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1.
Food Chem ; 336: 127675, 2021 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-32795781

RESUMO

The present study explores the biosorption potential of Pleurotus ostreatus immobilized magnetic iron oxide nanoparticles for solid-phase extractions of Ni(II) and Pb(II) ions from the water and food samples. It was characterized using FTIR, FE-SEM/EDX before and after analyte ions biosorption. Important operational parameters including the effect of initial pH, the flow rate of the sample solution and volume, amount of biomass and support material, interfering ions, best eluent, column reusability were studied. The biosorption capacities of fungus immobilized iron oxide nanoparticles were found as 28.6 and 32.1 mg g-1 for Ni(II) and Pb(II), respectively. The limit of detection (LOD) and limit of quantitation (LOQ) were achieved as 0.019 and 0.062 ng mL-1 for Ni(II), 0.041 and 0.14 ng mL-1 for Pb(II), respectively. The proposed method was validated by applying to certified reference materials and successfully applied for the preconcentrations of Ni(II) and Pb(II) ions from water and food samples by ICP-OES.


Assuntos
Chumbo/isolamento & purificação , Nanopartículas/química , Níquel/isolamento & purificação , Pleurotus/química , Extração em Fase Sólida/métodos , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Células Imobilizadas , Compostos Férricos/química , Análise de Alimentos/instrumentação , Análise de Alimentos/métodos , Contaminação de Alimentos/análise , Concentração de Íons de Hidrogênio , Limite de Detecção , Fenômenos Magnéticos , Níquel/química , Reprodutibilidade dos Testes , Extração em Fase Sólida/instrumentação , Poluentes Químicos da Água/química
2.
Food Chem ; 334: 127563, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32791433

RESUMO

A new magnetic Cu(II) IIP (Fe3O4@IIP-IDC) is synthesized by polymerization of Imidazole-4,5-dicarboxylic acid functionalized Allyl chloride, and significant improvement of its performance has been compared. SPE parameters were optimized using Box-Behnken design to achieve the twin objectives of quantitative determination and removal of Cu(II). FLPSO kinetic model and BS isotherm model fits well with the capacity of 175 mg g-1. Analytical figures of merit includes a linearity range of 10-5,000 µg L-1 (R2 = 0.9986), preconcentration factor of 50 after eluting with 5 mL of 1 M HNO3, LOD of 1.03 µg L-1 and LOQ of 4.5 µg L-1. Accuracy was assessed by analysis of SRM (Standard Reference Material) and recovery experiments after spiking in food samples (Tea, coffee, chocolate, spinach, infant milk substitute) and battery wastewater. Ease of use, reusability (15 cycles), rapid adsorption and high selectivity makes it a promising candidate for efficient and selective removal and trace determination.


Assuntos
Cobre/análise , Análise de Alimentos/métodos , Impressão Molecular/métodos , Polímeros/química , Poluentes Químicos da Água/análise , Adsorção , Compostos Alílicos/química , Cobre/isolamento & purificação , Ácidos Dicarboxílicos/química , Análise de Alimentos/instrumentação , Contaminação de Alimentos/análise , Imidazóis/química , Limite de Detecção , Fenômenos Magnéticos , Águas Residuárias/análise , Poluentes Químicos da Água/isolamento & purificação
3.
Chemosphere ; 261: 128179, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33113649

RESUMO

Understanding how wastewater treatment plants (WWTPs) process microplastics (MPs) will help informing management practices to reduce MP emissions to the environment. We show that composite 24 h samples taken at three replications from the outflow of the grit chamber, primary settling tank and clarifier of the WWTP of Sari City, on the southern coast of the Caspian Sea, contained 12667 ± 668, 3514 ± 543 and 423 ± 44.9 MP/m3, respectively. Fibers accounted for 94.9%, 89.9% and 77.5% of the total number of MPs, respectively. The MP removal efficiency was 96.7%. MP shape (fiber, particle), size and structure were the most important factors determining their removal in different steps of the wastewater treatment process. The structure of microfibers (polyester, acrylic and nylon) and the consequent higher density than water explained their high removal (72.3%) in the primary settling tank. However, size was more important in microparticle removal with particles ≥500 µm being removed in the primary settling tank and <500 µm in the clarifier unit. The smallest particles (37-300 µm) showed the lowest removal efficiency. The predominant types of fibers and particles were polyester and polyethylene, respectively, which are likely to originate from the washing of synthetic textiles and from microbeads in toothpaste and cosmetics. Despite the efficiency of the Sari WWTP in removing MPs, it remains a major emission source of MPs to the Caspian Sea due to its high daily discharge load.


Assuntos
Microplásticos/isolamento & purificação , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/isolamento & purificação , Mar Cáspio , Cidades , Irã (Geográfico) , Microplásticos/química , Nylons/química , Nylons/isolamento & purificação , Poliésteres/química , Poliésteres/isolamento & purificação , Polietileno/química , Polietileno/isolamento & purificação , Têxteis , Águas Residuárias/química , Poluentes Químicos da Água/química
4.
Sheng Wu Gong Cheng Xue Bao ; 36(8): 1493-1503, 2020 Aug 25.
Artigo em Chinês | MEDLINE | ID: mdl-32924348

RESUMO

Nitrite is a by-product of the nitrogen cycle. The excessive nitrite not only constrains growth and metabolism of bacteria, but also impairs health of humans and aquatic organisms. On the other hand, the continuous maintaining of nitrite accumulation could achieve the shortcut nitrification process, and reduce energy consumption of biological nitrogen removal to save cost. This article reviews the biological processes and causes of nitrite accumulation in the water environment, and summarizes the factors that affect the accumulation of nitrite, to provide reference for wastewater treatments, including improving the nitrogen removal efficiency, reducing operating costs, decreasing discharge of sewage and nitrite nitrogen in natural water.


Assuntos
Nitritos , Poluentes Químicos da Água , Água , Reatores Biológicos , Nitrificação , Nitritos/metabolismo , Esgotos , Água/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/isolamento & purificação
5.
PLoS One ; 15(9): e0238837, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32913353

RESUMO

The liquid foodstuffs such as edible oil products remain a problem of excessive aflatoxin B1 (AFB1) content. This paper focused on the preparation of magnetic mesoporous silica (MMS) from rice husk ash for the removal of AFB1 in oil system. The MMS preparation process, adsorption conditions, structural characteristics, and adsorption mechanism were investigated. The optimum conditions for MMS preparation were pH 11.0 and 80°C for 24 h. The characterization results showed that magnetic particles were successfully embedded in the MMS and had high responsiveness to a magnetic field, which was advantageous for recyclability. The MMS had ordered uniform channels with a specific surface area of 730.98 m2/g and pore diameter of 2.43 nm. The optimum adsorption conditions were 2 h at 20°C. For AFB1 with an initial concentration of 0.2 µg/mL, the MMS adsorption capacity was 171.98 µg/g and the adsorption rate was 94.59%. The MMS adsorption isotherm fitted the Langmuir model well under the assumption of monolayer AFB1 adsorption with uniformly distributed adsorption sites on the MMS surface. The maximum amount of AFB1 adsorbed according to the Langmuir isotherm was 1118.69 µg/g. A quasi-second-order kinetic model gave a better fit to the process of AFB1 adsorption on MMS. The values of ΔH (-19.17 kJ/mol) and ΔG (-34.09, -34.61, and -35.15 kJ/mol at 283, 293, and 303 K, respectively) were negative, indicating that AFB1 adsorption on MMS was a spontaneous exothermic process. The results indicated that MMS was a promising material for AFB1 removal in oil system, and this study will serve as a guide for practical MMS applications.


Assuntos
Aflatoxina B1/isolamento & purificação , Nanopartículas de Magnetita/química , Oryza/química , Dióxido de Silício/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/normas , Adsorção , Aflatoxina B1/análise , Concentração de Íons de Hidrogênio , Microesferas , Poluentes Químicos da Água/análise , Purificação da Água/métodos
6.
Chemosphere ; 254: 126842, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957273

RESUMO

Diffusion, sorption-desorption, and biodegradation influence chlorinated solvent storage in, and release (mass flux) from, low-permeability media. Although bioenhanced dissolution of non-aqueous phase liquids has been well-documented, less attention has been directed towards biologically-mediated enhanced diffusion from low-permeability media. This process was investigated using a heterogeneous aquifer cell, packed with 20-30 mesh Ottawa sand and lenses of varying permeability (1.0 × 10-12-1.2 × 10-11 m2) and organic carbon (OC) content (<0.1%-2%), underlain by trichloroethene (TCE)-saturated clay. Initial contaminant loading was attained by flushing with 0.5 mM TCE. Total chlorinated ethenes removal by hydraulic flushing was then compared for abiotic and bioaugmented systems (KB-1® SIREM; Guelph, ON). A numerical model incorporating coupled diffusion and (de)sorption facilitated quantification of bio-enhanced TCE release from low-permeability lenses, which ranged from 6% to 53%. Although Dehalococcoides mccartyi (Dhc) 16S rRNA genes were uniformly distributed throughout the porous media, strain-specific distribution, as indicated by the reductive dehalogenase (RDase) genes vcrA, bvcA, and tceA, was influenced by physical and chemical heterogeneity. Cells harboring the bvcA gene comprised 44% of the total RDase genes in the lower clay layer and media surrounding high OC lenses, but only 2% of RDase genes at other locations. Conversely, cells harboring the vcrA gene comprised 50% of RDase genes in low-permeability media compared with 85% at other locations. These results demonstrate the influence of microbial processes on back diffusion, which was most evident in regions with pronounced contrasts in permeability and OC content. Bioenhanced mass transfer and changes in the relative abundance of Dhc strains are likely to impact bioremediation performance in heterogeneous systems.


Assuntos
Chloroflexi/metabolismo , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Biodegradação Ambiental , DNA Bacteriano/genética , Difusão , Água Subterrânea , Dinâmica Populacional , Porosidade , RNA Ribossômico 16S/análise , RNA Ribossômico 16S/genética , Tricloroetileno/isolamento & purificação , Tricloroetileno/metabolismo , Poluentes Químicos da Água/metabolismo
7.
Chemosphere ; 261: 127737, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32738712

RESUMO

Magnetic mesoporous silica material was tested as adsorbent for removal of two usual colored compounds present in industrial wastewater. The magnetic mesoporous silica was synthesized by modified sol-gel method and characterized from the morpho-textural, structural and magnetic point of view. The specific surface area and the total pore volume indicate a good adsorption capacity of the material, and the obtained saturation magnetization strength value denotes a good magnetic separation from solution. The adsorption capacity of magnetic mesoporous silica increases with the increase of the initial dye concentration, and the removal efficiency of the dyes was dependent on the pH of the solution and decreased with increasing temperature. The pseudo-second-order kinetic model described best the adsorption mechanism, and the maximum adsorption capacities were determined from the Sips isotherm model, being 88.29 mg/g for Congo Red and 208.31 mg/g for Methylene Blue. A complete thermodynamic evaluation was performed, by determining the free energy, enthalpy and entropy, and the result showed a spontaneous and exothermic adsorption process. The recovery and reutilization of the adsorbent were estimated in five cycles of adsorption-desorption, and the results indicated a good stability and reusability of magnetic mesoporous silica. The new magnetic mesoporous silica can be easily separated from solution, via an external magnetic field, and may be effectively applied as adsorbent for elimination of dyes from colored polluted waters.


Assuntos
Corantes/isolamento & purificação , Dióxido de Silício/síntese química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Vermelho Congo/isolamento & purificação , Concentração de Íons de Hidrogênio , Fenômenos Magnéticos , Azul de Metileno/isolamento & purificação , Porosidade , Dióxido de Silício/química , Temperatura , Termodinâmica , Fatores de Tempo , Poluentes Químicos da Água/química
8.
Artigo em Inglês | MEDLINE | ID: mdl-32784702

RESUMO

In this study, the adsorption of Fe(III) from aqueous solution on zeolite and bentonite was investigated by combining batch adsorption technique, Atomic adsorption spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses. Although iron is commonly found in water and is an essential bioelement, many industrial processes require efficient removal of iron from water. Two types of zeolite and two types of bentonite were used. The results showed that the maximum adsorption capacities for removal of Fe (III) by Zeolite Micro 20, Zeolite Micro 50, blue bentonite, and brown bentonite were 10.19, 9.73, 11.64, and 16.65 mg.g-1, respectively. Based on the X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence (XRF) analyses of the raw samples and the solid residues after sorption at low and high initial Fe concentrations, the Fe content is different in the surface layer and in the bulk of the material. In the case of lower initial Fe concentration (200 mg.dm-3), more than 95% of Fe is adsorbed in the surface layer. In the case of higher initial Fe concentration (4000 mg.dm-3), only about 45% and 61% of Fe is adsorbent in the surface layer of zeolite and bentonite, respectively; the rest is adsorbed in deeper layers.


Assuntos
Adsorção , Bentonita/química , Ferro/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Zeolitas/química , Compostos Férricos , Concentração de Íons de Hidrogênio , Cinética
9.
J Environ Public Health ; 2020: 5383842, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32774394

RESUMO

Textile industries generate large quantities of dye containing wastewater which pose a serious environmental problem. Currently, biosorbents have become desirable for the removal of dyes from textile effluents. In this study, batch experiments were conducted to investigate the biosorption characteristics of cactus peel on the removal of reactive red dye from aqueous solutions. The effects of solution pH, biosorbent dosage, contact time, and initial concentration were studied. The interaction effects of process variables were analysed using response surface methodology. The results showed that removal efficiency increased as initial dye concentration and solution pH decreased and as biosorbent dosage and contact time increased. The highest removal efficiency (99.43%) was achieved at solution pH, initial dye concentration, biosorbent dose, and contact time of 3.0, 40 mg/l, 6 g, and 120 min, respectively. From regression analysis, the Langmuir isotherm was found to better (R 2 = 0.9935) represent the biosorption process as compared with the Freundlich isotherm (R 2 = 0.9722). Similarly, the pseudo-second-order model was seen to represent very well the biosorption kinetics. The results show that cactus peel has good potential for the removal of reactive red dye.


Assuntos
Cactaceae/química , Corantes/isolamento & purificação , Indústria Têxtil , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Corantes/química , Recuperação e Remediação Ambiental , Concentração de Íons de Hidrogênio , Cinética , Termodinâmica , Poluentes Químicos da Água/química
10.
J Chromatogr A ; 1628: 461428, 2020 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-32822999

RESUMO

A covalent organic framework modified graphitic carbon nitride (g-C3N4@TpBD) was synthesized by modifying the graphitic carbon nitride (g-C3N4) with a covalent organic framework (COF-TpBD). The synthesis conditions including the mass ratio between g-C3N4 and benzidine (BD), solvent type, reaction temperature and reaction time were optimized. Under the optimal synthetic conditions, a novel spiny dendritic g-C3N4@TpBD adsorbent was obtained. The g-C3N4@TpBD was then coated on stainless-steel wire by sol-gel technique and the coated fiber was used for the solid phase microextraction of polycyclic aromatic hydrocarbons prior to gas chromatography-mass spectrometric detection. The established method was successfully applied to determine eight PAHs in six environmental water samples. Under the optimal extraction conditions, a wide linear quantification range for the analytes was obtained from 0.07 to 60.0 ng mL-1 with the coefficients of determination varying from 0.9979 to 0.9998, and the limits of detection (S/N = 3) ranged from 0.02 to 0.05 ng mL-1. The relative recoveries of the analytes for the six environmental water samples at the spiked concentrations of 0.2, 0.5, 3.0 and 30.0 ng mL-1 were between 83.6% and 118% with the relative standard deviations ranging from 2.4% to 11.3%.


Assuntos
Grafite/química , Estruturas Metalorgânicas/química , Compostos de Nitrogênio/química , Hidrocarbonetos Policíclicos Aromáticos/isolamento & purificação , Microextração em Fase Sólida/métodos , Poluentes Químicos da Água/isolamento & purificação , Benzidinas/química , Limite de Detecção , Reprodutibilidade dos Testes , Temperatura
11.
J Chromatogr A ; 1626: 461324, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797817

RESUMO

Sorption of PFASs onto surfaces of laboratory materials has been frequently reported. Due to the often complex and poorly understood nature of such sorption, workarounds have often included use of whole samples only, accompanied by sample vessel rinsing to desorb active surfaces. The resulting methods tend to require considerable sample preparation times and preclude typical activities such as aliquoting and dilution of water samples prior to extraction. This manuscript reports an approach for PFAS analysis which uses subsampling of water matrices from vessels including centrifuge tubes and autosampler vials, through the optimized use of solvent to reduce PFAS retention on subsampling vessels. Online solid phase extraction (SPE) using a weak anion exchange resin is then used to concentrate sample aliquots to improve sensitivity and allow for removal of matrix interferences. With the technique of ultra performance liquid chromatography (UPLC) coupled to isotope dilution tandem mass spectrometry, statistically based quantitation limits ranged from sub ng/L to single digit ng/L for carboxylate, sulfonate, and sulfonamide PFASs analytes from C4 to C12. Linear calibration ranges were from 0.25 to 4000 ng/L. Matrix effects relevant for drinking water treatment studies, such as cations, organic carbon, and competing PFAS compounds, were evaluated and found to not impact method performance within QC criteria consistent with study data quality objectives.


Assuntos
Fluorcarbonetos/análise , Indicadores e Reagentes/análise , Espectrometria de Massas em Tandem/métodos , Cromatografia Líquida de Alta Pressão , Fluorcarbonetos/isolamento & purificação , Água Doce/análise , Indicadores e Reagentes/isolamento & purificação , Marcação por Isótopo , Sais/química , Extração em Fase Sólida , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/isolamento & purificação
12.
J Chromatogr A ; 1626: 461359, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797838

RESUMO

The enantiomeric determination of chiral drugs in the environment is of emerging concern since their enantiomers often exhibit stereoselectivity in environmental occurrence, fate and toxicity. In this study a method based on solid-phase extraction followed by chiral liquid chromatography and high-resolution mass spectrometry has been developed for the enantiomeric determination of a group of cathinones in river water and effluent wastewater. The enantioseparation was carried out using a Chiralpak CBH column in reversed-phase mode, and optimised by evaluating the effects of flow rate, buffer concentration and organic modifier. Under optimal conditions, good enantioseparations (Rs ≥1.2) were achieved for all the analytes. Two mixed-mode cation-exchange sorbents (Oasis WCX and Oasis MCX) in solid-phase extraction were evaluated in river water. Oasis MCX sorbent showed better performance with apparent recoveries ranging from 57 to 91% and matrix effect ranging from -10 to 15%. It is worth noting that a shifting of retention times and loss of enantioresolutions in environmental water samples was observed for all the analytes when the Oasis WCX sorbent was used. The method was validated with river water and effluent wastewater samples and its overall performance was satisfactory. The method quantification limits for all the analyte enantiomers ranged from 1.0 to 2.9 ng/L in river water, and from 2.3 to 6.0 ng/L in effluent wastewater. The repeatability and reproducibility values, expressed as% relative standard deviation (n = 5) were less than 15%. The method was then applied to the analysis of river water and effluent wastewater. The racemic methylone and methedrone (EF=0.49 and 0.46, respectively) were detected at low ng/L in some of the river water samples.


Assuntos
Alcaloides/análise , Cromatografia Líquida/métodos , Espectrometria de Massas/métodos , Alcaloides/química , Alcaloides/isolamento & purificação , Reprodutibilidade dos Testes , Rios/química , Extração em Fase Sólida/métodos , Estereoisomerismo , Águas Residuárias/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação
13.
J Chromatogr A ; 1626: 461360, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797839

RESUMO

Conjugated microporous polymers (CMPs) with uniform morphology have shown fascinating application in the separation science. In this study, metal-free Knoevenagel condensation was adopted to prepare spherical sp2 carbon-conjugated microporous polymers, which used tetrakis(4-formylphenyl)methane and 1,4-phenylenediacetonitrile as monomers. Due to the remarkable extraction capability for carbamate pesticides (CPs), the as-synthesized CMPs were fabricated as the coating for solid-phase microextraction (SPME). After optimized SPME parameters (adsorption time, salt concentration, sample pH, adsorption temperature, desorption time, desorption solvent and desorption volume), ten CPs in water samples were quantified by ultrahigh performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Linearity in the range 0.005-100 ng mL-1 with low detection limits of 0.00060-0.017 ng mL-1 was obtained. The intra-day and inter-day precisions expressed as relative standard deviations were 1.5-8.1% and 1.1-8.0%, respectively. Fiber-to-fiber reproducibility was below 7.3%. The CMPs-SPME-UPLC-MS/MS method was applied to detect trace CPs in real water samples with relative recoveries from 91.8% to 108%.


Assuntos
Carbamatos/análise , Microextração em Fase Sólida/métodos , Poluentes Químicos da Água/análise , Adsorção , Carbamatos/isolamento & purificação , Cromatografia Líquida de Alta Pressão , Praguicidas/análise , Praguicidas/isolamento & purificação , Polímeros/química , Porosidade , Reprodutibilidade dos Testes , Espectrometria de Massas em Tandem , Poluentes Químicos da Água/isolamento & purificação
14.
J Chromatogr A ; 1626: 461377, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797853

RESUMO

This study reports the use ofa natural deep eutectic solvent (NADES) with hollow fiber-microporous membrane liquid-liquid microextraction (HF-MMLLE) for the multiclass determination of 11 compounds classified as emerging contaminantsin water. Different deep eutectic solvents were synthetized and Thymol: Camphor (1:1 molar fraction) wasused as extraction solvent. The Thymol:Camphor was impregnated into the polypropylene membrane porous for 10 min, replacing commonly used solvents (ex. hexane and octanol). The optimized parameters were obtained by multi and univariate models. Extractions were carried out for 50 min using 1.5 mL of water sample at pH 6 and without addition of salt while desorption was made in a mixture of acetone: methanol (3:1, v/v) for 15 min. Separation/quantification was conducted by HPLC with a diode array detection (DAD)and calibration curves were obtained for each analyte. Determination coefficients higher than 0.9906 and limits of detection ranged from 0.3 to 6.1 µg L-1. Intraday precision (n = 3) ranged from 1.6 to 18.4% and inter day from 5.0 to 21.3%. Relative recoveries were performed in tap and stream water and ranged from 64 to 123%.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Microextração em Fase Líquida/métodos , Solventes/química , Poluentes Químicos da Água/análise , Calibragem , Cromatografia Líquida de Alta Pressão/normas , Interações Hidrofóbicas e Hidrofílicas , Membranas Artificiais , Polipropilenos/química , Porosidade , Espectrofotometria , Poluentes Químicos da Água/isolamento & purificação , Poluentes Químicos da Água/normas
15.
PLoS One ; 15(8): e0237389, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32797116

RESUMO

In the present work, a series of magnetically separable Fe3O4/g-C3N4/MoO3 nanocomposite catalysts were prepared. The as-prepared catalysts were characterized by XRD, EDX, TEM, FT-IR, UV-Vis DRS, TGA, PL, BET and VSM. The photocatalytic activity of photocatalytic materials was evaluated by catalytic degradation of tetracycline solution under visible light irradiation. Furthermore, the influences of weight percent of MoO3 and scavengers of the reactive species on the degradation activity were investigated. The results showed that the Fe3O4/g-C3N4/MoO3 (30%) nanocomposites exhibited highest removal ability for TC, 94% TC was removed during the treatment. Photocatalytic activity of Fe3O4/g-C3N4/MoO3 (30%) was about 6.9, 5, and 19.9-fold higher than those of the MoO3, g-C3N4, and Fe3O4/g-C3N4 samples, respectively. The excellent photocatalytic performance was mainly attributed to the Z-scheme structure formed between MoO3 and g-C3N4, which enhanced the efficient separation of the electron-hole and sufficient utilization charge carriers for generating active radials. The highly improved activity was also partially beneficial from the increase in adsorption of the photocatalysts in visible range due to the combinaion of Fe3O4. Superoxide ions (·O2-) was the primary reactive species for the photocatalytic degradation of TC, as degradation rate were decreased to 6% in solution containing benzoquinone (BQ). Data indicate that the novel Fe3O4/g-C3N4/MoO3 was favorable for the degradation of high concentrations of tetracycline in water.


Assuntos
Óxido Ferroso-Férrico/química , Grafite/química , Molibdênio/química , Nanocompostos/química , Compostos de Nitrogênio/química , Óxidos/química , Processos Fotoquímicos , Tetraciclina/química , Água/química , Catálise , Luz , Imãs/química , Tetraciclina/isolamento & purificação , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação
16.
Chemosphere ; 261: 127747, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32721695

RESUMO

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


Assuntos
Carvão Vegetal/química , Sulfatos/química , Purificação da Água/métodos , Adsorção , Carbono/química , Domínio Catalítico , Compostos Orgânicos/isolamento & purificação , Oxirredução , Pirólise , Oxigênio Singlete/química , Águas Residuárias/química , Poluentes Químicos da Água/isolamento & purificação
17.
Chemosphere ; 259: 127491, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32650167

RESUMO

The reuse of cooling tower blowdown (CTBD) in the cooling tower itself requires CTBD deionization and a pre-treatment before deionization to remove organic compounds (OCs) that induce membrane fouling. This study assesses the potential of electrochemical oxidation (EO) with a boron-doped diamond (BDD) and a Ti/RuO2 mixed-metal oxide (MMO) anode for CTBD pre-treatment. Also, the influence of the applied current density (j), initial pH, hydrodynamic conditions, and supporting electrolyte on the process performance was evaluated. Results show that COD and TOC removal were 85 and 51%, respectively, with the BDD-anode; however, they were 50 and 12% with MMO-anode at a j-value of 8.7 mA cm-2 and neutral pH. An increased j-value increased the COD and TOC removal; however, different pHs, hydrodynamic conditions, and the addition of supporting electrolytes had a minor impact on the removal with both anodes. Liquid chromatography-organic carbon detection analysis showed that the OC in CTBD mainly consisted of humic substances (HS). EO with the BDD-anode resulted in 35% HS mineralization, while the rest of the HS were partially oxidized into low molecular weight compounds and building blocks. However, HS mineralization was limited with the MMO-anode. The mineralization and oxidation were accompanied by the formation of organic and inorganic chlorinated species. These species increased the toxicity to Vibrio fischeri 20-fold compared to the initially low-toxic CTBD. Thus, EO with a BDD-anode is a promising pre-treatment technology for the removal of OCs before CTBD deionization, but measures to minimize the chlorinated species formation are required before its application.


Assuntos
Boro/química , Diamante/química , Técnicas Eletroquímicas/métodos , Compostos Orgânicos/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Incrustação Biológica/prevenção & controle , Eletrodos , Substâncias Húmicas/análise , Oxirredução , Águas Residuárias/química , Poluentes Químicos da Água/análise
18.
Chemosphere ; 260: 127566, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32663674

RESUMO

Ball milling was used to fabricate a nanocomposite of 20% hickory biochar (600 °C) and 80% expanded vermiculite (20%-BC/VE). This novel composite adsorbent had much higher removal of As(V) from aqueous solutions than ball-milled biochar and expanded vermiculite. Characterization of these adsorbents showed that the enhanced As(V) adsorption was ascribed to much larger surface area and pore volume (2-6 times), notable changes in crystallinity, activation of cations, and increased functional groups in the nanocomposite compared with the ball-milled products of their pristine counterparts. The As(V) adsorption process by the 20%-BC/VE fitted well with the pseudo-second-order kinetic model (R2= 0.990) and Langmuir isotherm model (R2= 0.989) with a maximum adsorption capacity of 20.1 mg g-1. The 20%-BC/VE best performed at pH about 6. The adsorption efficiency was not sensitive to the competition of NO3-, Cl-, SO42-, as well as the coexistence of humic acid. However, the adsorption capacity for As(V) was significantly reduced by coexisting with PO43-. The 20%-BC/VE composite can potentially serve as a superior low-cost adsorbent for As(V) removal in real-world applications.


Assuntos
Silicatos de Alumínio/química , Arsenicais/isolamento & purificação , Carvão Vegetal/química , Nanocompostos/química , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Cinética , Poluentes Químicos da Água/análise , Purificação da Água/métodos
19.
Chemosphere ; 260: 127560, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32688314

RESUMO

This study aimed to investigate the performance of a magnetic nano-biocomposite, chitosan conjugated magnetite nanoparticle (CH-MNP), for the removal of lead ions. The magnetite nanoparticles were synthesized through a controlled co-precipitation technique and were stabilized with citric acid. Subsequently, they were covalently bonded to chitosan via carbodiimide chemistry using EDAC/NHS activation. One of the notable advantages of this nano-biocomposite is its chemical conjugation, which does not have the weakness of the ultimate chitosan detachment of a physical bond and makes it an encouraging candidate for magnetic separation with no secondary waste production. The CH-MNPs had a diameter of ∼10 nm, with a saturation magnetization of 76.01 emu/g ensuring a superparamagnetic property. The response surface methodology (RSM) with a central composite design (CCD) framework was used for optimizing the adsorption process. The optimum conditions to achieve 92.15% of Pb(II) removal were found to be at a pH of 6.1 with the nano-adsorbent concentration of 1.04 g/L and a contact time of 59.92 min. Our adsorption isotherm data were fitted well with the Langmuir adsorption isotherm model, and the equilibrium data followed the pseudo-second-order kinetics and intraparticle diffusion kinetic model. The maximum Langmuir Pb(II) adsorption capacity was calculated to be 192.308 mg/g. These results suggest that the proposed synthetic nano-biocomposite is quite an ideal nano-adsorbent for Pb(II) removal in wastewater treatment technology.


Assuntos
Quitosana/química , Chumbo/isolamento & purificação , Nanopartículas de Magnetita/química , Purificação da Água/métodos , Adsorção , Concentração de Íons de Hidrogênio , Íons , Cinética , Águas Residuárias/química , Poluentes Químicos da Água/isolamento & purificação
20.
Food Chem ; 333: 127529, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32679419

RESUMO

A solid-phase extraction (SPE) method for enriching and purifying estrogenic disrupting compounds (EDCs) based on the estrogen response element was established. The estrogen receptor was used for molecular recognition, as it specifically binds EDCs. An estrogen response element was used to maintain the activity of the estrogen receptor. High-performance liquid chromatography (HPLC) was used to quantify the EDCs. This method combined with HPLC was applied to detect three kinds of EDCs, such as bisphenol A (BPA), 17ß-estradiol, and diethylstilbestrol in a liquid milk matrix, with recoveries of 84.1 ± 8.2% to 113.6 ± 2.9%. The limits of detection and quantification of the established method were 1 × 10-6 mg·mL-1 and 5 × 10-6 mg·mL-1. The method was further applied to analyze market samples, including liquid milk, fermented milk, and milk powder. Only BPA was detected from one brand of liquid milk and it was below the regulatory level.


Assuntos
Disruptores Endócrinos/isolamento & purificação , Estrogênios/metabolismo , Elementos de Resposta , Extração em Fase Sólida/métodos , Animais , Cromatografia Líquida de Alta Pressão , Disruptores Endócrinos/análise , Leite/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/isolamento & purificação
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