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1.
Toxicon ; 180: 18-27, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32278765

RESUMEN

The presence of potent hepatotoxic cyanotoxins such as nodularin (NOD) in drinking water, groundwater, surface water, seawater and recreational waters presents a major risks to human and environmental health. Human exposure to cyanotoxins could lead to various health effects such as liver damage, jaundice, neurotoxicity and gastroenteritis. Therefore, it is critical to investigate their occurrence in environmental matrices. This study reports the use of tyre-based activated carbon (WTAC) as an adsorbent for preconcentration and removal of nodularin from environmental matrices prior to high performance liquid chromatographic analysis. The preconcentration and adsorption experiments were carried out in presence of other environmental components to consider the external effect on WTAC adsorption of nodularin. Under optimum conditions, the linear dynamic range was 0.05-70 µg L- 1 with a correlation coefficient of 0.9991. The LOD and LOQ (n = 10) in the absence and in the presence of humic acids were 0.012-0.025 µg L- 1 and 0.040-0.083, n = 10), respectively. The repeatability (n = 10) and reproducibility (n = 5) of the method expressed as relative standard deviation (%RSD) were 3.7 and 5.1%, respectively. The maximum adsorption capacity of WTAC was 345 µg g -1. Furthermore, the results demonstrated that the presence of humic acid has an effect on the nodularin adsorption to WTAC. However, high concentrations other coexisting ions such a Cl-, NO3-, PO43-, HCO3-, SO42- had no significant the effect on the adsorption process. The proposed technique was then used for a preconcentration and elimination of NOD trace levels in different water matrices. The results showed that the WTAC was an effective adsorbent for the preconcentration and removal of NOD from the complex matrices.


Asunto(s)
Monitoreo del Ambiente , Péptidos Cíclicos/análisis , Contaminantes Químicos del Agua/análisis , Adsorción , Carbón Orgánico/química , Agua Dulce/química , Agua de Mar/química , Aguas Residuales/química , Purificación del Agua/métodos
2.
Chemosphere ; 250: 126133, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32234615

RESUMEN

The metal-organic frameworks MOF-525 and MOF-545 comprised of Zr-oxide clusters and porphyrin moieties in different geometries were synthesized solvothermally and applied for the adsorptive removal of the broadly used organic contaminant sulfamethoxazole (SMX) from water. Both MOFs were found highly efficient for the adsorption of SMX with the maximum adsorption capacities of 585 and 690 mg/g for MOF-525 and MOF-545, respectively. The latter value is the highest adsorption capacity reported so far for the adsorption of SMX molecules on any adsorbent. The adsorption equilibrium could be modeled successfully by the Langmuir model, which showed close to matching with the experimental data. Their adsorption equilibriums were attained within 120 and 30 min for MOF-525 and MOF-545, respectively. MOF-545 with mesopores demonstrated superior adsorption kinetics to MOF-525 with micropores, and the simulation by the pseudo-second-order kinetic model indicated ca. 20 times faster adsorption by MOF-545 than MOF-525. Both showed pH-dependent adsorption of SMX with a gradual reduction at high pH due to the repulsion between negatively charged adsorbent and SMX. The adsorption of SMX conducted over a group of representative MOFs with different physicochemical properties and detailed characterization confirmed that the high adsorption capacity of the porphyrin MOFs is achieved by H-bonding between the SMX molecule and the N-sites of the porphyrin units in the MOFs, π-π interaction, and the high surface area. The adsorbents were easily regenerated by simple washing with acetone and reusable with >95% efficiency during 4 repeated adsorption-desorption cycles.


Asunto(s)
Sulfametoxazol/química , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Adsorción , Cinética , Estructuras Metalorgánicas , Óxidos , Agua , Contaminantes Químicos del Agua/análisis
3.
Chemosphere ; 250: 126606, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32234628

RESUMEN

A cost-effective artificial humic substances (humic acid-modified biochar, HA-BCs) is fabricated by using conventional hydrothermal-assisted pyrolysis technique, and then is considered as a promising adsorbent material for removing mercury ions from aqueous solution. Artificial humic acid (A-HA), humic acid-modified biochar (HA-BCs) are analyzed by using SEM, EA, XRD, FTIR, XPS, and BET techniques. The removal efficiency of mercury ions was greater than 95% after reaching the adsorption equilibrium. Meanwhile, the adsorption kinetics coincided with the pseudo-second-order model and the isotherms for mercury ion sorption can be best interpreted using Freundlich isotherm model, with high regression coefficients (R2 = 0.967-0.990). Furthermore, the surface properties of HA-BCs before and after mercury adsorption are compared and evaluated, realizing that the mechanisms of removal of mercury ions on HA-BCs mainly include surface complexation with oxygen/nitrogen functional groups (-OH, -COOH and -NH2) and formation of precipitation with CO32- and OH-. Furthermore, the used HA-BCs can be regenerated via 0.05 mol/L KI solution and the adsorption capacity of mercury still reaches at 32.57 mg/g after four cyclic utilization.


Asunto(s)
Sustancias Húmicas/análisis , Mercurio/química , Contaminantes Químicos del Agua/química , Adsorción , Carbón Orgánico , Concentración de Iones de Hidrógeno , Iones , Cinética , Mercurio/análisis , Espectroscopía Infrarroja por Transformada de Fourier , Propiedades de Superficie , Agua , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos
4.
Ecotoxicol Environ Saf ; 194: 110440, 2020 May.
Artículo en Inglés | MEDLINE | ID: mdl-32169729

RESUMEN

MOFs are usually used as efficient adsorbents to remove specific pollutants in water. However, because of their poor water stability relatively small particle size, their application in adsorbing and removing pollutants from water is limited. In this paper, with nitrile rubber sponge as the substrate, UiO-66-NH2/sponge composites were firstly in-situ synthesized and systematically evaluated UiO-66-NH2 as an adsorbent to remove 2,4-dichlorophenoxyacetic acid from water. This composite could not only remain the adsorption capacity for 2,4-dichlorophenoxyacetic acid of UiO-66-NH2, but also was much more convenient for separation after the adsorption compared to UiO-66-NH2. In addition, the mechanism of the adsorption of UiO-66-NH2 for 2,4-dichlorophenoxyacetic acid were discussed in detail. Electrostatic interaction between UiO-66-NH2 and 2,4-dichlorophenoxyacetic acid was the main adsorption mechanism. The adsorption was mainly suitable for Langmuir isotherm models, and its maximum adsorption capacity of 2,4-dichlorophenoxyacetic acid was 72.99 mg g-1.


Asunto(s)
Ácido 2,4-Diclorofenoxiacético/química , Herbicidas/química , Contaminantes Químicos del Agua/química , Adsorción , Agua , Purificación del Agua/métodos
5.
Chemosphere ; 250: 126240, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32114340

RESUMEN

The unexpected incorporation of ionic Mn and Fe in the crystalline structure of titanate nanowires was accomplished when a contaminated a titanium source was used. The presence of Mn (8.1 mg L-1) and Fe (4.3 mg L-1) result in the production of a novel co-doped (Fe,Mn) titanate nanowires (TNW) material with improved optical and photocatalytic properties. After structural characterization, the results indicate that both Mn and Fe were incorporated in the TNW structure by replacement of Na+ in the interlayers, together with Ti4+ substitution in the TiO6 octahedra. The potential of this new material to be used for pollutants photocatalytic degradation was further investigated. The terephthalic acid was used as probe molecule to first evaluate the catalytic ability of the pristine and FeMnTNW modified powders for the photo-assisted hydroxyl radical formation. Afterwards, the degradation process of a model emergent pollutant, caffeine, was studied. The results showed that FeMnTNW was the best photocatalyst, with the complete caffeine removal (20 mg L-1) within 60 min of radiation (13 mg catalyst/L solution). The action of several oxidant species, including h+, OH• and O2•-, during caffeine removal was carefully analyzed using specific radical scavengers. A mechanism for the charge-transfer in irradiated FeMnTNW particles, including the possibility of a photo-Fenton and photodegradation combination process, is proposed and discussed.


Asunto(s)
Nanocables/química , Fotólisis , Contaminantes Químicos del Agua/química , Catálisis , Contaminantes Ambientales , Radical Hidroxilo , Ácidos Ftálicos , Titanio/química , Purificación del Agua/métodos
6.
Chemosphere ; 250: 126316, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32120153

RESUMEN

Per- and polyfluoroalkyl substances (PFASs) are artificial refractory organic pollutants which are widely presented in aqueous environment. Due to the unquiet strength of the highly polarized carbon-fluorine bond (C-F) and their hydrophobic/lipophobic feature as well as biological persistence properties, the remediation and treatment of PFASs is a big challenge. Preliminary studies indicate that a few kinds of technical approaches could remove or transfer PFASs, but the effectiveness is not high as expected or limited while most of the techniques are only tested at laboratory scale. A review of existing treatment technologies was thus conducted for the purpose to outlook these technologies, and more importantly, to propose the foreseeable technique. As such, a constructed wetland-microbial fuel cell (CW-MFC) technology was recommended, which is a newly emerged technology by integrating physical, chemical and enhanced biological processes plus the wetland plants function with strong eco-friendly feature for a comprehensive removal of PFASs. It is expected that the review can strengthen our understanding on PFASs' research and thus can help selecting reasonable technical means of aqueous PFASs control.


Asunto(s)
Purificación del Agua/métodos , Fuentes de Energía Bioeléctrica , Contaminantes Ambientales , Flúor , Fluorocarburos/análisis , Agua , Contaminantes Químicos del Agua/análisis , Humedales
7.
Chemosphere ; 250: 126257, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32113089

RESUMEN

Magnetic algal carbon supported flower-like sulfidated nanoscale zerovalent iron (S-nZVI/AC) composite was firstly synthesized through one-pot method and used for removing bromate. More than 98% of bromate was efficiently removed within 48 min. Compared with the individual S-nZVI treatment, the removal rate constant of the S-nZVI/AC composite treatment was almost doubled. The removal rate constant of bromate increased three times when the S/Fe ratio increased from 0 to 0.3. According to the synergistic effect between the algal carbon and S-nZVI on the bromate removal, the introduction of carbon and sulfide-modification of nZVI were efficient modification approaches for enhancing the removal of bromated using S-nZVI/AC composite. The removal efficiency of bromate increased sharply to more than 98% when the composite dose increased from 0 to 40 mg L-1. The removal rate constant increased linearly from 0.08 to 0.31 min-1 when the initial concentration increased from 50 to 200 µg L-1. The removal efficiency of the bromate still maintained at high level (>85%) after 5 recycles of the S-nZVI/AC composite. Bromate was readily removed under neutral or slight acidic conditions. The bromate removal rate constant increased from 0.10 to 0.27 min-1 when the temperature increased from 15 to 35 °C. The bromate removal rate constant increased almost 4 times when the ionic strength increased from 0 to 3 g L-1. This study demonstrates that S-nZVI/AC composite synthesized through one-pot method is a promising water purification material for efficient removal of bromated disinfection by-product.


Asunto(s)
Contaminantes Químicos del Agua/química , Bromatos/química , Carbono , Desinfección , Hierro , Fenómenos Magnéticos , Nanopartículas del Metal/química , Modelos Químicos , Sulfuros , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos
8.
Chemosphere ; 250: 126299, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32113095

RESUMEN

Emerging pollutants represent a new global problem for water quality. As these compounds get into the environment, they cause severe threats to aquatic environments and human health and are typically resistant to conventional wastewater treatments. In this work, TiO2 nanoparticles surface was functionalized with silver (Ag) nanoparticles, and solvent cast and electrospun membranes of poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) were prepared with different concentrations of TiO2 and Ag-TiO2 to produce a multifunctional material. The photocatalytic activity of the nanocomposites was evaluated through the degradation of norfloxacin under ultraviolet (UV) and visible radiation. It is shown that nanocomposites with Ag-TiO2 show the highest degradation efficiencies: 64.2% under UV and 80.7% under visible radiation, for 90 and 300 min, respectively. Furthermore, the recyclability of the membranes has also been demonstrated. Finally, it is shown the antimicrobial activity of the nanocomposite membranes, demonstrating the suitability of the Ag-TiO2/PVDF-HFP nanocomposites as multifunctional photocatalytic and antimicrobial membranes for water remediation applications.


Asunto(s)
Nanocompuestos/química , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos , Antibacterianos , Luz , Membranas Artificiales , Plata , Titanio , Eliminación de Residuos Líquidos/métodos , Aguas Residuales , Agua , Contaminantes del Agua
9.
Chemosphere ; 250: 126225, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32114338

RESUMEN

For the purification of heavy metal wastewater, internal micro-electrolysis (IME) was considered as an effective method but some disadvantage greatly restricts its application. Electrocatalytic internal micro-electrolysis (ECIME) fluidized bed using iron-carbon particles was proposed to avoid disadvantaging of IME. The principal aim of this study was to investigate the enhanced removal characteristics, mechanism, and kinetic behavior of Cu(II) that none clear before. ECIME reactor shows a better copper removal performance and depends much on the polarization of the external electric field (EEF). Both the reaction rate and removal efficiency of copper electrodeposition improved obviously. Noteworthy is more than 88.0% of Cu(II) in aqueous solutions was removed by enhanced electrodeposition, and only about 10.0% of Cu(II) was absorbed and flocculated through the in situ formed iron hydroxyl compounds. Through scanning electron microscopy (SEM) and electrochemical analysis, copper can effectively electrodeposition on the surface of iron-carbon particles in ECIME reactor and accordingly the enhanced mechanisms were proposed. 1) Iron-carbon particles of ECIME formation of microelectrodes with high surface potential, larger specific area, and active sites through electrode collision and repolarization. 2) Copper electrodeposition on the formed microelectrodes exhibited greater reduction peak potential, reaction overpotential and exchange current density, which influenced by the polarization voltage significantly. 3) The electrocatalytic environment tend to in situ generate iron polymer hydroxyl compounds help to further remove residual Cu(II). ECIME fluidized-bed has promised potential for heavy metal containing wastewater purification and metal recovery. In addition, the proposed reaction models will be useful for field application.


Asunto(s)
Cobre/química , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Técnicas Electroquímicas/métodos , Electrodos , Electrólisis/métodos , Hierro/química , Cinética , Metales Pesados/análisis , Aguas Residuales/química , Agua/análisis , Contaminantes Químicos del Agua/análisis
10.
Chemosphere ; 250: 126329, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32126334

RESUMEN

The increasing contamination of lead ions (Pb(II)) in groundwater has become a serious environmental issue, which provides the impetus for intense research on Pb(II) removal. ε-MnO2 nanoflowers were successfully fabricated through a simple decomposition reaction. And the obtained ε-MnO2 nanoflowers were employed to remove Pb(II) from water. The detailed microstructure and surface properties of ε-MnO2 were systematically characterized. The results indicate that the pure ε-MnO2 phase was obtained and the specific surface area is 96.33 m2 g-1. Batch adsorption experiments of Pb(II) were carried out, and the ε-MnO2 nanoflowers exhibited outstanding adsorption performance. The maximum adsorption capacity for Pb(II) and Cd(II) achieved to 239.7 mg g-1 and 73.6 mg g-1 at the dosage of 0.2 g L-1. Besides, the prepared ε-MnO2 nanoflowers show much higher removal efficiency toward Pb(II) compared with commercial MnO2. The XRD results reveal the stability of ε-MnO2 nanoflowers, and the XPS results suggest that both the electrostatic interaction and structural tunnels are responsible for the removal mechanisms of Pb(II). This work finds a facile method to synthesize ε-MnO2 nanoflowers, showing great potential for Pb(II) removal.


Asunto(s)
Plomo/química , Compuestos de Manganeso/química , Nanoestructuras/química , Óxidos/química , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Adsorción , Agua Subterránea , Iones , Propiedades de Superficie , Aguas Residuales/química , Agua , Contaminantes Químicos del Agua/análisis
11.
Chemosphere ; 249: 126518, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32213390

RESUMEN

Biochar pyrolysed at 300 °C, 500 °C, 700 °C was modified by hydrochloric acid (HCl), hydrofluoric acid (HF), sodium hydroxide (NaOH), hydrogen peroxide (H2O2), nitric acid (HNO3) and potassium permanganate (KMnO4), and subsequently evaluated for removal efficiency of 1,2,4-trichlorobenzene (1,2,4-TCB) by biochar supported nanoscale zero-valent iron (nZVI) and palladium (Pd) composites. Under the initial 1,2,4-TCB concentration of 10 mg L-1 and the solid-liquid ratio of 0.16 g L-1, the synthesized composites of nZVI-Pd with BC700 modified by HF (FBC700-nZVI-Pd) and nZVI-Pd with BC300 modified by NaOH (SBC300-nZVI-Pd) demonstrated significantly enhanced removal efficiencies for 1,2,4-TCB achieving 98.8% and 94.7% after 48 h, respectively. The physicochemical properties of biochar including specific surface area, aromaticity and hydrophobicity after the modification by HF and NaOH were improved. Increased the supporting sites for Fe/Pd nanoparticles and the contact between composites and 1,2,4-TCB were mainly responsible for enhanced removal efficiency for 1,2,4-TCB. Both the adsorption by biochar and reduction by Fe/Pd nanoparticles effectively contributed to the removal of 1,2,4-TCB. It is estimated that the proportion of reduction was about twice that of adsorption in the first 12 h, which produced 1,2-DCB, benzene and other degradation products. Therefore, biochar treated with HF and NaOH and supported Fe/Pd nanoparticles could be effective functional materials for remediation of groundwater contaminated by 1,2,4-TCB.


Asunto(s)
Clorobencenos/química , Hierro/química , Paladio/química , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Adsorción , Carbón Orgánico , Agua Subterránea/química , Peróxido de Hidrógeno , Nanopartículas , Contaminantes Químicos del Agua/análisis
12.
Chemosphere ; 249: 126480, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32220683

RESUMEN

Anodic oxidation process is considered as an effective solution for the treatment of refractory effluents. Its performance is strongly depending on the stability of the anodes used during the process. For this reason, we aim to enhance the stability of the SS/PbO2 anodes electrodeposited by pulsed current while studying their performance for the anodic oxidation of methylene blue and industrial textile wastewater. The basic idea deals with the possibility to replace the expensive alternatives used for reinforcing the steadiness of the anodes during the anodic oxidation by a simple method based on coupling electrochemical oxidation with biosorption by vegetable material (Luffa cylindrica). The performance of the coupling process was optimized based on its performance in colored and industrial wastewater depollution. Results confirmed the efficiency of the coupling process where 98.7 and 80.02% of methylene blue were removed, respectively, after 60 and 120 min for alternating and direct current. Otherwise, 62.84 and 46.87% of methylene blue were removed by anodic oxidation, respectively, after 120 and 180 min for alternating and direct current. The % COD obtained for the anodic oxidation and the coupling process reached 57.45, 33.61, 91.32 and 75.48% respectively for alternating and direct current. The use of alternating current for both processes has enhanced the speed and the efficiency. Atomic absorption analysis has confirmed that the rates obtained of Pb2+ complied with those allowed by the Standards. LC/MS analysis allowed the identification of by-products generated and the germination tests proved the reuse of the treated water.


Asunto(s)
Eliminación de Residuos Líquidos/métodos , Electricidad , Electrodos , Galvanoplastia , Azul de Metileno/análisis , Oxidación-Reducción , Textiles , Aguas Residuales/análisis , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos
13.
Environ Monit Assess ; 192(4): 243, 2020 Mar 19.
Artículo en Inglés | MEDLINE | ID: mdl-32193684

RESUMEN

Elimination of toxic dyes from industrial effluents before discharge into the environment is very essential to reduce the impact created on the environment. The process of adsorption is widely used for the removal of toxic dyes through suitable adsorbents. In the present study, a novel adsorbent prepared from Cereus sp. for the removal of Congo red from the aqueous solution phase. Adsorption experiment was conducted in batch mode and the effect of adsorbent dose (1-12 g/l), dye concentration (100-250 mg/l), and contact time (5-120 min) was determined. Twelve isotherm models namely Langmuir, Freundlich, Jovanovic, Temkin, Elovich, Dubinin-Radushkevich, Halsey, Hill-Deboer, Flory-Huggins, Flower-Guggenheim, Kiselev, and Harkins-Jura were fitted with the experimental data. Cuticle-removed cladodes (CRC) from biomass gave maximum adsorption capacity of 27.02 mg/g, whereas cuticle (C) resulted in maximum adsorption capacity of 52.63 mg/g according to Langmuir isotherm. Pseudo-first-order, pseudo-second-order, and intra-particle diffusion kinetic models were examined. Pseudo-second-order kinetics better fitted for both adsorbents. This is the first exhaustive study to systematically find cuticle portion has better adsorption of Congo red than the cladodes of Cereus sp. The study also highlights that cutin polyesters present in the cuticle might be responsible for higher adsorption of dyes compared with its counterpart CRC. The present study provides the first evidence that cutin polymer can be used for adsorption of Congo red. It significantly contributes to advancement for new biobased materials for monitoring and remediation of water resources contaminated with toxic dyes.


Asunto(s)
Rojo Congo , Anémonas de Mar , Contaminantes Químicos del Agua , Agua , Adsorción , Animales , Rojo Congo/aislamiento & purificación , Concentración de Iones de Hidrógeno , Cinética , Anémonas de Mar/metabolismo , Termodinámica , Agua/química , Purificación del Agua/métodos
14.
Chemosphere ; 248: 126042, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32032878

RESUMEN

For the practical capture of heavy metal ions from wastewater, fabricating environmental friendly adsorbents with high stability and super adsorption capacity are pursuing issue. In this work, we develop magnetic supramolecular polymer composites (M-SMP) by using a simple two-step hydrothermal method. Systematical characterizations of morphological, chemical and magnetic properties were conducted to confirm the formation of M-SMP composites. The resulting M-SMP composites were applied to remove Pb(II) from aqueous solution and from real battery wastewater, and easy separation was achieved using a permanent magnet. By investigating the effects of various parameters, we optimized their operating condition for Pb(II) adsorption by the M-SMP. The uptake of Pb(II) onto M-SMP fitted well the pseudo-second-order and Langmuir isotherm models, and favourable thermodynamics showed a spontaneous endothermic process. The SMP endowed M-SMP with ultrahigh adsorption capacity for Pb(II) (946.9 mg g-1 at pH = 4.0, T = 298 K), remarkable selectivity, satisfactory stability and desirable recyclability. In Pb-contaminated lead-acid battery industrial wastewater, the concentration of Pb(II) declined from 18.070 mg L-1 to 0.091 mg L-1, which meets the current emission standard for the battery industry. These merits, combined with simple synthesis and convenient separation, make M-SMP an outstanding scavenger for the elimination of industrial Pb(II) wastewater.


Asunto(s)
Plomo/química , Polímeros/química , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Adsorción , Suministros de Energía Eléctrica , Concentración de Iones de Hidrógeno , Cinética , Plomo/análisis , Fenómenos Magnéticos , Magnetismo , Imanes , Metales Pesados , Termodinámica , Aguas Residuales/química , Agua/química , Contaminantes Químicos del Agua/análisis
15.
PLoS One ; 15(2): e0228644, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32027709

RESUMEN

Pyrocatalysis uses thermally excited pyroelectric materials for the generation of reactive oxygen species in water. This unique feature allows it to harvest energy in the form of natural temperature gradients or waste heat from industrial processes in order to degrade organic pollutants at low costs. Its further development into an advanced oxidation process for water remediation is dependent on the availability of pH-robust and nonspecific redox assays for the determination of its oxidation capability. Nevertheless, previous studies neglected the influence of pH changes and they were focused mainly on the degradation of one organic compound or specific chemical dosimetries. In this study, a pH-robust and nonspecific reaction protocol of the dichlorofluorescein assay was established for the investigation of the oxidation capability of the pyrocatalytic process. This reaction protocol was tested on three pyroelectric powders (LiNbO3, LiTaO3, BaTiO3) in different amounts and it overcomes major constraints of a previously used dichlorodihydrofluorescein diacetate-based reaction protocol. Instead of its diacetate, dichlorodihydrofluorescein was used as fluorogenic probe and its concentration was drastically reduced to 1 µM. For the first time, these changes enable the determination and comparison of the oxidation capability independently of pH-rising processes, which are present for all investigated pyroelectric powders up to a pH of 11. Additionally, the precision of the dichlorofluorescein assay was drastically increased and the determination and consideration of autoxidation processes was enabled. Of all three pyroelectric powders, BaTiO3 exhibited the highest oxidation capability with a linear increase with respect to the powder amount.


Asunto(s)
Restauración y Remediación Ambiental/métodos , Purificación del Agua/métodos , Fluoresceínas/química , Calor , Concentración de Iones de Hidrógeno , Oxidación-Reducción , Polvos , Especies Reactivas de Oxígeno/química , Contaminantes Químicos del Agua/química
16.
Chemosphere ; 248: 126076, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32032882

RESUMEN

The use of waste sludge as a precursor of catalysts for environmental applications has been encouraged during the past few years. In this study, a series of magnetic Fe,N-codoped carbon catalysts (UBC-x) were successfully prepared by a facile one-pot pyrolysis method using Fe-rich sludge and N-rich urea as the raw materials. By carefully controlling the mass ratio of urea/dry sludge (x = 0-3), a significant amount of N (1-10 mass%) were incorporated, and the UBC-x catalysts, especially UBC-0.5 and UBC-0.75, could be imparted with high catalytic activity, convenient magnetic separation and high recycle stability. Phenolic contaminants like phenol and bisphenol A (BPA) could be nearly completely removed through peroxymonosulfate (PMS)-induced degradation by using UBC-x as the catalysts under a wide pH range (2-11) and with the co-existence of water constituents (chloride Cl- and sodium humate NaH, 0-50 mM). Among the several reactive oxidative species (ROS), singlet oxygen (1O2) was deemed as the main reactive species responsible for BPA degradation. Both Fe and N active sites contributed to the high catalytic activity of UBC-x, and their coordination made the catalysts rather stable with no significant Fe leaching under a wide pH range. Therefore, after an easy magnetic separation, the UBC-x could be recycled and reused efficiently in another BPA removal cycle. The as-synthesized magnetic Fe,N-codoped carbon catalysts provided a new route for sludge reutilization and showed potential applications in wastewater treatment.


Asunto(s)
Carbono/química , Hierro/química , Nitrógeno/química , Peróxidos/química , Fenoles/análisis , Aguas del Alcantarillado/química , Contaminantes Químicos del Agua/análisis , Catálisis , Fenómenos Magnéticos , Modelos Teóricos , Oxidación-Reducción , Reciclaje , Aguas Residuales/química , Purificación del Agua/métodos
17.
Chemosphere ; 248: 126078, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32041070

RESUMEN

The surface properties of graphene oxide (GO) have been identified as the key effects on the adsorption of Pb(II) from aqueous solutions in this study. This study reveals the effect of the surface reactivity of GO via Carbon Disulfide (CS2) functionalization for Pb(II) adsorption. After successfully preparing CS2 functionalized GO (GOCS), the specific techniques were applied to investigate Pb(II) adsorption onto GOCS. Results indicated that the new sulfur-containing functional groups incorporated onto GOCS significantly enhanced Pb(II) adsorption capacity on GOCS than that of GO, achieving an improvement of 31% in maximum adsorption capacity increasing from 292.8 to 383.4 mg g-1. The equilibrium adsorption capacity for GOCS was 280.2 mg g-1 having an improvement of 83.2% over that of 152.97 mg g-1 for GO at the same initial concentration of 150 mg L-1 under the optimal pH of 5.7. Moreover, the results of adsorption experiments showed an excellent fit to the Langmuir and Pseudo-Second-Order models indicating the monolayer and chemical adsorption, respectively. The mechanism for Pb(II) adsorption on GOCS was proposed as the coordination, electrostatic interactions, cation-pi interactions, and Lewis acid-base interactions. The regeneration study showed that GOCS had an appreciable reusability for Pb(II) adsorption with the adsorption capacity of 208.92 mg g-1 after five regeneration cycles. In summary, GOCS has been proved to be a novel, useful, and potentially economic adsorbent for the high-efficiency removal of Pb(II) from aqueous solutions.


Asunto(s)
Disulfuro de Carbono/química , Grafito/química , Plomo/análisis , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos , Adsorción , Cinética , Propiedades de Superficie
18.
Chemosphere ; 247: 125954, 2020 May.
Artículo en Inglés | MEDLINE | ID: mdl-32069725

RESUMEN

Landfill leachate is challenging to treat due to its complex composition. Advanced oxidation processes such as Fenton process can be effective to treat leachate. Herein, a previously developed membrane electrochemical reactor (MER) was coupled with Fenton oxidation through providing synergistic benefits with the low solution pH, reduced organics, and ammonia removal/recovery. This two-stage coupled system reduced the leachate COD by 88%, much higher than that from the standalone Fenton process treating raw leachate. In addition, the usage of chemical reagents has been greatly reduced. At a dimensionless oxidant dose of 1.0, the coupled MER-Fenton system reduced the consumption of both FeSO4⋅7H2O and H2O2 by 39%, H2SO4 by 100%, and NaOH by 55%. Consequently, the sludge production was reduced by 51% in weight and 12% in volume. Despite electricity consumption by the MER, the coupled system cost $4.76 per m3 leachate less than the standalone Fenton treatment. More notably, direct Fenton oxidation removed only 21% of ammonia; in comparison the MER-Fenton system removed ammonia by 98% with the possibility for recovery at a rate of 30.6-55.2 kg N m-3 reactor d-1. Those results demonstrate that coupling MER with Fenton process could mitigate some inherent drawbacks of Fenton oxidation such as ineffective ammonia removal, high acid and chemical reagents dose requirements, and a large amount of sludge generation. This system may be moved towards practical applications by addressing a few challenges such as using renewable energy to power MER.


Asunto(s)
Técnicas Electroquímicas/métodos , Peróxido de Hidrógeno/química , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Amoníaco/aislamiento & purificación , Hierro/química , Oxidantes/química , Oxidación-Reducción , Aguas del Alcantarillado , Contaminantes Químicos del Agua/análisis , Purificación del Agua/economía
19.
Chemosphere ; 247: 125966, 2020 May.
Artículo en Inglés | MEDLINE | ID: mdl-32069731

RESUMEN

Industrial wastewaters represent a serious threat to the environment due to their variable and complex composition. Though mostly mechanical systems are used for treatment of such wastewater, there is growing need for sustainable and cost-effective solutions, especially in low-income regions. In this study, a horizontal sub-surface flow Constructed Wetland (HSFCW) system was used for the first time to treat wastewater from a glass manufacturing industry in Iran. In order to de-risk the treatment approach, a pilot system consisting of a settling tank and a HSFCW was first tested for 4 months. The results of the pilot study were then used to build the full-scale CW system treating 10 m³/day. In general, the tested design proved to be very effective reaching high removal rates of BOD5, COD, and TSS (90, 90, and 99, respectively), as also for TN and TP (>90%). The high efficiency of the tested system allowed for the recycle and reuse of the treated effluent in the glass manufacturing processes, reducing this way the fresh water consumption in the glass industry and the related operational costs.


Asunto(s)
Proyectos Piloto , Eliminación de Residuos Líquidos/métodos , Aguas Residuales , Purificación del Agua/métodos , Humedales , Residuos Industriales , Irán , Reciclaje , Eliminación de Residuos Líquidos/economía , Purificación del Agua/economía
20.
Chemosphere ; 247: 125977, 2020 May.
Artículo en Inglés | MEDLINE | ID: mdl-32069735

RESUMEN

Great progresses have been made to carry out Fenton oxidation under neutral or alkaline pH in which, nevertheless, organic acids and other acidic intermediates usually result in acidic Fenton effluent. To eliminate the classical neutralization step prior to biological treatment, acid-tolerant microbes were here screened and used for purification of acidic Fenton effluent to achieve pH increase and further COD (chemical oxygen demand) removal. The bacterial and fungal community diversity was analyzed before and after screening for acid-tolerant microbes. After screening the bacterial diversity sharply decreased while the fungal diversity at the genus level became richer, mainly including Phialemoniopsis (relative abundance 38.69%), Vanrija (20.08%), Hypocreaceae (18.44%) and Candida (14.74%). Acidic pH and residual H2O2 are the features of Fenton effluent; hence, effects of pH and H2O2 on the screened acid-tolerant microbes were investigated in the aspects of growth rate and oxygen uptake rate. The kinetic parameters, including YH-biomass yield coefficient; Kd-biomass decay coefficient; µm-specific maximum COD removal rate; Ks-half saturation constant for COD removal, of the acid-tolerant microbes using 1/5 YM (yeast extract and malt extract culture medium) as substrate at 25 °C were measured by respirometric methodology. In BAC (biological activated carbon) inoculated with acid-tolerant microbes to treat actual Fenton effluent, the average COD removal efficiency was 72% at HRT (hydraulic retention time) of 3 h and the effluent pH was above 6 after removing the dissolved CO2 by air stripping. This study will provide a basis for developing a new combined process including Fenton and biological oxidation without pH adjustment.


Asunto(s)
Hongos/metabolismo , Peróxido de Hidrógeno/química , Eliminación de Residuos Líquidos/métodos , Purificación del Agua/métodos , Bacterias/metabolismo , Análisis de la Demanda Biológica de Oxígeno , Concentración de Iones de Hidrógeno , Hierro/química , Cinética , Contaminantes Químicos del Agua/aislamiento & purificación
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