RESUMO
Cresols and chlorophenols are chemical contaminants that are potentially toxic to humans and can be found in sewage sludge. These chemical contaminants can migrate into the sludge-soil-water system when sludge is used as a conditioner for agricultural soils. Thus, the objective of this study was to develop methodologies based on extraction with low-temperature partitioning (LTP) to determine cresols and chlorophenols in sewage sludge, soil, and water. The analysis was performed by gas chromatography coupled with mass spectrometry (GC-MS). The validated methods were applied to monitor cresols and chlorophenols in a column-leaching study of a sludge-soil-water system. Satisfactory results were achieved for selectivity, limit of quantification (LOQ), linearity, accuracy, and precision. In the column leaching study, only 2,4,6-trichlorophenol was quantified in sludge samples after 20 days of the experiment. None of the studied compounds were quantified in soil and leached water samples, due to the degradation promoted by the microorganisms present in the sewage sludge. Finally, validated methods were suitable for monitoring cresols and chlorophenols in the sludge-soil-water system.
Assuntos
Clorofenóis , Poluentes do Solo , Humanos , Esgotos/análise , Cresóis/análise , Solo/química , Clorofenóis/análise , Temperatura , Poluentes do Solo/análiseRESUMO
Chlorophenols are inhibitory compounds that can be biodegraded by aerobic granules in discontinuous processes. Many industrial wastewaters are characterized by transient pH variation over time. These pH changes could affect the overall granule structure and microbial activity during the chlorophenol biodegradation. The objective of this research was to evaluate the effects of transient pH variation on the specific degradation rate (q), granule integrity coefficient (IC), and size in sequencing batch reactors treating 4-chlorophenol (4-CP). First, aerobic granules were acclimated for efficient 4-CP degradation (>99%). The acclimated granules consisted of 55.7% of the phyla Proteobacteria and 40.6% of Bacteroidetes. The main bacteria belong to the order Sphingobacteriales (24%), as well as Amaricoccus, Acidovorax, Shinella, Rhizobium, and Flavobacterium, some of which are new genera reported in acclimated granules degrading 4-CP. Then, pH changes were applied to the acclimated aerobic granules, observing that acid pHs decreased to a greater extent the specific degradation rate (67% to 99%) than basic pHs (34% to 80%). These pH changes caused the granule disaggregation but with lower effects on the IC. The effects of pH change were mainly on the microbial activity more than the physical characteristics of aerobic granules degrading 4-CP.
Assuntos
Reatores Biológicos/microbiologia , Clorofenóis/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Aerobiose , Biodegradação Ambiental , Concentração de Íons de Hidrogênio , Esgotos/química , Sphingobacterium/metabolismoRESUMO
Biodegradability of 2-Chlorophenol (2-CP), 3-Chlorophenol (3-CP), 4-Chlorophenol (4-CP), 2,4-Dichlorophenol (2,4-DCP) and 2,4,6 Trichlorophenol (2,4,6-TCP) has been tested in surface waters in the urban area of Buenos Aires. Samples were taken from the La Plata River and from the Reconquista and Matanza-Riachuelo basins, with a total amount of 18 sampling points. Water quality was established measuring chemical oxygen demand (COD), biochemical oxygen demand (BOD5), and both Escherichia coli and Enterococcus counts. Biodegradability was carried out by a respirometric method, using a concentration of 20 mg L-1 of chlorophenol, and the surface water as inoculum. Chlorophenols concentration in the same water samples were simultaneously measured by a solid phase microextraction (SPME) procedure followed by gas chromatography-mass spectrometry (GC-MS). 2,4-DCP was the most degradable compound followed by 2,4,6-TCP, 4-CP, 3-CP and 2-CP. Biodegradability showed no correlation with compound concentration. At most sampling points the concentration was below the detection limit for all congeners. Biodegradability does not correlate even with COD, BOD5, or fecal contamination. Biodegradability assays highlighted information about bacterial exposure to contaminants that parameters routinely used for watercourse characterization do not reveal. For this reason, they might be a helpful tool to complete the characterization of a site.
Assuntos
Clorofenóis/análise , Monitoramento Ambiental/métodos , Rios/química , Urbanização , Poluentes Químicos da Água/análise , Argentina , Biodegradação Ambiental , Análise da Demanda Biológica de Oxigênio , Cidades , Cromatografia Gasosa-Espectrometria de Massas , Limite de Detecção , Microextração em Fase SólidaRESUMO
Anaerobic bioreactors are often used for removal of xenobiotic and highly toxic pollutants from wastewater. Most of the time, the pollutant is so toxic that the stability of the reactor becomes compromised. It is well known that methanogens are one of the most sensitive organisms in the anaerobic consortia and hence the stability of the reactors is highly dependant on methanogenesis. Unfortunately few studies have focused on recovering the methanogenic activity once it has been inhibited by highly toxic pollutants. Here we establish a quick recovery strategy for neutralization of an acidified UASB reactor after failure by intoxication with an excess of TCP in the influent. Once the reactor returned to pH values compatible with methanogenesis, biogas production was re-started after one day and the system was re-acclimated to TCP. Successful removal of TCP from synthetic wastewater was shown for concentrations up to 70mg/L after restoration.
Assuntos
Reatores Biológicos/microbiologia , Clorofenóis/análise , Metano/análise , Esgotos/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Anaerobiose , Concentração de Íons de Hidrogênio , Modelos Teóricos , Águas Residuárias/químicaRESUMO
An approach based on the electrochemical detection of the horseradish peroxidase enzymatic reaction by means of square wave voltammetry was developed for the determination of phenolic compounds in environmental samples. First, a systematic optimization procedure of three factors involved in the enzymatic reaction was carried out using response surface methodology through a central composite design. Second, the enzymatic electrochemical detection coupled with a multivariate calibration method based in the partial least-squares technique was optimized for the determination of a mixture of five phenolic compounds, i.e. phenol, p-aminophenol, p-chlorophenol, hydroquinone and pyrocatechol. The calibration and validation sets were built and assessed. In the calibration model, the LODs for phenolic compounds oscillated from 0.6 to 1.4 × 10(-6) mol L(-1). Recoveries for prediction samples were higher than 85%. These compounds were analyzed simultaneously in spiked samples and in water samples collected close to tanneries and landfills.
Assuntos
Aminofenóis/análise , Catecóis/análise , Clorofenóis/análise , Hidroquinonas/análise , Fenol/análise , Poluentes Químicos da Água/análise , Água/química , Calibragem , Técnicas Eletroquímicas , Análise Fatorial , Peroxidase do Rábano Silvestre/química , Humanos , Peróxido de Hidrogênio/química , Limite de DetecçãoRESUMO
This paper proposes a new analytical procedure based on the headspace solid-phase microextraction (HS-SPME) technique and gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS) for the determination of 16 phenols extracted from leather samples. The optimized conditions for the HS-SPME were obtained through two experimental designs - a two-level fractional factorial design followed by a central composite design - using the commercial SPME fiber polyacrylate 85 µm (PA). The best extraction conditions were as follows: 200 µL of derivatizing agent (acetic anhydride), 20 mL of saturated aqueous NaCl solution and extraction time and temperature of 50 min and 75°C, respectively. All optimized conditions were obtained with fixed leather sample mass (250 mg), vial volume (40 mL) and phosphate buffer pH (12) and concentration (50 mmol/L). Detection limits ranging from 0.03 to 0.20 ng/g, and relative standard deviation (RSD) lower than 10.23% (n=6) for a concentration of 800 ng/g (chlorophenols) and 1325 ng/g (2-phenylphenol) in the splitless mode were obtained. The recovery was studied at three concentration levels by adding different amounts of phenols to the leather sample and excellent recoveries ranging from 90.0 to 107.2% were obtained. The validated method was shown to be suitable for the quantification of phenols in leather samples, as it is simple, relatively fast and sensitive.
Assuntos
Clorofenóis/análise , Pele/química , Microextração em Fase Sólida , Cromatografia Gasosa-Espectrometria de MassasRESUMO
OBJECTIVE: Guedes-Pinto paste (GPP) is an iodoform paste used in most dental schools in Brazil. The paste is a composite of medicines (Rifocort , camphorated paramonochlorophenol [PMCC], and iodoform) used for endodontic treatment of primary teeth. The aim of this study was to evaluate the proportion variability of GPP components when mixed by undergraduate dentistry students and pediatric dentists. MATERIALS AND METHODS: The study was divided into 4 groups: G1 (15 undergraduate students), G2 (15 specialists in Pediatric Dentistry), G3 (15 professors with clinical activity), and G4 (7 professors-researchers). All volunteers prepared GPP according to the original specifications: the same visual proportion for each component. The components were weighed using an analytical balance and the percentage was calculated. RESULT: After normality (Kolmogorov-Smirnov) and homogeneity tests (Levene test), the data were submitted to analysis of variance and intraclass correlation coefficient tests (P<0.05). The percentage means of each respective group were as follows: Rifocort 20.2%, 20.8%, 26.7%, 27.3%; camphorated PMCC 9.2%, 8.1%, 6.7%, 5.1%; and the iodoform 70.6%, 71.1%, 64.7%, 67.6%. There were no significant differences between groups for the component percentages. There was a high intraclass correlation coefficient (G1 0.945; G2 0.951; G3 0.921; and G4 0.870). CONCLUSION: The proportion of GPP was similar in all the groups, allowing us to conclude that ideal GPP proportion, based on the entire group mean, was 23.8% of Rifocort® ; 7.0% of camphorated PMCC; and 69.2% of iodoform.
Assuntos
Anti-Infecciosos Locais/análise , Hidrocarbonetos Iodados/análise , Odontopediatria , Materiais Restauradores do Canal Radicular/análise , Estudantes de Odontologia , Brasil , Cânfora/análise , Clorofenóis/análise , Combinação de Medicamentos , Composição de Medicamentos , Endodontia , Docentes de Odontologia , Humanos , Prednisolona/análogos & derivados , Prednisolona/análise , Rifamicinas/análiseRESUMO
Chlorophenols are harmful pollutants, frequently found in the effluents of several industries. For this reason, many environmental friendly technologies are being explored for their removal from industrial wastewaters. The aim of the present work was to study the scale up of 2,4-dichlorophenol (2,4-DCP) removal from synthetic wastewater, using Brassica napus hairy roots and H(2)O(2) in a discontinuous stirred tank reactor. We have analyzed some operational conditions, because the scale up of such process was poorly studied. High removal efficiencies were obtained (98%) in a short time (30 min). When roots were re-used for six consecutive cycles, 2,4-DCP removal efficiency decreased from 98 to 86%, in the last cycle. After the removal process, the solutions obtained from the reactor were assessed for their toxicity using an acute test with Lactuca sativa L. seeds. Results suggested that the treated solution was less toxic than the parent solution, because neither inhibition of lettuce germination nor effects in root and hypocotyl lengths were observed. Therefore, we provide evidence that Brassica napus hairy roots could be effectively used to detoxify solutions containing 2,4-DCP and they have considerable potential for a large scale removal of this pollutant. Thus, this study could help to design a method for continuous and safe treatment of effluents containing chlorophenols.
Assuntos
Brassica napus/química , Clorofenóis/isolamento & purificação , Resíduos de Praguicidas/isolamento & purificação , Poluentes do Solo/isolamento & purificação , Reatores Biológicos , Clorofenóis/análise , Clorofenóis/toxicidade , Peróxido de Hidrogênio/análise , Lactuca/fisiologia , Oxirredução , Resíduos de Praguicidas/análise , Resíduos de Praguicidas/toxicidade , Raízes de Plantas/química , Sementes , Poluentes do Solo/análise , Poluentes do Solo/toxicidade , SoluçõesRESUMO
Langmuir-Blodgett (LB) and layer-by-layer films (LbL) of a PPV (p-phenylenevinylene) derivative, an azo compound and tetrasulfonated phthalocyanines were successfully employed as transducers in an "electronic tongue" system for detecting trace levels of phenolic compounds in water. The choice of the materials was based on their distinct electrical natures, which enabled the array to establish a fingerprint of very similar liquids. Impedance spectroscopy measurements were taken in the frequency range from 10 Hz to 1 MHz, with the data analysed with principal component analysis (PCA). The sensing units were obtained from five-layer LB films of (poly[(2-methoxy-5-n-hexyloxy)-p-phenylenevinylene]), OC(1)OC(18)-PPV (poly(2-methoxy,5-(n-octadecyl)-p-phenylenevinylene)), DR (HEMA-co-DR13MA (poly-(hydroxyethylmethacrylate-co-[4'-[[2-(methacryloyloxy)-ethyl]ethylamino]-2-chloro-4-nitroazobenzene]))) and five-bilayer LbL films of tetrasulfonated metallic phthalocyanines deposited onto gold interdigitated electrodes. The sensors were immersed into phenol, 2-chloro-4-methoxyphenol, 2-chlorophenol and 3-chlorophenol (isomers) solutions at 1 x 10(-9) mol L(-1), with control experiments carried out in ultra pure water. Samples could be distinguished if the principal component analysis (PCA) plots were made with capacitance values taken at 10(3) Hz, which is promising for detection of trace amounts of phenolic pollutants in natural water.
Assuntos
Fenol/análise , Análise Espectral/métodos , Técnicas de Química Analítica/métodos , Clorofenóis/análise , Impedância Elétrica , Eletroquímica/métodos , Desenho de Equipamento , Modelos Químicos , Nanoestruturas/química , Nanotecnologia/métodos , Análise de Componente Principal , Reprodutibilidade dos Testes , Propriedades de Superfície , Água/químicaRESUMO
Solid phase microextraction (SPME) of chlorophenols [2-chlorophenol (2CP), 2,4-dichlorophenol (24CP), 4-chloro-3-methylphenol (43CP), 2,4,6-tri-chlorophenol (246CP) and pentachlorophenol (PCP)] followed by direct mass spectrometric analysis has been performed by fiber introduction mass spectrometry (FIMS). Two SPME fibers (65 microm PDMS/DVB and 85 microm PA fibers) were tested, and FIMS was performed via selective ion monitoring (SIM). The extractions were evaluated at 10% ionic strength and pH 1. Best extraction times were determined for both fibers. Limits of detection (LOD) and limits of quantification (LOQ) for both fibers were in the low microg L(-1) range. Coefficients of correlation for the analytical curves showed linear responses and mineral water and river water samples spiked with 50 microg L(-1) presented high recoveries. FIMS, as compared to current EPA methods, is demonstrated to allow faster and simpler (elimination of pre-separation or derivatization steps) analysis of chlorophenols in water with the required sensitivity.