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1.
Chemosphere ; 248: 125992, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32006832

RESUMO

Natural colloids can influence the binding mechanisms between nano-hydroxyapatite (nHAP) and Cd(II). In this study, the effects of organic and inorganic natural colloids on Cd(II) sorption onto nHAP were compared. Different experimental approaches combined with the additivity model and the Extended-Derjaguin-Landau-Verwey-Overbeek model were used to quantify the distribution of Cd(II) in the systems of nHAP and natural colloid, and the interaction energy between particles. The results showed that both fulvic acid (FA) and montmorillonite colloid (MONT) had the promotion and inhibition effects on Cd(II) sorption onto nHAP. Coexistence of FA or MONT could stabilize nHAP particles. FA could adsorb onto nHAP particle surface via carboxylic and phenolic groups, which increased nHAP electronegativity and formed steric resistance effect. Coexistence of MONT mainly increased nHAP electronegativity. These effects prevented the reduction of the specific surface area of nHAP particles and increased the Cd(II) sorption onto nHAP. However, the inhibition effect on Cd(II) sorption was enhanced with increasing concentration of FA or MONT because more soluble FA-Cd or suspended MONT-Cd complexes formed in the system. In nHAP-FA-Cd systems, the Cd(II) sorption onto FA was well predicted but that onto solid phase was underestimated by the additivity model. In nHAP-MONT-Cd systems, Cd(II) sorbed onto mixtures of nHAP and MONT was well described by the additive model. The findings of this study can help to understand the fate of Cd(II) in natural water and soil.


Assuntos
Bentonita/química , Benzopiranos/química , Cádmio/química , Modelos Químicos , Poluentes do Solo/química , Adsorção , Cádmio/metabolismo , Coloides/química , Durapatita/química , Solo/química , Poluentes do Solo/análise , Água
2.
Chemosphere ; 248: 125927, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32014634

RESUMO

Composting is an acceptable and economically feasible process for recycling agricultural biomass waste. The addition of external additives to adjust the process of composting has been attracted lots of research attention. To investigate the effects of external additives on nutrients transformation process of composting, a laboratory reactors scale co-composting based on swine manure and corn straw (CK) with the additives of phosphate (MP), calcium bentonite (CB) and biochar (BC) were performed for 30 days. The results showed the addition of phosphate and biochar could contribute to accelerating temperature rise and shorten the thermophilic phase. The germination index (GI) of MP and BC achieved 180% and 150%, respectively. The excitation-emission matrix (EEM) demonstrated the intensities of the peak C (humic acids) of the MP treatment was 829.5, and the PV,n/PIII,n value (9.59) of MP treatment was particularly higher compared to other three treatments according to the fluorescence regional integration (FRI) analysis. The Fourier Transform Infrared spectroscopy (FTIR) indicated the rate of decomposition of aliphatic C substances was higher than that of aromatic C substances. According to the X-ray diffraction (XRD) spectra results, characteristic peaks at both 16° and 22° were decreased, indicating cellulose and amorphous components were degraded. It further proved the formation of struvite component in MP treatment. Therefore, based on the maturity indicators, EEM and XRD results, phosphate is an efficient additive and recommended for swine manure and corn straw co-composting.


Assuntos
Compostagem , Fosfatos/química , Bentonita/química , Carvão Vegetal/química , Germinação , Substâncias Húmicas , Esterco , Nitrogênio , Solo/química , Temperatura , Zea mays/química
3.
Chemosphere ; 249: 126131, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32058135

RESUMO

Lanthanum-modified bentonite (LMB, commercially called Phoslock®) has been widely applied in freshwater systems to manage eutrophication. Little is known, however, about its behaviour and efficiency in binding filterable reactive phosphorus (FRP) in saline environments. We assessed if LMB would adsorb phosphate over a range of salinities (0-32 ppth) comparing the behaviour in seawater salts and equivalent concentrations of NaCl. Lanthanum release from the bentonite matrix was measured and the La species prevailing in saline environments were evaluated through chemical equilibrium modelling. We demonstrated that LMB was able to adsorb FRP in all the salinities tested. Filterable lanthanum (FLa) concentrations were similarly low (<5 µgL-1) at all seawater salinities but considerably elevated, on occasion >2000 times greater in equivalent NaCl salinities. Mineralogical analysis indicates that La present in the clay interlayer was (partially) replaced by Na/Ca/Mg present in the seawater and a possible secondary P-reactive phase was formed, such as kozoite (LaCO3OH) or lanthanite (La2(CO3)3·8H2O) that may be physically dissociated from the LMB. Geochemical modelling also indicates that most FLa dissociated from LMB would be precipitated as a carbonate complex. In light of the identification of reactive intermediate phases, further studies including ecotoxicologial assays are required to assess any deleterious effects from the application of LMB to saline waters.


Assuntos
Bentonita/química , Lantânio/química , Fosfatos/química , Águas Salinas/química , Purificação da Água/métodos , Adsorção , Eutrofização , Lagos , Lantânio/metabolismo , Fosfatos/análise , Fósforo/análise , Salinidade
4.
Food Chem ; 313: 126062, 2020 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-31931422

RESUMO

In sparkling wine, foam characteristics are one of the major attributes. The foam quality depends on wine components. Bentonite is added to the base wine to facilitate the riddling process, but causes a loss of foamability. Acacia gum can be used as additive in wine. We have studied if the addition of Acacia senegal gum (AsenG), Acacia seyal gum (AseyG) and different AsenG fractions could improve the foamability of different base wines treated with bentonite. The foamability differs depending on the gum or the gum fraction treatment but also on the wine, being these differences linked to some aspects of their respective compositions and molecular parameters. AsenG and AseyG increase the foamability (by Mosalux - sparging procedure), respectively, in five and seven out of eight base wines treated with bentonite. Therefore, AsenG and AseyG are potential treatments increasing the foamability of these wines.


Assuntos
Goma Arábica/química , Vinho/análise , Bentonita/química , Cromatografia Líquida de Alta Pressão , Gases/química
5.
Chemosphere ; 242: 125109, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31675586

RESUMO

Organoclays have been applied as efficient adsorbents for pharmaceutical pollutants from aqueous solution. In this work, dodecylpyridinium chloride (C12pyCl) and hexadecylpyridinium chloride (C16pyCl) cationic surfactants were used for the preparation of organobentonites destined for diclofenac sodium (DFNa) adsorption, an anionic drug widely detected in wastewater. The organofunctionalization of the clay samples was performed under microwave irradiation at 50 °C for 5 min with surfactant amounts of 100% and 200% in relation to the cation exchange capacity (CEC) of the pristine bentonite. The amount of incorporated ammonium salts based on CHN elemental analysis was higher for all samples prepared with 200% of the CEC. The basal spacings of the organoclays ranged from 1.54 to 2.13 nm, indicating the entrance of organic cations into the interlayer spacing of the clay samples, and the spacing depended on the size of the alkyl organic chain. The hydrophobic character of the organobentonites was verified by thermogravimetry and infrared spectroscopy (FTIR). The adsorption isotherms showed that the drug capacity adsorption was influenced by the amount of surfactant incorporated into the bentonite, the packing density and the arrangement of the surfactants in the interlayer spacing. Zeta potential measurements of the organobentonites and FTIR analysis after drug adsorption suggested that electrostatic and nonelectrostatic interactions contributed to the mechanism of adsorption.


Assuntos
Bentonita/química , Diclofenaco/química , Adsorção , Anti-Inflamatórios não Esteroides/química , Cátions/química , Interações Hidrofóbicas e Hidrofílicas , Eletricidade Estática , Tensoativos/química , Água/química , Difração de Raios X
6.
Chemosphere ; 241: 125096, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31629242

RESUMO

In this study, the acidic-modified bentonite (AMB) was developed to enhance conditioning and dewatering processes of anaerobically digested sludge (ADS) for the first time and its performance was compared with inorganic salts, e.g. FeCl3, AlCl3, Al2(SO4)3 and Fe2(SO4)3. AMB structural changes were investigated employing XRD, XRF, FT-IR and specific surface area tests. AMB reduced the specific resistance to filterability (SRF), capillary suction time (CST) and time to filter (TTF) of the sludge by 95.8%, 90.4% and 80.8%, respectively. Moreover, it reduced the sludge compressibility and increased filtration yield significantly. Also, sludge conditioning with the AMB resulted in a significant increase in the sludge particles size and formation of denser and stronger flocs. In order to evaluate the related sludge conditioning mechanism, zeta potential, bound water, extracellular polymeric substances (EPS) and XRF tests were conducted. It was determined that AMB acts as physical and chemical conditioner. Dewatering of conditioned sludge with AMB utilizing a filter press resulted in the sludge with 41% dry solids (DS). In addition, the economic survey showed that the cost of conditioning by using AMB is $ 33.79 USD/t DS. In general, it can be concluded that AMB has an effective performance in conditioning and dewatering of anaerobically digested sludge and is economically affordable in comparison to common polymers.


Assuntos
Anaerobiose , Bentonita/química , Dessecação/métodos , Esgotos/química , Bentonita/economia , Filtração , Tamanho da Partícula , Polímeros/química , Espectroscopia de Infravermelho com Transformada de Fourier
7.
Chemosphere ; 238: 124664, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31472349

RESUMO

Chemosensors have already demonstrated potential for the detection and imaging of metal ions in solutions and biological systems, however, their applications to soil analysis are limited. This study explores the potential of utilizing a chemosensor for the detection of exchangeable Cu2+ in soils via qualitative (solution visual color change) and quantitative (UV-Vis spectrophotometry) approaches. Montmorillonite and kaolin clays were doped with Cu(NO3)2 solutions from 2.5 to 50 mM, and contaminated soil samples were collected from a historic copper mine. The exchangeable Cu2+ was extracted using a standard CaCl2 cation exchange approach, and the Cu2+ concentration in the resulting solutions determined by UV-Vis spectrophotometry, using a chemosensor, and compared to traditional ICP-MS analysis. Analytical results showed that the chemosensor provided a visual response in contaminated soils at concentrations of 25 µM and quantitative detection to concentrations of 1 µM using UV-Vis spectrophotometry. This work demonstrates the first reported chemosensor for exchangeable Cu2+ with application to soil systems.


Assuntos
Colorimetria/métodos , Cobre/análise , Poluentes do Solo/análise , Bentonita/química , Cátions , Argila/química , Mineração , Solo , Espectrofotometria
8.
Chemosphere ; 239: 124768, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31518917

RESUMO

There is a need for cheap but, efficient methods for the removal of precious metals from wastewaters, which are normally lost during mineral processing. Moreover, the disposal of yeast waste from brewing has been a problem in many parts of the world. In this study, the removal of Pt(IV) from aqueous solutions using the readily available bentonite clay functionalised with spent yeast from brewing was investigated. The maximum adsorption capacity of Pt(IV) with 100 mg yeast-functionalised bentonite at pH 2 within 90 min was 255 µg g-1 (98.5% efficiency) but, decreased as pH increased. The adsorption capacity of Pt(IV) was insignificantly (p > 0.05) affected by the presence of competing ions (Fe(III), Ca(II), Mg(II), K(I), Co(II), Ni(II), Hf(IV), Zn(II) and other platinum group metals (PGMs)). Moreover, most of these metals were significantly adsorbed along with Pt(IV). The indicative cost-benefit analysis showed that 1 kg of the yeast-functionalised bentonite can remove ∼700 g Pt(IV) in which a profit of more than USD20000 can be made. The bentonite functionalised with spent yeast from brewing has a potential to recover lost PGMs in wastewater. Since, this is a cheap process, the mining and other industries can make much profit from such recoveries.


Assuntos
Bentonita/química , Platina/isolamento & purificação , Saccharomyces cerevisiae/química , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Concentração de Íons de Hidrogênio , Resíduos Industriais , Metais/química , Soluções , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias , Água/química
9.
Chemosphere ; 239: 124840, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31526996

RESUMO

Organic-magnetic bentonites (OMBts), i.e., amphoteric modified MBt (BS-MBt), amphoteric-cationic modified MBt (BS-CT-MBt) and amphoteric-anionic modified MBt (BS-SDS-MBt), obtained by modifying magnetic bentonite (MBt) with amphoteric surfactant (BS), cationic surfactant (CT) and anionic surfactant (SDS) were investigated with the aim to remove cadmium (Cd2+). The modifier contents, surface charge and Cd2+ adsorption performances of OMBts were compared, and the influences of pH, temperature and ionic strength on Cd2+ removal were evaluated. Results showed that modifier contents of OMBts increased in the order: BS-CT-MBt > BS-MBt > BS-SDS-MBt. Although CEC of adsorbents increased in the order: MBt > BS-MBt > BS-SDS-MBt > BS-CT-MBt. The BS-MBt exhibited the highest Cd2+ adsorption capacity (233.19 mmol kg-1) than other adsorbents. The adsorption isotherms could be well described by Langmuir model. The Cd2+ adsorption capacities on MBt and OMBts increased with an increase in pH, temperature and with a decrease of ionic strength. According to characterizations (FT-IR and XPS) and experiments, Cd2+ adsorption on MBt and OMBts most possibly involved electrostatic interaction, ion exchange, and surface complexation. Furthermore, the adsorption of Cd2+ on BS-MBt was also attributed to the chelation. The amidocyanogen group of BS-CT-MBt inhibited adsorption of Cd2+ due to electrostatic repulsion, while Cd2+ was adsorbed on BS-SDS-MBt through electrostatic attraction induced by the sulfo group.


Assuntos
Bentonita/química , Cádmio/isolamento & purificação , Tensoativos/química , Adsorção , Ânions , Cádmio/química , Cátions , Concentração de Íons de Hidrogênio , Fenômenos Magnéticos , Concentração Osmolar , Eletricidade Estática , Temperatura , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação
10.
Chemosphere ; 238: 124693, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31524627

RESUMO

In this work, self-assembled gels were prepared with exfoliated montmorillonite and chitosan (EMCG) as the adsorbent for removing methyl orange (MO) from water in absence and presence of methylene blue (MB). Several techniques including scanning electron microscope (SEM), zeta potential, fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used for the characterization of the EMCG before and after removal of MO. The EMCG performed well in the removal of MO attributing to the electrostatic attraction, cation exchange and hydrogen bond. The adsorption behaviors were followed pseudo-second-order and Langmuir isotherm. More surprisingly, the maximum adsorption capacity of MO was obviously enhanced in the presence of MB that it increased from 545 mg g-1 (absence of MB) to 1060 mg g-1 with the shielding effect of MB on EMCG which allowed MO and MB to alternately arrange at the adsorption sites. This finding of the synergistic effect between the two dyes on the proposed composite opens up new vistas to imagine the enhanced purification of the wastewater with multiple dyes co-existed using the multifunctional adsorbents.


Assuntos
Compostos Azo/análise , Bentonita/química , Quitosana/química , Azul de Metileno/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Compostos Azo/química , Corantes/química , Géis , Espectroscopia Fotoeletrônica , Espectroscopia de Infravermelho com Transformada de Fourier , Águas Residuárias/química , Poluentes Químicos da Água/química
11.
Ecotoxicol Environ Saf ; 187: 109763, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31644987

RESUMO

An eco-friendly corncob biochar based montmorillonite composite (Cc-Mt) was synthesized for the single adsorption and co-adsorption of lead (Pb(II)) and a pharmaceutical emerging organic contaminant Atenolol (ATE). In single adsorption system, the maximum equilibrium capacity of Cc-Mt for Pb (II) and ATE were 139.78 mg g-1 and 86.86 mg g-1, respectively, but for montmorillonite just 98.69 mg g-1 and 69.68 mg g-1, for corncob biochar just 117.54 mg g-1 and 47.29 mg g-1. Meanwhile,co-adsorption properties of ATE and Pb(II) on Cc-Mt composite were performed and found that the influence of ATE on the adsorption of Pb(II) was greater than the effect of Pb(II) on that of ATE. Moreover, Multiwfn program based on quantum chemical calculation was used to quantitatively analyze electrostatic potential (ESP) distribution, average local ionization energy (ALIE) distribution and their minimum points on neutral ATE and protonated ATE (PATE) molecules to reveal the microscopic adsorption mechanism of Cc-Mt composite to ATE, the results showed that the amino N and amide oxygen atom were easier to provide lone pair of electrons, generating hydrogen bonds or strong electrostatic interactions with functional groups on the surface of Cc-Mt, meanwhile hydroxyl O atom was also a possible reaction site. For PATE molecules, only the oxygen atom of the amide group was the most likely reactive site.


Assuntos
Atenolol/análise , Bentonita/química , Carvão Vegetal/química , Chumbo/análise , Poluentes Químicos da Água/análise , Adsorção , Íons , Cinética , Modelos Teóricos , Propriedades de Superfície , Purificação da Água/métodos
12.
Ecotoxicol Environ Saf ; 187: 109712, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31654867

RESUMO

Mycotoxicosis is the second most important problem faced by the Pakistan poultry industry, after high feed prices. The present experimental study was designed to investigate the toxicopathological effects of aflatoxin B1 (AFB1) in commercial broiler chicks and its amelioration with locally produced mycotoxin binder. Total of 125 broiler chicks was divided into five equal groups (A-E). Group A served as negative control, group B (300 µg AFB1/kg feed) as positive control, group C (300 µg AFB1/kg + Local Mycotoxin Binder (LMB), 1 g/kg feed), group D (300 µg AFB1/kg + 2 g LMB/kg feed), and group E (300 µg AFB1/kg + Commercial Mycotoxin Binder (CMB), 2 g/kg of feed). Parameters studied included mortality, feed intake, bodyweights, absolute and relative organ weights, and gross and microscopic lesions in visceral organs. Clinical signs including alertness, fecal consistency, and feather shine were significantly lower in group B compared with control group A. The feed intake of 2 g/kg LMB treated group was significantly higher than that of the positive control group B. Also mean bodyweights of group D birds was higher than that of group B birds indicating an ameliorative effect of LMB. Histopathological results showed that moldy feed produced necrotic changes in the liver and kidneys in group B birds. However, in group D and E birds, the hepatic and renal parenchyma was normal, showing a protective effect of LMB. In the present study, a higher dose of LMB (2 g/kg) in group D showed higher bodyweights and feed intake. In group D, birds hepatic and renal parenchyma was also normal. The results suggested that local mycotoxin binder ameliorated the toxicopathological effects of AFB1 in mortality, feed intake, bodyweights, organ weights and, gross and microscopic lesions in visceral organs. These ameliorative effects of LMB were dose-dependent. The results of the present study concluded that AFB1 intoxication leads to decrease in bodyweights, feed intake in dose-related manner. The mortality was also dose-dependent. Gross and microscopic changes in the aflatoxin groups were more pronounced, however, all these deleterious effects were ameliorated in higher dose of LMB (group D) and CMB (group E). In group C, these deleterious effects were partially ameliorated. Local mycotoxin binder is an economical solution for aflatoxicosis problem, making poultry production more cost-effective.


Assuntos
Aflatoxina B1/toxicidade , Ração Animal/análise , Contaminação de Alimentos/prevenção & controle , Micotoxicose/prevenção & controle , Doenças das Aves Domésticas/prevenção & controle , Aflatoxina B1/química , Animais , Bentonita/administração & dosagem , Bentonita/química , Galinhas , Contaminação de Alimentos/análise , Rim/efeitos dos fármacos , Rim/patologia , Fígado/efeitos dos fármacos , Fígado/patologia , Micotoxicose/veterinária , Tamanho do Órgão , Paquistão , Saccharomyces cerevisiae/química
13.
Food Chem ; 305: 125484, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31514048

RESUMO

Grape pathogenesis-related proteins can cause haze in wine that is undesirable for consumers. Bentonite is used to remove these proteins but is a non-renewable natural material and reduces wine volume due to poor settling. As a potential bentonite alternative, grape seeds powder (GSP) was added to four wines and two grape juice varieties. Addition to wine required high doses (25-32 g/L) for protein removal and haze prevention and this induced changes to wine composition. By contrast, addition to grape juice prior to fermentation required substantially lower doses of GSP (5 g/L) to prevent haze formation. Further 20 g/L of GSP added to the must induced less changes to wine composition than direct addition of GSP to the wine. No changes were recorded in the efficacy of protein removal by changing the GSP source (red or white grape marc), or by using grape seed roasting. Despite the need for additional trials, these preliminary results suggest that GSP may be considered as a viable alternative to bentonite especially when added to juice prior to fermentation.


Assuntos
Pós/química , Vitis/química , Adsorção , Bentonita/química , Cor , Estudos de Viabilidade , Qualidade dos Alimentos , Sucos de Frutas e Vegetais/análise , Proteínas de Plantas/química , Sementes/química , Sementes/metabolismo , Vitis/metabolismo , Vinho/análise
14.
Chemosphere ; 245: 125643, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31877460

RESUMO

The cationic surfactants cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC) can exert inhibitory effects on micro-organisms responsible for their biodegradation. However, under environmentally relevant exposure scenarios the presence of and sorption to organic and inorganic matter can lead to significant reduction of inhibitory effects. In our studies we investigated silica gel and seven clays as inert sorbents to mitigate these inhibitory effects in a 28 day manometric respirometry biodegradation test. CTAB was not inhibitory to the used inoculum, but we did observe that seven out of eight sorbents increased maximum attainable biodegradation, and four out of eight decreased the lag phase. The strongly inhibitory effect of CPC was successfully mitigated by most sorbents, with five out of eight allowing >50% biodegradation within 28 days. Results further indicate that bioaccessibility of the sorbed fractions in the stirred manometric test systems was higher than in calmly shaken headspace test systems. Bioaccessibility might also be limited depending on characteristics of test chemical and sorbent type, with montmorillonite and bentonite apparently providing the lowest level of bioaccessibility with CPC. Clay sorbents can thus be used as environmentally relevant sorbents to mitigate potential inhibitory effects of test chemicals, but factors that impede bioaccessibility should be considered. In addition to apparently increased bioaccessibility due to stirring, the automated manometric respirometry test systems give valuable and highly cost-effective insights into lag phase and biodegradation kinetics; information that is especially relevant for test chemicals of gradual biodegradability.


Assuntos
Biodegradação Ambiental , Argila/química , Desinfetantes/química , Adsorção , Silicatos de Alumínio/química , Bentonita/química , Cátions , Cetilpiridínio , Tensoativos/química
15.
Mater Sci Eng C Mater Biol Appl ; 105: 110048, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31546367

RESUMO

A simple, inexpensive, highly sensitive, selective, and novel electrochemical method was developed for determination of the Bisphenol A in samples of tap water, blood serum, and urine using a bentonite-modified carbon paste electrode. The graphite, bentonite and the working electrodes (without and chemically modified) were characterized by scanning electron microscopy, infrared absorption spectroscopy, and X-ray diffraction. The electrodes were electrochemically characterized using cyclic voltammetry, square wave voltammetry, and electrochemical impedance spectroscopy. The studied electrochemical variables were: electrode area, standard heterogeneous rate constant, charge transfer coefficient and double-layer capacitance. The bentonite as a sensor modifier had a strong influence on these variables. For the development of the methodology to quantify Bisphenol A, the instrumental parameters (frequency, amplitude, and step potential) and experimental parameters (pH, bentonite quantity) were optimized. The analytical curve to Bisphenol showed a linear response of the oxidation peak current intensity vs. the concentration in the range of 6.8 × 10-10 to 1.5 × 10-8 mol mL-1, with a limit of detection (LOD) of 2.11 × 10-11 mol mL-1 and limit of quantification (LOQ) of 7.04 × 10-11 mol mL-1. Recovery experiments were performed by adding known amounts of Bisphenol A in tap water, blood serum, and urine samples. Recovery rates using the standard addition method were in the range of 97.8-101.8%. The results demonstrated the method feasibility for quantifying Bisphenol A in these samples.


Assuntos
Bentonita/química , Compostos Benzidrílicos/análise , Técnicas Eletroquímicas , Fenóis/análise , Eletrodos , Grafite/química , Limite de Detecção , Oxirredução
16.
Chemosphere ; 235: 1180-1188, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31561309

RESUMO

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are a class of highly persistent contaminants with high bioaccumulation and toxicity. Our previous studies showed that perfluorooctanoic acid (PFOA) can be completely defluorinated under UV irradiation in organo-montmorillonite/indole acetic acid (IAA) system. However, there is still lack of information for the degradation mechanism and the test for wastewater treatment. Here, we systematically investigated the defluorination reaction in the presence of different organo-montmorillonites and found that the degradation process was apparently controlled by the configuration of surfactants. In hexadecyltrimethyl ammonium (HDTMA)-modified montmorillonite, HDTMA exists as a tilt conformation and isolated clay interlayer from the aqueous solution, protecting hydrated electrons generated by photo-irradiation of IAA from quenching by oxygen. Defluorination hydrogenation process was the dominant degradation pathway. While in poly-4-vinylpyridine-co-styrene (PVPcoS)-modified montmorillonite, due to the multiple charges of PVPcoS, a flat conformation parallel to clay surface was expected. Hydroxyl radicals, which were generated by the reaction of hydrated electrons with oxygen molecules diffused into clay interlayer, are also involved in the degradation process. Our results further demonstrate that mixture modified montmorillonite could combine the advantages of both modifications, thus showing superior reactivity even for actual industrial wastewater without any pretreatment. This technique would have great potential for treatment of actual wastewater.


Assuntos
Bentonita/química , Caprilatos/química , Argila/química , Elétrons , Fluorcarbonetos/química , Tensoativos/química , Adsorção , Radical Hidroxila/química , Conformação Molecular , Purificação da Água/métodos
17.
Undersea Hyperb Med ; 46(4): 447-459, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31509901

RESUMO

Introduction: The mining and tunneling industries are historically associated with hazardous exposures that result in significant occupational health concerns. Occupational respiratory exposures causing pneumoconiosis and silicosis are of great concern, silicosis being non-curable. This work demonstrates that compressed-air workers (CAWs) performing tunnel hyperbaric interventions (HIs) may be at risk for hazards related to bentonite exposure, increasing the likelihood of developing harmful illnesses including cancer. Bentonite dust inhalation may result in respiratory levels of silica exceeding acceptable industrial hygiene standards. Methods: A qualitative observational exposure assessment was conducted on CAWs while they were performing their HI duties. This was followed by quantitative data collection using personal and area air sample techniques. The results were analyzed and interpreted using standard industrial hygiene principles and guidelines from NIOSH and OSHA. Results: Our work suggests bentonite dust exposure may be an emerging particulate matter concern among CAWs in the tunneling industry. Aerosolized bentonite particles may have potential deleterious effects that include pneumoconiosis and silicosis. Silicosis can result in the development of pulmonary carcinoma. Conclusions: The modern tunneling industry and required hyperbaric interventional tasks represent a potential public health and occupational concern for CAWs. This paper introduces the modern tunneling industry and the duties of CAWs, the hazardous environment in which they perform their duties, and describes the risks and potential harmful health effects associated with these hazardous exposures.


Assuntos
Bentonita/toxicidade , Ar Comprimido , Materiais de Construção/toxicidade , Poeira , Arquitetura de Instituições de Saúde , Exposição Ocupacional/efeitos adversos , Poluentes Ocupacionais do Ar/química , Poluentes Ocupacionais do Ar/toxicidade , Bentonita/química , Indústria da Construção , Materiais de Construção/análise , Segurança de Equipamentos , Filtração/instrumentação , Humanos , Pressão , Pesquisa Qualitativa , Dispositivos de Proteção Respiratória , Estados Unidos , United States Occupational Safety and Health Administration/normas
18.
Anal Chim Acta ; 1082: 152-164, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31472704

RESUMO

Development of simultaneous bacteria detection and eradication with simple, rapid, and reusable material is important in addressing bacterial contamination issues. In this study, we utilized the expression of alkaline phosphatase (ALP) from bacteria to design fluorescence ON/OFF system for bacteria detection, also using metal oxide nanoparticle for obtaining antibacterial activity and recyclability. The fluorescent-based biosensor with antibacterial activity was prepared by intercalating ALP-sensitive polymer dot (PD) containing ß-cyclodextrin (ß-CD) onto montmorillonite (MMT) as loading matrix via ionic exchange reaction, followed by immobilization of magnetic iron oxide (Fe3O4) and NIR-responsive cesium tungsten oxide (CsWO3). The PD-ßCD-MMT/Fe3O4-CsWO3 nanocomposite exhibited strong fluorescence intensity, which was quenched in the presence of bacterial ALP (0-1000 U/L) due to hydrolysis of p-nitrophenyl phosphate (NPP) into p-nitrophenol (NP) in the hydrophobic site of ß-CD. Furthermore, the nanocomposite could detect both gram-negative Escherichia coli and gram-positive Staphylococcus aureus in the range of 101-107 CFU/mL (LOD 5.09 and 4.62 CFU/mL, respectively), and showed high antibacterial activity against bacteria by generating photothermal heat under 5 min NIR irradiation, causing damage to bacterial cells. This material also demonstrated recyclability via magnetic field exposure due to the presence of Fe3O4. In addition, the fluorescence can be recovered following pH shock and re-conjugation of ß-CD molecules. After 4 cycles, nanocomposite still showed stable photothermal effects and fluorescence-based bacteria detection. Thus, this reusable material offers promising approach for simultaneous bacteria detection and killing, which is simple, rapid, and effective.


Assuntos
Fosfatase Alcalina/química , Antibacterianos/farmacologia , Escherichia coli/isolamento & purificação , Nanopartículas de Magnetita/química , Pontos Quânticos/química , Staphylococcus aureus/isolamento & purificação , Antibacterianos/química , Bentonita/química , Césio/química , Césio/efeitos da radiação , Colorimetria/instrumentação , Colorimetria/métodos , Reutilização de Equipamento , Escherichia coli/efeitos dos fármacos , Calefação , Raios Infravermelhos , Limite de Detecção , Nanopartículas de Magnetita/efeitos da radiação , Testes de Sensibilidade Microbiana/instrumentação , Testes de Sensibilidade Microbiana/métodos , Nanocompostos/química , Nitrofenóis/química , Compostos Organofosforados/química , Polímeros/química , Staphylococcus aureus/efeitos dos fármacos , Compostos de Tungstênio/química , Compostos de Tungstênio/efeitos da radiação , beta-Ciclodextrinas/química
19.
Environ Pollut ; 255(Pt 1): 113180, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31525559

RESUMO

Despite the strong association of azithromycin (AZM), a macrolide antibiotic, and levofloxacin (LVF), a quinolone antibiotic, to sediment, sorption data are scarce. We conducted sorption experiments with eight river sediments, their major clay minerals (illite and chlorite), a highly negatively charged clay mineral (montmorillonite), and an organic-matter-rich soil (Andosol). The sorption of AZM and LVF to the sediments was influenced by the concentration and type of coexisting inorganic cations as much as by reported organic cations. In addition, their linear sorption coefficients (Kd) to sediments were correlated with cation exchange capacity (CEC) but not organic carbon content, so cation exchange is the dominant sorption mechanism. Multiple linear regression analysis showed improved prediction of sediment Kd from CEC contributed by minerals and organic matter for AZM, but not for LVF. Kcec (= Kd/CEC) values of AZM were 2-3 orders of magnitude higher on minerals than on Andosol, but those of LVF ranged within a factor of 4. Therefore, mineral and organic components need to be separated in estimating AZM sorption to sediments. Sediment Kd values of AZM and LVF were satisfactorily predicted by a cation-exchange-based model using individual Kcec values on illite, chlorite, and Andosol (mean absolute error of 0.57 and 0.22 log units, respectively). Kcec values on montmorillonite and chlorite ranged within a factor of about 3 from those of illite for both antibiotics, and Kcec differences by mineral type would generally be negligible in model estimation. Because AZM was sorbed mostly to minerals in sediments, the model and sorption data can be applicable to various soils or sediments. Overall, the trend of LVF sorption corresponds to reported sorption of other organic cations, whereas remarkably higher AZM Kcec to minerals than to Andosol is attributable to its large lactone ring, higher molecular weight, or two charged amines.


Assuntos
Antibacterianos/química , Azitromicina/química , Levofloxacino/química , Poluentes do Solo/química , Solo/química , Adsorção , Bentonita/química , Cátions , Argila/química , Sedimentos Geológicos/química , Minerais/química , Rios/química , Poluentes da Água/química
20.
Chemosphere ; 236: 124384, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31545191

RESUMO

This study evaluates a novel adsorbent for ciprofloxacin (CPX) removal from water using a composite derived from municipal solid waste biochar (MSW-BC) and montmorillonite (MMT). The composite adsorbent and pristine materials were characterized using powder X-Ray Diffraction (PXRD), Fourier-Transform Infrared (FTIR) spectroscopy, and Scanning Electron Microscope (SEM) before and after the adsorption. Batch experiments were conducted to study the mechanisms involved in the adsorption process. Ciprofloxacin sorption mechanisms were interpreted in terms of its pH-dependency and the distribution coefficients. The SEM images confirmed the successful binding of MMT onto the MSW-BC through flaky structure along with a porous morphology. Encapsulation of MMT onto MSW-BC was exhibited through changes in the basal spacing of MMT via PXRD analysis. Results from FTIR spectra indicated the presence of functional groups for both pristine materials and the composite that were involved in the adsorption reaction. The Hill isotherm model and pseudo-second-order and Elovich kinetic models fitted the batch sorption data, which explained the surface heterogeneity of the composite and cooperative adsorption mechanisms. Changes made to the MSW-BC through the introduction of MMT, enhanced the active sites on the composite adsorbent, thereby improving its interaction with ionizable CPX molecules giving high sorption efficiency.


Assuntos
Antibacterianos/isolamento & purificação , Bentonita/química , Carvão Vegetal/química , Ciprofloxacino/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Antibacterianos/química , Ciprofloxacino/química , Cinética , Resíduos Sólidos/análise , Espectroscopia de Infravermelho com Transformada de Fourier , Poluentes Químicos da Água/química , Purificação da Água/instrumentação
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