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1.
Sci Total Environ ; 740: 140388, 2020 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-32927556

RESUMO

In this paper, red mud-sewage sludge derived biochar (RSDBC) was synthesized and employed as the heterogenous activator of peroxymonosulfate (PMS) for sulfamethoxazole (SMX) degradation. With the incorporation of red mud, 82.5% degradation of SMX was achieved by RSDBC/PMS system in a process dominated by 1O2, which was attributed to the participation of oxygen vacancy, ketone groups and graphitic carbon. On the other hand, in the absence of red mud, OH and SO4•- were dominantly accounted for SMX degradation in sewage sludge derived biochar (SDBC)/PMS system. In this case heterogeneous Fe species, ketone groups and graphitic carbon were responsible for PMS activation. Due to the different Reactive Oxygen Species (ROS), effects of reaction conditions including initial pH, common anions and natural organic matter (NOM) were not in full accord. Besides, Fe leaching from RSDBC (0.67 ppm) was much lower than that of SDBC (3.07 ppm), leading to a better reuse ability for RSDBC. Less degradation intermediates were disclosed in RSDBC/PMS system, along with lower residual toxicity. In addition, eco-toxicity of all the intermediates was predicted by ECOSAR program for the further understanding of the detoxification of SMX. Advantages of RSDBC/PMS system as disclosed in this paper further suggest its potential full-scale application of environmental remediation.


Assuntos
Esgotos , Poluentes Químicos da Água/análise , Carvão Vegetal , Peróxidos , Oxigênio Singlete
2.
Huan Jing Ke Xue ; 41(4): 1743-1751, 2020 Apr 08.
Artigo em Chinês | MEDLINE | ID: mdl-32608681

RESUMO

In this paper, the effects and mechanism of ciprofloxacin (CIP) degradation with peroxymonosulfate (PMS) catalyzed by solid waste red mud (RM) was firstly studied. The results indicated that RM has large specific surface area (10.96 m2·g-1) and complex pore structure, containing ferric, alumina and calcium oxide, which enhanced ciprofloxacin degradation by PMS effectively. Radical quenching experiments revealed that SO4-·and HO·were contributed to ciprofloxacin oxidation, and the reaction was mainly occurred on RM's surface. An increase in temperature could accelerate CIP degradation, and the corresponding reaction activation energy Ea was about 5.74 kJ·mol-1. Meanwhile, CIP degradation rate increased with PMS concentration and the optimal dosage of RM was 1.0 g·L-1. Eight degradation intermediates were identified using HPLC/MS/MS, and consequently, CIP was degraded mainly through two pathways; the piperazine groups were preferentially attacked by active free radicals. This study further indicated that RM is a cheap catalyst and can be potentially used in the treatment of antibiotic contaminated wastewater.


Assuntos
Ciprofloxacino , Poluentes Químicos da Água , Peróxidos , Espectrometria de Massas em Tandem
3.
Water Res ; 182: 116030, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32679388

RESUMO

Low cost, green, regenerable catalyst for persulfate activation is the popularly concerned topic for the degradation of persistent organic micropollutants in drinking water. In this work, natural montmorillonite (MMT) saturated with Fe(III) ions was used to activate peroxymonosulfate (PMS) for the degradation of atrazine in raw drinking water. Results showed that the adsorption of atrazine was quickly completed within 1 min and the percentage degradation was finally increased up to 94.1% in 60 min. The d001-spacing of MMT was enlarged to 2.91 nm at the most by Fe(III) saturation. Atrazine was adsorbed into the nanoscale interlayer of Fe(III)-saturated montmorillonite (Fe-MMT), where the Fe(III)/Fe(II) cycle was sustainably realized through the accelerated transformation of electrons between Fe(III) and PMS. Meanwhile, the in-situ generated Fe(II) accelerated the decomposition of PMS to further proceed the degradation of atrazine through the oxidation of HO• and SO4•- radicals. This nanoconfined effect of PMS activation by Fe(III) was further confirmed through the degradation of various micropollutants in the backgrounds of river water. The selective catalytic oxidation of micropollutants through PMS activation was attributed to the 2D mesoporous structure of Fe-MMT, inhibiting the interlayer adsorption of larger molecular backgrounds (humic acids etc.). Fe(III)-saturated montmorillonite (Fe-MMT) provided a feasible and scalable method of PMS activation by Fe(III) for the degradation of micropollutants in drinking water.


Assuntos
Bentonita , Poluentes Químicos da Água/análise , Compostos Férricos , Compostos Ferrosos , Peróxidos
4.
Sci Total Environ ; 744: 140862, 2020 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-32687994

RESUMO

In this study, a group of nitrogen-doped sludge biochar were prepared by a single-step pyrolysis method and employed as catalysts for the activation of peroxymonosulfate (PMS). The N content of as-synthesized biochar composites was altered by adding a different ratio of melamine with the precursors. The sample characterization results indicated that the N content of sludge-melamine-blended biochar named SM-(0.5:1) significantly increased from 1.91 to 9.93% compared with that of raw sludge biochar. Consequently, the surface area and mesoporosity also enhanced. SM-(0.5:1) exhibited excellent degradation ability of reluctant organic pollutants in PMS/acidic media, which outperformed many previously reported carbocatalysts. Complete color removal of a mixture solution of seven cationic and anionic dyes (10 mg L-1 of each) was achieved within 50 min by using 200 mg L-1 of SM-(0.5:1) and 350 mg L-1 of PMS. A mechanism study indicated that the non-radical process performed by the pyridine N dominated the oxidative degradation of pollutants rather than that of SO4- and OH radical process governed by graphitic N, CO, and surface metal oxides. This study concurrently provides a facile route of enhancing N functionality of sludge-based carbocatalysts and an efficient way of sludge valorization.


Assuntos
Carvão Vegetal , Esgotos , Peróxidos , Triazinas
5.
Environ Pollut ; 266(Pt 2): 115140, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32653722

RESUMO

Water management such as drainage for creating aerobic conditions is considered to be an adequate method for reducing the accumulation of arsenic (As) in rice grains; however, it is difficult to conduct drainage operations in some areas that experience a lengthy rainy season as well as in soils with poor drainage. In this regard, application of oxygen-releasing compounds (ORCs) may be an alternative method for maintaining aerobic conditions even under flooding in paddy soils. Therefore, a pot experiment was conducted to investigate the effects of application of an ORC, calcium peroxide (CaO2), on the growth and accumulation of As in rice plants grown in As-contaminated paddy soils. The rice plants were grown in two soils with different characteristics and As levels, and all of the tested soils were treated with 0, 5, 10, and 20 g CaO2 kg-1. Results revealed that the concentration of As and the distribution of arsenite in the pore water of all tested soils was reduced by CaO2 application. In addition, the grain yields increased and the concentration of inorganic As in brown rice decreased by 25-45% upon CaO2 treatment of low-As-level soils (<16 mg kg-1). However, the effect of CaO2 application on the accumulation of inorganic As in brown rice in As-enriched soils (>78 mg kg-1) could not found in this study, due to the rice plant suffered from serious As phytotoxicity. It suggests that CaO2 amendment may be suitable for reducing the As concentration of rice grains grown in low-As-level paddy soils, but for As-enriched soils, the proposed CaO2 application method is not feasible.


Assuntos
Arsênico/análise , Oryza , Poluentes do Solo/análise , Peróxidos , Solo
6.
J Environ Manage ; 270: 110907, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32721342

RESUMO

Cu-ZSM-5 zeolite membrane catalysts prepared by ion exchange method were synthesized on paper-like sintered stainless fibers (PSSFs) with three-dimensional net structure for the catalytic wet peroxide oxidation (CWPO) of phenol in structured fixed bed reactor. The experimental results exhibited that the BET of optimal catalyst was 165 m2/g with the ion exchange concentration of 0.1 M and time of 24 h, respectively, at temperature of 40 °C and one time ion exchange. The FT-IR results illustrated that band intensity was the lowest, and original Cu+ species and lattice oxygen were predominant in optimal catalyst according to the XPS results. Then, the effects of ion exchange concentration, time, temperature and times on catalytic performance of phenol were also investigated in structured fixed bed. It was found that the phenol was completely removed, TOC conversion (around 76.6%), high CO2 selectivity (about 78%) and low copper leaching rate (about 30%) were achieved with only 1.91 wt% copper loading over the optimal catalyst. Finally, a reasonable reaction mechanism occurring in the presence of H2O2 for CWPO of phenol was proposed by analyzing the HPLC results, which indicated Fenton-like reactions were mainly based on the HO· production by catalytic decomposition of hydrogen peroxide with Cu+ species.


Assuntos
Cobre , Fenol , Catálise , Peróxido de Hidrogênio , Troca Iônica , Oxirredução , Peróxidos , Espectroscopia de Infravermelho com Transformada de Fourier
7.
J Toxicol Environ Health B Crit Rev ; 23(6): 255-275, 2020 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-32568623

RESUMO

Gap junctions in liver, as in other organs, play a critical role in tissue homeostasis. Inherently, these cellular constituents are major targets for systemic toxicity and diseases, including cancer. This review provides an overview of chemicals that compromise liver gap junctions, in particular biological toxins, organic solvents, pesticides, pharmaceuticals, peroxides, metals and phthalates. The focus in this review is placed upon the mechanistic scenarios that underlie these adverse effects. Further, the potential use of gap junctional activity as an in vitro biomarker to identify non-genotoxic hepatocarcinogenic chemicals is discussed.


Assuntos
Comunicação Celular/efeitos dos fármacos , Junções Comunicantes/efeitos dos fármacos , Fígado/efeitos dos fármacos , Animais , Conexinas/biossíntese , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos , Humanos , Fígado/metabolismo , Metais/toxicidade , Peróxidos/toxicidade , Praguicidas/toxicidade , Ácidos Ftálicos/toxicidade , Medição de Risco , Solventes/toxicidade , Toxinas Biológicas/toxicidade
8.
PLoS Genet ; 16(6): e1008838, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32544191

RESUMO

Reactive oxygen species (ROS) are signalling molecules whose study in intact organisms has been hampered by their potential toxicity. This has prevented a full understanding of their role in organismal processes such as development, aging and disease. In Caenorhabditis elegans, the development of the vulva is regulated by a signalling cascade that includes LET-60ras (homologue of mammalian Ras), MPK-1 (ERK1/2) and LIN-1 (an ETS transcription factor). We show that both mitochondrial and cytoplasmic ROS act on a gain-of-function (gf) mutant of the LET-60ras protein through a redox-sensitive cysteine (C118) previously identified in mammals. We show that the prooxidant paraquat as well as isp-1, nuo-6 and sod-2 mutants, which increase mitochondrial ROS, inhibit the activity of LET-60rasgf on vulval development. In contrast, the antioxidant NAC and loss of sod-1, both of which decrease cytoplasmic H202, enhance the activity of LET-60rasgf. CRISPR replacement of C118 with a non-oxidizable serine (C118S) stimulates LET-60rasgf activity, whereas replacement of C118 with aspartate (C118D), which mimics a strongly oxidised cysteine, inhibits LET-60rasgf. These data strongly suggest that C118 is oxidized by cytoplasmic H202 generated from dismutation of mitochondrial and/or cytoplasmic superoxide, and that this oxidation inhibits LET-60ras. This contrasts with results in cultured mammalian cells where it is mostly nitric oxide, which is not found in worms, that oxidizes C118 and activates Ras. Interestingly, PQ, NAC and the C118S mutation do not act on the phosphorylation of MPK-1, suggesting that oxidation of LET-60ras acts on an as yet uncharacterized MPK-1-independent pathway. We also show that elevated cytoplasmic superoxide promotes vulva formation independently of C118 of LET-60ras and downstream of LIN-1. Finally, we uncover a role for the NADPH oxidases (BLI-3 and DUOX-2) and their redox-sensitive activator CED-10rac in stimulating vulva development. Thus, there are at least three genetically separable pathways by which ROS regulates vulval development.


Assuntos
Proteínas de Caenorhabditis elegans/genética , Caenorhabditis elegans/crescimento & desenvolvimento , Regulação da Expressão Gênica no Desenvolvimento , Peróxidos/metabolismo , Vulva/crescimento & desenvolvimento , Proteínas ras/genética , Animais , Animais Geneticamente Modificados , Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Feminino , Mutação com Ganho de Função , Genes de Helmintos/genética , Oxirredução , Oxirredutases/metabolismo , Peróxidos/análise , Transdução de Sinais/genética , Fatores de Transcrição/metabolismo , Proteínas rac de Ligação ao GTP/metabolismo , Proteínas ras/metabolismo
9.
Ying Yong Sheng Tai Xue Bao ; 31(5): 1467-1475, 2020 May.
Artigo em Chinês | MEDLINE | ID: mdl-32530223

RESUMO

To explore the effects of different coated slow-release calcium peroxide on soil microbial characteristics in gleyed paddy field, we set seven treatments by simulation test in a greenhouse, including CK (none calcium peroxide), calcium peroxide powder, calcium peroxide particle and other four coated slow-release calcium peroxide treatments. Samples were collected in same tillering stage of early season rice. The results showed that all the applications of calcium peroxide could improve the concentrations of active soil organic carbon, soil available nutrients, soil microbial biomass, culturable microorganism population, as well as soil enzyme activity. The coated slow-release calcium peroxide had stronger effects than calcium peroxide particles and calcium peroxide powder. The calcium peroxide coated by ethyl cellulose was the most effective, which enhanced soil active organic carbon, soil microbial biomass carbon, nitrogen, phosphorus by 19.4%, 11.4%, 121.5% and 127.2%, soil alkaline hydrolysis nitrogen and available phosphorus by 4.0% and 45.5%, soil culturable bacteria and culturable microorganism population by 137.3% and 113.7%, fungi and actinomyces number were increased by 33.6% and 44.7%. The enzyme activities of invertase, phosphatase, urease as well as catalase were increased by 92.4%, 91.8%, 112.5% and 17.1%, respectively. The results could provide reference for improving gleyed paddy field with coated calcium peroxide.


Assuntos
Oryza , Solo , Biomassa , Carbono , Nitrogênio , Peróxidos , Microbiologia do Solo
10.
Aquat Toxicol ; 225: 105527, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32599436

RESUMO

A diverse range of chemicals are used in agriculture to increase food production on a large scale, and among them is the use of pesticides such as chlorothalonil, a broad-spectrum fungicide used in the control of foliar fungal diseases. This study aimed to elucidate the effects of chlorothalonil on biochemical biomarkers of oxidative stress in tissues of the fish Danio rerio. To achieve this, animals were exposed for 4 and 7 days, to nominal concentrations of chlorothalonil at 0 µg/L (DMSO, 0.001%), 0.1 µg/L and 10 µg/L, and after the exposure period, the tissues (gills and liver) were removed for biochemical analysis. Antioxidant capacity against peroxyl radicals (ACAP) and enzyme activities, such as superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) and glutamate cysteine ligase (GCL), were evaluated in both tissues. In addition, the concentration of reactive oxygen species (ROS), reduced glutathione (GSH) and lipid peroxidation (LPO) levels were also analysed. A significant increase in ROS concentration, ACAP levels, GST and GCL activities and a significant reduction of LPO levels in gills exposed to the highest concentration were observed after 4 days. However, there was a significant reduction of ACAP and CAT activity, as well as a significant increase of GST activity and LPO levels in gills exposed to the lower concentration after 7 days. The liver was less affected, presenting a significant reduction in CAT activity and LPO levels after 4 days. However, a significant increase in SOD activity and LPO levels occurred after 7 days. These results indicate that chlorothalonil, after 4 days, caused activation of the antioxidant defence system in gills of animals exposed to the highest concentration. However, after 7 days, the lowest concentration of this compound caused oxidative stress in this same organ. Also, the results show that gills were more affected than the liver, probably because gills can be involved in chlorothalonil metabolisation. Therefore, it is possible that the liver could be exposed to lower chlorothalonil concentrations or less toxic metabolites due to the metabolism taking place in the gills.


Assuntos
Antioxidantes/metabolismo , Fungicidas Industriais/toxicidade , Nitrilos/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Peixe-Zebra/metabolismo , Animais , Catalase/metabolismo , Brânquias/efeitos dos fármacos , Brânquias/enzimologia , Glutationa/metabolismo , Glutationa Peroxidase/metabolismo , Glutationa Transferase/metabolismo , Peroxidação de Lipídeos/efeitos dos fármacos , Peróxidos/metabolismo , Superóxido Dismutase/metabolismo
11.
PLoS Pathog ; 16(6): e1008485, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32589689

RESUMO

Ozonide antimalarials, OZ277 (arterolane) and OZ439 (artefenomel), are synthetic peroxide-based antimalarials with potent activity against the deadliest malaria parasite, Plasmodium falciparum. Here we used a "multi-omics" workflow, in combination with activity-based protein profiling (ABPP), to demonstrate that peroxide antimalarials initially target the haemoglobin (Hb) digestion pathway to kill malaria parasites. Time-dependent metabolomic profiling of ozonide-treated P. falciparum infected red blood cells revealed a rapid depletion of short Hb-derived peptides followed by subsequent alterations in lipid and nucleotide metabolism, while untargeted peptidomics showed accumulation of longer Hb-derived peptides. Quantitative proteomics and ABPP assays demonstrated that Hb-digesting proteases were increased in abundance and activity following treatment, respectively. Ozonide-induced depletion of short Hb-derived peptides was less extensive in a drug-treated K13-mutant artemisinin resistant parasite line (Cam3.IIR539T) than in the drug-treated isogenic sensitive strain (Cam3.IIrev), further confirming the association between ozonide activity and Hb catabolism. To demonstrate that compromised Hb catabolism may be a primary mechanism involved in ozonide antimalarial activity, we showed that parasites forced to rely solely on Hb digestion for amino acids became hypersensitive to short ozonide exposures. Quantitative proteomics analysis also revealed parasite proteins involved in translation and the ubiquitin-proteasome system were enriched following drug treatment, suggestive of the parasite engaging a stress response to mitigate ozonide-induced damage. Taken together, these data point to a mechanism of action involving initial impairment of Hb catabolism, and indicate that the parasite regulates protein turnover to manage ozonide-induced damage.


Assuntos
Adamantano/análogos & derivados , Antimaláricos/farmacologia , Eritrócitos , Hemoglobinas/metabolismo , Compostos Heterocíclicos com 1 Anel/farmacologia , Peróxidos/farmacologia , Plasmodium falciparum/metabolismo , Compostos de Espiro/farmacologia , Adamantano/farmacologia , Eritrócitos/metabolismo , Eritrócitos/parasitologia , Hemoglobinas/genética , Compostos Heterocíclicos/química , Compostos Heterocíclicos/farmacologia , Humanos , Plasmodium falciparum/genética , Proteômica
12.
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
13.
J Environ Manage ; 266: 110616, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32392147

RESUMO

Furfural is a toxic compound that can cause many problems for human health and the environment. In this study, we addressed the degradation of furfural in aqueous solution using the activated persulfate (SPS) and peroxymonosulfate (PMS) through the ultrasonic (US) wave. Besides, the effect of various parameters (pH, oxidizing dose, initial furfural concentration, US frequency, Inorganic anions concentration, and scavenger) on SPS + US (SPS/US) and PMS + US (PMS/US) processes were examined. The results showed, in order to furfural removal, the US had excellent efficiency in activating SPS and PMS, as in SPS/US and PMS/US processes, 95.3% and 58.4% of furfural (at 25 mg/L concentration) was decomposed in 90 min, respectively. The furfural degradation rate increased with increasing oxidizing dose and US frequency in both SPS/US and PMS/US processes. Considering the synergistic effect, the best removal rate has occurred in the SPS/US process. In the SPS/US and PMS/US processes, furfural removal increased at natural pH (pH 7), and the presence of inorganic anions such as NO3- and Cl- had negative effects on furfural removal efficiency. Also CO32- and HCO3- acted as a radical scavenger in the SPS/US process but these anions in the PMS/US process produced more SO4-° radicals, and subsequently, they increased the furfural degradation rate. The results also showed that the predominant radical in the oxidation reactions is the sulfate radical. This study showed that the SPS/US and PMS/US processes are promising methods for degrading organic pollutants in the environment.


Assuntos
Ondas Ultrassônicas , Poluentes Químicos da Água , Furaldeído , Oxirredução , Peróxidos
14.
Sci Total Environ ; 733: 139250, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32446064

RESUMO

Peroxymonosulfate (PMS) was employed as an activator of ozone (O3) to degrade non-steroidal anti-inflammatory drugs (NSAIDs) (aspirin (ASA) and phenacetin (PNT)) in study. The combination of PMS in O3 system promoted the O3 decomposition and NSAIDs removal significantly. O3 molecule, hydroxyl radical (OH) and sulfate radical (SO4-) were responsible for the removal of target pollutants in O3/PMS system. The second-rate constants between O3, OH and SO4- with ASA were determined to be 7.32, 4.18 × 109 and 3.46 × 108 M-1·s-1, and 37.3, 4.99 × 109 and 5.64 × 108 M-1·s-1 for PNT, respectively. The pattern of pollutant removal and contributions of oxidative species were fitted by experiments and two models. Nevertheless, the wide variety of two models suggested that a comprehensive model for O3/PMS based on a first-principles approach was not yet possible, due to the number of radicals and subsequent chain reaction, such as SO5- or O3-. In addition, the formation of five typical CX3R -type disinfection by products was evaluated from post­chlorine tests and theoretically calculation by frontier electron density calculation. The calculated toxicity of typical CX3R -type DBPs was found to decrease with the increase of pH. The results of this study provide a basis for exploring the mechanism of pollutant degradation in O3 system.


Assuntos
Ozônio , Poluentes Químicos da Água/análise , Anti-Inflamatórios , Oxirredução , Peróxidos
15.
J Environ Sci (China) ; 93: 30-40, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32446457

RESUMO

Peroxymonosulfate (PMS) decomposition, hydroxyl radical (•OH) generation, and acetaminophen (ACT) degradation by the Co/PMS system using homogeneous (dissolved cobalt) and heterogeneous (suspended Co3O4) cobalt were assessed. For the homogeneous process, >99% PMS decomposition was observed and 10 mmol/L of •OH generation was produced using 5 mmol/L of PMS and different dissolved cobalt concentrations after 30 min. A dissolved cobalt concentration of 0.2 mmol/L was used to achieve >99% ACT degradation using the homogeneous process. For the heterogeneous process, 60% PMS decomposition and negligible •OH generation were observed for 5 mmol/L of the initial PMS concentration using 0.1 and 0.2 g/L of Co3O4. Degradation of ACT greater than 80% was achieved for all experimental runs using 5 mmol/L of the initial PMS concentration independently of the initial Co3O4 load used. For the heterogeneous process, the best experimental conditions for ACT degradation were found to be 3 mmol/L of PMS and 0.2 g/L of Co3O4, for which >99% ACT degradation was achieved after 10 min. Because negligible •OH was produced by the Co3O4/PMS process, a second-order kinetic model was proposed for sulfur-based free radical production to allow fair comparison between homogeneous and heterogeneous processes. Using the kinetic data and the reaction by-products identified, a mechanistic pathway for ACT degradation is suggested.


Assuntos
Acetaminofen , Peróxidos , Cobalto , Cinética
16.
Chemosphere ; 255: 126939, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32402883

RESUMO

This study proposes a novel approach for utilizing granular sludge discharged from anaerobic reactors to prepare an effective and stable catalyst for the removal of refractory contaminants in catalytic wet peroxide oxidation (CWPO). By implementing the response surface methodology, the experimental conditions for m-cresol degradation in CWPO with a HNO3-modified sludge carbon (GSC-M) as catalyst were explored. The removal efficiencies for m-cresol and total organic carbon (TOC) were 100% and 91.4%, respectively, at the optimal conditions of 60 °C for 120 min with a pH of 3, H2O2 dosage of 1.85 g/L, and catalyst dosage of 0.75 g/L. A continuous experiment was conducted for 6 d to investigate the durability and catalytic performance of GSC-M, resulting in a TOC removal above 90% with the catalyst maintaining its original morphology. GSC-M catalyst exhibited excellent stability and low iron leaching (0.34%). The high catalytic degradation could be attributed to a high content of iron species, various types of surface functional groups, porous structures, and the π-π interaction between aromatic clusters in sludge carbon and the benzene ring of m-cresol. Interestingly, GSC-M catalyst exhibited magnetic properties which are beneficial for recycling. Based on the identified intermediates, a possible degradation pathway of m-cresol was proposed.


Assuntos
Cresóis/metabolismo , Eliminação de Resíduos Líquidos/métodos , Anaerobiose , Carbono/química , Catálise , Cresóis/química , Peróxido de Hidrogênio/química , Ferro , Oxirredução , Peróxidos/química , Pirólise , Reciclagem , Esgotos
17.
Chemosphere ; 255: 126961, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32402886

RESUMO

Sulfate radical-based advanced oxidation processes (SR-AOPs) have received increasing attention as viable technology for recalcitrant organics removal from polluted waters. As for heterogeneous catalyst, it is crucial to reveal the effect of morphology on its catalytic activity and mechanism, providing guidelines for rational design of morphology-dependent catalysts. Hence, in this study, we selected manganese oxyhydroxide (MnOOH) as the peroxymonosulfate (PMS) activator and synthesized different morphological MnOOH with the same crystal structure. The catalytic activity of MnOOH follows: nanowires > multi-branches > nanorods. Different morphological MnOOH had different physical and chemical characterization such as specific surface area, Lewis sites, ζ-potential and redox potential, which played positive roles in catalytic activity of MnOOH as PMS activator. Unexpectedly, it was found that ζ-potential was more crucial than specific surface area, redox potential and Lewis sites. Notably, nanowires exhibited higher positive zeta potential, which was favor of promoting interfacial reactivity between HSO5- and surface of MnOOH. Furthermore, •OH, SO4•-, O2•- and 1O2, were involved in the MnOOH/PMS system. Moreover, the cycle of Mn (III)/Mn (II) accelerated MnOH+ formation. This study provided a new understanding of manganese-catalyzed peroxymonosulfate activation and elucidated the relationships between morphology of catalyst and its catalytic activity.


Assuntos
Clorofenóis/química , Modelos Químicos , Catálise , Manganês , Oxirredução , Peróxidos , Fenóis , Sulfatos
18.
Proc Natl Acad Sci U S A ; 117(22): 11916-11922, 2020 06 02.
Artigo em Inglês | MEDLINE | ID: mdl-32414932

RESUMO

Lytic polysaccharide monooxygenases (LPMOs) have been proposed to react with both [Formula: see text] and [Formula: see text] as cosubstrates. In this study, the [Formula: see text] reaction with reduced Hypocrea jecorina LPMO9A (CuI-HjLPMO9A) is demonstrated to be 1,000-fold faster than the [Formula: see text] reaction while producing the same oxidized oligosaccharide products. Analysis of the reactivity in the absence of polysaccharide substrate by stopped-flow absorption and rapid freeze-quench (RFQ) electron paramagnetic resonance (EPR) and magnetic circular dichroism (MCD) yields two intermediates corresponding to neutral tyrosyl and tryptophanyl radicals that are formed along minor reaction pathways. The dominant reaction pathway is characterized by RFQ EPR and kinetic modeling to directly produce CuII-HjLPMO9A and indicates homolytic O-O cleavage. Both optical intermediates exhibit magnetic exchange coupling with the CuII sites reflecting facile electron transfer (ET) pathways, which may be protective against uncoupled turnover or provide an ET pathway to the active site with substrate bound. The reactivities of nonnative organic peroxide cosubstrates effectively exclude the possibility of a ping-pong mechanism.


Assuntos
Aminoácidos/metabolismo , Peróxido de Hidrogênio/metabolismo , Oxigenases de Função Mista/química , Polissacarídeos/metabolismo , Sítios de Ligação , Biocombustíveis , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Hypocrea/metabolismo , Cinética , Espectroscopia de Ressonância Magnética/métodos , Oxigenases de Função Mista/metabolismo , Oxirredução , Peróxidos/metabolismo , Triptofano/metabolismo , Tirosina/metabolismo
19.
Chemosphere ; 255: 126983, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32402867

RESUMO

The instability and rapid consumption of H2O2 limit the application of UV/H2O2 in water treatment. Recently, calcium peroxide (CaO2) has been demonstrated as an effective source of H2O2. However, the performance and mechanism of UV/CaO2 are still unknown. Herein, UV/CaO2 and UV/H2O2 were compared for degradation of aniline. The removal efficiency of aniline by UV/CaO2 was slightly lower than that by UV/H2O2, which could be attributed to the light scavenger by CaO2 suspended particles. HO‧ was identified to participate in aniline degradation in both UV/CaO2 and UV/H2O2, while O2-· was only involved in UV/CaO2. The efficiency of aniline degradation in UV/CaO2 was affected by the released H2O2 in the system. The release and decomposition rate of H2O2 in UV/CaO2 system were influenced by the CaO2 dosage and reaction pH, but slightly related with water matrix. Excessive CaO2 would scavenge aniline degradation through the released H2O2 to react with HO‧. Acidic condition would enhance the concentration of H2O2 in UV/CaO2 and promote the degradation of aniline. Cl- showed slight and almost no effect on aniline degradation in UV/CaO2 and UV/H2O2 systems, respectively, while HCO3- scavenged aniline degradation in UV/CaO2. NO3- inhibited aniline degradation in both UV/CaO2 and UV/H2O2. Compared to UV/H2O2, UV/CaO2 shows the similar efficiency on organics removal but conquers the limitations in UV/H2O2, which is a promising alternative choice in water treatment.


Assuntos
Peróxido de Hidrogênio/química , Peróxidos , Raios Ultravioleta , Poluentes Químicos da Água/química , Purificação da Água/métodos , Compostos de Anilina/química , Compostos de Anilina/isolamento & purificação , Carcinógenos/química , Cinética , Oxirredução , Purificação da Água/normas
20.
Sci Total Environ ; 728: 138853, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32353802

RESUMO

The high moisture content of wet sewage sludge generated from wastewater treatment process not only brings high cost of sewage disposal, but also limits its utilization as resource. In this study, an efficient strategy of directly utilizing wet sludge to develop advanced carbocatalyst via a hydrothermal coupled pyrolysis process was proposed. The possible application of as-synthesized carbocatalyst was evaluated by activating peroxymonosulfate (PMS) to degrade a model pollutant of sulfamethoxazole (SMX). Experimental results showed that about 100% of SMX and 59% of total organic carbon (TOC) could be removed within 15 min. Moisture content in wet sludge also affected the performances of as-obtained carbocatalysts. Further studies verified that singlet oxygen (1O2) dominated SMX degradation, which was generated in the process of PMS activation by CO groups on the surface of carbocatalyst. In the preliminary ecological test, a lower ecotoxicity of SMX degradation solution compared with the original solution was observed. This study demonstrated the feasibility of directly utilizing wet sludge for advanced carbocatalyst fabrication, which provided another solution for wet sludge treatment and utilization.


Assuntos
Sulfametoxazol , Poluentes Químicos da Água , Carbono , Peróxidos , Esgotos
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