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1.
Environ Sci Process Impacts ; 22(1): 95-104, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31897461

RESUMO

Cr(vi) has posed a serious risk for the environment and human beings because of its pollution and toxicity. It is essential to understand the equilibrium behavior of Cr(vi) in soils. In this study, the adsorption of Cr(vi) on fourteen soils was studied with batch experiments and quantitative modeling. The batch experiments included the adsorption edge and adsorption isotherm experiments, investigating the adsorption of Cr(vi) with varying soil properties, solution pH, and initial Cr(vi) concentrations. The experimental data were then modeled using the surface complexation models in Visual MINTEQ of CD-MUSIC by considering the adsorption of Cr(vi) and ions onto Fe (hydr)oxides and Al (hydr)oxides, and the Stockholm Humic Model and the fixed charge site model by accounting for the adsorption of the cations to soil organic matter and clay, respectively. Particularly, the modeling method of this study introduced an important parameter RO- to account for the amount of soil organic matter irreversibly adsorbed on soil minerals. Overall, the model predicted reasonably well for the equilibrium partition of Cr(vi) under various conditions with a root-mean-square-error of 0.35 for the adsorption edge data and 0.19 for the adsorption isotherm data. According to the model calculations, ferrihydrite dominated the binding of Cr(vi) at pH of 3.0-7.0. The content of ferrihydrite and reactive soil organic matter was found to be the main factor influencing RO-. The modeling results help to understand and predict Cr(vi) adsorption on different soils and are beneficial to environmental risk assessment and pollution remediation.


Assuntos
Cromo , Poluentes do Solo , Solo , Adsorção , Cromo/química , Humanos , Poluentes do Solo/química
2.
Chem Pharm Bull (Tokyo) ; 68(1): 70-76, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31902902

RESUMO

In this study, nickel-aluminium complex hydroxides at different molar ratios (nickel-aluminium = 1 : 2, 1 : 1, 2 : 1, 3 : 1, and 4 : 1, referred to as NA12, NA11, NA21, NA31, and NA41) were prepared, and their adsorption capability for chromium(VI) ion was investigated. Firstly, physicochemical characteristics (SEM images, X-ray diffraction (XRD) patterns, specific surface area, amount of hydroxyl groups, and surface pH) of nickel-aluminum complex hydroxide were evaluated. The amount of chromium(VI) ion adsorbed onto NA11 (15.3 mg/g) was greater than that adsorbed onto the other adsorbents. This research elucidated that the amount of chromium(VI) ion adsorbed using nickel-aluminium complex hydroxide was related to the adsorbent surface properties (r = 0.818-0.875). Subsequently, the adsorbent (NA11) surface before and after adsorption of chromium(VI) ion was evaluated, and chromium energy (577 and 586 eV) detected after adsorption onto the NA11 surface. These results revealed that the NA11 surface properties were very important for the removal of chromium(VI) ion from aqueous solution. In addition, the effects of pH, contact time, and temperature on the adsorption of chromium(VI) ion were evaluated. We confirmed a high recovery percentage of chromium(VI) ion when using sodium hydroxide solution at 10-1000 mmol/L (approximately greater than 80%) in this experimental condition. Thus, NA11 is a promising adsorbent for the removal of chromium(VI) ion from aqueous solution.


Assuntos
Alumínio/química , Cromo/química , Complexos de Coordenação/química , Hidróxidos/química , Níquel/química , Adsorção , Concentração de Íons de Hidrogênio , Íons/química , Temperatura Ambiente , Termodinâmica , Poluentes Químicos da Água/química
3.
Environ Pollut ; 256: 113462, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31706772

RESUMO

Natural birnessite-like minerals are commonly enriched in various transitional metals (TMs), which greatly modify the mineral structure and properties. However few studies are yet conducted systematically on the effects of TM doping on birnessite reactivity towards Cr(III) oxidation. In the present study, the transformation behaviors of Cr(III) on Co-, Ni-, V-containing birnessites were investigated. Co and Ni doping generally decrease the mineral crystalline sizes and hydrodynamic sizes (DH) while V-doping greatly decreases the crystalline sizes but not the DH, owing to particle aggregation. Co and Ni firstly decrease and then increase the mineral zeta potentials (ζ) at pH4 while V decreases ζ. Electrochemical specific capacitances for Co-containing birnessites are gradually reduced, while those for Ni-doped birnessites are slightly reduced and for V-doped birnessites increased, which have a positively linear relationship with the amounts of Cr(III) oxidized by these samples. Cr(III) removal efficiencies from solution by these Co-, Ni- and V-containing birnessites are 26-51%, ∼62-72% and ∼96-100%, respectively, compared to ∼92% by pure birnessite. Cr(III) oxidation kinetics analysis demonstrates the gradual decrease of Mn(IV) and concurrent increase of Mn(III) and the adsorption of mainly Cr(III) on mineral surfaces. A negatively linear relationship exists between birnessite lateral sizes and the proportions of Mn(IV/III) consumed to oxidize Cr(III). Apparent initial Cr(III) oxidation rate (kobs) for Co-containing birnessites are greatly reduced, while those for Ni-doped samples moderately decreased and for V-doped samples first increased and then decreased. A positively or negatively linear relationship exists between kobs or the amount of Mn(II) released and the mineral Mn(IV) content respectively. Cr(III) oxidation probably initiates from layer edge sites of Ni-doped birnessites but the vacancies of Co- and V-containing birnessites. These results provide insights into the reaction mechanisms of Cr(III) with natural birnessite-like minerals.


Assuntos
Óxidos/química , Adsorção , Cromo/química , Cobalto/química , Troca Iônica , Cinética , Minerais , Níquel/química , Oxirredução , Vanádio/química
4.
Chemosphere ; 242: 125235, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31698209

RESUMO

A core-shell structured zero-valent iron@carbon (ZVI@C) nanocompoiste was designed to improve the electron utilization of ZVI in the Cr(VI) reduction. The porosity of carbon layer in ZVI@C was optimized for improving the efficiency of electron utilization of ZVI in the Cr(VI) reduction process. The porous structure of carbon layer was controllably synthesized by adjusting the carbon source and the ratio of C/Fe in the precursor. The glucose was suggested as the optimal carbon source, and a high specific surface area (37.067 m2/g) was reached for the prepared ZVI@C when the ratio of C/Fe was controlled at 20. These ZVI@C performed well on Cr(VI) reduction, e.g. a complete reduction of Cr(VI) (2 mg/L) to Cr(III) within 10 min. The removal capacity (800 mg/g) exceeded previously recorded ZVI based adsorbents. The pH and initial Cr(VI) concentration were demonstrated as the key factors for the efficient electron utilization of ZVI. Furthermore, the efficiency of electron utilization of the ZVI increased up to 80% when the concentration of Cr(VI) was 2000 mg/L and the pH was controlled at 3, which was much higher than 8% of the naked ZVI.


Assuntos
Carbono , Cromo/química , Elétrons , Ferro/química , Nanopartículas/química , Concentração de Íons de Hidrogênio , Oxirredução
5.
Environ Pollut ; 256: 113417, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31662269

RESUMO

A facile method was developed to fabricate porous tube-like ZnS by sulfurizing rod-like ZIF-L with thioacetamide (TAA) at different durations and the formation mechanism of the porous tube-like ZnS was discussed in detail. The series of sulfide products (ZS-X) were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), solid-state nuclear magnetic resonance spectroscopy (SSNMR), transmission electron microscopy (TEM), UV-visible diffuse-reflectance spectroscopy (UV-vis DRS). The photocatalytic performances of ZS-X toward Cr(VI) reduction and organic pollutant degradation were explored. It was discovered that ZS-3 (porous tube-like ZnS) exhibited excellent activities under UV light and displayed good reusability and stability after several experimental cycles. In addition, Cr(VI) reduction and organic pollutant degradation were investigated under different pH values and existence of different foreign ions. The photocatalytic activities of ZS-3 were tested toward the matrix of Cr(VI) and reactive red X-3B. The mechanism was proposed and verified by both electrochemical analysis and electron spin resonance (ESR) measurement.


Assuntos
Cromo/química , Poluentes Ambientais/química , Catálise , Poluentes Ambientais/análise , Porosidade , Espectroscopia de Infravermelho com Transformada de Fourier , Sulfetos , Difração de Raios X , Compostos de Zinco
6.
Chemosphere ; 241: 125082, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31629246

RESUMO

Highly efficient and selective separation of Cr (VI) is great of importance in environmental pollution control. In this study, a novel family of hydrophobic DESs has been designed and synthesized by mixing parabens and quaternary ammonium, and then used to extract heavy metal Cr (VI) from water phase and the content of Cr (VI) is measured by 1,5-diphenylcarbazide spectrophotometry. It is found that the hydrophobic DESs exhibit excellent extraction performance towards Cr (VI). At the 1:1 M ratio of DES to Cr (VI), the extraction capacity is as high as 66.7 mg g-1, the extraction efficiency is greater than 90% for ultra-trace Cr (VI) (0.51 µg L-1), and the preconcentration factor is up to 700. When the concentration of coexisting metal ions (Cd2+, Cu2+) and organic compounds ((C6H10O5)n, C6H12O6·H2O) is 2000 times that of Cr (VI), the extraction efficiency is still above 90%. Compared with ionic liquid extractants, the preparation process of DES is very simple, the atomic utilization rate is 100%, and no waste is produced. These hydrophobic DESs have been used to separate and enrich Cr (VI) from actual water samples with satisfactory recoveries. The possible extraction mechanism is investigated by FT-IR and 1H NMR.


Assuntos
Cromo/química , Modelos Químicos , Interações Hidrofóbicas e Hidrofílicas , Metais Pesados , Solventes/química , Espectroscopia de Infravermelho com Transformada de Fourier , Água/química
7.
J Chromatogr Sci ; 57(10): 939-943, 2020 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-31665235

RESUMO

Chromium exists in its two stable oxidation states including trivalent chromium (Cr (III)) and hexavalent chromium (Cr (VI)) in natural waters. Chromium is an essential micronutrient in the trivalent form; however, the hexavalent form of chromium is considered to be a carcinogen. It is important to determine the chromium content along with speciation. There are a number of methods available for chromium determination. Speciation of chromium is essential to know the exact composition of chromium. Ion exchange chromatography is one of the techniques used to determine Cr (VI). The proposed method can be used to perform the speciation of Cr (III) and Cr (VI). It is a two-step process: first Cr (VI) is determined, followed by total chromium determination by treating the sample with potassium permanganate solution to oxidize the Cr (III) present in the sample to Cr (VI) and determining it as Cr (VI). Conductivity detector is used for the detection. Addition of potassium permanganate solution to the ground water samples for oxidizing the Cr (III) to Cr (VI) is the newly adopted sample preparation technique. The effect of potassium permanganate oxidation is studied in detail in the proposed method. This method can be used for chromium speciation in river water and ground water samples.


Assuntos
Cromatografia por Troca Iônica/métodos , Cromo/análise , Cromo/química , Condutividade Elétrica , Limite de Detecção , Modelos Lineares , Oxirredução , Permanganato de Potássio/química , Reprodutibilidade dos Testes
8.
Environ Pollut ; 256: 113407, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31672374

RESUMO

A composite material comprising of nanoscale zero-valent iron (nZVI) supported on vinegar residue (nZVI@VR) was prepared and applied for remediation of soils contaminated by hexavalent chromium (Cr(VI)). Sedimentation test results revealed that the nZVI@VR displayed enhanced stability in comparison to the bare-nZVI. Remediation experiments exhibited the immobilization efficiency of Cr(VI) and Crtotal was 98.68% and 92.09%, respectively, when using 10 g nZVI@VR (nZVI 5%) per 200 g Cr-contaminated soil (198.20 mg kg-1 Cr(VI), 387.24 mg kg-1 Crtotal) after two weeks of incubation. Further analyses demonstrated that almost all the exchangeable Cr was transformed into Fe-Mn oxide bound and organic matter bound. Moreover, the application of nZVI@VR enhanced soil organic carbon content and reduced redox potential. After granulation, the immobilization efficiency of Cr(VI) and Crtotal achieved 100% and 91.83% at a dosage of 10% granular nZVI@VR. Granular nZVI@VR also accelerated the transform of more available Cr (exchangeable and bound to carbonates) into less available fractions (Fe-Mn oxide bound and organic matter bound), thus resulting in a remarkable reduction in the Cr bioavailability. These results prove that nZVI@VR can be an effective remediation reagent for soils contaminated by Cr(VI).


Assuntos
Cromo/química , Recuperação e Remediação Ambiental/métodos , Poluentes do Solo/química , Ácido Acético/química , Carbono , Carvão Vegetal/química , Cromo/análise , Poluição Ambiental , Ferro/química , Óxidos , Solo/química , Poluentes do Solo/análise , Poluentes Químicos da Água/análise
9.
Chemosphere ; 239: 124735, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31499306

RESUMO

A key challenge in adsorption process of toxic organic and inorganic species is the design and development of adsorbent materials bearing an abundance of accessible adsorption sites with high affinity to achieve both fast adsorption kinetics and elevated adsorption capacity for toxic contaminants. Herein, a novel anion-exchange adsorbent based on fibrous silica nanospheres KCC-1 was synthesized by a facile hydrothermal-assisted post-grafting modification of KCC-1 with 1-methyl-3- (triethoxysilylpropyl)imidazolium chloride for the first time. Silica fibers with micro-mesoporous structure display the proper combination of features to serve as a potential scaffold for decorating adsorption sites to create desired ion-exchange adsorbent. The obtained N-methylimidazolium-functionalized KCC-1 (MI-Cl-KCC-1) with fibrous nanosphere morphology showed a high surface area (∼241 m2 g-1) and high pore volume (0.81 m2 g-1). The adsorption behaviors of toxic hexavalent chromium from aqueous media by the MI-Cl-KCC-1 were systematically studied using the batch method. The adsorption rate was relatively fast, and MI-Cl-KCC-1 possesses a high capacity for the adsorption of Cr(VI). The maximum Cr(VI) adsorption was obtained at pH 3.0-4.0. Different non-linear isotherm equations were tested for choosing an appropriate adorption isotherm behavior, and the adsorption data for MI-Cl-KCC-1 were consistent with the Langmuir model with a maximum adsorption capacity of 428 ±â€¯8 mg g-1.


Assuntos
Cromo/isolamento & purificação , Imidazóis/química , Nanoestruturas/química , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Ânions , Cromo/química , Imidazóis/síntese química , Troca Iônica , Cinética , Micro-Ondas , Dióxido de Silício/química , Poluentes Químicos da Água/química , Purificação da Água/métodos
10.
Chemosphere ; 239: 124733, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31526991

RESUMO

Lignin, natural aromatic polymer derived from plant dry matter, is second abundant biopolymer. Recently, interest in applications of lignin, especially as an adsorbent material is increasing. However, the physicochemical complexity of lignin significantly reduces access to practical environmental remediation processes. Also, there is a limitation because the adsorption performance of the pristine lignin materials is not superior to that of commercial adsorbent and ion exchange resin material. In this study, spherical lignin particles with high physicochemical stability and excellent Cr(VI) adsorption capacity are prepared using a polyethylenimine (PEI) modification strategy. This modification process significantly improves the mechanical properties and water stability of lignin by complementing the instability of lignin particles. In addition, the PEI-lignin particles exhibit a superior Cr(VI) removal capability (657.9 mg/g, the highest value for a PEI-modified natural adsorbent), which is attributed to their structural stability and introduced amine functional groups. The Cr(VI) removal with PEI-lignin particles is performed via intra-particle diffusion and adsorption followed by covalent bonding combined with a reduction process. Moreover, the PEI-lignin particles exhibit excellent reusability, which sustains their high adsorption efficiency over a long and repeated adsorption period. The results herein strongly support the potential use of PEI-lignin particles as a high performance bio-sorption material for heavy metal removal and its detoxification in aqueous wastewater streams. Evidently, this lignin-based bio-sorbent manufacturing system can provide sustainable bio-resource recycling and cost efficiency.


Assuntos
Cromo/isolamento & purificação , Lignina/química , Adsorção , Cromo/química , Recuperação e Remediação Ambiental , Concentração de Íons de Hidrogênio , Cinética , Espectroscopia Fotoeletrônica , Polietilenoimina/química , Espectroscopia de Infravermelho com Transformada de Fourier , Eliminação de Resíduos Líquidos/métodos , Água/química , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação
11.
Ecotoxicol Environ Saf ; 188: 109902, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31704325

RESUMO

In this study, polyethylene glycol (PEG)-stabilized nano zero-valent iron (nZVI) supported by biochar (BC) (PEG-nZVI@BC) was prepared to remedy Cr(VI) with high efficiency. The morphology, functional groups, and crystalline structure of PEG-nZVI@BC composites were characterized, revealing that when PEG was added, a large number of -OH functional groups were introduced, and nZVI was effectively dispersed on the BC surface with a smaller particle size. The results of Cr(VI) remediation experiments showed Cr(VI) removal rate by PEG-nZVI@BC (97.38%) was much greater than that by BC-loaded nZVI (nZVI@BC) (51.73%). The pseudo second-order and Sips isotherm models provide the best simulation for Cr(VI) removal experimental data, respectively. The main remediation mechanism of Cr(VI) was reduction and co-precipitation of Cr-containing metal deposits onto PEG-nZVI@BC. Ecotoxicity assessment revealed PEG-nZVI@BC (1.00 g/L) has little influence on rice germination and growth, but resisted the toxicity of Cr(VI) to rice. The modified Community Bureau of Reference (BCR) sequential extraction showed pyrolysis could increase the percentage of oxidizable and residual Cr and diminish the environmental risk of Cr release from post-removal composites.


Assuntos
Carvão Vegetal/química , Cromo/isolamento & purificação , Ferro/química , Polietilenoglicóis/química , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Precipitação Química , Cromo/química , Recuperação e Remediação Ambiental , Oxirredução , Tamanho da Partícula , Poluentes Químicos da Água/química
12.
Chemosphere ; 240: 124896, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31563716

RESUMO

Groundwater contaminated by hexavalent chromium (Cr(VI)) has posed severe threat to the environment and public health. Although heterotrophic bioremediation has been known as an efficient approach, little is explored on mineral nutrient source addition such as phosphorus minerals. In this study, the stabilization and sustainability of phosphorus minerals for providing phosphorus has been investigated, and the enhancement of Cr(VI) removal by mixed bacterial consortium coupled with phosphorus minerals was also observed and further verified, with 1.4-3.9 times K values (first-order) increase under different conditions. We demonstrated that the applied of phosphorus minerals facilitated the reduction of Cr(VI) and the removal of Cr(III), promoted the resistance of Cr(VI) and the generation of antioxidase, and engendered the evolution of microbial community structures and functional genes. These findings provide a new insight for enhancement of Cr(VI)-contaminated groundwater in-situ remediation.


Assuntos
Biodegradação Ambiental , Cromo/metabolismo , Fósforo/química , Poluentes Químicos da Água/metabolismo , Bactérias , Cromo/química , Água Subterrânea/química , Microbiota , Minerais , Oxirredução
13.
J Colloid Interface Sci ; 558: 106-114, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31585219

RESUMO

Green synthesis of nanoparticles is becoming increasingly popular as a simple and environmentally friendly method. In this study, iron-based nanoparticles (Fe-NPs) were successfully prepared using a peanut skin extract, where the peanut skin as an agricultural waste product was easy to obtain in large quantities, relatively inexpensive and also environmentally friendly. The average particle size of the produced Fe-NPs changed with their post-synthesis drying conditions. Under vacuum drying at 60 °C, the smallest average particle size obtained was 10.6 nm. The synthesized Fe-NPs had a core shell-like structure, in which the core was composed of Fe0, and the shell was a layered coating composed of biomolecules (e.g. anthocyanins, flavonols, phenolic compounds, epicatechin), iron oxides, Fe coordination compounds and iron-carbon alloys. Thereafter Fe-NPs (2 g L-1) prepared under different drying conditions were evaluated for their ability to remove Cr(VI) from aqueous solutions at pH of 4.7 and 25 °C. Fe-NPs obtained under vacuum drying at 60 °C performed the best, removing 100% of Cr(VI), from a 10 mg L-1 aqueous solution of Cr(VI) in just one min. Desorption and reuse experiments show that the desorption rate of Cr using 16 M hydrochloric acid and the recycling rate reached 70.2 and 59.9%, respectively. A potential mechanism for Fe NP synthesis involving the formation of intermediate complexes, an electron transfer reaction and adsorption of non-reducing organic macromolecules at the solid-liquid interfaces was proposed.


Assuntos
Arachis/química , Cromo/química , Ferro/química , Nanopartículas Metálicas/química , Extratos Vegetais/química , Poluentes Químicos da Água/química , Adsorção , Química Verde
14.
Talanta ; 206: 120206, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31514889

RESUMO

Hemoglobin (Hb) plays an important role in oxygen carriage for mammals, which is also a typical biomarker for certain diseases. Although numerous methods had been developed for the detection of Hb in red blood cells, analytical technology for the monitoring of low-abundance Hb in serum or plasma is still a challenge. Herein, persistent luminescence nanoparticles (PLNPs) with strong near-infrared (NIR) emission character behaving as a label-free probe for the highly sensitive and selective detection of Hb were developed. Further studies revealed that the sensing mechanism should be attributed to the Hb-induced dynamic quenching process. Moreover, the nanoprobe showed high selectivity to Hb against the common existing substances in human serum and a linear response to Hb ranging from 1 to 50 nM with an extremely high limit of detection (LOD) of 0.13 nM. Finally, applicability of the proposed probe for the detection of Hb in human serum samples was validated.


Assuntos
Hemoglobinas/análise , Substâncias Luminescentes/química , Nanopartículas Metálicas/química , Cromo/química , Gálio/química , Humanos , Limite de Detecção , Luminescência , Medições Luminescentes/métodos , Tamanho da Partícula , Zinco/química
15.
Chemosphere ; 240: 124885, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31568939

RESUMO

Chromium (Cr)-bearing electroplating sludge is a hazardous solid waste and has a detrimental effect on human health and the environment. In this study, an alkali-activated slag binders, namely, formed by the reaction of blast furnace slag (BFS) with alkali, was applied to the stabilization/solidification (S/S) of electroplating sludge. The effects of liquid-solid ratio, water glass modulus ratio (molar ratio of SiO2 to Na2O), water glass dosage, and electroplating sludge amount on the compressive strength and Cr leachability of binders were analyzed. The related mechanism of the S/S of electroplating sludge was discussed on the basis of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy-dispersive spectrometry (SEM-EDS). Results showed that the compressive strength of the alkali-activated slag binder first increased and then remained stable with the increase in liquid-solid ratio, water glass modulus ratio, and water glass dosage. By contrast, the leaching concentrations of Cr(VI) and total Cr decreased with the increase in liquid-solid ratio, water glass modulus ratio, water glass dosage, and curing time. In addition, XRD, FTIR, and SEM-EDS revealed that the hydration products of the binders were mainly low-crystallinity and dense calcium silicate hydrate gels, and Cr(VI) had been effectively immobilized in the structure. The reduction in Cr(VI) by the reductive components in the BFS boosted the stabilization of Cr-bearing electroplating sludge. Overall, the BFS binders containing electroplating sludge had relatively high compressive strengths and low Cr(VI) leaching concentrations. The physical encapsulation, chemical bonding, and absorption contributed the Cr immobilization during the S/S process of electroplating sludge.


Assuntos
Álcalis/química , Cromo/química , Galvanoplastia , Recuperação e Remediação Ambiental , Resíduos Perigosos/análise , Esgotos/química , Humanos
16.
Sci Total Environ ; 700: 134414, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31698277

RESUMO

This study synthesized magnetic greigite/biochar composites (MGBs) by a solvothermal method and tested their ability to remove Cr(VI) from heavy metal-polluted wastewater. X-ray diffraction (XRD), Fourier transformed infrared spectrometry (FT-IR) and scanning electron microscopy (SEM) revealed that magnetic greigite (Fe3S4) flakes were aggregated and anchored to the biochar surface, resulting in more active sites than pristine biochar. Maximum Cr removal efficiency and capacity of MGB-30 (greigite/biochar = 30%) at an initial Cr(VI) concentration of 20 mg/L were 93% and 23.25 mg/g, respectively. A pseudo-first-order kinetic model was determined for the Cr(VI) removal process and the Cr(VI) removal rate constants were highly dependent on the mass ratios of Fe3S4 loaded on biochar, initial MGB and Cr(VI) concentrations and solution pH. X-ray photoelectron spectroscopy (XPS) and flame atomic absorption spectrometric (FAAS) analysis demonstrated that Cr(VI) was preferentially adsorbed on MGBs and subsequently reduced to Cr(III) by MGBs. Electron paramagnetic resonance (EPR) spectroscopy and iron redox transformations revealed that the Cr(VI) removal enhancement was attributed to efficient surface Fe(III)/Fe(II) cycling via electron transfer with the persistent free radicals (PFRs) of biochar. These novel findings provide new insights into the Fe(III)/Fe(II) cycle induced by biochar and the prospects of using magnetic greigite/biochar composites for remediation of Cr(VI)-rich wastewaters.


Assuntos
Cromo/química , Ferro/química , Sulfetos/química , Poluentes Químicos da Água/química , Adsorção , Carvão Vegetal , Cromo/análise , Compostos Férricos/química , Fenômenos Magnéticos , Magnetismo , Espectroscopia de Infravermelho com Transformada de Fourier , Eliminação de Resíduos Líquidos , Águas Residuárias , Poluentes Químicos da Água/análise
17.
Environ Monit Assess ; 191(12): 766, 2019 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-31754863

RESUMO

Xenobiotic azo dyes and chromate (Cr(VI)) containing industrial wastewaters cause severe ecological problems. The present bioremediation study aims to treat wastewater containing Cr(VI) ions and mixed azo dyes (reactive red 21 (RR21) and reactive orange 16 (RO16)) by Pseudomonas aeruginosa 23N1. The process optimization of bioremediation is investigated using statistical designed experimental tool of response surface methodology. The ANOVA analysis is performed to evaluate optimal biodecolourization condition. This study shows that the amount of yeast extract has major influence on biodecolourization performance. The decolourization of individual RO16 and RR21 dye in presence of 60 mg/L of Cr(VI) ions is obtained as 88.5 ± 0.8 and 92.3 ± 0.7% for 100 and 150 mg/L initial dye concentrations, respectively. In this study, bacteria exhibit high Cr(VI) removal potential of ~ 99.1% against initial Cr(VI) concentration of 150 mg/L. The negative influence of Cr(VI) ions on biodecolourization is only noticed when initial Cr(VI) concentration in wastewater is found above 150 mg/L. The results reveal that bacteria studied here could be used to biodecolourize dyes even in high saline condition (> 6000 mg/L). The reduction of ~ 80% in American Dye Manufacturers Institute colour index value is achieved for mixed dyes solution containing 50 mg/L of both RR21 and RO16 dyes along with 50 mg/L Cr(VI) ions. Significant changes in the UV-visible and ATR-FTIR spectra are observed in treated water that confirms the biodegradation of dyes. Toxicity study with Vigna radiata reveals the non-toxicity of degraded metabolites and strain 23N1 is recommended as an effective bioremediation agent.


Assuntos
Biodegradação Ambiental , Cromo , Corantes , Águas Residuárias , Purificação da Água , Compostos Azo/química , Compostos Azo/metabolismo , Bactérias/metabolismo , Cromo/química , Cromo/metabolismo , Corantes/química , Corantes/metabolismo , Pseudomonas aeruginosa/metabolismo , Águas Residuárias/química , Purificação da Água/métodos
18.
Protein Pept Lett ; 26(10): 768-775, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31618171

RESUMO

INTRODUCTION: Metallothioneins (MTs) are members of a family of low molecular weight and cysteine-rich proteins that are involved in heavy metal homeostasis and detoxification in living organisms. Plants have multiple MT types that are generally divided into four subgroups according to the arrangement of Cys residues. METHODS: In the present study the E. coli cells which heterologously express four different rice MT (OsMT) isoforms were analyzed for the accumulation of two forms of chromium, Cr3+ and Cr6+. RESULTS: The results show that the transgenic bacteria were more tolerant than control cells when they were grown up in the medium comprising Cr(NO3)3.9H2O or Na2CrO4. The cells expressing OsMT1, OsMT2, OsMT3 and OsMT4 give rise to 6.5-, 2.7-, 5.5- and 2.1-fold improvements on the accumulation capacity for Cr3+ and 9-, 3-, 5- and 3- fold Cr6+ respectively compared with comparison to the control strain. Furthermore, the purified recombinant GST-OsMTs were tested for their binding ability to Cr+3 and Cr+6 in vitro. DISCUSSION: The data show that the recombinant GST-OsMT1 and GST-OsMT2 were able to bind both Cr3+ and Cr6+, in vitro. However, their binding strength was low with respect to previous tested divalent ions like Cd2+.


Assuntos
Cromo/química , Metalotioneína/química , Oryza/química , Proteínas de Plantas/química , Proteínas Recombinantes/química , Sequência de Aminoácidos , Cátions/química , Cisteína/química , Escherichia coli/genética , Concentração de Íons de Hidrogênio , Metalotioneína/genética , Proteínas de Plantas/genética , Ligação Proteica , Isoformas de Proteínas , Proteínas Recombinantes/genética
19.
Chem Commun (Camb) ; 55(87): 13078-13081, 2019 Oct 29.
Artigo em Inglês | MEDLINE | ID: mdl-31608909

RESUMO

The chiral spin-flip luminophore [Cr(ddpd)2]3+ can be resolved into enantiopure material by chiral HPLC. The corresponding enantiomers show very high luminescence dissymmetry factors of up to ∣glum ∣≈ 0.093 in circularly polarized luminescence (CPL) measurements for the "ruby-like" phosphorescence transition 2E/2T1 → 4A2 in the near-IR region around λ ≈ 775 nm.


Assuntos
Cromo/química , Complexos de Coordenação/química , Luminescência , Teoria da Densidade Funcional , Medições Luminescentes , Conformação Molecular
20.
Environ Int ; 133(Pt B): 105249, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31665676

RESUMO

Nanoscale zero-valent iron (NZVI) has been engineered as an attractive tool for in-situ groundwater remediation. However, the poor mobility and aqueous corrosion of NZVI in the porous subsurface have hindered its practical applications. In this research, the NZVI surface was coated with a novel Mg(OH)2 shell (NZVI@Mg(OH)2) to improve the feasibility of NZVI for remediation. In the column tests for continuous removal of Cr(VI) from the flowing water, the Mg(OH)2 shell greatly improved the delivery of NZVI into the sand columns. Coating NZVI with Mg(OH)2 shell also showed considerably greater chemical stability than bare NZVI and thus greater resistance to aqueous corrosion. In addition, the dissolution of Mg(OH)2 allowed the reactivity to be gradually recovered along the sand column for Cr(VI) reduction. As a result, compared to bare NZVI in the columns, NZVI@Mg(OH)2 significantly prolonged the breakthrough period of Cr(VI) and hence increased the columns' Cr(VI) removal capacity. Moreover, the Cr(III) produced was effectively immobilized by NZVI@Mg(OH)2, even under an acidic condition (pH 4.0). The results show that Mg(OH)2 coating is a promising technique to improve the longevity and capacity of NZVI for full-scale in-situ soil and groundwater remediation.


Assuntos
Cromo/química , Ferro/química , Hidróxido de Magnésio/química , Areia/química , Poluentes Químicos da Água/química , Recuperação e Remediação Ambiental , Água Subterrânea , Humanos
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