Navegando por Autor "Bellato, Carlos R."

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Arsenic and trace metals in river water and sediments from the southeast portion of the Iron Quadrangle, Brazil
(Environmental Monitoring and Assessment, 2010-03-18) Varejão, Eduardo V. V.; Bellato, Carlos R.; Fontes, Maurício P. F.; Mello, Jaime W. V.
The Iron Quadrangle has been one of the most important gold production regions in Brazil since the end of the seventeenth century. There, arsenic occurs in close association with sulfide-rich auriferous rocks. The most abundant sulfide minerals are pyrite and arsenopyrite, yet trace metal sulfides occur in subordinate phases as well. Historical mining activities have been responsible for the release of As and trace metals to both aquatic and terrestrial environments close to mining sites in the region. Therefore, this study was aimed to evaluate the distribution and mobility of As, Cd, Co, Cr, Cu, Ni, Pb, and Zn in streams in the southeast portion of the Iron Quadrangle between the municipalities of Ouro Preto and Mariana, the oldest Brazilian Au mining province. Total concentrations of some trace metals and arsenic in water were determined. The four-stage sequential extraction procedure proposed by the commission of the European Communities Bureau of Reference (BCR) was used to investigate the distribution of these elements in stream sediments. Arsenic concentration in water was >10 μg L ^− 1 (maximum limit permitted by Brazilian environmental regulations for water destined for human consumption) at all sampling sites, varying between 36.7 and 68.3 μg L ^− 1. Sequential extraction in sediments showed high concentrations of As and trace metals associated with easily mobilized fractions.
Arsenic and trace metals in water and sediment of the velhas river, southeastern iron quadrangle region, Minas Gerais, Brazil
(Química Nova, 2018-09) Silva, Danilo de C.; Bellato, Carlos R.; Marques Neto, José de O.; Fontes, Maurício P. F.
This work was undertaken in the Velhas River Basin, in the municipalities of Rio Acima, Nova Lima, Raposos and Sabará, upstream of the city of Belo Horizonte in Minas Gerais State, Brazil. Velhas River provides the public water supply for much of this region. The gold and iron mining activities in the Velhas River yield considerable amounts of suspended solids as well as metals to the hydrological system of the region. Thus, the present study sought to evaluate the concentrations of arsenic and trace metals in the waters and their distribution and mobility in sediment by BCR sequential extraction. Arsenic concentrations in the water samples were between 78.1 and 85.3 μg L -1 , which exceeded 10 μg L -1 (maximum limit permitted by Brazilian environmental regulations for water destined to human consumption, CONAMA Resolution 357/2005). The sequential extraction of the sediment showed considerable amounts of As (20%), Cd (55%), Co (56%), Cr (16%), Cu (23%), Ni (29%), Pb (47%) and Zn (71%) associated with the geochemical fractions considered potentially available for the remobilization to the aquatic environment. The presence of the elements in these fractions indicated high ecotoxicological risk and potential harm to the health of the local population.
Hydrotalcite-TiO2 magnetic iron oxide intercalated with the anionic surfactant dodecylsulfate in the photocatalytic degradation of methylene blue dye
(Journal of Environmental Management, 2015-04-07) Miranda, Liany D.L.; Bellato, Carlos R.; Milagres, Jaderson L.; Moura, Luciano G.; Mounteer, Ann H.; Almeida, Marciano F. de
The new magnetic photocatalysts HT/TiO2/Fe and HT-DS/TiO2/Fe, modified with the anionic surfactant sodium dodecylsulfate (DS) were successfully synthesized in this work. Titanium dioxide (anatase) followed by iron oxide were deposited on the hydrotalcite support. Several catalyst samples were prepared with different amounts of titanium and iron. The photocatalysts were characterized by infrared and Raman spectroscopy, X-ray diffraction, scanning electron microscopy. Photocatalytic performance was analyzed by UV–visible radiation (filter cutoff, λ > 300 nm) of an aqueous solution (24 mg/L) of methylene blue (MB). The most efficient catalyst was obtained at an iron oxide:TiO2 molar ratio of 2:3. This catalyst showed high photocatalytic activity, removing 96% of the color and 61% of total organic carbon from the MB solution after 120 min. It was easily removed from solution after use because of its magnetic properties. The reuse of the HT-DS/TiO2/Fe23 catalyst was viable and the catalyst was structurally stable for at least four consecutive photocatalytic cycles.
Mercury fractionation in stream sediments from the Quadrilátero Ferrífero gold mining region, Minas Gerais State, Brazil
(Environmental Monitoring and Assessment, 2008-09-11) Varejão, Eduardo V. V.; Bellato, Carlos R.; Fontes, Maurício P. F.
The Iron Quadrangle (IQ) region, located in the state of Minas Gerais, has been the most important gold producing area in Brazil since the end of seventeenth century. The use of mercury for gold amalgamation in small scale mines has been responsible for large release of Hg to aquatic and terrestrial environments during 300 years of mining. The present work sought to evaluate the fractionation of Hg in stream sediments is the southern region of the IQ by utilizing sequential extraction. Since mobility and availability of Hg are related to its distribution among sediment partitions, fractionation methods provide detailed information on the ecotoxicological impact and risks associated to the presence of Hg in sediments. The total Hg concentration varied from 179.3 to 690.1 μg kg − 1 and Hg0 accounted for the majority at all sample sites, ranging from 42% to 56% of the total.
Mobility and persistence of the herbicide fomesafen in soils cultivated with bean plants using SLE/LTP and HPLC/DAD
(Environmental Science and Pollution Research, 2014-09-23) Costa, Anna I. G.; Queiroz, Maria Eliana L. R.; Neves, Antônio A.; Assis, Roberta C. de; Soares, Carlos E. S. dos; Silva, Antônio A. da; D’Antonino, Leonardo; Oliveira, André F. de; Bellato, Carlos R.
A method has been optimized and validated for the determination of fomesafen in soils using solid–liquid extraction with low-temperature partitioning (SLE/LTP) and analysis by liquid chromatography with a high-efficiency diode array detector (HPLC/DAD). The method was used to evaluate the persistence and mobility of this herbicide in different soils cultivated with bean plants. Recovery values were ≥98.9 %, with variations in the repeatability coefficients of ≤15 %, and a detection limit of 7.3 μg kg−1. Half-life values of fomesafen were between 60 and 71 days in soil cultivated using a no-till system and 99 and 114 days in soil cultivated using a conventional tillage system. The mobility of fomesafen was moderate and mainly influenced by the organic matter content, pH, and soil type. In Red-Yellow Argisol, which has a higher content of organic matter, the leaching of fomesafen was less pronounced. In Red-Yellow Latosol, which has smaller amounts of organic matter and high pH, the leaching of fomesafen was more pronounced.
Preparation and evaluation of hydrotalcite-iron oxide magnetic organocomposite intercalated with surfactants for cationic methylene blue dye removal
(Chemical Engineering Journal, 2014-10-15) Miranda, Liany D.L.; Bellato, Carlos R.; Fontes, Maurício P.F.; Almeida, Marciano F. de; Milagres, Jaderson L.; Minim, Luis A.
Cationic dye adsorption by hydrotalcite-iron oxide magnetic modified with dodecylsulfate (DS) and dodecylbenzenesulfonate (DSB) anionic surfactants was examined using methylene blue (MB) dye as compound model in aqueous solutions and compared to the adsorption capacity of non-modified hydrotalcite (HT). The magnetic adsorbents were named by HT-CO3/Fe, HT-DS/Fe and HT-DSB/Fe e present the advantage of being easily removed from the aqueous solution by application of a magnetic field. These were characterized by infrared spectroscopy (IR), X-ray diffractometry (XDR), zeta potential and atomic adsorption spectrometry. The effects of the adsorbent dosage, contact time, pH and initial concentrations of the dye were evaluated. In accordance with the obtained results, the pseudo-second order kinetic model can fittingly describe the adsorption processes. The MB removal percentages by adsorbents HT-CO3/Fe, HT-DS/Fe and HT-DSB/Fe were 9%, 91%, and 82%, respectively, for the initial dye concentration of 150 mg/L of MB. Free energy variations, during MB adsorption were −25.88 and −27.40 kJ/mol for HT-DS/Fe and −26.36 and −27.80 kJ/mol for HT-DSB/Fe suggesting the spontaneity of the adsorption process. The positive value of ΔH° suggests that interaction of the AM dye adsorbed by the organocompounds HT-DS/Fe and HT-DSB/Fe is an endothermic process. The Dubinin-Radushkevich model indicated that the adsorption process is probably physisorption for both organocompounds.
Preparation and evaluation of magnetic chitosan particles modified with ethylenediamine and Fe(III) for the removal of Cr(VI) from aqueous solutions
(Química Nova, 2014-09-05) Toledo, Thiago V.; Bellato, Carlos R.; Souza, Carlos H. Ferreira de; Domingues, Junielly T.; Silva, Danilo de C.; Reis, César; Fontes, Maurício P. Ferreira
The adsorption of Cr(VI) in aqueous solution by magnetic particles of crosslinked chitosan-ethylenediamine-Fe(III) (MPCh-EDA-FeCL) was studied in a batch system. Fe3+ in the MPCh-EDA-FeCL permitted that adsorption of Cr(VI) occurred with maximum efficiency between pH 3 and 11. The maximum adsorption capacity at pH 7.0 was 81.04 mg g-1 at 25 ºC. The adsorption kinetic process was described by the pseudo-second-order model. Thermodynamic parameters indicated spontaneous, exothermic and chemical adsorption nature. The adsorbent was successively regenerated using a 0.1 mol L-1 NaOH solution. Results were satisfactory for treatment of wastewater from the electroplating industry.
Preparation of calcined hydrotalcite/TiO2-Ag composite and enhanced photocatalytic properties
(Ceramics International, 2017-02-01) Almeida, Marciano F. de; Bellato, Carlos R.; Miranda, Liany D. L.; Milagres, Jaderson L.
A series of calcined hydrotalcite/TiO2-Ag (HTC/TiO2-Ag) composites with different silver (Ag) contents were successfully prepared and investigated as a catalyst for the photodegradation of phenol using UV–vis light (λ>300 nm). The Ag nanoparticles were deposited on the surface of TiO2 (TiO2-Ag) through photodeposition method. The TiO2-Ag nanoparticles were supported on hydrotalcite (HT) by the co-precipitation method at variable pH (HT/TiO2-Ag), and then calcined at 500 °C to obtain the HTC/TiO2-Ag composites. The composites were characterized by inductively coupled plasma mass spectrometry (ICP-MS), N2 adsorption/desorption (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and diffuse reflectance spectra (DRS). Results show that there is an optimum silver ratio to obtain the highest photocatalytic performance in the HTC/TiO2-Ag photocatalyst which is 2 wt%, and is assigned as HTC/TiO2-Ag(2). The association of silver nanoparticles on TiO2 enhanced photocatalytic activity of the bare semiconductor composite. Only 56% of phenol was photodegraded when photodegradation was performed with HTC/TiO2, whereas ~100% was photodegraded using HTC/TiO2-Ag(2). The data gathered from the photocatalytic degradation of phenol were successfully fitted to Langmuir-Hinshelwood model, and can be described by pseudo-first order kinetics. The results showed the HTC/TiO2-Ag(2) as efficient photocatalyst, low cost, separable from solution by sedimentation, and reusable. The superior performance of HTC/TiO2-Ag(2) composite photocatalyst may be attributed to the synergic catalytic effect between silver and TiO2, dispersion of TiO2-Ag(2) nanoparticles supported on calcined hydrotalcite, and the calcined hydrotalcite like photocatalyst.
Sais de tetrafenilfosfônio e tris( 1,10- fenantrolina) ferro( ii) de complexos aniônicos de dibutilestanho( iv) com ditiocarbimatos: síntese, caracterização e atividade antifúngica
(Química Nova, 2016-06) Bottega, Fernanda C.; Oliveira, Marcelo R. L.; Rubinger, Mayura M. M.; Bellato, Carlos R.; Ardisson, José D.; Zambolim, Laercio
Six new salts of organometallic complexes of tin(IV) with the general formulae: (Ph4P)2[Sn(Bu)2(RSO2N=CS2)2] and [Fe(phen)3][Sn(Bu)2(RSO2N=CS2)2] [Ph4P = tetraphenylphosphonium, R = CH3 (1), C2H5 (2) and C4H9 (3); Fe(phen)3 = tris(1,10-phenanthroline)iron(II), R = CH3 (4), C2H5 (5) and C4H9 (6)] were synthetized from potassium dithiocarbimates (RSO2N=CS2K2.H2O) in reaction with dichlorobis-n-butyltin(IV) and tetraphenylphosphonium chloride (1-3) in N,N-dimethylformamide or tris(1,10-phenanthroline)iron(II) (4-6) in methanol. The new compounds were characterized by elemental analysis of Fe and Sn, and by vibrational, Mössbauer and nuclear magnetic resonance of 1H, 13C and 119Sn spectroscopies. High-resolution mass spectra in the negative and positive modes were also obtained. The elemental analyses and the exact masses obtained for the cations and the complex anions were consistent with the proposed formulae. The Mössbauer spectroscopic data were consistent with the presence of tin(IV) with coordination numbers between 4 and 5 (compounds 1-6), and of hexacoordinated iron(II) (compounds 4-6). The 1H and 13C NMR spectra presented all the expected signals for the cations and anions, and the signals observed in the 119Sn NMR spectra indicated an equilibrium between tetra- and pentacoordination around the tin atoms in solution. The in vitro activity of the new compounds was evaluated against Botrytis cinerea and Colletotrichum acutatum.
Trace elements in river waters and sediments before and after a mining dam breach (Bento Rodrigues, Brazil)
(Química Nova, 2018-08) Silva, Danilo de C.; Bellato, Carlos R.; Marques Neto, José de O.; Fontes, Maurício P. F.
On November 5, 2015, the Fundão dam ruptured which caused the spill of a large quantity of tailings from the extraction of iron ores to the Gualaxo do Norte, Carmo and Doce Rivers. Seven months prior to the rupture, our group had collected water and sediment samples at 13 points along the Tripuí Creek and the entire length of the Carmo River. Six months after deposition of the mud, new samples were collected in the Carmo River. Thus, the present study sought to evaluate the concentrations of trace elements in the waters and their distribution and mobility in sediment by BCR sequential extraction before and after the deposition of the tailings mud. Arsenic concentrations in the water samples were between 10.4 and 50.4 μg L -1 , which exceeded 10 ug L -1 (maximum limit permitted by Brazilian environmental regulations for water destined for human consumption) . The tailing mud layer on the sediments caused concentration increases of As (20%), Cd (13%), Co (5%), Cr (9%), Cu (11%), Ni (4%), Pb (7%) and Zn (19%) in the easily remobilized fractions. The presence of the elements in these fractions was indicative of high ecotoxicological risk and potential harm to the health of the local population.