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1.
Bioresour Technol ; 313: 123610, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32504871

RESUMO

A practical approach of synchronously recovering vivianite and volatile fatty acids (VFAs) by food waste (FW) and waste activated sludge (WAS) co-fermentation in continuous operation was investigated. Approximately 82.88% P as high-purity vivianite (95.23%) and 7894 mg COD/L VFAs were finally recovered. The simultaneous addition of FW and FeCl3 contributed to the fermentation conditions by adjusting pH biologically and increasing the concentration of organic substrates, which enhanced the Fe3+ reduction efficiency and microbial activities (e.g., hydrolases and acidogenic enzymes). Microbial analysis found the functional bacteria related to Fe3+ reduction and VFAs generation were further enhanced and enriched. Besides, results indicated that the efficiencies of Fe2+ and P release and VFAs recovery were highly linked to SRT, the satisfactory fermentation performance was obtained at SRT of 6 d. This research would provide a practical waste recycling technology to treat FW and WAS simultaneously for recovering vivianite and VFAs synchronously.


Assuntos
Eliminação de Resíduos , Esgotos , Reatores Biológicos , Ácidos Graxos Voláteis , Fermentação , Compostos Ferrosos , Alimentos , Concentração de Íons de Hidrogênio , Fosfatos
2.
Chemosphere ; 257: 127223, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32534295

RESUMO

The degradation performance of trichloroethylene (TCE) by sodium percarbonate (SPC) activated with citric acid (CA) chelated Fe(II) in the presence of nonionic surfactant Tween-80 was investigated. The addition of CA successfully prevented the precipitation of iron and facilitated TCE degradation. However, Tween-80 had an inhibitory effect on TCE degradation mainly due to the competition of ∗OH between Tween-80 and TCE. The effect of SPC and Fe(II) dosage on TCE degradation was also explored and the results displayed that 87.2% of TCE could be degraded in 15 min at the SPC/Fe(II)/CA/TCE molar ratio of 3/4/2/1. Free radical probe tests confirmed that both O2-∗ and ∗OH were generated in the SPC/Fe(II)/CA system. Free radical scavenging tests implied that the degradation of TCE in the SPC/Fe(II)/CA system was mainly attributed to ∗OH, while O2-∗ was only partially involved in the degradation of TCE. In addition, TCE removal was suppressed with the raising of the initial solution pH from 3.0 to 9.0. The actual groundwater (containing Tween-80) tests confirmed that 93.2% of TCE degradation could be achieved at the SPC/Fe(II)/CA/TCE molar ratio of 30/40/10/1 and strongly demonstrated that the SPC/Fe(II)/CA process has potential for the in situ treatment of TCE contaminated groundwater in the presence of surfactant Tween-80. In conclusion, TCE degradation by Fe(II) activated SPC system in the presence of Tween-80 can be significantly enhanced with the addition of CA, and this finding offers an innovative direction for removing chlorinated organic contaminants from groundwater in contaminated site after surfactant solubilization treatment.


Assuntos
Carbonatos/química , Tensoativos/química , Tricloroetileno/química , Poluentes Químicos da Água/química , Quelantes , Ácido Cítrico , Compostos Ferrosos/química , Água Subterrânea , Ferro , Oxirredução , Polissorbatos , Surfactantes Pulmonares , Poluentes Químicos da Água/análise
3.
Water Sci Technol ; 81(6): 1308-1318, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32597416

RESUMO

Inspired by metalloporphyrin-based enzymes, a biomimetic catalyst, R-N-Fe, was prepared by grafting iron phthalocyanine (FePc) covalently onto a macroporous chloromethylated polystyrene-divinylbenzene resin (R), which was pre-functionalized using 4-aminopyridine (4-ampy) as an axial ligand. The novel catalyst was used for the degradation of oxytetracycline hydrochloride (OTCH). The response surface methodology was employed to optimize the independent operating parameters, including temperature, catalyst amount, H2O2 dosage, and initial pH value. The results displayed that the initial pH and temperature had the most significant effect on the removal efficiency. Under optimum conditions, the OTCH removal efficiency was 93.98%. Additionally, the classical quenching experiment and electron paramagnetic resonance (EPR) test indicated that R-N-Fe could generate hydroxyl radicals by decomposing H2O2, which was the main active species for eliminating OTCH. Furthermore, R-N-Fe can be easily recycled and can maintain high stability in the reusability test, rendering it a good potential for practical application.


Assuntos
Oxitetraciclina , Poluentes Químicos da Água , Catálise , Compostos Ferrosos , Peróxido de Hidrogênio , Indóis , Ferro , Oxirredução , Poliestirenos
4.
Chemosphere ; 256: 127043, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32445999

RESUMO

Electrolytic manganese residue (EMR) is characterized by high silicon content, and thus, is an important silicon source. While considerable research has been conducted on bioleaching EMR for silicon recovery, sufficient information is not available on the impact of specific silicate mineral structures in EMR on silicon bioleaching. In the present study, the mineral composition of EMR was determined firstly, and then the leaching effect of Paenibacillus mucilaginosus on these different silicate minerals were investigated by shake flask experiments. Results showed that the silicon in EMR was mainly composed of quartz, sericite, muscovite, biotite, olivine and rhodonite; Paenibacillus mucilaginosus had a significantly different weathering and decomposition effects on different silicate minerals. Among them, sericite, muscovite and biotite with layered structure had the most obvious silicon leaching effect, followed by rhodonite with island structure, while silicon leaching from olivine with chained structure and quartz with frame structure was much more difficult. One can roughly judge the adaptability of bioleaching of silicon in EMR using Paenibacillus mucilaginosus if the main form of silicate minerals in EMR is determined.


Assuntos
Manganês/metabolismo , Paenibacillus/metabolismo , Silício/química , Silicatos de Alumínio , Eletrólitos , Compostos Ferrosos , Íons , Compostos de Ferro , Compostos de Magnésio , Minerais , Silicatos/química , Dióxido de Silício
5.
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
6.
PLoS One ; 15(5): e0232315, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32365071

RESUMO

The INTRABEAM Carl Zeiss Surgical system (Oberkochen, Germany) is a miniature accelerator producing low energy photons (50 keV maximum). The published dosimetric characterization of the INTRABEAM was based on detectors (radiochromic films or ionization chambers) not allowing measuring the absorbed dose in the first millimeters of the irradiated medium, where the dose is actually prescribed. This study aims at determining with Magnetic Resonance Imaging (MRI) the sensitivity of a paramagnetic gel in order to measure the dose deposit produced with the INTRABEAM from 0 to 20 mm. Although spherical applicators are mostly used with the INTRABEAM system for breast applications, this study focuses on surface applicators that are of interest for cutaneous carcinomas. The irradiations at 12 different dose levels (between 2 Gy and 50 Gy at the gel surface) were performed with the INTRABEAM and a 4 cm surface applicator. The gel used in this study is a new « sensitive ¼ material. In order to compare gel sensitivity at low energy with high energy, gels were irradiated by an 18 MV photon beam produced by a Varian Clinac 2100 CD. T2 weighted multi echo MRI sequences were performed with 16 echo times. The T2 signal versus echo times was fitted with a mono-exponential function with 95% confidence interval. The calibration curve determined at low energy is a linear function (r2 = 0.9893) with a sensitivity of 0.0381 s-1.Gy-1, a similar linear function was obtained at high energy (0.0372 s-1.Gy-1 with r2 = 0.9662). The calibration curve at low energy was used to draw isodose maps from the MR images. The PDD (Percent Depth Dose) determined in the gel is within 5%-1mm of the ionization chamber PDD except for one point. The dosimetric sensitivity of this new paramagnetic ferrous gel was determined with MRI measurements. It allowed measuring the dose distribution specifically in the first millimeters for an irradiation with the INTRABEAM miniature accelerator equipped with a surface applicator.


Assuntos
Compostos Ferrosos/química , Radiometria/instrumentação , Géis , Fenômenos Magnéticos , Miniaturização , Aceleradores de Partículas , Doses de Radiação , Razão Sinal-Ruído , Raios X
7.
Environ Sci Pollut Res Int ; 27(24): 30254-30264, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32451897

RESUMO

The sewage sludge flocculated with ferrous sulfate (SFS) was prepared by one-step pyrolysis to obtain magnetic Fe-containing carbon. Results showed that only a small amount of FexOy as well as extremely weak magnetism were observed at pyrolysis temperatures of less than 500 °C. SFS tended to exhibit intensive agglomeration, leading to the drastic increase of the crystalline-phase particle size at high pyrolysis temperature. The optimal pyrolysis temperature is 700 °C, corresponding to the production of some sulfides, an optimal content of FexOy, and a suitable BET surface. Hg0 removal efficiency of SFS700 (SFS pyrolyzed at 700 °C) reached 80.7% at the reaction temperature of 125 °C. The presence of O2 and low concentration of SO2 enhanced the Hg0 removal, while the H2O vapor and high SO2 concentration inhibited it. Meanwhile, good resistance for the adsorbent to moderate concentrations of SO2 and H2O was observed. Moreover, the good magnetism performance is conducive to the recovery and utilization of the SFS700 in flue gas. Therefore, SFS can be used for Hg0 removal without any chemical modification after undergoing one-step pyrolysis and this study has guiding significance for the resource utilization and engineering practices.


Assuntos
Poluentes Atmosféricos/análise , Mercúrio/análise , Carbono , Compostos Ferrosos , Fenômenos Magnéticos , Esgotos
8.
Environ Pollut ; 264: 114739, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32434113

RESUMO

Strategies for reducing cadmium (Cd) content in polluted farmland soils are currently limited. A type of composite with nanoparticles incorporated into a hydrogel have been developed to efficiently remove heavy metals from sewage, but their application in soils faces challenges, such as organic hydrogel degradation due to oxygen exposure and slow Cd2+ release from soil constituents. To overcome these challenges, a composite with superior stability for long-term application in soil is required. In this study, ferrous sulfide (FeS) nanoparticle@lignin hydrogel composites were developed. The lignin-based hydrogels inherited lignin's natural mechanical and environmental stability and the FeS nanoparticles efficiently adsorbed Cd2+ and enhanced Cd2+ desorption from soils by producing H+. The high sorption capacity (833.3 g kg-1) of the composite was attributed to four proposed mechanisms, including cadmium sulfide (CdS) precipitation via chemical reaction (84.06%), lignin complexation (13.19%), hydrogel swelling (0.61%), and nanoparticle sorption (2.15%). In addition, Fe2+ displaced from the composite was gradually oxidized to form solid iron oxide hydroxide, which increased Cd2+ sorption. The composite significantly reduced the total, surfactant-soluble, and fixed Cd in heavily and lightly polluted paddy soils by 22.4-49.6%, 13.5-68.6%, and 40.1-16.6%, respectively, in 7 days.


Assuntos
Cádmio/análise , Poluentes do Solo/análise , Compostos Ferrosos , Hidrogéis , Lignina , Solo
9.
J Environ Sci (China) ; 93: 164-169, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32446452

RESUMO

There are good prospects for phosphorus recovery from excess sludge by vivianite crystallization while a large number of extracellular polymeric substances in sludge will have impact on vivianite precipitation. In this study, as a representative of extracellular polymeric substance, the effect of sodium alginate (SA) on phosphorus recovery by vivianite precipitation under different initial SA concentrations (0-800 mg/L), pH values (6.5-9.0) and Fe/P molar ratios (1:1-2.4:1) was investigated using synthetic wastewater. The results showed that SA in low concentrations (≤400 mg/L) had little inhibitory effect on the phosphorus recovery rate. However, when the concentration of SA was larger than 400 mg/L, the phosphorus recovery rate decreased significantly with increasing SA concentrations. The inhibition rate of 800 mg/L SA was about 3 times as large as that of 400 mg/L SA. It was worth noting that the inhibitory effect of SA on vivianite precipitation decreased with increasing initial pH and Fe/P molar ratios. Additionally, SA has no obvious influence on the composition of products, but the morphology of harvested crystals was transformed from branches to plates or rods in uneven sizes.


Assuntos
Fósforo , Eliminação de Resíduos Líquidos , Alginatos , Precipitação Química , Matriz Extracelular de Substâncias Poliméricas , Compostos Ferrosos , Fosfatos , Esgotos
10.
Rev Bras Epidemiol ; 23: e200023, 2020.
Artigo em Inglês, Português | MEDLINE | ID: mdl-32401917

RESUMO

AIM: To verify the prevalence of recommendation of iron supplementation among children aged 12 and 24 months. METHODOLOGY: All children born in the maternities of Pelotas/RS in 2015 were eligible for the Cohort. The outcomes were the recommendation of ferrous sulphate by health professionals and its use. RESULTS: The cohort followed up 4,275 children. Approximately 64.0% of them were recommended to receive iron supplementation until 12 months of age. Among these, 68.8% used iron. From 12 to 24 months, 39.4% of the children received a prescription of iron supplementation, and among them, 26.2% actually used it. At 12 months, after adjusted analysis, higher maternal education, higher family income, lower parity, and low birth weight remained associated with the outcome. At 24 months, after adjusted analysis, we observed a higher recommendation of iron supplementation among mother with lower parity and for children with low birth weight. CONCLUSION: There was a low frequency of recommendation and low rate of use of iron among children. These findings are highly relevant given the high prevalence of anemia observed in children this year. The low recommendation of iron use among children up to 24 months of age, and the low use among those who are recommended to use it reflect the need for coordinated actions among health professionals and the expansion of knowledge among mothers to enable a wider reach of this important public policy.


Assuntos
Suplementos Nutricionais/estatística & dados numéricos , Compostos Ferrosos/uso terapêutico , Fatores Etários , Anemia Ferropriva/prevenção & controle , Brasil , Pré-Escolar , Feminino , Seguimentos , Humanos , Lactente , Recém-Nascido de Baixo Peso , Masculino , Mães/estatística & dados numéricos , Recomendações Nutricionais , Fatores Socioeconômicos , Cooperação e Adesão ao Tratamento
11.
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
13.
Chemosphere ; 255: 126942, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32387732

RESUMO

Knowledge of the geochemical behavior of uranium is critical for the safe disposal of radioactive wastes. Biotite, a Fe(II)-rich phyllosilicate, is a common rock-forming mineral and a major component of granite or granodiorite. This work comprehensively studied the sorption of U(VI) on biotite surface with batch experiments and analyzed the uranium speciation with various spectroscopic techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and time-resolved fluorescence spectra (TRFS). Our results indicated that uranyl ions could penetrate into the interlayer of biotite, this ion-exchange process was pH-dependent and only favorable under acidic condition. Instead of precipitation or reduction to uraninite, the TRFS results strongly suggests U(VI) forms surface complexes under the neutral and alkaline condition, though the number and structure of surface species could not be identified accurately. Besides, the oxidation of biotite with peroxide hydrogen showed that structural Fe(II) would have a very low redox reactivity. With leaching experiments, zeta potential analysis and thermodynamics calculation, we discussed the possible reasons for inhibition of U(VI) reduction at the biotite-water interface. Our results may provide insight on interaction mechanism of uranium at mineral-water interface and help us understand the migration behavior of uranium in natural environments.


Assuntos
Silicatos de Alumínio/química , Compostos Ferrosos/química , Urânio/química , Concentração de Íons de Hidrogênio , Troca Iônica , Minerais , Oxirredução , Espectroscopia Fotoeletrônica , Resíduos Radioativos , Dióxido de Silício , Termodinâmica
14.
Nat Commun ; 11(1): 1867, 2020 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-32313070

RESUMO

Plant halogenated natural products are rare and harbor various interesting bioactivities, yet the biochemical basis for the involved halogenation chemistry is unknown. While a handful of Fe(II)- and 2-oxoglutarate-dependent halogenases (2ODHs) have been found to catalyze regioselective halogenation of unactivated C-H bonds in bacteria, they remain uncharacterized in the plant kingdom. Here, we report the discovery of dechloroacutumine halogenase (DAH) from Menispermaceae plants known to produce the tetracyclic chloroalkaloid (-)-acutumine. DAH is a 2ODH of plant origin and catalyzes the terminal chlorination step in the biosynthesis of (-)-acutumine. Phylogenetic analyses reveal that DAH evolved independently in Menispermaceae plants and in bacteria, illustrating an exemplary case of parallel evolution in specialized metabolism across domains of life. We show that at the presence of azide anion, DAH also exhibits promiscuous azidation activity against dechloroacutumine. This study opens avenues for expanding plant chemodiversity through halogenation and azidation biochemistry.


Assuntos
Alcaloides/biossíntese , Compostos Ferrosos/metabolismo , Hidrolases/metabolismo , Ácidos Cetoglutáricos/metabolismo , Menispermaceae/metabolismo , Compostos de Espiro/metabolismo , Alcaloides/química , Alcaloides/genética , Bactérias/metabolismo , Biocatálise , Genes de Plantas/genética , Halogenação , Menispermaceae/embriologia , Menispermaceae/genética , Mutagênese , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Proteínas Recombinantes , Metabolismo Secundário/genética , Alinhamento de Sequência , Compostos de Espiro/química , Transcriptoma
15.
Sci Total Environ ; 720: 137653, 2020 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-32325594

RESUMO

Cyanobacterial blooms in drinking water are worldwide concern. It is known that pre-oxidation enhanced coagulation can be more efficient at removing algae than traditional coagulation. However, its application is hindered by high oxidant/coagulant consumption and the resultant potential health risk, in the form of algal organic matter (AOM) released during oxidation. To remove the cyanobacteria and meanwhile ensure cell integrity, H2O2/Fe(II) and H2O2/Fe(III), which have been widely used to degrade organic pollutants in waters, are proposed in this study. The removal efficiency of Microcystis aeruginosa (M. aeruginosa) under various oxidant/coagulant dosages, AOM release and cell integrity, as well as floc formation and morphology were investigated with these simultaneous oxidation/coagulation processes. The results show that the removal efficiency was higher than 95% with H2O2/Fe(II) and H2O2/Fe(III) under 100 µmol/L H2O2 and Fe. In addition, neither method was found to damage the algal cells in 50-200 µmol/L H2O2 dosing concentrations. It was also found that AOM, including microcystins (MCs), was well controlled owing to the oxidation of H2O2 or hydroxyl radicals, and in-situ Fe(III) settled down the cells in the processes. Compared with H2O2/Fe(II), H2O2/Fe(III) could remove algae efficiently and control AOM release with lower H2O2 (50 µmol/L) and Fe(III) (80 µmol/L) dosages, which suggests that a low chemical consumption is suitable for this simultaneous oxidation/coagulation processes. This is a promising technology for the removal of algae from drinking water in a clean, economical way.


Assuntos
Cianobactérias , Microcystis , Purificação da Água , Compostos Férricos , Compostos Ferrosos , Peróxido de Hidrogênio , Oxirredução
16.
Water Res ; 177: 115752, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32283433

RESUMO

As a common animal feed additive, p-arsanilic acid (p-AsA) is thought to be excreted with little uptake and unchanged chemical structure, threatening the environment by potentially releasing more toxic inorganic arsenic. We herein investigated the removal of arsenic by in situ formed ferric (oxyhydr)oxides with the promotion of p-AsA degradation in Fe(II)/peroxydisulfate (PDS) system. Results showed that under acid conditions, p-AsA degraded very quickly and over 99% of p-AsA (5 µM) was degraded within 10 min at the optimal dosage of Fe(II) (100 µM) and PDS (150 µM) at pH 3, while less than 66.4% of arsenic was removed at pH 3-5. Higher pH (3-7) would inhibit the degradation of p-AsA but promote the arsenic removal. At pH 6-7, over 98.5% of total arsenic was removed, while the degradation efficiency of p-AsA was lower than 52.4%. HPLC-ICP-MS results indicated that the arsenic group was cleaved from p-AsA in the form of As(III) and then rapidly oxidized to As(V). FTIR and XPS analysis indicated that both As(V) products and residual p-AsA were bonded to ferric (oxyhydr)oxides via hydroxyl groups. Common cations (e.g., Na+, Ca2+, Mg2+) and anions such as Cl-, SO42-, CO32- had no significant influence on arsenic removal, while SiO32-, PO43- and HA inhibited the removal of total arsenic, mainly by affecting the zeta potential of iron particles. In summary, the Fe(II)/PDS process, as an efficient method for partial oxidation and simultaneous adsorption of p-AsA under near-neutral conditions, is expected to control the potential environmental risks of p-AsA.


Assuntos
Arsênico , Poluentes Químicos da Água , Adsorção , Animais , Ácido Arsanílico , Compostos Férricos , Compostos Ferrosos , Concentração de Íons de Hidrogênio , Ferro , Oxirredução
17.
Environ Sci Technol ; 54(8): 4840-4846, 2020 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-32167294

RESUMO

Uranium (U) in situ bioremediation has been investigated as a cost-effective strategy to tackle U contamination in the subsurface. While uraninite was believed to be the only product of bioreduction, numerous studies have revealed that noncrystalline U(IV) species (NCU(IV)) are dominant. This finding brings into question the effectiveness of bioremediation because NCU(IV) species are expected to be labile and susceptible to oxidation. Thus, understanding the stability of NCU(IV) in the environment is of crucial importance. Fe(II) minerals (such as FeS) are often associated with U(IV) in bioremediated or naturally reduced sediments. Their impact on the stability of NCU(IV) is not well understood. Here, we show that, at high dissolved oxygen concentrations, FeS accelerates NCU(IV) reoxidation. We hypothesize that either highly reactive ferric minerals or radical S species produced by the oxidation of FeS drive this rapid reoxidation of NCU(IV). Furthermore, we found evidence for the contribution of reactive oxygen species to NCU(IV) reoxidation. This work refines our understanding of the role of iron sulfide minerals in the stability of tetravalent uranium in the presence of oxygen in a field setting such as contaminated sites or uranium-bearing naturally reduced zones.


Assuntos
Compostos de Urânio , Urânio , Biodegradação Ambiental , Compostos Ferrosos , Sedimentos Geológicos , Oxirredução , Espectroscopia por Absorção de Raios X
18.
J Environ Sci (China) ; 91: 73-84, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32172984

RESUMO

The effects of four conditioning approaches: Acid, Acid-zero-valent iron (ZVI)/peroxydisulfate (PMS), Fe(II)/PMS and ZVI/PMS, on wastewater activated sludge (WAS) dewatering and organics distribution in supernatant and extracellular polymeric substances (EPS) layers were investigated. The highest reduction in bound water and the most WAS destruction was achieved by Acid-ZVI/PMS, and the optimum conditions were pH 3, ZVI dosage 0.15 g/g dry solid (DS), oxone dosage 0.07 g/g DS and reaction time 10.6 min with the reductions in capillary suction time (CST) and water content (Wc) as 19.67% and 8.49%, respectively. Four conditioning approaches could result in TOC increase in EPS layers and supernatant, and protein (PN) content in tightly bound EPS (TB-EPS). After conditioning, organics in EPS layers could migrate to supernatant. Polysaccharide (PS) was easier to migrate to supernatant than PN. In addition, Acid, Acid-ZVI/PMS or Fe(II)/PMS conditioning promoted the release of some polysaccharides containing ring vibrations v PO, v C-O-C, v C-O-P functional groups from TB-EPS. ESR spectra proved that both radicals of SO4-· and ·OH contributed to dewatering and organics transformation and migration. CST value of WAS positively correlated with the ratios of PN/PS in LB-EPS and total EPS, while it negatively correlated with TOC, PN content and PS content in TB-EPS, as well as PS content in supernatant and LB-EPS. BWC negatively correlated to zeta potential and TOC value, PN content, and HA content in supernatant.


Assuntos
Esgotos , Águas Residuárias , Matriz Extracelular de Substâncias Poliméricas , Compostos Ferrosos , Ferro , Oxirredução , Água
19.
PLoS One ; 15(3): e0228740, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32214347

RESUMO

Parasitic diseases are a neglected and serious problem, especially in underdeveloped countries. Among the major parasitic diseases, Leishmaniasis figures as an urgent challenge due to its high incidence and severity. At the same time, the indiscriminate use of antibiotics by the population is increasing together with resistance to medicines. To address this problem, new antibiotic-like molecules that directly kill or inhibit the growth of microorganisms are necessary, where antimicrobial peptides (AMPs) can be of great help. In this work, the ferrocene molecule, one active compound with low levels of in vivo toxicity, was coupled to the N-terminus of the RP1 peptide (derived from the human chemokine CXCL4), aiming to evaluate how this change modifies the structure, biological activity, and toxicity of the peptide. The peptide and the conjugate were synthesized using the solid phase peptide synthesis (SPPS). Circular dichroism assays in PBS showed that the RP1 peptide and its conjugate had a typical spectrum for disordered structures. The Fc-RP1 presented anti-amastigote activity against Leishmania amazonensis (IC50 = 0.25 µmol L-1). In comparison with amphotericin B, a second-line drug approved for leishmaniasis treatment, (IC50 = 0.63 µmol L-1), Fc-RP1 was more active and showed a 2.5-fold higher selectivity index. The RP1 peptide presented a MIC of 4.3 µmol L-1 against S. agalactiae, whilst Fc-RP1 was four times more active (MIC = 0.96 µmol L-1), indicating that ferrocene improved the antimicrobial activity against Gram-positive bacteria. The Fc-RP1 peptide also decreased the minimum inhibitory concentration (MIC) in the assays against E. faecalis (MIC = 7.9 µmol L-1), E. coli (MIC = 3.9 µmol L-1) and S. aureus (MIC = 3.9 µmol L-1). The cytotoxicity of the compounds was tested against HaCaT cells, and no significant activity at the highest concentration tested (500 µg. mL-1) was observed, showing the high potential of this new compound as a possible new drug. The coupling of ferrocene also increased the vesicle permeabilization of the peptide, showing a direct relation between high peptide concentration and high carboxyfluorescein release, which indicates the action mechanism by pore formation on the vesicles. Several studies have shown that ferrocene destabilizes cell membranes through lipid peroxidation, leading to cell lysis. It is noteworthy that the Fc-RP1 peptide synthesized here is a prototype of a bioconjugation strategy, but it still is a compound with great biological activity against neglected and fish diseases.


Assuntos
Peptídeos Catiônicos Antimicrobianos/química , Peptídeos Catiônicos Antimicrobianos/farmacologia , Compostos Ferrosos/química , Metalocenos/química , Sequência de Aminoácidos , Animais , Peptídeos Catiônicos Antimicrobianos/metabolismo , Peptídeos Catiônicos Antimicrobianos/toxicidade , Bactérias/efeitos dos fármacos , Leishmania/efeitos dos fármacos , Camundongos , Testes de Sensibilidade Microbiana , Permeabilidade
20.
Biochim Biophys Acta Proteins Proteom ; 1868(6): 140413, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32179182

RESUMO

Only recently it was discovered that haemoglobin (Hb) belongs to the standard gene repertoire of insects, although their tracheal system is used for respiration. A classical oxygen-carrying function of Hb is only obvious for hexapods living in hypoxic environments. In other insect species, including the common fruit fly Drosophila melanogaster, the physiological role of Hb is yet unclear. Here, we study recombinant haemoglobin from the European honeybee Apis mellifera (Ame) and the malaria mosquito Anopheles gambiae (Aga). Spectroscopic evidence shows that both proteins can be classified as hexacoordinate Hbs with a strong affinity for the distal histidine. AgaHb1 is proposed to play a role in oxygen transport or sensing based on its multimeric state, slow autoxidation, and small but significant amount of five-coordinated haem in the deoxy ferrous form. AmeHb appears to behave more like vertebrate neuroglobin with a complex function given its diversified distribution in the genome.


Assuntos
Anopheles/metabolismo , Abelhas/metabolismo , Hemoglobinas/análise , Sistema Respiratório/metabolismo , Análise Espectral/métodos , Animais , Anopheles/genética , Abelhas/genética , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Evolução Molecular , Compostos Férricos/química , Compostos Ferrosos/química , Genoma , Heme/metabolismo , Hemoglobinas/genética , Insetos/genética , Insetos/metabolismo , Ligantes , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Modelos Moleculares , Oxigênio
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