Photocatalytic degradation of bisphenol-A (BPA) over titanium dioxide, and determination of its by-products by HF-LPME/GC-MS.

In this work, analytical strategies were developed based on the technique of hollow fiber liquid-phase microextraction and chromatographic methods (LC-UV and GC/MS). These methods allowed the identification of the main Bisphenol-A by-products applying heterogeneous photocatalysis in water samples. BPA degradation in this study was in the order of 90%, and the conditions used in the HF-LPME were optimized through 23 factorial design (6 cm fiber length, stirring speed of 750 rpm, and an extraction time of 30 min). Using a HF-LPME/GC-MS analytical strategy, it was possible to identify six by-products of BPA photodegradation, two of which have not been reported in the literature so far. This knowledge was quite important since the degradation can lead to the formation of more toxic and persistent by-products than the BPA. With the Toxtree software, three degradation products were found to be persistent to the environment, in addition to BPA; however, in 360 minutes of reaction, chromatographic peaks of the precursors were not identified, suggesting that there may have been a total degradation of these compounds. The results showed a great application potential of a miniaturized extraction technique to extract and pre-concentrate the degradation products of emerging contaminants.

Simultaneous multi-residue pesticide analysis in southern Brazilian soil based on chemometric tools and QuEChERS-LC-DAD/FLD method.

A simple and straightforward QuEChERS extraction method was proposed for the simultaneous determination of atrazine (ATZ), desethylatrazine (DEA), desisopropylatrazine (DIA), carbaryl (CBL), carbendazim (CBD), and diuron (DIU) in soil with high agricultural activity from southeastern Brazil, using high-performance liquid chromatography-diode-array detection/fluorescence detection. Screening studies carried out by 24 factorial design indicate better recoveries when less sample (1.0 g) and the volume of solvent (2.0 mL of ACN) were applied, compared to the original QuEChERS method. Furthermore, interactions between factors were not negligible in the experimental set, except for ATZ and DIU, in which only water volume influenced their recovery. The influence of the type (primary secondary amine (PSA), C18, and Florisil) and the sorbent amount ratio to the compounds' concentration were also considered. PSA (25 mg) was selected as the best sorbent without losing analytical response. The limits of quantification (LOQ) were estimated to be 5.0 to 15 µg kg-1 in the soil matrix. Analytical performances were consistent with linearity (R2 ≥ 0.998), recovery from 74.7 to 108%, and relative standard deviations (RSD) between 2.6 and 20.2%. Robustness was assessed by fractional factorial Plackett-Burman design. The method is recommended for chemicals that are soluble in water, and it was successfully applied in the analysis of real soil samples containing the analytes in the range of µg kg-1, proving to be suitable for the study of soils strongly impacted by agricultural activity.

Understanding the nature of Fenton processes in soil matrices: The role of iron forms and organic matter.

Understanding the processes of pollutants removal in soil remediation practices is crucial to apply the appropriate treatment method. Although widely employed in soil contamination events, the mechanisms of the Fenton reaction are still debatable. To investigate the catalytic performance of soils towards the degradation of p-xylene in Fenton reactions, we performed a series of experiments employing two soil samples with different physical-chemical properties, Oxisol and Alfisol. These soils were subjected to extraction procedures that separated the different types of pedogenic iron oxides (amorphous and crystalline) and produced soil fractions with different organic matter contents. We observed that Oxisol, which contains high amounts of amorphous pedogenic iron oxides, performed better in hydrogen peroxide decomposition and radical generation but worse in p-xylene degradation. These results originated from the presence of hematite in Oxisol, which has a lower catalytic activity than goethite, the pedogenic oxide present in Alfisol. Samples containing high concentrations of organic matter performed better in decomposing hydrogen peroxide but worse in degrading p-xylene due to the scavenging of active species by labile organic matter compounds.

Relationship of the physicochemical properties of novel ZnO/biochar composites to their efficiencies in the degradation of sulfamethoxazole and methyl orange.

Three different composites were produced, based on zinc oxide and biochar (ZnO/biochar), varying the type of biomass (Salvinia molesta: SM; exhausted husk of black wattle: EH; and sugarcane bagasse: SB), with pyrolysis under mild conditions at 350 and 450 °C. Evaluation was made of the capacities of the composites for photocatalytic degradation of sulfamethoxazole antibiotic (SMX) and methyl orange dye (MO). The properties of the prepared composites were influenced by the biomass source, with larger crystallite size (SB), lower band gap energy (SM), higher specific surface area (SB), and larger pore size (SM) resulting in higher photocatalytic efficiency. Good degradation results were obtained using these innovative photocatalysts prepared at low temperatures, when compared to ZnO/biochar materials reported in previous studies. The best degradation capacities were obtained for the composites produced at 450 °C from SB and SM, with 99.3 and 97% degradation of SMX after 45 min, and 90.8 and 88.3% degradation of MO after 120 min, respectively.

Use of scavenger agents in heterogeneous photocatalysis: truths, half-truths, and misinterpretations.

Even though a gap exists in understanding the behavior of radical scavengers and interfering species, they have been extensively employed to elucidate degradation mechanisms or to improve the degradation efficiency in heterogeneous photocatalysis. Focusing on the influence of different species, such as scavengers (t-butanol, formic acid, methanol, p-benzoquinone, oxalate, superoxide dismutase, and azide), interfering species (sulfite, dichromate, bromate, carbonate, chloride, and iodide) and inorganic ions (nitrate, sulfate, and phosphate), this work investigated the production of hydroxyl radicals and singlet oxygen during TiO2/UVA reactions. Electron paramagnetic resonance spectroscopy (EPR) was applied to investigate radicals formed in the presence of each interfering/scavenger species. Some scavengers and interfering species were studied during phenol degradation, chosen as a model substrate. All species, except bromate, hindered the degradation. para-Benzoquinone showed an increased hydroxyl radical production, attributed to the photo-reduction of quinones. Radicals other than hydroxyl radicals, such as carbon dioxide, hydroxymethyl, azide, and semiquinone, were identified in the presence of oxalate, methanol, azide, and para-benzoquinone, respectively. Some of these radicals can possibly interact with organic substrates due to their reduction potential; as a result, a critical interpretation must be done when these species are added to a heterogeneous photocatalysis process.

Visible-light reduced silver nanoparticles' toxicity in Allium cepa test system.

Silver nanoparticles (AgNPs) are widely used in consumer products due to their antibacterial property; however, their potential toxicity and release into the environment raises concern. Based on the limited understanding of AgNPs aggregation behavior, this study aimed to investigate the toxicity of uncoated (uc-AgNP) and coated with polyvinylpyrrolidone (PVP-AgNP), at low concentrations (0.5-100 ng/mL), under dark and visible-light exposure, using a plant test system. We exposed Allium cepa seeds to both types of AgNPs for 4-5 days to evaluate several toxicity endpoints. AgNPs did not cause acute toxicity (i.e., inhibition of seed germination and root development), but caused genotoxicity and biochemical alterations in oxidative stress parameters (lipid peroxidation) and activities of antioxidant enzymes (superoxide dismutase and catalase) in light and dark conditions. However, the light exposure decreased the rate of chromosomal aberration and micronuclei up to 5.60x in uc-AgNP and 2.01x in PVP-AgNP, and 2.69x in uc-AgNP and 3.70x in PVP-AgNP, respectively. Thus, light exposure reduced the overall genotoxicity of these AgNPs. In addition, mitotic index alterations and morphoanatomical changes in meristematic cells were observed only in the dark condition at the highest concentrations, demonstrating that light also reduces AgNPs cytotoxicity. The light-dependent aggregation of AgNPs may have reduced toxicity by reducing the uptake of these NPs by the cells. Our findings demonstrate that AgNPs can be genotoxic, cytotoxic and induce morphoanatomical and biochemical changes in A. cepa roots even at low concentrations, and that visible-light alters their aggregation state, and decreases their toxicity. We suggest that visible light can be an alternative treatment to remediate AgNP residues, minimizing their toxicity and environmental risks.

Evaluation of the Fenton process effectiveness in the remediation of soils contaminated by gasoline: Effect of soil physicochemical properties.

The remediation of four different soils contaminated by gasoline was performed using Fenton processes. Herein, the effect of the main physicochemical characteristics of the soils in the Fenton performance is emphasized. Fenton processes were applied in a column system, with and without addition of soluble iron (II), using undisturbed soil samples collected in four regions of the Paraná State (Brazil). Two groups of contaminants were monitored during the remediation process: BTEX (benzene, toluene, ethylbenzene and xylenes) and TRHs (total recoverable hydrocarbons). Superior degradation efficiencies were observed in the soils with elevated mineral iron content (Red Argisol, Red-Yellow Argisol and Red Latosol), while the soils with low iron content (Spodosol) presented comparable degradation efficiencies only in the presence of soluble Fe2+. Although the presence of mineral iron enabled the Fenton processes, a good correlation between the iron content and the degradation efficiency was not observed, suggesting a dependence on the chemical nature of the native iron. BTEX leaching was observed in all systems, suggesting that the process should be applied with caution, especially in soils with high drainage.

Evaluation of a Hollow-Fiber Liquid-Phase Microextraction Technique for the Simultaneous Determination of PPI Drugs in Human Plasma by LC-DAD.

This study involved the development, validation and application of a three-phase hollow-fiber liquid-phase microextraction (HF-LPME) and liquid chromatography with diode array detection (LC-DAD) method for the simultaneous determination of the proton pump inhibitor (PPI) drugs omeprazole, pantoprazole and lansoprazole in human plasma. The evaluation of the HF-LPME parameters was crucial for the determination of the drugs and the conditions selected were: 1-octanol as solvent; phosphate buffer at pH 5 as donor phase; borate buffer at pH 10 as acceptor phase; extraction time of 15 min; stirring at 750 rpm and NaCl was added at 5% (w/v). Validation of the method according to US-FDA recommendations showed a good linear range (0.2-2.0 µg/mL) for all analytes, with a determination coefficient >0.9910. Precision was evaluated using intra- and inter-day assays, which showed relative standard deviations (RSD), <15% for all concentrations, with a limit of quantification (LOQ) of 0.2 µg/mL. Accuracy was also assessed at these concentration levels and was in the range from 80 to 130%. Finally, the sensitive, selective and reproducible HF-LPME/LC-DAD developed method was successfully applied to human plasma samples from patients undergoing therapy with the PPI drugs.

Statistical analysis of wheat under different seed treatments: development of a discriminative model based on physicochemical and rheological properties.

BACKGROUND: Quality control in the wheat industry comprises numerous analyses that are time-consuming and demand numerous procedures and specific apparatus. The application of multivariate calibration techniques contributes to the interpretation of the data generated during these analyses. The present study aimed to correlate a representative number of wheat properties with the treatment applied to the wheat seeds using multivariate calibration techniques. RESULTS: In the present study, a wheat pilot planting experiment applying different fungicides combination as a seed treatment (carbendazim, carbendazim + thiram, carboxin + thiram, and triadimenol) was conducted. The resulting wheat grains were subjected to 33 analyses routinely performed in industry. A principal components analysis indicated all analyses were relevant for the different seed treatment discrimination. Afterwards, a k-nearest neighbors discriminative model was developed and was able to classify the seed treatments. In accordance with this model, the most relevant variables for the seed treatment discrimination were the rheological properties of the dough. CONCLUSION: It was possible to develop a discriminative model that directly correlated the wheat seed treatment with the properties of the resulting grains and flours. © 2017 Society of Chemical Industry.

New insight into monitoring degradation products during the TiO2-photocatalysis process by multivariate molecular spectroscopy.

This study focuses on the feasibility of a spectroscopic multivariate method for monitoring the concentration of phenol and its main degradation products during heterogeneous photocatalysis. Phenolic compounds were chosen as model to evaluate the degradation process due to their toxicity and persistence in the environment and also their well-known degradation pathway. The predictive capability of the multivariate method developed by partial least squares regression (PLSR) over the spectral range of 200-350 nm was satisfactory, allowing mean predicted errors below 5.0 % in the simultaneous determination of the target compounds using six latent variables and smoothing spectra. Suitable results were reported for the simultaneous determination of hydroquinone, resorcinol, pyrocatechol, and p-benzoquinone in accordance to the chromatographic method. Characteristics such as simplicity, low cost, and fast data acquisition are remarkable in this procedure, which makes it appropriate for this type of analytical control.

Poluição por resíduos contendo compostos farmaceuticamente ativos: aspectos ambientais, geração a partir dos esgotos domésticos e a situação do Brasil / Pollution from wastes containing pharmaceutical active compounds: environmental aspects and the situation of Brazil

O tratamento e a disposição adequada do esgoto doméstico representam uma preocupação universal, em função do seu reconhecido potencial poluente, Os sistemas de tratamento objetivam a remediação de parâmetros físico-químicos que fazem parte da legislação, Nos últimos anos, entretanto, outro tipo de poluição tem sido evidenciada, envolvendo micropoluentes capazes de provocar efeitos deletérios em concentrações da ordem de µg L-1 e ng L-1, Dentro deste contexto se destacam os compostos farmaceuticamente ativos (PhACs), os quais, veiculados pelo esgoto, contaminam praticamente todos os compartimentos ambientais, O estudo de tecnologias avançadas de tratamento de efluentes, com o objetivo de incrementar a remoção de PhACs tem sido realizado especialmente em países desenvolvidos, No Brasil o foco principal do tratamento de águas residuárias ainda está voltado para o tratamento básico, uma vez que o acesso a este serviço não está acessível a toda a população, o que torna a poluição por micropoluentes um problema secundário, Neste cenário, são discutidos antecedentes relacionados com o consumo de fármacos, a sua presença no esgoto, a usual baixa capacidade de remoção apresentada pelos sistemas convencionais de tratamento e, consequentemente, sua relação com a contaminação do meio hídrico...

The proper treatment and disposal of sewage are a universal concern, according to their recognized potential pollutant. In general, many treatment systems aim to remediate physical and chemical parameters that are part of the legislation. In recent years, however, another type of pollution has been evidenced involving micropollutants able to cause deleterious effects in concentrations of the order of mg L-1 and ng L-1. In this context the pharmaceutical active compounds (PhACs), which, conveyed by sewage, contaminate virtually all environmental compartments are highlighted. The study of advanced wastewater treatment, with the goal of enhancing the removal of PhACs has been conducted mainly in developed countries. In Brazil, the main focus of wastewater treatment is still facing the basic treatment, since access to this service is not accessible to the entire population, which makes pollution from micropollutants a secondary problem. In this scenario are discussed antecedents related to the consumption of pharmaceuticals, their presence in the sewage, the usual low removal capacity presented by the conventional treatment systems and, therefore, its relationship with the contamination of the water...

TiO2 and ZnO mediated photocatalytic degradation of E2 and EE2 estrogens.

In this work, the photocatalytic degradation of selected estrogens (E2 and EE2) was evaluated, using bench-scale and continuous treatment systems assisted by artificial UV-A and solar radiation. Processes based on the use of TiO2 permit an efficient degradation of E2 and EE2 estrogens, usually at reaction times lower than 15 min. Especially remarkable is the high degradation efficiency shown by sunlight-assisted processes, which are extremely favored by the high efficiency of compound parabolic collectors.

Microcystin-LR degradation by solar photo-Fenton, UV-A/photo-Fenton and UV-C/H2O2: a comparative study.

This work assessed the effectiveness of several methods on degradation of microcystin-LR (MC-LR) by different Advanced Oxidation Processes, like solar photo-Fenton, UV-A/photo-Fenton and UV-C/H2O2. UV-C/H2O2 and UV-A/photo-Fenton processes were carried out in a bench scale photochemical apparatus and the solar photo-Fenton treatment was performed in a CPC photoreactor. MC-LR degradation was monitored by LC-ESI-MS/MS and kinetic parameters were calculated for all systems evaluated. The results demonstrated that UV-C/H2O2 was the most efficient method, showing a reduction of over 90% of initial MC-LR after 5 min of reaction. Solar and photo-Fenton/UVA had a rate decrease of 88 and 76% after the same time, respectively. The kinetic study indicated that the solar photo-Fenton and artificial radiation (UV-A) processes were very similar in their efficiency. The use of sunlight instead of artificial UV radiation significantly reduced the cost of photocatalytic treatment systems; it is also an environmentally friendly method, since it utilizes renewable energy.

Photocatalytic degradation of microcystin-LR in aqueous solutions.

In this work, the photocatalytic degradation of aqueous microcystin-LR was studied using TiO(2) and ZnO as photocatalysts. The process was optimised and characterised at the bench scale (200 mL); both semiconductors exhibited a high degradation capacity at reaction times of 1 min (degradation greater than 95%). The transient species that were observed indicate that the degradation occurs via the multiple hydroxylation and elimination of the labile peptide residues of the molecule. When photocatalysis was applied in a continuous treatment system (20-50 L), the photocatalytic process exhibited a high degradation efficiency, which resulted in residual microcystin-LR concentrations that were less than 1 µg L(-1) (C(0)=5 µg L(-1)).

Multivariate optimization of mercury determination by flow injection-cold vapor generation-inductively coupled plasma optical emission spectrometry.

In this work a procedure for mercury determination by Flow Injection-Cold Vapor Generation-Inductively Coupled Plasma Optical Emission Spectrometry (FI-CVG-ICP OES) has been developed. The system uses a small homemade glass separator constructed to drive the Hg vapor to the plasma. An evolutionary operation factorial design was used to evaluate the optimal experimental conditions for mercury vapor generation, aiming at the low consumption of reagents, the improvement of the analytical signal and consequently greater sensitivity. The procedure allowed the determination of mercury and showed excellent linearity for the concentration range from 0.50 µg L(-1) to 100.0 µg L(-1), with Limits of Detection (LOD) and Quantification (LOQ) of 0.11 µg L(-1) and 0.36 µg L(-1), respectively, and a sampling rate of 36 analyses per hour. The optimized procedure showed good accuracy and precision, and the method was validated by the analysis of two certified reference materials: Buffalo River Sediment (NIST 2704) and human hair (IAEA 085). A good agreement with the certified values was achieved, with recovery values of 99% and 98% and relative standard deviation close to 2%.

Distribution and origin of polycyclic aromatic hydrocarbons in surface sediments from an urban river basin at the Metropolitan region of Curitiba, Brazil.

The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in surface sediment samples from nine sites located at the Iguaçu River Basin in the Metropolitan Region of Curitiba, Brazil to evaluate their distribution and sources. The total concentration of the PAHs was greater for sediments from highly urbanized areas, while the sediments from the Iraí Environmental Protection Area (Iraí EPA) showed significantly low concentrations. The sediments from the Iguaçu and Barigui rivers were classified as highly contaminated, while those from the Cercado and Curralinho rivers were classified as moderately contaminated. The predominance of PAHs containing two to four aromatic rings in most of the samples suggested the direct input of raw sewage into the water resources evaluated. Benzo[g,h,i]perylene, dibenzo[a,h]anthracene and indeno[1,2,3-cd]pyrene were predominant in sediments from the areas under the greatest urban and industrial development. The correlation between thermodynamic stability and the kinetics of evolution presented by the isomeric pairs indicated that combustion is the predominant source of PAHs in the sediments because the combustion of fossil fuels affected most of the points evaluated, followed by combustion of biomass and eventually combustion of oil product inputs. In general, the results showed that areas under strong urban influence, as well as the Iraí EPA, receive contributions of PAHs from similar sources.

Multifactorial optimization approach for the determination of polycyclic aromatic hydrocarbons in river sediments by gas chromatography-quadrupole ion trap selected ion storage mass spectrometry.

A procedure for the determination of very low polycyclic aromatic hydrocarbons (PAHs) concentrations in sediment samples has been developed by gas chromatography-quadrupole ion trap mass spectrometry (GC-QIT MS) after extraction with dichloromethane and purification by using silica gel cleanup. Identification and quantification of analytes were based on the selected ion storage (SIS) strategy using deuterated PAHs as internal standards. In order to search out the main factors affecting the SIS mass spectrometry efficiency, four MS parameters, including target total ion count (TTIC), waveform amplitude (WA), transfer line (XLT) and ion trap temperatures (ITT) were subjected to a complete multifactorial design. The most relevant parameters obtained (TTIC and WA) were optimized by a rotatable and orthogonal composite design. Optimum values for these parameters were selected for the development of the method involving PAH determination in sediment samples. The optimized method exhibited a range of 111-760% higher signal-to-noise (S/N) ratios for PAHs in comparison with the method operated by the default conditions, demonstrating that the multifactorial optimization contributed to substantially improve the sensitivity of the GC-QIT MS determination. The accuracy of the method was verified by analyzing NWRI EC-3 certified reference material (Lake Ontario sediment). The selectivity, sensitivity (limits of quantification were in the range of 0.02-11.0 ng g(-1)), accuracy (recoveries >or=77%) and precision (RSD

Degradação redutiva de azo-corantes utilizando-se ferro metálico / Reductive degradation of azo-dyes by metallic iron

Corantes azo são extensivamente utilizados em processos de tingimento de fibras têxteis, sendo caracterizados por elevada resistência frente a processos aeróbios de biodegradação e, por conseqüência, persistência nos processos convencionais de tratamento de resíduos. Neste trabalho reporta-se a degradação redutiva de corantes azo, utilizando-se ferro metálico. Em condições experimentais otimizadas (pH 7 e 10 g de lã de aço comercial) a completa descoloração do corante modelo (preto reativo 5) foi conseguida em um sistema contínuo, operando com tempos de retenção de 6 min. Nestas condições, o ferro solubilizado alcança concentrações compatíveis com os limites impostos pela atual legislação brasileira (12 mg L-1). Trata-se de um resultado bastante promissor, principalmente levando-se em consideração o caráter recalcitrante dos azo corantes e a simplicidade do sistema proposto.

Photochemically-assisted electrochemical degradation of landfill leachate.

In this work, the treatment of landfill leachates by a photoelectrochemical procedure is reported. When applied to untreated leachates the photochemical system was significantly hindered on account of the characteristic dark coloration of the samples. At this condition the degradation process was essentially electrochemical permitting typical color and COD removal of about 50% and 20%, respectively. When a previous chemical precipitation process was applied aiming the elimination of colored species (mainly humic substances) the decolorization and COD removal was extended to 90% and 60%, respectively. Considering the extremely complex character of the leachates and its usual resistance to conventional degradation processes the result reported here attest the high potentiality of photoelectrochemical processes to remediation of recalcitrant residues.

Degradation of aqueous solutions of camphor by heterogeneous photocatalysis.

In this study the photocatalytic degradation of aqueous solutions of camphor was investigated by using TiO2 and ZnO photocatalysts. In the presence of artificial UV-light the highly photosensitive camphor was almost totally degraded after reaction times of 60 min. However, under these conditions the mineralization degree was lower than 25%. In the presence of semiconductors the degradation was complete after a treatment time of about 30 min. Moreover, the mineralization was considerably greater, mainly with the use of TiO2 (> 80% at reaction time of 60 min). Heterogeneous photocatalytic processes applied in the presence of solar radiation show a promising degradation capability. TiO2-based processes afforded mineralization degrees of about 90% after a reaction time of 120 min, when the system was assisted by aeration.