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1.
Chemosphere ; 262: 128352, 2021 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-33182087

RESUMEN

As organic pollution of soil and groundwater increases, the effective and economical remediation of contaminated sites has drawn growing attention. In this study, running-water (RW) was designed to modify alkali-heat/persulfate (MAH/PS) for integrated remediation of an actual organic-contaminated site. The degradation efficiency mainly reached 60%-99% for Benz[a]anthracene, Benzo[a]pyrene and total petroleum hydrocarbons (TPHs). MAH/PS was more effective in degrading Benzene and 1,2-Dichloroethane with simple molecular configurations. The pollutant degradation efficiencies decreased with increasing site depth and increased with increasing pollutant concentrations. Migration with RW enhanced site remediation. By monitoring the groundwater after remediation, it was found that residual TPHs presented anomalous diffusion; SO42- ranged from 8.00 to 237.00 mg L-1 to 8.00-290.00 mg L-1 and pH presented alkalescence (7.00-8.20). Mathematical models were established to describe the reaction process including the solubility equilibrium of calcium hydroxide, temperature equilibrium, and reaction kinetics. Moreover, MAH/PS provided a cost-saving approach for site remediation.


Asunto(s)
Restauración y Remediación Ambiental/métodos , Contaminantes del Suelo/análisis , Contaminantes del Suelo/química , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/química , Álcalis , Benzo(a)pireno/química , China , Agua Subterránea/análisis , Agua Subterránea/química , Calor , Hidrocarburos/química , Modelos Teóricos , Oxidación-Reducción , Petróleo/análisis , Contaminación por Petróleo , Suelo/química , Sulfatos/química
2.
Chemosphere ; 261: 127844, 2020 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-33113647

RESUMEN

Biochar supported nanosized iron (nFe(0)/BC) was synthesized and used as a persulfate (PS) activator to degradation tetracycline (TC). The influence of the initial pH values, PS and nFe(0)/BC dosage, initial TC concentration, and coexist anions were investigated. In the nFe(0)/BC-PS system, TC could be effectively removed at various pH values (3.0-9.0). The degradation efficiency of TC (100 mg/L) was 97.68% using nFe(0)/BC (0.4 g/L) and persulfate (1 mM) at pH 5.0. Coexisting ions (HCO3- and NO3-) had an inhibitory effect on TC degradation. The removal of TC could be fitted by a pseudo-second-order model. Electron-Spin Resonance (ESR) analysis and scavenging tests suggested that sulfate radicals (SO4·-) and hydroxyl radicals (HO·) were responsible for TC degradation. Details of the advanced oxidation process (AOP)-induced degradation pathways of TC were determined based on liquid chromatography mass-spectrometry (LC-MS) analysis. The nFe(0)/BC could still maintain 86.38% of its original removal capacity after five cycles. The findings of this study proved that nFe(0)/BC can be applied to activate PS for the treatment of pollution caused by TC.


Asunto(s)
Carbón Orgánico/química , Hierro/química , Nanopartículas/química , Compuestos de Sodio/química , Sulfatos/química , Tetraciclina/análisis , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos , Radical Hidroxilo/química , Modelos Teóricos , Oxidación-Reducción , Aguas Residuales/química
3.
Chemosphere ; 254: 126899, 2020 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-32957294

RESUMEN

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.


Asunto(s)
Carbón Orgánico/química , Electrólisis/métodos , Hierro/química , Nitrofenoles/análisis , Sulfatos/química , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos , Modelos Teóricos , Nitrofenoles/química , Oxidación-Reducción , Aguas Residuales/química , Contaminantes Químicos del Agua/química
4.
Chemosphere ; 258: 127288, 2020 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-32947659

RESUMEN

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.


Asunto(s)
Compuestos Férricos/química , Sustancias Peligrosas/análisis , Sulfatos/química , Acidithiobacillus , Acidithiobacillus thiooxidans , Bacterias , Sustancias Peligrosas/toxicidad , Metales Pesados , Minerales , Solubilidad , Sulfuros/química , Difracción de Rayos X
5.
Food Funct ; 11(9): 7415-7420, 2020 Sep 23.
Artículo en Inglés | MEDLINE | ID: mdl-32966484

RESUMEN

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.


Asunto(s)
Antivirales/farmacología , Betacoronavirus/efectos de los fármacos , Phaeophyta/química , Polisacáridos/farmacología , Rhodophyta/química , Pepinos de Mar/química , Animales , Antivirales/química , Betacoronavirus/fisiología , Infecciones por Coronavirus/virología , Humanos , Pandemias , Neumonía Viral/virología , Polisacáridos/química , Tiburones , Sulfatos/química , Internalización del Virus/efectos de los fármacos
6.
Ecotoxicol Environ Saf ; 204: 110977, 2020 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-32739673

RESUMEN

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.


Asunto(s)
Carbonatos/toxicidad , Peróxido de Hidrógeno/toxicidad , Fenacetina/toxicidad , Sulfatos/toxicidad , Pruebas de Toxicidad Aguda , Pruebas de Toxicidad Crónica , Animales , Carbonatos/química , Chlorophyta/efectos de los fármacos , Daphnia/efectos de los fármacos , Peces , Peróxido de Hidrógeno/química , Iones/química , Iones/toxicidad , Cinética , Modelos Químicos , Oxígeno/química , Fenacetina/química , Sulfatos/química , Agua/química
7.
Biomolecules ; 10(8)2020 08 09.
Artículo en Inglés | MEDLINE | ID: mdl-32784891

RESUMEN

Elevated matrix metalloproteinase-8 (MMP-8) activity contributes to the etiology of many diseases, including atherosclerosis, pulmonary fibrosis, and sepsis. Yet, very few small molecule inhibitors of MMP-8 have been identified. We reasoned that the synthetic non-sugar mimetics of glycosaminoglycans may inhibit MMP-8 because natural glycosaminoglycans are known to modulate the functions of various MMPs. The screening a library of 58 synthetic, sulfated mimetics consisting of a dozen scaffolds led to the identification of only two scaffolds, including sulfated benzofurans and sulfated quinazolinones, as promising inhibitors of MMP-8. Interestingly, the sulfated quinazolinones displayed full antagonism of MMP-8 and sulfated benzofuran appeared to show partial antagonism. Of the two, sulfated quinazolinones exhibited a >10-fold selectivity for MMP-8 over MMP-9, a closely related metalloproteinase. Molecular modeling suggested the plausible occupancy of the S1' pocket on MMP-8 as the distinguishing feature of the interaction. Overall, this work provides the first proof that the sulfated mimetics of glycosaminoglycans could lead to potent, selective, and catalytic activity-tunable, small molecular inhibitors of MMP-8.


Asunto(s)
Glicosaminoglicanos/química , Metaloproteinasa 8 de la Matriz/química , Inhibidores de la Metaloproteinasa de la Matriz/química , Sulfatos/química , Benzofuranos/química , Biomimética , Biología Computacional , Descubrimiento de Drogas , Metaloproteinasa 9 de la Matriz/química , Modelos Moleculares , Quinazolinonas/química , Bibliotecas de Moléculas Pequeñas
8.
Ecotoxicol Environ Saf ; 202: 110921, 2020 Oct 01.
Artículo en Inglés | MEDLINE | ID: mdl-32800256

RESUMEN

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.


Asunto(s)
Bacterias/metabolismo , Compuestos Férricos/química , Fosfatos/química , Sulfatos/química , Adsorción , Biodegradación Ambiental , Compuestos Ferrosos , Hierro/química , Compuestos de Hierro/química , Minerales , Minería , Oxidación-Reducción
9.
Chemosphere ; 260: 127558, 2020 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-32693256

RESUMEN

In this work, the degradation of chloroquine (CLQ), an antiviral and antimalarial drug, using electro-Fenton oxidation was investigated. Due to the importance of hydrogen peroxide (H2O2) generation during electro-Fenton oxidation, effects of pH, current density, molecular oxygen (O2) flow rate, and anode material on H2O2 generation were evaluated. H2O2 generation was enhanced by increasing the current density up to 60 mA/cm2 and the O2 flow rate up to 80 mL/min at pH 3.0 and using carbon felt cathode and boron-doped diamond (BDD) anode. Electro-Fenton-BDD oxidation achieved the total CLQ depletion and 92% total organic carbon (TOC) removal. Electro-Fenton-BDD oxidation was more effective than electro-Fenton-Pt and anodic oxidation using Pt and BDD anodes. The efficiency of CLQ depletion by electro-Fenton-BDD oxidation raises by increasing the current density and Fe2+ dose; however it drops with the increase of pH and CLQ concentration. CLQ depletion follows a pseudo-first order kinetics in all the experiments. The identification of CLQ degradation intermediates by chromatography methods confirms the formation of 7-chloro-4-quinolinamine, oxamic, and oxalic acids. Quantitative amounts of chlorides, nitrates, and ammonium ions are released during electro-Fenton oxidation of CLQ. The high efficiency of electro-Fenton oxidation derives from the generation of hydroxyl radicals from the catalytic decomposition of H2O2 by Fe2+ in solution, and the electrogeneration of hydroxyl and sulfates radicals and other strong oxidants (persulfates) from the oxidation of the electrolyte at the surface BDD anode. Electro-Fenton oxidation has the potential to be an alternative method for treating wastewaters contaminated with CLQ and its derivatives.


Asunto(s)
Cloroquina/química , Peróxido de Hidrógeno/química , Purificación del Agua/métodos , Carbono/aislamiento & purificación , Electrodos , Radical Hidroxilo/química , Cinética , Oxidación-Reducción , Sulfatos/química , Aguas Residuales/química , Contaminantes Químicos del Agua/química
10.
Chemosphere ; 261: 127747, 2020 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-32721695

RESUMEN

To develop a metal-free biochar with high and inherent catalytic activity towards refractory and highly toxic contaminants in advanced oxidation processes, it is necessary to explore its reaction pathways and responsible catalytic sites. Herein, a metal-free biochar derived from corn cob (CCBC) was prepared and used for reaction pathway analysis during peroxydisulfate (PDS) activation. The pyrolysis temperature played an important role for regulating the biochar structure and properties, and CCBC obtained at 800 °C showed the best adsorption capacity and catalytic activity towards five typical organic pollutants, including 2, 4-dichlorophenol, Tetracycline hydrochloride, Ciprofloxacin, Methyl orange and Rhodamine B, due to its richer pore and defect structure. Further treatment of pharmaceutical wastewater demonstrated the good efficiency and potential of this metal-free catalyst for practical application. Radical (58% contribution) and non-radical (42% contribution) pathways were both found in CCBC/PDS system. More importantly, further redox experiments manifested that the carbon framework (defects, sp2-hybrid carbon, etc.) only made a contribution to the free radical pathway, while the ketone group (CO) of CCBC was proved to be mainly responsible for the non-radical pathway, namely the generation of singlet oxygen (1O2).


Asunto(s)
Carbón Orgánico/química , Sulfatos/química , Purificación del Agua/métodos , Adsorción , Carbono/química , Dominio Catalítico , Compuestos Orgánicos/aislamiento & purificación , Oxidación-Reducción , Pirólisis , Oxígeno Singlete/química , Aguas Residuales/química , Contaminantes Químicos del Agua/aislamiento & purificación
11.
Ecotoxicol Environ Saf ; 202: 110893, 2020 Oct 01.
Artículo en Inglés | MEDLINE | ID: mdl-32615495

RESUMEN

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.


Asunto(s)
Compuestos Férricos/química , Metalurgia/métodos , Reciclaje , Sulfatos/química , Zinc/análisis , Polvo/análisis , Electricidad , Hierro/química , Tamaño de la Partícula , Ácidos Sulfúricos , Temperatura , Óxido de Zinc
12.
Chemosphere ; 261: 127715, 2020 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-32717514

RESUMEN

Advanced oxidation processes (AOPs) based on the activation of hydrogen peroxide (H2O2) and persulfate (PS) by minerals have received increasing interest for environmental remediation. Herein, H2O2 and PS activation systems employing goethite as a catalyst were discovered for the rapid degradation of BPA with the generation of reactive oxidation species (ROS) and for the reduction of total organic carbon (TOC) in aqueous solutions. The morphology of goethite were characterized by XRD, SEM, BET, TEM, etc. As a result, the oxidant efficiency of the goethite/H2O2 system (75.9%) was higher than that of the goethite/PS system (61.4%) after 240 min due to the restricted radical scavenging. According to the results of electron paramagnetic resonance (EPR) and radical quenching experiments, the main active ROS during the BPA degradation process were OH and SO4-. The two reaction systems were all pH-dependent that BPA can be effectively degraded in the goethite/PS system under acidic, neutral and weakly alkaline conditions, while the most inefficient degradation under alkaline conditions in the goethite/H2O2 system. Moreover, goethite showed good structural stability in the two systems. Several reaction products were detected using LC-MS, and the mechanisms for three systems were proposed. Density functional theory (DFT) was employed to study the conceivable degradation pathways of BPA in the two processes. This work reveals novel mechanistic insights regarding H2O2 and PS activation over goethite and implies the great potential application of the PS/mineral process in water and wastewater treatment.


Asunto(s)
Compuestos de Bencidrilo/química , Fenoles/química , Contaminantes Químicos del Agua/química , Restauración y Remediación Ambiental , Peróxido de Hidrógeno/química , Compuestos de Hierro , Minerales , Oxidantes , Oxidación-Reducción , Sulfatos/química , Aguas Residuales , Contaminantes Químicos del Agua/análisis
13.
Chemistry ; 26(51): 11814-11818, 2020 Sep 10.
Artículo en Inglés | MEDLINE | ID: mdl-32515841

RESUMEN

Heparin binds to and activates antithrombin (AT) through a specific pentasaccharide sequence, in which a trisaccharide subsite, containing glucuronic acid (GlcA), has been considered as the initiator in the recognition of the polysaccharide by the protein. Recently it was suggested that sulfated iduronic acid (IdoA2S) could replace this "canonical" GlcA. Indeed, a heparin octasaccharidic sequence obtained by chemoenzymatic synthesis, in which GlcA is replaced with IdoA2S, has been found to similarly bind to and activate antithrombin. By using saturation-transfer-difference (STD) NMR, NOEs, transferred NOEs (tr-NOEs) NMR and molecular dynamics, we show that, upon binding to AT, this IdoA2S unit develops comparable interactions with AT as GlcA. Interestingly, two IdoA2S units, both present in a 1 C4 -2 S0 equilibrium in the unbound saccharide, shift to full 2 S0 and full 1 C4 upon binding to antithrombin, providing the best illustration of the critical role of iduronic acid conformational flexibility in biological systems.


Asunto(s)
Anticoagulantes/química , Antitrombinas/química , Ácido Glucurónico/química , Heparina/química , Ácido Idurónico/química , Oligosacáridos/química , Polisacáridos/química , Anticoagulantes/farmacología , Antitrombinas/metabolismo , Espectroscopía de Resonancia Magnética , Conformación Molecular , Sulfatos/química
14.
Chemosphere ; 257: 127215, 2020 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-32505950

RESUMEN

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.


Asunto(s)
Cerio/química , Adsorción , Amoníaco/química , Catálisis , Óxidos de Nitrógeno , Oxidación-Reducción , Óxidos/química , Oxígeno , Sulfatos/química , Propiedades de Superficie
15.
Chemosphere ; 259: 127400, 2020 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-32593002

RESUMEN

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.


Asunto(s)
Compuestos Azo/química , Sulfatos/química , Contaminantes Químicos del Agua/química , Bencenosulfonatos , Catálisis , Carbón Orgánico/química , Oxidación-Reducción , Reciclaje , Agua
16.
Chemosphere ; 256: 127092, 2020 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-32559887

RESUMEN

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.


Asunto(s)
Sulfatos/química , Eliminación de Residuos Líquidos/métodos , Compuestos de Amonio , Bacterias , Reactores Biológicos/microbiología , Desnitrificación , Nitrificación , Nitritos , Nitrógeno , Oxidación-Reducción , Aguas del Alcantarillado/microbiología , Azufre , Aguas Residuales/química , Aguas Residuales/microbiología
17.
Chemosphere ; 258: 127268, 2020 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-32569955

RESUMEN

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.


Asunto(s)
Acetaminofén/análisis , Peróxido de Hidrógeno/química , Oxidantes/química , Compuestos de Sodio/química , Sulfatos/química , Rayos Ultravioleta , Contaminantes Químicos del Agua/análisis , Bismuto/química , Catálisis , Radical Hidroxilo/química , Modelos Teóricos , Oxidación-Reducción
18.
Chemosphere ; 257: 127294, 2020 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-32535362

RESUMEN

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.


Asunto(s)
Cobre/química , Sulfametazina/química , Sulfatos/química , Contaminantes Químicos del Agua/química , Antibacterianos , Humanos , Sustancias Húmicas , Oxidación-Reducción , Contaminantes Químicos del Agua/análisis
19.
Chemosphere ; 258: 127275, 2020 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-32535445

RESUMEN

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.


Asunto(s)
Asbestos Serpentinas/química , Cadmio/aislamiento & purificación , Zinc/aislamiento & purificación , Precipitación Química , Aguas del Alcantarillado/química , Soluciones , Sulfatos/química
20.
Ecotoxicol Environ Saf ; 199: 110678, 2020 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-32402898

RESUMEN

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.


Asunto(s)
Nitrógeno/análisis , Cloruro de Sodio/química , Suelo/química , Sulfatos/química , Humedales , Aerobiosis , Chenopodiaceae/crecimiento & desarrollo , China , Nitrificación , Ríos/química , Salinidad , Cloruro de Sodio/administración & dosificación , Microbiología del Suelo , Sulfatos/administración & dosificación , Ureasa/metabolismo
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