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2.
Water Sci Technol ; 81(12): 2664-2673, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32857751

RESUMO

Horseradish peroxidase (HRP) characteristics were improved by two techniques, Na-alginate entrapment and glutaraldehyde crosslinking prior to alginate entrapment, in order to enhance the stability, functionality and removal of dyes in waste water. Free, entrapped and crosslinked-entrapped enzymes were compared by activity assays, which indicated the optimum temperature is 25 °C and pH 4.0-5.0. Kinetics results showed that alginate entrapment and crosslinking prior to entrapment increased Vmax and did not cause any significant decrease in Km. The thermal resistance of the free enzyme was short-term, zero residual activity after 250 min, while the immobilized enzymes preserved more than 50% of their activity for 5 h at 60 °C. Immobilized HRP was resistant to methanol, ethanol, DMSO and THF. The storage stability of free HRP ended in 35 days whereas entrapped and crosslinked-entrapped HRPs had 87 and 92% residual activity at the 60th day, respectively. HRP was used in the decolorization of azo dye Acid yellow 11 and total decolorization (>99%) was obtained using crosslinked-entrapped HRP. Reusability studies presented the improvement that crosslinked-entrapped HRP reached 74% decolorization after 10 batches. The results demonstrated that the novel immobilized HRP can be used as an effective catalyst for dye degradation of industrial waste effluents.


Assuntos
Compostos Azo , Enzimas Imobilizadas , Cor , Corantes , Peroxidase do Rábano Silvestre , Concentração de Íons de Hidrogênio , Cinética , Temperatura
3.
J Environ Sci (China) ; 96: 171-177, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32819691

RESUMO

Microbial fuel cells (MFC) utilize microbes as catalysts to convert chemical energy to electricity. Inocula used for MFC operation must therefore contain active microbial population. The dye reduction-based electron-transfer activity monitoring (DREAM) assay was employed to evaluate different inocula used in MFCs for their microbial bioelectrical activity. The assay utilizes the redox property of Methylene Blue to undergo color change from blue to colorless state upon microbial reduction. The extent of Methylene Blue reduction was denoted as the DREAM assay coefficient. DREAM assay was initially performed on a microbial culture along with the growth curve and estimation of colony forming units (CFUs). DREAM coefficient correlated to the CFU/mL obtained over time as growth progressed. The assay was then extended to water samples (domestic sewage, lake and a man-made pond) serving as inocula in MFCs. Domestic wastewater gave the highest DREAM coefficient (0.300 ± 0.05), followed by pond (0.224 ± 0.07) and lake (0.157 ± 0.04) water samples. Power density obtained conformed to the DREAM coefficient values, with the three samples generating power densities of 46.45 ± 5.1, 36.12 ± 3.2 and 25.08 ± 4.3 mW/m2 respectively. We have also studied the role of addition of various carbon sources and their concentrations towards improving the sensitivity of the assay. The DREAM assay is a rapid, easy-to-perform and cost-effective method to assess inocula for their suitability as anolytes in terms of electron transfer potential in MFCs.


Assuntos
Fontes de Energia Bioelétrica , Corantes , Eletricidade , Eletrodos , Elétrons , Oxirredução , Águas Residuárias
4.
J Environ Manage ; 273: 111143, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32734894

RESUMO

Environmental concerns have been raised regarding the intense contamination of water resources. Currently, numerous contaminants that reach water bodies are not efficiently removed by conventional water treatment methods. Therefore, there arises the need for development and optimization of efficient treatment methods for the removal of such recalcitrant contaminants. Given the circumstances, the present study aims to use of advanced oxidative processes for dye degradation. For this purpose, copper and zinc doped cobalt ferrites were synthesized by coprecipitation, targeting the degradation of methylene blue dye. The photocatalysts were characterized by XRD, WD-XRF, FE-SEM, N2 physisorption isotherms, UV-Vis diffuse reflectance spectroscopy, molecular fluorescence spectroscopy and zeta potential. According to the investigation of the degradation mechanism, the holes and hydroxyl radicals were mainly responsible for the dye's degradation. The obtained photocatalysts displayed promising results with up to 99% of dye degradation, employing conventional visible LED lamps, making the practical use of the catalyst highly viable, as well as the economic matters. Additionally, the synthesized materials' magnetic properties allowed total and efficient separation of the catalyst for its reutilization up to 4 cycles, with no decrease in photocatalytic activity and with low leaching of iron ions to solution.


Assuntos
Purificação da Água , Catálise , Corantes , Luz , Água
5.
J Environ Manage ; 273: 111125, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32738744

RESUMO

In the present work, a novel (2D/2D) accordion like CS@g‒C3N4/MX hybrid composite was prepared through one-pot hydro-thermal synthesis method and utilized as a catalyst for the degradation of organic persistent dyes such as methylene blue (MB) and rhodamine B (RhB). Because the removal of such organic compounds is a major dispute in environmental aspects. In this study, the bio-assisted g‒C3N4/MX nanosheets was utilized for the removal of organic dyes from aqueous solution under visible light irradiation, respectively. The CS@g-C3N4/MX photocatalyst showed high catalytic activity based on ~99% and ~98.5% degradation of MB and RhB within 60 and 40 min using visible light irradiation. This outcome could have resulted in greater catalytic enactment towards the degradation of other persistent pollutants with enhanced light absorption property and it can efficiently suppress photo-generated charge recombination, thus improving the interfacial charge transfer rate. The OH radical was being effective oxidative species involved in the CS@g-C3N4/MX system for the degradation of organic contaminants. Furthermore, CS@g-C3N4/MX showed excellent photo-stability over five consecutive cycles for the degradation of organic dyes with negligible loss of photocatalytic activity. Finally, the purposed catalytic mechanisms and degradation pathways of MB and RhB were systematically discussed in detail based on experimental results. Thus, the organics which oxidized into ring-opened compounds such as ethoxyethane, butadiene etc., to non-toxic products like H2O, CO2 and some mineral salts.


Assuntos
Corantes , Poluentes Químicos da Água/análise , Catálise , Luz , Azul de Metileno
6.
Ecotoxicol Environ Saf ; 202: 110924, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32800211

RESUMO

Fabrication of poly-(N-isopropylmethacrylamide-co-methacrylic acid) [p(NMA)] microgels to be utilized as microreactors to synthesize stable Ag nanoparticles for catalytic reductive degradation of dyes has been addressed in this work. Both p(NMA) microgel and Ag-p(NMA) hybrid microgel systems have been analyzed by Fourier transform infra-red and Dynamic light scattering, Ultraviolet-Visible spectroscopy, X-ray diffraction and Transmission electron microscopy. Catalytic activity of Ag-p(NMA) towards reductive degradation of Congo Red (CR), Methyl Orange (MO) and Alizarin Yellow (AY) was investigated under different operating conditions. Spectrophotometry was employed to check the progress of reaction while the rate constant (kapp) value of degradation reaction was determined under various conditions to optimize reaction parameters for rapid and economical degradation of these dyes. An increase in kapp value was observed by increasing feed content of dye up to a certain value that decreases again by further increment in dye concentration which reflects that catalysis follows Langmuir-Hinshelwood mechanism. A gradual increase in the kapp value was also observed with increasing quantity of hybrid microgel used as a catalyst. By comparing kapp values of degradation of aforementioned dyes, it was found that Ag-p(NMA) hybrid microgel gives better activity for MO dye degradation in comparison to catalytic degradation of CR and AY.


Assuntos
Compostos Azo/química , Nanopartículas Metálicas/química , Prata/química , Catálise , Corantes/química , Vermelho Congo/química , Hidrogéis/química , Microscopia Eletrônica de Transmissão , Polímeros/química , Espectrofotometria , Difração de Raios X
7.
Ecotoxicol Environ Saf ; 202: 110939, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32800222

RESUMO

Pulp and paper mill wastewater (PPMWW) contains high concentrations of recalcitrant compounds that cause toxicity to organisms. Advanced oxidation processes (AOPs) have the ability to degrade these compounds and reduce overall toxicity. Physicochemical characterization and Lactuca sativa toxicity test were conducted to compare the effectiveness of two post-treatments: UV/H2O2 and photo-Fenton. A comparison of four phytotoxicity indexes was carried out. PPMWW from a Brazilian treatment plant was characterized by high values of phenols, color, integrated spectral area (ISA), and chemical oxygen demand (COD), and caused significant inhibition to seedling development. The use of both post-treatments allowed the removal of over 75% of phenols, color, ISA, and COD. Although UV/H2O2 was more effective in removing phenols and ISA, photo-Fenton better reduced phytotoxicity. The most sensitive phytotoxicity indexes were RGIC0.8 and GIC80%, whereas SGC0, REC-0.25 and REC-0.50 better showed the effectiveness of the post-treatments. We suggest the combined use of two phytotoxicity indexes: one that evaluates the effects on seed germination and, another, on root elongation, e.g., SGC0 and RGIC0.8. Additionally, we recommend the use of ISA for monitoring programs of wastewater treatments because it is a cost-effective approach that allows narrowing down the search and identification of compounds present in complex mixtures.


Assuntos
Papel , Fenóis/toxicidade , Eliminação de Resíduos Líquidos/métodos , Análise da Demanda Biológica de Oxigênio , Brasil , Cor , Corantes/toxicidade , Peróxido de Hidrogênio/química , Resíduos Industriais/análise , Oxirredução , Fenóis/análise , Plantas/efeitos dos fármacos , Águas Residuárias/química
8.
J Environ Manage ; 271: 110962, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32778272

RESUMO

In this work, silver nanoparticles have been synthesized with an average particle size of 35 nm, within 90s, using microwave and Sapindus mukorossi extract as a stabilizing agent. The AgNps were surface immobilized on eggshells (ES) to obtain Ag@ES, which was characterized by UV-Vis, UV-DRS, FT-IR, ICP-OES, TGA-DSC, SEM-EDX, XRD and XPS. Its applicability as an environmental catalyst was evaluated by Cr (VI) adsorption, photocatalytic degradation of methyl orange, eriochrome black-T, methylene blue, rhodamine-B as model dyes and microbial inhibition against Staphylococcus aureus, Escherichia coli and Candida albicans. The results revealed that Ag@ES exhibited maximum adsorption capacity of 93 mg/g for Cr (VI) ion and degradation efficiency of ~90-98% for removing anionic and cationic dyes. Further, it showed a minimum inhibitory concentration of 15.6, 7.8 and 31.2 µg/mL for S. aureus, E. coli and C. albicans respectively. Moreover, the Ag@ES being a heterogeneous catalyst can be regenerated and reused without significant loss in its efficiency.


Assuntos
Nanopartículas Metálicas , Nanocompostos , Animais , Corantes , Casca de Ovo , Escherichia coli , Prata , Espectroscopia de Infravermelho com Transformada de Fourier , Staphylococcus aureus , Água
9.
Medicine (Baltimore) ; 99(31): e21441, 2020 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-32756157

RESUMO

INTRODUCTION: We report a case of type III uveal effusion syndrome (UES) suspected to be related to pachychoroid spectrum disease. PATIENT CONCERNS: A 42-year-old man became aware of visual field constriction and deterioration of visual acuity in his right eye. DIAGNOSIS: Upon examination, a bullous non-rhegmatogenous retinal detachment was observed in the inferior 2 quadrants of the right eye fundus, and the subretinal fluid moved with postural changes. The axial length in that eye was 22.36 mm, thus indicating no nanophthalmia. Preoperative indocyanine green angiography revealed dilated choroidal vessels in the posterior pole of the right eye and mild leakage in the late phase. Optical coherence tomography examination revealed choroidal thickening in both eyes. INTERVENTIONS: For treatment, we first performed sclerotomy, and the intraoperative findings showed no thickening of the sclera. Following surgery, reattachment of the retina was not achieved. OUTCOMES: Thus, we next performed vitrectomy, which led to successful reattachment of the retina. LESSONS: In this case, we theorize that pachychoroid spectrum disease might have been involved in the pathogenesis of type III UES.


Assuntos
Doenças da Coroide/patologia , Corioide/irrigação sanguínea , Síndrome da Efusão da Úvea/etiologia , Transtornos da Visão/etiologia , Adulto , Angiografia/métodos , Corioide/diagnóstico por imagem , Doenças da Coroide/cirurgia , Corantes/administração & dosagem , Angiofluoresceinografia/métodos , Fundo de Olho , Humanos , Verde de Indocianina/administração & dosagem , Masculino , Microftalmia/etiologia , Descolamento Retiniano , Esclera/cirurgia , Tomografia de Coerência Óptica/métodos , Resultado do Tratamento , Síndrome da Efusão da Úvea/classificação , Síndrome da Efusão da Úvea/diagnóstico , Síndrome da Efusão da Úvea/cirurgia , Transtornos da Visão/diagnóstico , Vitrectomia/métodos
10.
Water Sci Technol ; 81(11): 2337-2350, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32784278

RESUMO

In this study, 4,4'-(hexafluoroisopropene) diphthalic acid (PDA)-CD polymers containing ß-cyclodextrin (CD) were synthesized for the adsorption of endocrine disrupting chemicals (EDCs) and dyes. It features great adsorption of bisphenol A (BPA), methylene blue (MB) and neutral red (NR). The maximum adsorption capacities of MB, NR and BPA can reach 113.06, 106.8 and 51.74 mg/g, respectively. The tandem adsorption results revealed that adsorptions of dyes and BPA onto PDA-CD polymer were two independent processes: non-polar BPA entrapment by cyclodextrin cavities while dyes were captured by the carboxyl groups and π-π stacking interactions. The adsorption processes performed well in a wide range of pH (4.0-10.0) and were not affected by fulvic acid (FA) and inorganic ions.


Assuntos
Poluentes Químicos da Água , beta-Ciclodextrinas , Adsorção , Compostos Benzidrílicos , Corantes , Fenóis
11.
Water Sci Technol ; 81(11): 2401-2409, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32784283

RESUMO

Two-stage anaerobic system (S1: R1 (acidogenic phase) + R2 (methanogenic phase)) and the one-stage control (S0) were established to investigate the effect of phase separation on the removal of an azo dye orange II, i.e., Acid Orange 7 (AO7), with starch as the primary co-substrate. Although final AO7 removal from two systems showed no statistical differences, the first-order rate constants for AO7 removal (kAO7-) and sulfanilic acid (SA) formation (kSA) were higher in S1. Kinetic analysis showed that kAO7- and kSA in S1 were 2.7-fold and 1.7-fold of those in S0, respectively, indicating the benefit of phase separation to the AO7 reduction. However, this benefit only appeared in the period with influent AO7 concentrations higher than 2.14 mM. Otherwise, this advantage would be hidden due to the longer HRT (5 d) and sufficient electron donor (1.0 g starch L-1). Within S1, R1 only contributed about 10% of the entire AO7 removal, and kAO7- in R1 (0.172 h-1) was much lower than in R2 (0.503 h-1). The methanogenic phase rather than acidogenic phase was the main contribution to AO7 removal, because the influent of R2 had more available electron donors and suitable pH condition (pH 6.5-7.0) for the bio-reduction process.


Assuntos
Compostos Azo , Amido , Anaerobiose , Benzenossulfonatos , Corantes , Cinética
12.
J Environ Manage ; 270: 110904, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32721339

RESUMO

An efficient valorization of tea residues into value-added product was developed by Trametes versicolor in solid-state fermentation (SSF). The laccase production of 25.7 U/g dry substrate was obtained by optimizing culture medium and condition, resulting in a 4.0-fold increase compared to that of 6.4 U/g dry substrate under unoptimized condition. During the 7-day cultivation under SSF, 44.7%, 12.2% and 9.8% degradation occurred for lignin, hemicellulose and cellulose in tea residues, respectively. Laccase production reached 31.2 U/g dry substrate by the scaling-up culture in shallow tray system. The dry fermented tea residues were directly used as crude enzyme in the decolorization of malachite green. It possessed a decolorization rate of more than 95% within 120 min and remained 81.3% of decolorization capacity after 6 cycles. The present study provided a useful strategy for low-cost laccase production by SSF and it exhibited great potential for the application in dye decolorization.


Assuntos
Lacase , Trametes , Corantes , Fermentação , Lignina , Chá
13.
Water Res ; 182: 116005, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32645457

RESUMO

Terrestrial organic matter occupies an important position in the oceanic organic carbon pool. Some terrestrial proxies, like the Branched and Isoprenoid Tetraether (BIT) index, have been applied successfully to indicate the relative abundance of terrestrial organic matter in marine sediments. A new terrestrial proxy derived from sediment pore water fluorescent dissolved matter (fluorescent dissolved organic matter (FDOM)) was developed in this study. Surface sediment samples were collected from forty-two sites in the coastal region of the East China Sea (ECS) to examine the distributional patterns of FDOM. Three protein-like components (C1, C4 and C5) and two humic-like components (C2 and C3) of FDOM were identified using fluorescence excitation-emission matrices parallel factor analysis (EEMs-PARAFAC). Spatially, the intensity of these five components generally increased from the coast to the ocean with protein-like components showing a more obvious trend, which suggested that all five components had autochthonous contribution. However, the C2 and C3 proportions, especially C2 that mainly corresponds to the proportion of peak A in fluorescence excitation-emission matrices, significantly decreased from the coast to the ocean and significantly correlated with the BIT index from corresponding solid fractions. We posit that part of the humic-like components from terrestrial organic matter in sediments are released into the C2 and C3 pools in pore waters, which may be constrained by specific environmental conditions. Thus, the FDOM from pore waters can be integrated with BIT index to validate the nature of FDOM and use it as a biomarker to reflect the terrestrial input of organic matter mediated by different biogeochemical processes in coastal oceans. The proportion of peak A responsible for the fluorescence of C2 was suggest as a new terrestrial derived from FDOM.


Assuntos
Corantes , China , Análise Fatorial , Oceanos e Mares , Espectrometria de Fluorescência
14.
J Chromatogr A ; 1625: 461305, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709348

RESUMO

A novel kind of magnetic porous carbon nano-fibers (Fe3O4@P-CNFs) materials was successfully prepared and used as an adsorbent. Based on the above-mentioned adsorbent, a simple and effective magnetic disperse solid-phase extraction (MSPE) method was developed and first utilized to the enrichment and purification of five Sudan dyes (including Sudan I, Sudan II, Sudan III, Sudan IV, and Sudan Red 7B) in foodstuffs for the first time. High-performance liquid chromatography was used to determine the content of the Sudan dyes. The parameters affecting the extraction performance were studied and optimized, including the amount of the adsorbent and inorganic salt, type and the volume of the eluent, pH of the sample solution and extraction time. Under the optimized experimental conditions, the results show that the proposed method has a good linear relationship (r≥ 0.9993). The limits of detection range from 0.88 µg L-1 to 1.27 µg L-1. The recoveries range from 86.6% to 99.7% with the relative standard deviations ranging from 0.6% to 7.9% in the methodology validation. The above-mentioned results indicate that the proposed method is a sensitive and reliable procedure with good reproducibility for the detection of Sudan dyes residues in foodstuffs.


Assuntos
Compostos Azo/análise , Fibra de Carbono/química , Corantes/análise , Análise de Alimentos , Fenômenos Magnéticos , Nanofibras/química , Adsorção , Compostos Azo/química , Corantes/química , Concentração de Íons de Hidrogênio , Limite de Detecção , Nanofibras/ultraestrutura , Porosidade , Análise de Regressão , Reprodutibilidade dos Testes , Sais/química , Fatores de Tempo
15.
BMC Bioinformatics ; 21(1): 332, 2020 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-32709217

RESUMO

BACKGROUND: In cell biology, increasing focus has been directed to fast events at subcellular space with the advent of fluorescent probes. As an example, voltage sensitive dyes (VSD) have been used to measure membrane potentials. Yet, even the most recently developed genetically encoded voltage sensors have demanded exhausting signal averaging through repeated experiments to quantify action potentials (AP). This analysis may be further hampered in subcellular signals defined by small regions of interest (ROI), where signal-to-noise ratio (SNR) may fall substantially. Signal processing techniques like blind source separation (BSS) are designed to separate a multichannel mixture of signals into uncorrelated or independent sources, whose potential to separate ROI signal from noise has been poorly explored. Our aims are to develop a method capable of retrieving subcellular events with minimal a priori information from noisy cell fluorescence images and to provide it as a computational tool to be readily employed by the scientific community. RESULTS: In this paper, we have developed METROID (Morphological Extraction of Transmembrane potential from Regions Of Interest Device), a new computational tool to filter fluorescence signals from multiple ROIs, whose code and graphical interface are freely available. In this tool, we developed a new ROI definition procedure to automatically generate similar-area ROIs that follow cell shape. In addition, simulations and real data analysis were performed to recover AP and electroporation signals contaminated by noise by means of four types of BSS: Principal Component Analysis (PCA), Independent Component Analysis (ICA), and two versions with discrete wavelet transform (DWT). All these strategies allowed for signal extraction at low SNR (- 10 dB) without apparent signal distortion. CONCLUSIONS: We demonstrate the great capability of our method to filter subcellular signals from noisy fluorescence images in a single trial, avoiding repeated experiments. We provide this novel biomedical application with a graphical user interface at https://doi.org/10.6084/m9.figshare.11344046.v1 , and its code and datasets are available in GitHub at https://github.com/zoccoler/metroid .


Assuntos
Razão Sinal-Ruído , Software , Algoritmos , Animais , Automação , Corantes/química , Simulação por Computador , Fluorescência , Humanos , Potenciais da Membrana , Análise de Componente Principal , Ratos , Processamento de Sinais Assistido por Computador , Frações Subcelulares/metabolismo , Interface Usuário-Computador
16.
Environ Sci Pollut Res Int ; 27(30): 37938-37945, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32617809

RESUMO

Adsorption of tartrazine yellow food dye, in a fixed-bed column, was carried out using a single system, a binary system (in the presence of sunset yellow food dye), and in a real effluent provides from an ice cream industry. Chitosan was used to coat sand particles by the dip-coating technique, and these particles were applied in fixed-bed adsorption. The assays were performed in flow rates of 3 mL min-1 and 5 mL min-1. The best performance was reached at 3 mL min-1. In this flow rate, for single and binary systems, the breakthrough time was 95 min and 65 min, and the maximum capacity of the column was around 595 mg g-1 and 497 mg g-1, respectively. In the assay conducted with the real effluent, the breakthrough time was 10 min, and the maximum adsorption capacity of the column was reduced to 191 mg g-1 for tartrazine dye. The dynamic models of Thomas and Yoon-Nelson were used, and both were suitable to represent the breakthrough curves.


Assuntos
Quitosana , Poluentes Químicos da Água , Purificação da Água , Adsorção , Corantes , Areia
17.
Environ Pollut ; 266(Pt 2): 115102, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32650200

RESUMO

Current study deals with the surface modification of acid activated carbon (prepared from Pongamia pinnata shells) with Cetyltrimethylammonium bromide (CTAB) and its role as an adsorbent in eliminating anionic azo dyes viz. Congo red (CR) and Direct blue 6 (DB) from single and binary adsorptive systems. Binary adsorptive system involved the synergistic and antagonistic influence of one dye over the adsorption of other dye. Physico-chemical alterations due to surfactant modification and post adsorption were studied using atomic force microscopy (AFM), Zeta Potential, scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), surface area analysis and Fourier-transformed infrared spectroscopy (FTIR). Process parameters influencing efficient adsorption of CR and DB species viz. initial pH of dye solution, adsorbent dosage, incubation temperature and initial concentration of dye species were optimised. Sorbate-sorbent interaction studies for single adsorptive system revealed sorbate's monolayer formation over adsorbent's surface and the involvement of chemisorption, as verified by Langmuir isotherm model and pseudo-second order model, respectively. Langmuir maximum adsorption capacity of the adsorbent was 555.56 mg/g for CR and 625.00 mg/g for DB. Meanwhile, for binary adsorptive system, competitive Langmuir model verified both CR and DB had antagonistic/competitive effect over each other's adsorption. Thermodynamic analysis revealed the adsorptive process as exothermic, spontaneous and thermodynamically favourable with an elevated degree of dis-orderedness. Co-existing cations and anions has nominal effect on the adsorption capacity of dyes. Recyclability studies verified a modest efficiency of 62.52% for CR and 50.47% for DB species after the end of 4th adsorption-desorption cycle; thus affirming its recyclability potential. Phytotoxic assay affirmed the effectivity of the adsorbent in adsorbing dye species from aqueous solutions using Vigna mungo seeds as the model.


Assuntos
Carvão Vegetal , Poluentes Químicos da Água/análise , Adsorção , Ânions , Compostos Azo , Corantes , Concentração de Íons de Hidrogênio , Cinética , Termodinâmica
18.
Chemosphere ; 259: 127421, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32603965

RESUMO

Nanocomposites with ultrahigh adsorption capabilities are highly desired for efficient wastewater remediation. Unfortunately, most of the nanomaterial based adsorbents showing inevitable limitation such as leaching and agglomeration led to the emerging field of carbonaceous hybrid materials with nanocomposites. Herein, we demonstrated a simple and low-temperature hydrothermal assisted preparation of Fe-Al based nanocomposites immobilized using carbon spheres. Towards this, we have approached two different routes one is hybridizing with nanocomposite and another is doping on the surface of the carbon spheres. Iron doping played a dual-faceted role of active site for robust adsorption as well as induce magnetic property to the composites. The micro-cleaners have been extensively characterized for their physicochemical properties and adsorption capacities using FTIR, Raman, XRD, BET isotherms and XPS techniques. Remarkably, microcleaners shows robust adsorption where >99% removal was obtained within 10 min for 50 mg L-1 concentrated Eriochrome Black T (EBT) dye using 0.01 g of materials. Further, adsorption data followed the pseudo second order kinetics while the equilibrium data fitted perfectly into the Langmuir adsorption equation. As synthesized user friendly microcleaner (HTC-2) exhibits maximum adsorption capacity (qmax) of 564.97 mg g-1 for EBT dye at pH 4. Hence, the preliminary results highlight the potential of the composites to be used in pretreatment steps of industry effluents.


Assuntos
Corantes/química , Nanocompostos/química , Poluentes Químicos da Água/química , Adsorção , Ânions , Compostos Azo , Carbono , Concentração de Íons de Hidrogênio , Ferro , Cinética , Águas Residuárias , Poluentes Químicos da Água/análise
19.
Extremophiles ; 24(5): 705-719, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32617733

RESUMO

Biocatalytic decolorization of azo dyes is hampered by their recalcitrance and the characteristics of textile effluents. Alkaline pH and heavy metals present in colored wastewaters generally limit the activity of enzymes such as laccases of fungal origin; this has led to an increasing interest in bacterial laccases. In this work, the dye decolorization ability of LAC_2.9, a laccase from the thermophilic bacterial strain Thermus sp. 2.9, was investigated. Its resistance towards different pHs and toxic heavy metals frequently present in wastewaters was also characterized. LAC_2.9 was active and highly stable in the pH range of 5.0 to 9.0. Even at 100 mM Cd+2, As+5 and Ni+2 LAC_2.9 retained 99%, 86% and 75% of its activity, respectively. LAC_2.9 was capable of decolorizing 98% of Xylidine, 54% of RBBR, 40% of Gentian Violet, and 33% of Methyl Orange after 24 h incubation at pH 9, at 60 °C, without the addition of redox mediators. At acidic pH, the presence of the mediator 1-hydroxybenzotriazole generally increased the catalytic effectiveness. We analyzed the degradation products of laccase-treated Xylidine and Methyl Orange by capillary electrophoresis and mass spectrometry, and propose a degradation pathway for these dyes. For its ability to decolorize recalcitrant dyes, at pH 9, and its stability under the tested conditions, LAC_2.9 could be effectively used to decolorize azo dyes in alkaline and heavy metal containing effluents.


Assuntos
Compostos Azo , Lacase , Águas Residuárias , Biodegradação Ambiental , Cor , Corantes
20.
Chemosphere ; 255: 127052, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32679636

RESUMO

In this study, polypyrrole/carboxymethyl cellulose nanocomposite particles (PPy/CMC NPs) were synthesized and applied for removal of reactive red 56 (RR56)and reactive blue 160 (RB160) as highly toxic dyes. The amount of CMC was found significantly effective on the surface adsorption efficiency. Different optimization methods including the genetic programming, response surface methodology, and artificial neural network (ANN) were used to optimize the effect of different parameters including pH, adsorption time, initial dye concentration and adsorbent dose. The maximum adsorption of RR56 and RB160 were found under the following optimum conditions: pH of 4 and 5, adsorption time of 55 min and 52 min for RR56 and RB160, respectively, initial dye concentration of 100 mg/L and adsorbent dose of 0.09 g for both dyes. were obtained for RR56 and RB160, respectively. Also, the results indicated that ANN method could predict the experimental adsorption data with higher accuracy than other methods. The analysis of ANN results indicated that the adsorbent dose is the main factor in RR56 removal, followed by time, pH and initial concentration, respectively. However, initial concentration mostly determines the RB160 removal process. The isotherm data for both dyes followed the Langmuir isotherm model with a maximum adsorption capacity of 104.9 mg/g and 120.7 mg/g for RR56 and RB160, respectively. In addition, thermodynamic studies indicated the endothermic adsorption process for both studied dyes. Moreover, DFT calculations were carried out to obtain more insight into the interactions between the dyes and adsorbent. The results showed that the hydrogen bondings and Van der Waals interactions are dominant forces between the two studied dyes and PPy/CMC composite. Furthermore, the interaction energies calculated by DFT confirmed the experimental adsorption data, where PPy/CMC resulted in higher removal of both dyes compared to PPy. The developed nanocomposite showed considerable reusability up to 3 cylces of the batch adsorption process.


Assuntos
Carboximetilcelulose Sódica/química , Corantes/química , Nanocompostos/química , Adsorção , Compostos Azo , Benzenossulfonatos , Teoria da Densidade Funcional , Cinética , Nanopartículas , Polímeros , Pirróis , Termodinâmica , Poluentes Químicos da Água
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