RESUMO
Films made from neat chitosan and chitosan with magnetic nanoparticles (MNPs) were tested as adsorbents of arsenate ions. Sorption equilibrium and sorption kinetics studies are reported, including different models applied to enlighten experimental observations and predict results. The sorption of As (V) was reasonably explained using Freundlich isotherm for neat chitosan film although it was better represented by Langmuir equation for the composite sample. The experimental kinetics results showed that the adsorption of arsenate ions is very fast during the first minutes and then the composite seems to reach saturation, while a slow desorption in the chitosan film was observed and acceptably fitted with a pseudo first order reversible model. The adsorbent containing MNPs presented higher adsorption capacity, which was associated to the additional adsorbent capacity provided by the MNPs and its much more irregular surface area that leads to an enhanced adsorption surface. For instance, at 10 mg/L equilibrium concentration, which corresponds to an initial concentration of As (V) much higher than the normal concentration of arsenate in natural water, chitosan-MNP sample exhibits a removal capacity of 10.4 mg/g that is more than six times higher than the 1.6 mg/g shown by the chitosan film.
Assuntos
Arsênio/isolamento & purificação , Quitosana/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção/efeitos dos fármacos , Arsênio/toxicidade , Compostos Férricos/química , Cinética , Nanopartículas/química , Água/química , Poluentes Químicos da Água/toxicidadeRESUMO
The aim of this work is to evaluate the application of a steel waste, basic oxygen furnace sludge (BOFS), rich in iron, to treat water contaminated with elevated arsenic and sulfate concentrations. In the first step, three doses (10, 60, and 80 g L-1) of BOFS were tested to investigate the removal of As(III) and As(V) (67 mg L-1) and sulfate (3700 mg L-1) separately from an aqueous solution. In the second step, the efficacies of BOFS (10 g L-1) and commercial ZVI (5 g L-1) were compared to simultaneously remove arsenic and sulfate. The pH of the feed solution was adjusted to 2.5 and monitored during the experiment. The use of BOFS achieved arsenic removal up to 92% and sulfate removal of nearly 40% after 72 h of contact time. Use of BOFS also increased the solution pH to 12. Similar removal levels were achieved with both BOFS and ZVI. These results confirm the potential application of BOFS to remove high arsenic and sulfate concentrations from acidic solutions. The data obtained here should be used as a basis for further studies on the remediation of acid mine drainage with high concentrations of arsenic and sulfate using an abundant and low-cost steel waste.
Assuntos
Arsênio/isolamento & purificação , Sulfatos/isolamento & purificação , Resíduos , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Concentração de Íons de Hidrogênio , Resíduos Industriais , Ferro , AçoRESUMO
The present work introduces a simple methodology of carbon modification with zirconium, using an organic complexing ligand, as efficient media for selective As(V) removal. It is hypothesized that the incorporation of Zr-nanoparticles improves the attraction of anionic species such as arsenates (HAsO42-/H2AsO4-) making the material highly selective. The effects of pH (3-11) and temperature (15, 25 and 35⯰C) were studied. Furthermore, potentiometric titrations, the effect of competing anions, thermodynamics, and adsorption kinetics were evaluated in order to clarify the rate-controlling process and the adsorption mechanism for arsenic removal. Results demonstrated that OH and COOH groups play an important role during the arsenic adsorption process; a small amount of Zr(IV) species (0.77%) increased the adsorption capacity of activated carbon in about a 43%. Thermodynamic analysis showed the spontaneous exothermic nature of the adsorption process was favored at lower temperatures. The presence of anions, such as chloride, sulfate, carbonate, nitrate and phosphate, did not affect the adsorption capacity, while kinetic studies demonstrated that the arsenic adsorption process in Zr-modified activated carbon is not exclusively controlled by intraparticle diffusion.
Assuntos
Arsênio/isolamento & purificação , Carvão Vegetal , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Carbono , Concentração de Íons de Hidrogênio , Cinética , TermodinâmicaRESUMO
Jarosite [KFe3(SO4)2(OH)6] minerals are effective scavengers of potentially toxic elements (PTEs) and are abundant, for example, in acid rock/mine drainage scenarios. The retention process is highly relevant for environmental attenuation of heavy metals and metalloids since these are usually highly soluble and thus mobile under acidic conditions. We investigated both macroscopically and at the molecular scale the extent and the effects of concomitant incorporation of As(v) and Pb(ii) into synthetic jarosite at different As/Pb starting molar ratios, using XRD-Rietveld, SEM, ATR-FTIR spectroscopy and wet chemistry. The amount of arsenate substituted in the jarosite structure was larger when Pb(ii) was also incorporated, the former filling up to approximately 33% of the tetrahedral sites normally occupied by SO42-, as compared to 21% when Pb(ii) was absent. Similarly, the amount of Pb(ii) incorporated in the structure was larger when As(v) was also taken up. The jarosite unit cell volume increased as higher amounts of As(v) incorporated into its structure, but simultaneous Pb(ii) incorporation seemed to limit this increase due to its smaller size as compared to K+. The extent to which As and Pb can accommodate in the jarosite structure was found to be limited by concentration maxima under the imposed synthesis conditions. At As/Pb ratios up to 1, Pb-As-jarosites were the only crystalline products. Above this ratio, a mixture of Pb-As-jarosite, anglesite (PbSO4) and poorly-crystalline ferric arsenate (AFA) phases was observed. At the highest As/Pb ratio investigated of 1.80 Pb-As-jarosite was no longer formed. Infrared spectroscopy analysis was applied for the first time here to substituted jarosites with both cations and anions, showing spectral changes in the solids as the As/Pb ratio increased: a characteristic As-O doublet at â¼810 and â¼855 cm-1 was observed upon Pb incorporation, showing an indirect effect of Pb(ii) on the As-O bonds in the jarosite structure. Thus, structural incorporation of Pb plays a pivotal role in the unit cell environment of jarosite to balance the distortion caused by AsO4-for-SO4 substitution. The retention processes found in this work have important environmental implications and impacts: through the synergistic incorporation encountered, remediation enhancement of cationic pollutants such as Pb(ii) is possible in a concomitant fashion with As(v) attenuation in acidic mining and metallurgical environments.
Assuntos
Arsênio/isolamento & purificação , Poluentes Ambientais/isolamento & purificação , Compostos Férricos/química , Chumbo/isolamento & purificação , Minerais/química , Sulfatos/química , Sinergismo Farmacológico , Recuperação e Remediação Ambiental , MineraçãoRESUMO
The application of different ionic liquids (ILs) as modifiers for chromatographic separation and determination of arsenite [As(III)], arsenate [As(V)], dimethylarsonic acid (DMA) and monomethylarsonic acid (MMA) species in wine samples, by reversed-phase high performance liquid chromatography coupled to hydride generation atomic fluorescence spectrometry detection (RP-HPLC-HG-AFS) was studied in this work. Several factors influencing the chromatographic separation of the As species, such as pH of the mobile phase, buffer solution concentration, buffer type, IL concentration and length of alkyl groups in ILs were evaluated. The complete separation of As species was achieved using a C18 column in isocratic mode with a mobile phase composed of 0.5% (v/v) 1-octyl-3-methylimidazolium chloride ([C8mim]Cl) and 5% (v/v) methanol at pH 8.5. A multivariate methodology was used to optimize the variables involved in AFS detection of As species after they were separated by HPLC. The ILs showed remarkable performance for the separation of As species, which was obtained within 18min with a resolution higher than 0.83. The limits of detection for As(III), As(V), MMA and DMA were 0.81, 0.89, 0.62 and 1.00µg As L(-1). The proposed method was applied for As speciation analysis in white and red wine samples originated from different grape varieties.
Assuntos
Arsênio/análise , Arsênio/isolamento & purificação , Líquidos Iônicos/química , Espectrometria de Fluorescência/métodos , Espectrofotometria Atômica/métodos , Vinho/análise , Arsênio/química , Arsenicais/análise , Arsenicais/isolamento & purificação , Arsenitos/análise , Arsenitos/isolamento & purificação , Soluções Tampão , Cromatografia Líquida de Alta Pressão , Concentração de Íons de Hidrogênio , Limite de Detecção , Vitis/química , Vitis/classificaçãoRESUMO
The contamination of water with arsenic has aroused concern around the world due to its toxic effects. Thus, the development of low-cost technologies for treating water contaminated with toxic metals is highly advisable. Adsorption is an attractive technology for purification of contaminated water, but it only transfers the contaminant from water to the solid adsorbent, which provokes another problem related to solid residue disposal. In this work, we developed a sustainable method for purifying water contaminated with arsenic by using δ-FeOOH nanoparticles. The adsorption capacities of nanomaterial for As3+ and As5+ species were 40 and 41 mg g-1, respectively, and were highly efficient to purify arsenic-contaminated water from a Brazilian river. The concentration of arsenic in water was close to zero after the water treatment by δ-FeOOH. Once the arsenic is adsorbed, it can be recovered by treatment with NaOH solutions. Approximately 85 % of the total adsorbed arsenic could be recovered and used as a precursor to produce useful material (Ag3AsO4) with excellent photocatalytic activity. It was active under visible light and had a high recyclability for oxidation of rhodamine B. Finally, the simple method described is promising to design sustainable process of environmental remediation with minimum residue generation.
Assuntos
Arsênio/isolamento & purificação , Nanopartículas Metálicas/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Arseniatos/química , Brasil , Concentração de Íons de Hidrogênio , Oxirredução , Fotólise , Reciclagem , Prata/química , Termodinâmica , Água , Abastecimento de ÁguaRESUMO
New methods to remediate arsenic-contaminated water continue to be studied, particularly to fill the need for accessible methods that can significantly impact developing communities. A combination of cactus mucilage and ferric (Fe(III)) salt was investigated as a flocculation-coagulation system to remove arsenic (As) from water. As(V) solutions, ferric nitrate, and mucilage suspensions were mixed and left to stand for various periods of time. Visual and SEM observations confirmed the flocculation action of the mucilage as visible flocs formed and settled to the bottom of the tubes within 3 min. The colloidal suspensions without mucilage were stable for up to 1 week. Sample aliquots were tested for dissolved and total arsenic by ICP-MS and HGAFS. Mucilage treatment improved As removal (over Fe(III)-only treatment); the system removed 75-96% As in 30 min. At neutral pH, removal was dependent on Fe(III) and mucilage concentration and the age of the Fe(III) solution. The process is fast, achieving maximum removal in 30 min, with the majority of As removed in 10-15 min. Standard jar tests with 1000 µg/L As(III) showed that arsenic removal and settling rates were pH-dependent; As removal was between 52% (high pH) and 66% (low pH).
Assuntos
Arsênio/isolamento & purificação , Cactaceae/química , Compostos Férricos/química , Nitratos/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Arsênio/análise , Concentração de Íons de HidrogênioRESUMO
A combined system employing photochemical oxidation (UV/H2O2) and adsorption for arsenic removal from water was designed and evaluated. In this work, a bench-scale photochemical annular reactor was developed being connected alternately to a pair of adsorption columns filled with titanium dioxide (TiO2) and granular ferric hydroxide (GFH). The experiences were performed by varying the relation of As concentration (As (III)/As (V) weight ratio) at constant hydrogen peroxide concentration and incident radiation. Experimental oxidation results were compared with theoretical predictions using an intrinsic kinetic model previously obtained. In addition, the effectiveness of the process was evaluated using a groundwater sample. The mathematical model of the entire system was developed. It could be used as an effective tool for the design and prediction of the behaviour of these types of systems. The combined technology is efficient and promising for arsenic removal to small and medium scale.
Assuntos
Arsênio/isolamento & purificação , Compostos Férricos/química , Titânio/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Arsênio/efeitos da radiação , Estudos de Viabilidade , Peróxido de Hidrogênio , Cinética , Oxirredução , Fotólise , Raios Ultravioleta , Água , Poluentes Químicos da Água/efeitos da radiaçãoRESUMO
The objective of this work was to investigate the interaction of arsenic species (As(III) and As(V)) with tropical peat. Peat samples collected in Brazil were characterized using elemental analysis and 13C NMR. Adsorption experiments were performed using different concentrations of As with peat in natura and enriched with Fe or Al, at three different pH levels. Peat samples, in natura or enriched with metals, were analysed before and after adsorption processes using Fourier transform infrared spectroscopy (FTIR) spectroscopy. The adsorption kinetics was evaluated, and the data were fitted using the Langmuir and Freundlich models. The results showed that interaction between As and peat was dependent on the levels of organic matter (OM) and the metals (Fe and Al). As(III) was not adsorbed by in natura peat or Al-enriched peat, although small amounts of As(III) were adsorbed by Fe-enriched peat. Adsorption of As(V) by the different peat samples ranged from 21.3 to 52.7 µg g(-1). The best fit to the results was obtained using the pseudo-second-order kinetic model, and the adsorption of As(V) could be described by the Freundlich isotherm model. The results showed that Fe-enriched peat was most effective in immobilizing As(V). FTIR analysis revealed the formation of ternary complexes involving As(V) and peat enriched with metals, suggesting that As(V) was associated with Al or Fe-OM complexes by metal bridging.
Assuntos
Alumínio/química , Arsênio/isolamento & purificação , Ferro/química , Compostos Orgânicos/química , Poluentes do Solo/química , Poluentes do Solo/isolamento & purificação , Adsorção , Arsênio/química , Recuperação e Remediação Ambiental , Solo/química , Ultrafiltração/métodosRESUMO
In this study, a method is proposed for the selective retention of As(V) using diffusive gradient in thin film (DGT) samplers containing a strongly basic anion exchange resin (Amberlite IRA 910) supported on a polyacrylamide gel. In addition, the total arsenic content is determined by ferrihydrite gel discs. Subsequently, the concentration of As(III) was obtained by determining the difference between the total As and As(V). DGT experiments showed linear accumulation of As(V) (up to 280 ng) until a deployment time of 8 h deployment (R(2) > 0.99). The retention of As(V) was appropriate (97.9-112.3%) between pH 5 and 9. For a solution with an ionic strength ranging from 0.001 to 0.05 mol L(-1), the As(V) uptake ranged from 90-120%. The proposed method was applied for the speciation of arsenic in river water. For the analysis of spiked samples collected at the Furnas stream, the recoveries of total arsenic content ranged between 103.9% and 118.8%. However, the recoveries of As(III) and As(V) were 43.3-75.2% and 147.3-153.4%, respectively. These differences were probably because of the oxidation of As(III) to As(V) during deployments. For spiked samples collected at the Ribeirão Claro, the recoveries of dissolved As(III), As(V) and As(T) were 103.1%, 108.0% and 106.3%, respectively. Thus, the DGT technique with Amberlite IRA 910 resin as the binding phase can be employed for the in situ redox speciation of inorganic arsenic.
Assuntos
Resinas Acrílicas/química , Arseniatos/análise , Arsênio/análise , Arsenitos/análise , Resinas Sintéticas/química , Rios/química , Poluentes Químicos da Água/análise , Arseniatos/isolamento & purificação , Arsênio/isolamento & purificação , Arsenitos/isolamento & purificação , Difusão , Monitoramento Ambiental/métodos , Compostos Férricos/química , Concentração Osmolar , Oxirredução , Poluentes Químicos da Água/isolamento & purificaçãoRESUMO
The aim of this study was to investigate the presence of arsenic, lead and cadmium residues in samples of liver, kidney and muscle of poultry and swine during the years from 2002 to 2008. A total of 1978 samples were analyzed: 1031 of poultry and 947 of swine from Brazilian slaughterhouses. The samples were analyzed at the National Agricultural Laboratory using the atomic absorption spectrometry technique. In poultry, the arsenic residues were detected in 53.6% of liver samples, although no results have exceeded the MRL. In kidneys, 39.7% of the samples showed measurable residues and there was no violation of the limits. Regarding lead, there were 5 contaminated liver samples and 24 contaminated kidney samples (1.5 and 3.6% respectively). In muscle tissue there was only one sample with residues. For cadmium, 3.8% of the samples were found below MRL. Cadmium residues were found in 110 kidney samples (16.3% of tested), but only one exceeded the legislation limits. In swine, arsenic residues were detected in 15.3% of liver samples, although no results exceeded the MRL. In kidneys, 14.2% of samples showed measurable residues. However, there was no violation of limits. Regarding lead levels, 7 liver samples and 18 kidney samples were contaminated (2.6 and 2.7% respectively). Cadmium was found below MRL in 14.9% of the analyzed samples. In kidneys, 448 samples (67.8% of the total tested) had cadmium residues and 4 samples exceeded the legislation limits. During the seven years of study (2002-2008), only 5 (0.25%) out of 1978 tested samples violated the Brazilian law. However, even with low levels of violation, monitoring is essential, since the number of samples with residues was often greater than the number of violations, and in some cases, such as cadmium in the kidneys, the majority of samples contained quantifiable residues and with levels often near the limits.(AU)
Objetivou-se investigar a presença de resíduos de arsênico, chumbo e cádmio em amostras de fígado, rins e músculo de aves e suínos, durante os anos de 2002 a 2008. Um total de 1.978 amostras foi analisado: 1031 de aves e 947 de suínos provenientes de matadouros brasileiros. As amostras foram analisadas no Laboratório Nacional Agropecuário (Lanagro), sendo utilizada a técnica de espectrometria de absorção atômica. Em aves, os resíduos de arsênico foram detectados em 53,6% das amostras de fígado, embora sem exceder o LMR. Nos rins, 39,7% das amostras mostraram resíduos mensuráveis e não houve violação dos limites. Em relação ao chumbo, cinco amostras de fígado e 24 de amostras de rins estavam contaminadas (1,5 e 3,6%, respectivamente). No tecido muscular, houve apenas uma amostra com resíduos. Para o cádmio, 3,8% das amostras apresentavam valores abaixo do LMR. Resíduos de cádmio foram encontrados em 110 amostras de rins (16,3% testados), mas apenas uma ultrapassou o limite máximo permitido pela legislação nacional. Em suínos, resíduos de arsênico foram detectados em 15,3% das amostras de fígado, sem exceder o LMR. Nos rins, 14,2% das amostras apresentaram resíduos mensuráveis, sem, no entanto, haver violação dos limites. No que diz respeito aos níveis de chumbo, sete amostras de fígado e 18 amostras de rins estavam contaminadas (2,6 e 2,7%, respectivamente). O cádmio foi encontrado abaixo do LMR em 14,9% das amostras analisadas. Nos rins, 448 amostras (67,8% do total analisado) tinham resíduos de cádmio e quatro amostras excederam o LMR. Durante os sete anos de estudo (2002-2008), apenas cinco (0,25%) das 1.978 amostras analisadas (de aves e suínos) violaram a lei brasileira. Entretanto, mesmo com baixos níveis de violação, o controle é essencial, uma vez que o número de amostras com resíduos foi muitas vezes maior do que o número de violações e, em alguns casos, como o cádmio nos rins, a maioria das amostras continha resíduos quantificáveis e com níveis, muitas vezes, perto do LMR.(AU)
Assuntos
Animais , Aves/metabolismo , Suínos/metabolismo , Arsênio/isolamento & purificação , Chumbo/isolamento & purificação , Cádmio/isolamento & purificação , Rim , Fígado , Metais Pesados/análise , Limites Permissíveis de Riscos Ocupacionais/análise , Concentração Máxima PermitidaRESUMO
The aim of this study was to investigate the presence of arsenic, lead and cadmium residues in samples of liver, kidney and muscle of poultry and swine during the years from 2002 to 2008. A total of 1978 samples were analyzed: 1031 of poultry and 947 of swine from Brazilian slaughterhouses. The samples were analyzed at the National Agricultural Laboratory using the atomic absorption spectrometry technique. In poultry, the arsenic residues were detected in 53.6% of liver samples, although no results have exceeded the MRL. In kidneys, 39.7% of the samples showed measurable residues and there was no violation of the limits. Regarding lead, there were 5 contaminated liver samples and 24 contaminated kidney samples (1.5 and 3.6% respectively). In muscle tissue there was only one sample with residues...
Objetivou-se investigar a presença de resíduos de arsênico, chumbo e cádmio em amostras de fígado, rins e músculo de aves e suínos, durante os anos de 2002 a 2008. Um total de 1.978 amostras foi analisado: 1031 de aves e 947 de suínos provenientes de matadouros brasileiros. As amostras foram analisadas no Laboratório Nacional Agropecuário (Lanagro), sendo utilizada a técnica de espectrometria de absorção atômica. Em aves, os resíduos de arsênico foram detectados em 53,6% das amostras de fígado, embora sem exceder o LMR. Nos rins, 39,7% das amostras mostraram resíduos mensuráveis e não houve violação dos limites. Em relação ao chumbo, cinco amostras de fígado e 24 de amostras de rins estavam contaminadas (1,5 e 3,6%, respectivamente). No tecido muscular, houve apenas uma amostra com resíduos. Para o cádmio, 3,8% das amostras apresentavam valores abaixo do LMR. Resíduos de cádmio foram encontrados em 110 amostras de rins (16,3% testados), mas apenas uma ultrapassou o limite máximo permitido pela legislação nacional. Em suínos, resíduos de arsênico foram detectados em 15,3% das amostras de fígado, sem exceder o LMR. Nos rins, 14,2% das amostras apresentaram resíduos mensuráveis...
Assuntos
Animais , Arsênio/isolamento & purificação , Aves/metabolismo , Cádmio/isolamento & purificação , Chumbo/isolamento & purificação , Fígado , Rim , Suínos/metabolismo , Limites Permissíveis de Riscos Ocupacionais/análise , Concentração Máxima Permitida , Metais Pesados/análiseRESUMO
The presence of the arsenic oxidation, reduction, and extrusion genes arsC, arrA, aioA, and acr3 was explored in a range of natural environments in northern Chile, with arsenic concentrations spanning six orders of magnitude. A combination of primers from the literature and newly designed primers were used to explore the presence of the arsC gene, coding for the reduction of As (V) to As (III) in one of the most common detoxification mechanisms. Enterobacterial related arsC genes appeared only in the environments with the lowest As concentration, while Firmicutes-like genes were present throughout the range of As concentrations. The arrA gene, involved in anaerobic respiration using As (V) as electron acceptor, was found in all the systems studied. The As (III) oxidation gene aioA and the As (III) transport gene acr3 were tracked with two primer sets each and they were also found to be spread through the As concentration gradient. Sediment samples had a higher number of arsenic related genes than water samples. Considering the results of the bacterial community composition available for these samples, the higher microbial phylogenetic diversity of microbes inhabiting the sediments may explain the increased number of genetic resources found to cope with arsenic. Overall, the environmental distribution of arsenic related genes suggests that the occurrence of different ArsC families provides different degrees of protection against arsenic as previously described in laboratory strains, and that the glutaredoxin (Grx)-linked arsenate reductases related to Enterobacteria do not confer enough arsenic resistance to live above certain levels of As concentrations.
Assuntos
Arsênio/isolamento & purificação , Arsênio/metabolismo , Bactérias/genética , Bactérias/metabolismo , Meio Ambiente , Poluentes Ambientais/isolamento & purificação , Poluentes Ambientais/metabolismo , Biodegradação Ambiental , OxirreduçãoRESUMO
Multiwall carbon nanotubes (MWCNTs) were oxidized with different agents and a characterization study was carried out. Then, hybrid-magnetic nanoparticles (HMNPs) were synthesized as iron oxide supported on the selected multiwalled carbon nanotubes (MWCNTs-Fe3O4) obtained from MWCNTs oxidized with HNO3. The HMNPs characterization revealed the presence of iron oxide as magnetite onto the MWCNTs surfaces. These HMNPs were used for arsenic removal from groundwater. The adsorption process variables were optimized (concentration of NPs, contact time, and pH), and these systems could remove 39.93 mg As/g adsorbent. Therefore, these nanoparticles appear as a good alternative for removing arsenic from water samples.
Assuntos
Arsênio/química , Arsênio/isolamento & purificação , Água Subterrânea/química , Nanopartículas de Magnetita/química , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Água Subterrânea/análise , Nanopartículas de Magnetita/ultraestrutura , Tamanho da PartículaRESUMO
Arsenic is an element widely present in nature. Additionally, it may be found as different species in several matrices and therefore it is one of the target elements in chemical speciation. Although the number of studies in terrestrial plants is low, compared to matrices such as fish or urine, this number is raising due to the fact that this type of matrix are closely related to the human food chain. In speciation analysis, sample preparation is a critical step and several extraction procedures present drawbacks. In this review, papers dealing with extraction procedures, analytical methods, and studies of species conservation in plants cultivated in terrestrial environment are critically discussed. Analytical procedures based on extractions using water or diluted acid solutions associated with HPLC-ICP-MS are good alternatives, owing to their versatility and sensitivity, even though less expensive strategies are shown as feasible choices.
Assuntos
Arsênio/isolamento & purificação , Microextração em Fase Líquida/métodos , Plantas/química , Microextração em Fase Sólida/métodos , Ácidos , Arsênio/metabolismo , Transporte Biológico , Cromatografia Líquida de Alta Pressão , Conservação dos Recursos Naturais , Espectrometria de Massas , Plantas/metabolismo , Solventes , Manejo de Espécimes , Espectrofotometria Atômica , ÁguaRESUMO
The removal from the solution and the accumulation of As, Cd and Cr by Typha latifolia was studied. Small plants of T. latifolia, collected from a non-contaminated site, were exposed to individual concentrations of As, Cd and Cr for 10 days. The ability of T. latifolia for the removal of toxic elements ranged from 23% to 54% for As, 43%-55% for Cd and 28%-73% for Cr. The accumulation of toxic elements in T. latifolia occurred mainly in the roots. The results suggest that T. latifolia can be considered as an interesting alternative for treating aquatic effluents polluted with toxic trace elements.
Assuntos
Arsênio/isolamento & purificação , Cádmio/isolamento & purificação , Cromo/isolamento & purificação , Typhaceae/metabolismo , Poluentes Químicos da Água/isolamento & purificação , Arsênio/metabolismo , Biodegradação Ambiental , Cádmio/metabolismo , Cromo/metabolismo , Raízes de Plantas/metabolismo , Brotos de Planta/metabolismo , Poluentes Químicos da Água/metabolismoRESUMO
Different activated carbons modified with iron hydro(oxide) nanoparticles were tested for their ability to adsorb arsenic from water. Adsorption isotherms were determined at As (V) concentrations < 1 ppm, with varying pH (6, 7, 8) and temperature (25 and 35 °C). Also, competition effect of anions on the As (V) adsorption capacity was evaluated using groundwater. The surface areas of the modified activated carbons ranged from 632 m(2) g(-1) to 1101 m(2) g(-1), and their maximum arsenic adsorption capacity varied from 370 µg g(-1) to 1250 µg g(-1). Temperature had no significant effect on arsenic adsorption; however, arsenic adsorption decreased 32% when the solution pH increased from 6 to 8. In addition, when groundwater was used in the experiments, the arsenic adsorption considerably decreased due to the presence of competing anions (mainly SO(4)(2-), Cl(-) and F(-)) for active sites. The data from kinetic studies fitted well to the pseudo-second-order model (r(2) = 0.98-0.99). The results indicated that sample CAZ-M had faster kinetics than the other two materials in the first 10 min. However, sample F400-M was only 5.5% slower than CAZ-M. The results of this study show that iron modified activated carbons are efficient adsorbents for arsenic at concentrations lower than 300 µg L(-1).
Assuntos
Arsênio/isolamento & purificação , Carvão Vegetal/química , Compostos Férricos/química , Nanopartículas Metálicas/química , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Modelos Químicos , Temperatura , TermodinâmicaRESUMO
A highly efficient separation and pre-concentration method for arsenic species determination, based on ionic liquid (IL) dispersive microextraction technique implemented in a flow analysis system, is proposed. Highly selective separation of arsenite species [As(III)] was achieved by chelation with sodium diethyldithiocarbamate (DDTC) followed by dispersion with 40 mg of 1-octyl-3-methylimidazolium hexafluorophosphate ([C(8)mim][PF(6)]) IL. Analyte extraction, retention and separation of IL phase were achieved with a packed microcolumn and As(III) was determined in eluent solution by electrothermal atomic absorption spectrometry (ETAAS). Concentration of As(V) was deduced by the difference between total inorganic arsenic and As(III). Thus, determination of total arsenic was performed by previous degradation of organo-arsenic species, followed by a reduction. Under optimal conditions, As(III) extraction efficiency was 100% and a sensitivity enhancement factor of 46 was obtained with only 4.0 ml of sample The method was successfully applied for arsenic speciation studies in mono-varietal wines.
Assuntos
Arsênio/isolamento & purificação , Microextração em Fase Líquida/métodos , Vinho/análise , Arsênio/análise , Contaminação de Alimentos/análise , Líquidos Iônicos/química , Microextração em Fase Líquida/instrumentação , Espectrofotometria AtômicaRESUMO
This manuscript presents the synthesis of carbon modified with iron nanoparticles (CFe) and iron carbide (CarFe) from the pyrolyzed crown leaves of pineapple (Ananas comosus) treated with iron salts. The materials that were obtained were used for the removal of As(V) from aqueous media. The carbonaceous materials were characterized by Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS) and Mossbauer Spectroscopy. The specific area (BET), number site density and point of zero charge (pH(pzc)) were also determined. The kinetic parameters were obtained by fitting the experimental data to the pseudo-first-order and pseudo-second-order models. Different isotherm models were applied to describe the As(V) adsorption behavior. The kinetics of As(V) sorption by CFe and CarFe was well defined for the pseudo-second-order model (R(2) = 0.9994 and 0.999, respectively). The maximum As(V) uptake was 1.8 mg g(-1) for CFe and 1.4 mg g(-1) for CarFe. The results obtained indicated that both materials are equally useful for As(V) sorption. The As(V) experimental isotherm data were described by the Freundlich model for CFe and CarFe.
Assuntos
Ananas/química , Arsênio/isolamento & purificação , Ferro/química , Nanopartículas Metálicas/química , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Compostos Inorgânicos de Carbono/síntese química , Compostos de Ferro/síntese química , Nanopartículas Metálicas/ultraestrutura , Microscopia Eletrônica de Transmissão , Espectroscopia Fotoeletrônica , Espectroscopia de Mossbauer , Propriedades de Superfície , Termodinâmica , Purificação da Água/métodos , Difração de Raios XRESUMO
A pre-concentration procedure with solid-phase extraction was developed for the determination of arsenic (As) in chicken feed using hydride generation atomic absorption spectrometry (HG-AAS). The procedure was based on the sorption of As(III) ions as complexes with ammonium pyrrolidine dithiocarbamate onto a mini-column packed with polyurethane foam. After pre-concentration, the As was removed from the mini-column by acid solution, and the analyte content in the eluate was measured by HG-AAS. The following main experimental conditions were established: adjustment of the As solution pH with 0.05 mol l⻹ HCl, 2.88 × 10⻳ mol l⻹ complexing agent concentration and 6.0 mol l⻹ eluting hydrochloric acid concentration. The proposed method produced an enrichment factor of 67, with 0.050 and 0.165 µg g⻹ limits of detection and quantification, respectively. The procedure was applied to the determination of As content in two types of chicken feed using the proposed procedure and atomic absorption spectrometry with electrothermal atomisation (ETAAS). The t-test indicated that the results were not significantly different at a confidence level of 95%.