 (AO7) in water. EPR spectra and radical quencher experiments were employed to identify the active species for AO7 oxidation in the PDS/GAC system. Linear sweep voltammetry (LSV) and chronoamperometry test were carried out to identify the contribution of nonradical mechanism for AO7 decay. The investigation of crucial operational parameters on the decolorization indicated 100 mg/L AO7 can be almost totally decolorized in a broad range of pH. Common inorganic anions adversely affect the AO7 decolorization process and the inhibition was in the order of: HCO3- > H2PO4- > SO42- > Cl- > NO3-. UV-vis spectra showed the destruction of the aromatic moiety of AO7 molecule during the oxidation reaction of the PDS/GAC system. The transformation of nitrogen related to the azo bond in AO7 molecule in this system was observed by monitoring the released N-containing inorganic ions. Recycle experiments showed GAC cannot be reused directly but its catalytic ability can be restored by using electrochemical method.


Assuntos
Compostos Azo/química , Sulfatos/química , Poluentes Químicos da Água/química , Benzenossulfonatos , Catálise , Carvão Vegetal/química , Oxirredução , Reciclagem , Água
12.
Chemosphere ; 258: 127268, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32569955

RESUMO

In this work, UVA radiation that is part of solar light is taken as the irradiation source and radicals (HO, SO4- and HO2/O2-) are generated through activation of hydrogen peroxide (H2O2), sodium persulfate (Na2S2O8) and Bismuth catalyst (BiOCl), respectively. The distinguished performance in removing acetaminophen (ACTP), a model pharmaceutical pollutant, by these three radicals was compared for the first time. Effect of pH, halide ions concentration and interfacial mechanism have been investigated in detail. Interestingly, results show that heterogeneous UVA/BiOCl process has higher degradation efficiency than homogeneous UVA/H2O2 and UVA/Na2S2O8 systems whatever the solution's pH. To explain these results, second order reaction rate constant (kradical, ACTP) have been determined with laser flash photolysis (LFP) or radical scavenging experiments. The strongly interfacial-depended HO2/O2- radicals have the lowest second order rate constant with ACTP but highest steady state concentration. BiOCl is much easier activated by UVA, and outstanding ACTP mineralization can be achieved. Combination of BiOCl and Na2S2O8 exhibits synergistic effects rather than antagonism effects with H2O2. This study highlights the relative effective utilization of solar light through interfacial directed BiOCl photocatalysis and its synergistic effects with traditional oxidants.


Assuntos
Acetaminofen/análise , Peróxido de Hidrogênio/química , Oxidantes/química , Compostos de Sódio/química , Sulfatos/química , Raios Ultravioleta , Poluentes Químicos da Água/análise , Bismuto/química , Catálise , Radical Hidroxila/química , Modelos Teóricos , Oxirredução
13.
Chemosphere ; 256: 127061, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32470729

RESUMO

Cobalt is part of vitamin B12, which is essential to maintain human health, and trace levels of cobalt ions are ubiquitous in water and soil environments. In this study, the destruction of 1,4-dioxane (1,4-D) by peroxymonosulfate (PMS) under the catalysis of trace levels of Co2+ was investigated under buffered conditions. The results showed that near 100% removal of 1,4-D was achieved after reaction for 6 and 10 min with 50 and 25 µg/L Co2+, respectively, in the presence of 5 mM phosphate ions. Mechanism studies revealed that radicals mediated the destruction of 1,4-D and sulfate radicals were the primary reactive species. The traces of Co2+ had the greatest reactivity for the catalysis of PMS in neutral environments (pH 7.0). However, pH 5.5 was observed to be the best condition for 1,4-D destruction, which was probably caused by the involvement of phosphate radicals. Common water components including chloride ions and bicarbonate ions were observed to have promoting and inhibiting effects, respectively, on the removal of 1,4-D. To further demonstrate the potential of Co2+-PMS in practical applications, we explored the simultaneous degradation of 20 antibiotics using trace levels of Co2+. The results showed that all the investigated antibiotics, except for lomefloxacin, could be efficiently degraded by Co2+-PMS with removal rates of greater than 97%. The findings from this study demonstrate the promise of using trace levels of cobalt for environmental remediation applications, even when high concentrations of phosphate ions are co-present.


Assuntos
Cobalto/química , Recuperação e Remediação Ambiental , Sulfatos/química , Catálise , Dioxanos , Oxirredução , Peróxidos
14.
PLoS One ; 15(4): e0232265, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32353009

RESUMO

The groundwater biome is a poorly characterized habitat hypothesized to harbor uniquely diverse bacterial communities; the degree to which these communities differ from associated soils is a central question in environmental microbiology. We characterized the Bacterial community composition in 37 aquifer and 32 surface soil samples across the island of O'ahu, Hawai'i. Several bacterial phyla (Acetothermia, Omnitrophica, Parcubacteria, Peregrinibacteria) relatively abundant in the aquifer samples were rare to absent in the soils. Immense bacterial diversity detected in the deep aquifers indicates that these environments are not as homogenous as expected, but provide various niches and energy sources for wide variety of bacteria. A small proportion of OTUs were widespread in all the basal (0.63%) and all the dike aquifer (0.31%) samples. However, these core bacteria comprised an average of 31.8% (ranging 16.2%-62.0%) and 15.4% (0.1%-31.5%) of all sequences isolated from the basal and dike aquifers respectively. Bacterial community composition correlated significantly with the sodium, sulfate, potassium, total dissolved solids, nitrate, conductivity, and pH in the basal aquifers, while phosphate and bicarbonate levels were also highly important when dike water samples were included in the analyses. This was consistent with high relative abundance of putative chemolithoautoroph taxa in the aquifer communities relative to soils. Targeted molecular and culture-based fecal indicator microbial analyses indicated good water quality of aquifers. The dominance of unique, deeply branching lineages in tropical aquifers emphasizes a large adaptive potential in O'ahu's aquifers; variability among groundwater samples suggests that aquifer habitats are surprisingly variable potentially harboring a variety of chemolithotrophic energy sources. Although parallel analyses of conventional and alternative indicators indicated good groundwater quality, this study calls for groundwater monitoring programs which would consider public as well as ecosystem health.


Assuntos
Bactérias/classificação , Água Subterrânea/química , Água Subterrânea/microbiologia , Ecossistema , Monitoramento Ambiental/métodos , Ilhas , Nitratos/química , Filogenia , Sulfatos/química , Microbiologia da Água , Qualidade da Água
15.
Chemosphere ; 252: 126570, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32443266

RESUMO

Hydrotalcite precipitation is a promising technology for the on-site treatment of acid mine drainage (AMD). This technology is underpinned by the synthesis of hydrotalcite that can effectively remove various contaminants. However, hydrotalcite precipitation has only limited capacity to facilitate sulfate removal from AMD. Therefore, the feasibility of coupling biological sulfate reduction with the hydrotalcite precipitation to maximize sulfate removal was evaluated in this study. AMD emanating from a gold mine (pH 4.3, sulfate 2000 mg L-1, with various metals including Al, Cd, Co, Cu, Fe, Mn, Ni, Zn) was first treated using the hydrotalcite precipitation. Subsequently, biological treatment of the post-hydrotalcite precipitation effluent was conducted in an ethanol-fed fluidized bed reactor (FBR) at a hydraulic retention time (HRT) of 0.8-1.6 day. The hydrotalcite precipitation readily neutralized the acidity of AMD and removed 10% of sulfate and over 99% of Al, Cd, Co, Cu, Fe, Mn, Ni, Zn. The overall sulfate removal increased to 73% with subsequent FBR treatment. Based on 454 pyrosequencing of 16S rRNA genes, the identified genera of sulfate-reducing bacteria (SRB) included Desulfovibrio, Desulfomicrobium and Desulfococcus. This study showed that sulfate-rich AMD can be effectively treated by integrating hydrotalcite precipitation and a biological sulfate reducing FBR.


Assuntos
Hidróxido de Alumínio/química , Hidróxido de Magnésio/química , Eliminação de Resíduos/métodos , Sulfatos/química , Ácidos , Reatores Biológicos/microbiologia , Concentração de Íons de Hidrogênio , Metais , Mineração , Oxirredução , RNA Ribossômico 16S
16.
Ecotoxicol Environ Saf ; 199: 110678, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32402898

RESUMO

NaCl and Na2SO4 are the foremost salt compositions in coastal wetlands, while their effects on soil net nitrogen mineralization still remain unclear. Aimed at investigating the two salt compositions on soil net nitrogen mineralization, a 30-day laboratory incubation experiment was respectively conducted by adding 5‰ NaCl and Na2SO4 to incubated coastal wetland soils under aerobic conditions. Our results showed that Na2SO4 addition increased the rates of mineralization (Rmin) by an average of 33.03% and nitrification (Rnit) by 23.84% during the incubation (p < 0.05). In contrast, NaCl addition significantly reduced Rmin by 71% and Rnit by 44% at day 7 (p < 0.05). The activities of fluorescein diacetate, arylamidase and urease in Na2SO4 addition treatments were higher than those in NaCl addition treatment. These results demonstrated the ion-specific effects of salt type on nitrogen mineralization rates and enzyme activities.


Assuntos
Nitrogênio/análise , Cloreto de Sódio/química , Solo/química , Sulfatos/química , Áreas Alagadas , Aerobiose , Chenopodiaceae/crescimento & desenvolvimento , China , Nitrificação , Rios/química , Salinidade , Cloreto de Sódio/administração & dosagem , Microbiologia do Solo , Sulfatos/administração & dosagem , Urease/metabolismo
17.
Chemosphere ; 256: 127139, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32470737

RESUMO

The existence of ß-naphthoxyacetic acid (BNOA) pesticide in water system has aroused serious environmental problem because of its potential toxicity for humans and organisms. Therefore, exploiting an efficient method without secondary pollution is extremely urgent. Herein, a promising Ti/PbO2-Co-Pr composite electrode has been successfully fabricated through simple one-step electrodeposition for efficiently electrocatalytic degradation of BNOA. Compared with Ti/PbO2, Ti/PbO2-Co and Ti/PbO2-Pr electrodes, Ti/PbO2-Co-Pr electrode with smaller pyramidal particles possesses higher oxygen evolution potential, excellent electrochemical stability and outstanding electrocatalytic activity. The optimal degradation condition is assessed by major parameters including temperature, initial pH, current density and Na2SO4 concentration. The degradation efficiency and chemical oxygen demand removal efficiency of BNOA reach up to 94.6% and 84.6%, respectively, under optimal condition (temperature 35 °C, initial pH 5, current density 12 mA cm-2, Na2SO4 concentration 8.0 g L-1 and electrolysis time 3 h). Furthermore, Ti/PbO2-Co-Pr electrode presents economic energy consumption and superior repeatability. Finally, the possible degradation mechanism of BNOA is put forward according to the main intermediate products identified by liquid chromatography-mass spectrometer. The present research paves a new path to degrade BNOA pesticide wastewater with Ti/PbO2-Co-Pr electrode.


Assuntos
Eletrólise/métodos , Glicolatos/química , Chumbo/química , Praguicidas/química , Titânio/química , Águas Residuárias/análise , Poluentes Químicos da Água/química , Análise da Demanda Biológica de Oxigênio , Eletrodos , Eletrólise/instrumentação , Galvanoplastia , Oxirredução , Óxidos/química , Sulfatos/química
18.
Chemosphere ; 251: 126469, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32443245

RESUMO

Cinnamic acid was chosen as an exemplar molecule to study the effect of potential contaminants on the kinetics and mechanism of the photocatalytic destruction of hydrocarbons in aqueous solutions. We identify the principal intermediates in the photocatalytic reaction of the acid and corresponding alcohol, and propose a mechanism that explains the presence of these species. The impact of two likely contaminants of aqueous systems, sulfate and chloride ions were also studied. Whereas sulfate ions inhibit the degradation reaction at all concentrations, chloride ions, up to a concentration of 0.5 M, accelerate the removal of cinnamic acid from solution by a factor of 1.6. However, although cinnamic acid is removed, the pathway to complete oxidation is blocked by the chloride, with the acid being converted (in the presence of oxygen) into new products including acetophenone, 2-chloroacetophenone, 1-(2-chlorophenyl)ethenone and 1,2-dibenzoylethane. We speculate that the formation of these products involves chlorine radicals formed from the reaction of chloride ions with the photoinduced holes at the catalyst surface. Interestingly, we have shown that the 1-(2-chlorophenyl)ethenone and 1,2-dibenzoylethane products form from 2-chloroacetophenone when irradiated with 365 nm light in the absence of the catalyst. The formation of potentially dangerous side products in this reaction suggest that the practical implementation of the photocatalytic purification of contaminated water needs to considered very carefully if chlorides are likely to be present.


Assuntos
Cinamatos/análise , Luz , Propanóis/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Catálise , Cloro/química , Cinamatos/efeitos da radiação , Oxirredução , Propanóis/efeitos da radiação , Sulfatos/química , Titânio/química , Poluentes Químicos da Água/efeitos da radiação
19.
Chemosphere ; 256: 126997, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32473466

RESUMO

Syringic acid (Syr) is an abundant component in aerosol particles. Multiphase photo-oxidation in aerosol phase provides an important oxidation pathway for Syr in the atmosphere. In this work, we studied the multiphase degradation of Syr by measuring rate coefficients of its reactions with potential radical oxidants (OH and SO4-) in aqueous solutions and by theoretical calculations, and degradation mechanisms by identifying the (intermediate) products. Rate coefficients, in 109 M-1 s-1, were obtained as 32 ± 2 (pH 3) and 25 ± 2 (pH 6) for reactions with OH radical, and 1.7 ± 0.1 (pH 3) and 0.9 ± 0.02 (pH 6) for reactions with SO4-. Reactions of Syr with OH and SO4- were all in diffusion-control limit. Rate coefficients' difference under pH 6 and pH 3 in SO4- reaction was caused by Coulomb's force between negatively charged species. Theoretical calculations showed that the reaction of Syr with OH starts mainly by hydrogen atom transfer (HAT) from phenolic groups and secondly by OH addition to the aromatic ring. No product was identified in the reaction of Syr and OH radical at pH 3 due probably to the rapid mineralization of phenoxy radical formed from HAT, while products after OH additions were identified for a reaction at pH 6. On the other hand, reaction of Syr with SO4- starts by single-electron transfer (SET), forming Syr+, which can undergo hydrolysis, sulfation, and dimerization with Syr and other aromatic intermediates, etc. Dimerization products from the phenoxy-type radical were not found here.


Assuntos
Ácido Gálico/análogos & derivados , Poluentes Químicos da Água/química , Atmosfera , Transporte de Elétrons , Ácido Gálico/química , Hidrogênio , Concentração de Íons de Hidrogênio , Radical Hidroxila/química , Cinética , Oxirredução , Sulfatos/química , Água
20.
Chemosphere ; 255: 126938, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32388258

RESUMO

Jarosite is an important scavenger for arsenic (As) due to its strong adsorption capacity and ability to co-precipitate metal(loid)s in acid mine drainage (AMD) environments. When subjected to natural organic matter (NOM), metastable jarosite may undergo dissolution and transformation, affecting the mobility behavior of As. Therefore, the present study systematically explored the dissolution and transformation of jarosite, and the consequent redistribution of coprecipitated As(V) under anoxic condition in the presence of a common phenolic acid-gallic acid (GA). The results suggested that As(V) incorporating into the jarosite structure stabilized the mineral and inhibited the dissolution process. Jarosite persisted as the dominant mineral phase at pH 2.5 up to 60 d, though a large amount of structural Fe(III) was reduced by GA. However, at pH 5.5, jarosite mainly transformed to ferrohexahydrite (FeSO4·6H2O) with GA addition, while the principal end-product was goethite in GA-free system. The dissolution process enhanced As(V) mobilization into aqueous and surface-complexed phase at pH 2.5, while co-precipitated fraction of As(V) remained dominant under pH 5.5 condition. Result of XPS indicated that no reduction of As(V) occurred during the interaction between GA and As(V)-bearing jarosite, which would limit the toxicity to the environment. The reductive process involved that GA promoted the dissolution of jarosite via the synergistic effect of ligand and reduction, following by GA and release As(V) competing for active sites on mineral surface. The findings demonstrated that phenolic groups in NOM can exert great influence on the stability of jarosite and partitioning behavior of As(V).


Assuntos
Arsênico/química , Compostos Férricos/química , Ácido Gálico/química , Sulfatos/química , Adsorção , Compostos de Ferro , Minerais , Mineração , Oxirredução
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