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1.
J Hazard Mater ; 421: 126709, 2022 01 05.
Artículo en Inglés | MEDLINE | ID: mdl-34315021

RESUMEN

Nanoscale zero-valent iron nanoparticles (nZVI) have been used for groundwater remediation and wastewater treatment due to their high reactivity, high adsorption capacity and nontoxicity. However, side reactions generally occur in tandem with the target contaminants removal process, resulting in poor electron selectivity (ES) of nZVI, and subsequently restricting its commercial application. Major efforts to increase ES of nZVI have been made in recent years. This review's objective is to provide a progress report on the significant developments in nZVI's ES during the past decade. Firstly, the definition of ES and its quantification approaches were documented, and the intrinsic (i.e. particle size, crystallinity, and surface area) and extrinsic factors (i.e. solutions pH, target contaminant concentration, and presence of co-contaminants) affecting the ES of nZVI were reported. The latest techniques for increasing ES were summarized in detail, with reference made to sulfidation, magnetization, carbon loading and other features. Then the mechanisms of those strategies for ES enhancement were described. Finally, some constructive suggestions on future research directions concerning nZVI's ES in the future were proposed.


Asunto(s)
Restauración y Remediación Ambiental , Agua Subterránea , Contaminantes Químicos del Agua , Purificación del Agua , Electrones , Hierro , Contaminantes Químicos del Agua/análisis
2.
J Environ Manage ; 301: 113894, 2022 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-34638045

RESUMEN

A biotic iron (Fe0) treatment system combined with mixed microorganisms was applied to remediate cadmium (Cd)-contaminated groundwater under the intervention of sulfate. Due to hydrogenotrophic desulfuration effect, severe iron corrosion was observed in this microbe-collaborative Fe0 system according to surface morphology analysis as lots of secondary minerals (e.g. magnetite, green rust and lepidocrocite) were generated, which was essential for Cd(II) adsorption and immobilization. The sulfate-mediated biotic Fe0 system thereafter achieved a significantly enhanced Cd(II) removal efficiency of 86.1%, over 3.3 times than that in the abiotic Fe0 system. Increasing initial sulfate concentration could improve the removal of cadmium, which further proved that hydrogenotrophic desulfuration played a key role for enhanced Cd removal. According to the experimental results and current reports, the mechanism of Cd(II) removal was revealed into three pathways including adsorption to secondary iron minerals, co-precipitation with iron (hydr)oxides and formation of cadmium sulfide precipitation. Increasing Fe0 dosages showed positive correlation to Cd(II) removal and neutral pH was preferred to sulfate-mediated biotic Fe0 corrosion. These results indicated that sulfate-mediated biotic Fe0 corrosion could greatly relieve the limitation of Fe0 in Cd(II) immobilization, which could be a promising method to eliminate Cd(II) pollution from groundwater.


Asunto(s)
Cadmio , Agua Subterránea , Cadmio/análisis , Corrosión , Hierro , Sulfatos
3.
Sci Total Environ ; : 152089, 2021 Nov 29.
Artículo en Inglés | MEDLINE | ID: mdl-34856267

RESUMEN

The content of active components in magnetic biochar, especially Fe(II), is closely related to its activation performance. Therefore, improving Fe(II) content in magnetic biochar is an ideal strategy to enhance the activation performance of magnetic biochar. In this study, the potassium-doped magnetic biochar was prepared and employed to activate persulfate for degradation of metronidazole. The degradation efficiency of metronidazole in potassium-doped magnetic biochar/persulfate system was 98.4%, which was 13.1 times higher than that in magnetic biochar/persulfate system. Free radicals quenching experiments and electron spin resonance analyses confirmed that surface-bound free radicals were responsible for metronidazole degradation followed the order of 1O2 > OH > SO4- > O2-. The doping of magnetic biochar with potassium increased its Fe(II) content, approximately 3.1 times higher than that of pristine magnetic biochar. The differences in Fe(II) content between potassium-doped magnetic biochar and magnetic biochar were the key reasons for the activation performance differences. Based on the ultra-high pressure liquid chromatography-quadrupole tandem time-of-flight mass spectrometer, the primary degradation intermediates of metronidazole were identified, and possible degrading pathways were proposed. Overall, this work provides an effective strategy to improve the activation performance of magnetic biochar.

4.
J Hazard Mater ; 416: 126183, 2021 08 15.
Artículo en Inglés | MEDLINE | ID: mdl-34492954

RESUMEN

In this work, a modified g-C3N4/MgZnAl-calcined layered double hydroxide composite (M-CN/cLDH) was successfully fabricated via a template method. The composite material is a hierarchical porous flower-like nanostructure self-assembled from stacked hybrid flakes. The 3D M-CN/cLDH architectures exhibit a synergistic effect of adsorption and photocatalysis for eliminating typical tetracycline antibiotics in seawater, i.e., oxytetracycline (OTC), tetracycline (TC), chlortetracycline (CTC), and doxycycline (DXC). The synergistic removal rate of OTC in seawater of M-CN/cLDH is 2.73 times higher than that of g-C3N4 after 120 min of visible-light illumination, and M-CN/cLDH also performs better adsorption-photocatalytic degradation on OTC in the continuous flow reaction process. The superior adsorption capability of the M-CN/cLDH is attributed to the open porous structures of cLDH, and its excellent photocatalytic degradation activity is ascribed to the closely bonded heterojunctions between g-C3N4 (CN) and cLDH double layers. The mass spectra reveals the degradation pathways of OTC, and its byproducts are less toxic after degradation for 120 min. The exploration of the M-CN/cLDH in synthetic mariculture wastewater suggested a huge potential for its practical application. With the assistance of magnesium ammonium phosphate (MAP) precipitation pretreatment, the material can effectively retain the high OTC removal rate in the synthetic mariculture wastewater circumstance.


Asunto(s)
Antibacterianos , Aguas Residuales , Adsorción , Catálisis , Porosidad , Agua de Mar
5.
Bioresour Technol ; 341: 125743, 2021 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-34438283

RESUMEN

Reducing the preparation cost of magnetic biochar is necessary for its large-scale application as an adsorbent. In this study, stainless steel pickling waste liquor and rice straw were successfully applied to synthesize of magnetic biochar (SPWL-MBC). Several iron oxides adhered on the biochar matrix, mainly Fe3O4, Fe2O3 and FeO. SPWL-MBC exhibited superparamagnetism, and its specific surface area was 274.29 m2/g. The material was able to adsorb a model contaminant, crystal violet (CV), with a maximum adsorption capacity of approximately 111.48 mg/g. Adsorption mechanism analysis showed that iron oxides, π-π interaction, hydrogen bonding and electrostatic interaction were responsible for the adsorption of CV. The CV adsorption efficiency of SPWL-MBC remained 71.91% after three adsorption-regeneration cycles. These outcomes illustrate that the magnetic biochar prepared from stainless steel pickling waste liquor can effectively remove CV from wastewater.


Asunto(s)
Oryza , Contaminantes Químicos del Agua , Adsorción , Carbón Orgánico , Violeta de Genciana , Cinética , Fenómenos Magnéticos , Acero Inoxidable
6.
J Environ Manage ; 299: 113595, 2021 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-34450304

RESUMEN

Mechanochemistry has been proved to be an effective method to remediation of organic-contaminated sites. However, the high ball-to-powder mass ratio (CR) limits the large-scale application of mechanochemistry. In this study, co-milling additives were introduced to enhance the mechanochemical degradation of decabromodiphenyl ether (BDE209)-contaminated soil under the condition of low CR. Based on additive screening experiments, sodium borohydride was selected as the ideal additive to assist the mechanochemical degradation of BDE209, and the resulting removal efficiency was approximately 100% with 2 h of ball milling at a rotational speed of 550 rpm. The main degradation intermediates and degradation pathway of BDE209 were identified using gas chromatography-tandem mass spectrometry. It was proposed that the degradation of BDE209 by sodium borohydride-assisted mechanochemistry was a concurrent process of stepwise and multistage debromination. Meanwhile, the meta-bromine atom in BDE209 was more susceptible to debromination than those at the para and ortho positions. The evolution of the concentration of Br- was monitored by ion chromatography, which revealed that reduction and oxidation both occurred in the removal of BDE209. This paper provides a new perspective for reducing the CR in the mechanochemical remediation of BDE209-contaminated soil.


Asunto(s)
Éteres Difenilos Halogenados , Contaminantes del Suelo , Contaminación Ambiental , Oxidación-Reducción , Suelo , Contaminantes del Suelo/análisis
7.
Artículo en Inglés | MEDLINE | ID: mdl-33629161

RESUMEN

Although biochar (BC) has been widely used to adsorb pollutants in environment due to its natural and green characteristics, the structural defects of BC limit the ability to remove various environmental pollutants in aqueous solution. In this study, oxidized biochar (OBC) and sulfhydryl biochar (SBC) derived from pomelo peel (PP) were prepared through an oxidation and esterification reaction. BC and modified BC were used for the removal of methylene blue (MB), Cd2+, and phenanthrene (PHE) in aqueous solution. The adsorption behavior and efficiency toward different types of pollutants were studied by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), Raman, X-ray photoelectron spectroscopy (XPS), kinetics, and isotherm model fitting. The results showed that the change of pH had great effect on MB and Cd2+ adsorption, but not on PHE. SBC not only possessed the newly formed sp2-hybridized domains with easy access to aromatic pollutants but also had multiple functional groups (-COOH, -OH, -SH, -NH2) that provided adsorption sites for positively charged pollutants. SBC was more flexible and efficient in purifying pollutants compared to BC and OBC, with the saturated adsorption capacities of MB (209.16 mg/g), Cd2+ (786.19 mg/g), and PHE (521.58 mg/g). Moreover, the adsorption kinetic and isotherms fitting showed that the adsorption mechanisms were closely related to the structure of biochar and the properties of pollutants, including π-π interaction, surface charge, electrostatic interaction, surface functional groups, and Van der Waals force. In addition, the analysis of structure-function relationship demonstrated the enhanced hydrophilicity and the easy exposure of the binding sites on OBC and SBC. Hence, it was significantly effective to regulate microstructure and interfacial properties to promote its adsorption behaviors of biochar.

8.
Sci Total Environ ; 764: 142813, 2021 Apr 10.
Artículo en Inglés | MEDLINE | ID: mdl-33097246

RESUMEN

Exploiting the full potential of copper-based nanoparticles in the activation of peroxymonopersulfate (PMS) is a great challenge due to their insufficient dispersity and electronic properties. We report here a novel iron­nitrogen co-doped carbon nanotube (FNC) modified with a Cu2O nanocomposite (Cu2O/FNC) that exhibits ultrahigh catalytic performance in the activation of PMS to degrade fluconazole (~95%). Catalytic performance evaluation illustrated that Cu2O/FNC also has wide pH applicability (3.0-11.0), long-term stability and excellent adaptability. In addition, luminescent bacteria toxicity tests confirm that Cu2O/FNC/PMS significantly reduced the acute biotoxicity of various recalcitrant pollutants (reduced by 45-83%). By identifying the reactive oxygen species (ROS) and catalytic performance for various pollutants, we propose that pollutants that interact weekly with activators are mostly destroyed by sulfate radicals and hydroxyl radicals, whilst both radical and non-radical routes were involved in the degradation of pollutants that were easily adsorbed. By modifying Cu2O with FNC, several crucial properties such as the specific surface area, surface defects, active sites and the charge transfer rate were significantly improved, leading to excellent catalytic performance for pollutant removal. Finally, a reasonable reaction mechanism is advanced for the fluconazole degradation pathway. This study not only develops a novel PMS oxidation system for fluconazole degradation, but also provides a new strategy to improve the reactivity and applicability of PMS activators by combining radical and non-radical activation pathways.


Asunto(s)
Hierro , Nanotubos de Carbono , Electrónica , Nitrógeno , Peróxidos
9.
J Hazard Mater ; 404(Pt A): 124171, 2021 02 15.
Artículo en Inglés | MEDLINE | ID: mdl-33049640

RESUMEN

Due to the rapid development of modern industry, the coexistence of antibiotics and inorganic heavy metals pollutants in wastewater has become a universal phenomenon. Therefore, developing efficient and eco-friendly photocatalyst for mixed pollutants degradation is significant. In this work, a well-designed phosphorus and sulfur co-doped g-C3N4 with feeble N vacancies catalyst (P/S-g-C3Nx) was fabricated by supramolecular self-assembly method, and was applied to remove berberine hydrochloride (BH) and Cr(VI) simultaneously with the synergy of adsorption-photocatalysis. A series of experiments was conducted to unveil the synergistic mechanism. The kinetic models indicated that the adsorption of P/S-g-C3Nx improved the BH removal process by accelerating the photo-degradation, because the adsorption rate > surface degradation rate > bulk degradation rate. Besides, the photo-degradation process improved the BH removal rate by regenerating the adsorption sites of P/S-g-C3Nx. Moreover, from the experiments in BH-Cr(VI) mixed solution system, the existence of BH also enhanced the surface adsorption of Cr(VI) in P/S-g-C3Nx sample, and the reduction rate of Cr(VI) was also promoted with the existence of BH. Overall, the results of this investigation suggest that the adsorption-photocatalysis synergy method is an efficient way to eliminate organic pollutant and Cr(VI) simultaneously.


Asunto(s)
Nanoestructuras , Contaminantes Químicos del Agua , Adsorción , Antibacterianos , Cromo/análisis , Contaminantes Químicos del Agua/análisis
10.
Artículo en Inglés | MEDLINE | ID: mdl-33246281

RESUMEN

Phytoremediation has proven to be an effective in-situ treatment technique for antibiotic contamination. Due to the immature methods of extracting multi-antibiotics in different plant tissues, the antibiotic absorption and transportation mechanism in the phytoremediation process has yet to be resolved. Therefore, an improved Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) pretreatment with ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) detection method for 28 antibiotics in different plant tissues (root, stem, leaf and seed) was developed in this study. The optimized method showed satisfactory performance with recoveries for most antibiotics ranging from 70% to 130% (except sulfadoxine with 138 ± 8.84% in root, sulfameter with 68.9 ± 1.87% and sulfadoxine with 141 ± 10.0% in seed). The limits of detection (LODs) of the target compounds in root, stem, leaf and seed were 0.04 ± 0.02 ~ 2.50 ± 1.14 ng/g, 0.05 ± 0.02 ~ 1.78 ± 0.42 ng/g, 0.06 ± 0.01 ~ 2.50 ± 0.14 ng/g and 0.13 ± 0.10 ~ 3.64 ± 0.74 ng/g, respectively. This developed method was successfully applied to the determination of antibiotics in different tissues of hydroponic wetland plants exposed to antibiotics-spiked water for one-month. Sixteen of 28 spiked antibiotics were detected in plant tissue samples. Overall, of these 16 antibiotics, all were detected in root samples (from < LOQ to 1478 ± 353 ng/g), eleven in stem samples (from < LOQ to 425 ± 47.0 ng/g), and nine in leaf samples (from < LOQ to 429 ± 84.5 ng/g). This developed analytical method provided a robust tool for the simultaneous screening and determination of antibiotics in different plant tissues.


Asunto(s)
Antibacterianos/análisis , Cromatografía Líquida de Alta Presión/métodos , Residuos de Medicamentos/análisis , Componentes Aéreos de las Plantas/química , Raíces de Plantas/química , Límite de Detección , Modelos Lineales , Magnoliopsida/química , Reproducibilidad de los Resultados , Espectrometría de Masas en Tándem/métodos
11.
J Environ Qual ; 49(3): 654-662, 2020 May.
Artículo en Inglés | MEDLINE | ID: mdl-33016401

RESUMEN

Continuous-flow iron and bio-iron columns were used to evaluate the effects of seepage velocity and concentration on Cr(VI) removal from groundwater. Solid-phase analysis showed that microorganisms accelerated iron corrosion by excreting extracellular polymeric substances and generated highly reactive minerals containing Fe(II), which gave the bio-iron column a longer life span and enhanced capacity for Cr(VI) removal via enhanced adsorption and reduction by reactive minerals. The bio-iron column showed much higher Cr(VI) removal capacity than the iron column with increasing Cr(VI) loading, which was obtained by increasing the seepage velocity or influent Cr(VI) concentration from 95 to 1138 m yr-1 and from 5 to 40 mg L-1 , respectively. When the Cr(VI) loading varied in a range of 0 to 10 mg L-1 h-1 , the bio-iron column had a 60% longer longevity and one- to sixfold higher Cr(VI) elimination capacity than the iron column. This result indicated that, under fluctuating hydraulic conditions [e.g., seepage velocity and Cr(VI) concentration], the presence of microorganisms can significantly boost Cr(VI) removal using Fe0 -based permeable reactive barriers.


Asunto(s)
Agua Subterránea , Contaminantes Químicos del Agua/análisis , Adsorción , Cromo , Hierro
12.
Water Sci Technol ; 81(7): 1452-1460, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-32616697

RESUMEN

In the process of preparing magnetic palygorskite from waste pickling liquor of the steel industry, the dosage of NaOH will affect the properties of the magnetic palygorskite. The experimental results showed that magnetic palygorskite can be effectively prepared when NaOH dosage is between 255 and 330 g/L. Vibration sample magnetometry proved that different NaOH dosages can affect the saturation magnetization of magnetic palygorskite. The catalytic performance of five catalysts synthesized with different NaOH dosages hardly changed after five cycles of Fenton-like catalytic degradation of tetracycline (TC). The magnetic palygorskite prepared by this method had good catalytic performance even when the catalyst preparation conditions were magnified ten times, which can provide a reference for large-scale preparation of magnetic palygorskite.


Asunto(s)
Contaminantes Químicos del Agua/análisis , Compuestos de Magnesio , Fenómenos Magnéticos , Compuestos de Silicona , Hidróxido de Sodio
13.
Sci Total Environ ; 744: 140715, 2020 Nov 20.
Artículo en Inglés | MEDLINE | ID: mdl-32698046

RESUMEN

In this study, nitrate mediated biotic zero-valent iron (Fe0) corrosion was employed to enhance cadmium (Cd) removal from groundwater. In comparison with a 17.5% Cd(II) removal treated with abiotic Fe0, a 3.9 times higher Cd(II) removal of 86.2% was recorded in the nitrate-mediated biotic Fe0 system. Solids phase characterization confirmed that biogenic minerals such as green rust and iron sulfide could be formed in the nitrate-amended biotic Fe0 system, offering large amount of adsorption sites for Cd(II) removal. The decrease of nitrate concentration and the competition with cathodic hydrogen for biological nitrate reduction by extra organic substance such as sodium acetate both showed significant inhibition on Cd(II) removal, further proving that hydrogenotrophic denitrification was the main mechanism for enhanced Cd(II) removal. Besides, a relatively high Cd(II) removal efficiency was observed over a pH range of 5-8, and it increased with declining pH values. These results demonstrated that the bio-amended iron corrosion technology coupled Fe0-assisted H2 production with hydrogenotrophic denitrification exhibited excellent Cd(II) removal capacity, which enabled this technology a promising potential for Cd(II)-contaminated groundwater treatment and an alternative strategy for Cd(II) and nitrate co-contaminated groundwater remediation.

14.
J Hazard Mater ; 393: 122366, 2020 07 05.
Artículo en Inglés | MEDLINE | ID: mdl-32120212

RESUMEN

Thin 2D/2D WO3/g-C3N4 Step-scheme (S-scheme) heterojunction with carbon doping and bridge (C-W/N) was constructed with anionic polyacrylamide (APAM), in which APAM functioned as an assistant templet and a carbon source. APAM and WO3 were inserted into g-C3N4 nanosheet. The carbon, thin planar structure and WO3 with oxygen vacancies result in fast charge transfer, high quantum efficiency and strong driving force for photocatalytic reaction. Consequently, as-prepared C-W/N ternary composite photocatalyst exhibited significantly enhanced photocatalytic performance for tetracycline (TC) degradation under visible light compared to pure g-C3N4, WO3 and other binary composites. Moreover, the material showed high stability and reusability in cyclic TC degradation. The principal intermediate products over C-W/N photocatalyst were revealed by HPLC-MS analysis. Corresponding degradation pathway of TC was also presented in this work. According to the trapping experiments, analysis of electron spin resource (ESR) and band gap, possible charge transfer pathways of C-W/N are proposed and discussed in detail. Based on the results, carbon derived from APAM works not only as electron mediator but also as acceptor for photocatalytic degradation reaction. It is a promising way to further modulate heterojunction for varies applications.


Asunto(s)
Resinas Acrílicas/química , Grafito/química , Compuestos de Nitrógeno/química , Óxidos/química , Tetraciclina/química , Tungsteno/química , Catálisis/efectos de la radiación , Contaminantes Ambientales/química , Grafito/efectos de la radiación , Luz , Compuestos de Nitrógeno/efectos de la radiación , Óxidos/efectos de la radiación , Tungsteno/efectos de la radiación
15.
J Colloid Interface Sci ; 558: 163-172, 2020 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-31586736

RESUMEN

This study examined the relationship between surface oxygen vacancies (OVs) and ceria-based heterogeneous Fenton catalytic activity. Compared with pure iron oxide and ceria, iron-doped ceria with abundant OVs (FeCeOx) exhibits higher rhodamine B (RhB) degradation efficiency (98%) and has a wider applicable pH range (3.0-9.0). The surface hydroxyl radicals are proved to be the predominant reactive species in the oxidation of RhB. Annealing the FeCeOx in an oxygen atmosphere appears to eliminate the OVs, significantly inhibiting the decomposition of H2O2 and the degradation of target pollutants. As multifunctional active sites, OVs are energetically more favorable for the adsorption of reactants than other sites, due to their high electron density. They not only accelerate the Fe(III)/Fe(II) cycle, they also immediately activate H2O2, dissolved oxygen or even water molecules to produce oxidative species, which accounts for the ideal degradation of RhB in the heterogeneous Fenton system. This study clarifies the mechanism of the ceria-based heterogeneous Fenton and provides a better understanding of the surface design of heterogeneous Fenton catalysts.

16.
J Hazard Mater ; 382: 121027, 2020 01 15.
Artículo en Inglés | MEDLINE | ID: mdl-31446346

RESUMEN

Developing inexpensive and stable photocatalysts without noble metals, yet remarkably enhancing the photocatalytic activities, is highly needed. Here, a novel carbon and cerium co-doped porous g-C3N4 (C/Ce-CN) has been successfully prepared through thermal polymerization of the supramolecular aggregation. The morphologies, chemical structures, optical and photoelectrochemical properties of the synthesized photocatalysts were analyzed via a series of characterization measurements. Experimental results indicated that C/Ce-CN showed remarkably enhanced photocatalytic activity of TC and RhB degradation, which is about 2.6 and 2.4 times higher than that of pristine CN, and it also exhibited a good stability. Compared with bare CN, the enhanced performance of C/Ce-CN is mainly attributed to the stronger utilization rate of visible light, the rapider charge transfer rate, the longer lifetime of carriers and the larger surface specific area. The main intermediates in degradation process of antibiotics were tested by the HPLC-MS. Finally, the possible photocatalytic degradation pathways and mechanisms were proposed.


Asunto(s)
Cerio/química , Contaminantes Ambientales/química , Nitrilos/química , Rodaminas/química , Tetraciclina/química , Catálisis , Luz
17.
J Environ Manage ; 257: 109951, 2020 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-31868635

RESUMEN

A collaborative system of carboxymethyl cellulose stabilized nanosized zero-valent iron (CMC-nFe0) and microorganisms was set up to enhance the stabilization of Cr(VI) in soil. In comparison with an aqueous-bound Cr(VI) removal of 18.9% in the nFe0 system, a higher Cr(VI) removal of 68.9% was achieved in the nFe0 and microorganisms system after 14 d remediation because the microorganisms on the nFe0 surface promoted nFe0 corrosion and enhanced abiotic and biotic Cr(VI) stabilization by generating highly active minerals such as magnetite, lepidocrocite and green rust on the nFe0 surface. As a stabilizing agent for nFe0 and an organic substrate for microorganisms, CMC on the nFe0 surface not only enhanced the dispersion of nFe0, but also boosted the activity of microorganisms, resulting in a promotion of 0.9 and 0.5 times higher aqueous-bound Cr(VI) removal via the improvement of nFe0 and microorganisms respectively, thus a total 4 times higher aqueous-bound Cr(VI) removal of 95.3% was achieved in the CMC-nFe0 and microorganisms system as compared to the nFe0 system. After 14 d remediation, easily available species of Cr(VI) and Crtotal, such as water soluble (WS), exchangeable (EX) and bounded to carbonates (CB), were mainly transformed to less available Fe-Mn oxides-bounded (OX) and residual (RS) species because of the production of ferrochrome precipitates (CrxFe1-xOOH or CrxFe1-x(OH)3). Besides, the stabilization of Cr(VI) in the CMC-nFe0 and microorganisms system was pH-dependent and it increased with CMC-nFe0 dosage. Due to excellent Cr(VI) stabilization and Cr immobilization, coupled CMC-nFe0 and anaerobic microorganisms process is of great potential in remediating Cr(VI)-containing soil.


Asunto(s)
Suelo , Contaminantes Químicos del Agua , Anaerobiosis , Carboximetilcelulosa de Sodio , Cromo
18.
Bioresour Technol ; 298: 122468, 2020 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-31839494

RESUMEN

The difficulty of separating the powdered biochar from the environmental medium may lead to secondary pollution and hinder the large-scale application of biochar as an adsorbent. An effective strategy to solve this bottleneck is to introduce transition metals and their oxides into the biochar matrix, creating easily separable magnetic biochar. Magnetic biochar is also effective for the removal of pollutants from aqueous solution. This review comprises a systematic analysis of 109 papers published in recent years (From 2011 to June 2019), and summarises the synthetic methods and raw materials required for magnetic biochar preparation. The basic physicochemical properties of magnetic biochar are expounded, together with findings from relevant studies, and the application of magnetic biochar as an adsorbent or catalyst in environmental remediation are summarised. Other applications of magnetic biochar are also discussed. Finally, some constructive suggestions are given for the future direction of magnetic biochar research.


Asunto(s)
Restauración y Remediación Ambiental , Contaminantes del Suelo , Adsorción , Carbón Orgánico , Contaminación Ambiental , Fenómenos Magnéticos , Suelo
19.
Environ Sci Pollut Res Int ; 26(27): 28361-28371, 2019 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-31372953

RESUMEN

Aging effects play a crucial role in determining applications of green-synthesised iron-based nanoparticles in wastewater treatment from laboratory scale to practical applications. In this study, iron-based nanoparticles (Ec-Fe-NPs) were synthesised using the extract of Eichhornia crassipes and ferric chloride. Scanning electron microscopy (SEM) revealed that the fresh Ec-Fe-NPs were spherical and had a narrow particle size range (50 to 80 nm). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) demonstrated that the Ec-Fe-NPs were mainly amorphous in nature and consisted of Fe0, FeO, Fe2O3 and Fe3O4. As they aged, the particle size of the liquid Ec-Fe-NPs gradually increased and then tended to stabilise. Ec-Fe-NPs that were aged for 28 days were only 19% less efficient than fresh material at removing Cr(VI). Extracts aged up to 28 days were also tested, and their antioxidant capacity was found to be 15.4% lower than that of the fresh extracts. Furthermore, the removal efficiency of Cr(VI) using iron-based nanoparticles synthesised with the aged extracts was 67.2%. Finally, the active components of the extracts, which were responsible for the reactivity and stability of the iron-based nanoparticles, were identified by liquid chromatography-mass spectrometry. Overall, green-synthesised iron-based nanoparticles show promise for Cr(VI) removal from wastewater in practical applications.


Asunto(s)
Cloruros/química , Eichhornia/química , Compuestos Férricos/química , Compuestos de Hierro/síntesis química , Nanopartículas del Metal/química , Extractos Vegetales/química , Aguas Residuales/análisis , Compuestos de Hierro/química , Microscopía Electrónica de Rastreo , Tamaño de la Partícula , Espectroscopía de Fotoelectrones , Difracción de Rayos X
20.
Bioresour Technol ; 289: 121613, 2019 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-31202177

RESUMEN

In this study, Fenton-like catalysts (magnetic biochar) were synthesised by pyrolysis the different biomass pre-impregnated with steel pickling waste liquor. The results of degradation of metronidazole illustrated that the catalytic performance of magnetic biochar was significantly affected by biomass feedstocks. Electron spin resonance (ESR) and radical quenching experiments showed that the hydroxide radicals (OH) were the key reactive oxygen species responsible for the metronidazole removal. Levels of OH varied among different systems consistent with the removal of metronidazole. The activation of H2O2 by carbon-containing components and Fe species (Fe2O3 and Fe3O4) in magnetic biochar were confirmed to be less crucial to the degradation of metronidazole. Moreover, the Fe(II) (FeO) in magnetic biochar played the dominating role in degradation of metronidazole, and the Fe(II) content difference caused by biomass feedstocks was responsible for differences in the catalytic performance of different types of magnetic biochar.


Asunto(s)
Metronidazol , Acero , Biomasa , Carbón Orgánico , Peróxido de Hidrógeno , Pirólisis
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