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URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11800
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Item Chromium speciation using aqueous biphasic systems: Development and mechanistic aspects(Separation and Purification Technology, 2016-01-28) Patrício, Pamela R.; Cunha, Roselaine C.; Vargas, Silvia J. Rodriguez; Coelho, Yara Luiza; Silva, Luis Henrique Mendes da; Silva, Maria C. Hespanhol daThe two principal oxidation states of chromium diverge significantly in their biological and toxicological properties, and it is very important to distinguish between them. Develop procedures that are efficient, fast, easier and cheaper for chromium speciation is an analytical challenge. Chromium speciation was investigated using aqueous biphasic systems (ABS) formed by polyethylene oxide (PEO1500) or a triblock copolymer (L64), an electrolyte (Li2SO4, Na2SO4, MgSO4, C6H5Na3O7, or C4H4Na2O6) and water, without the presence of any extractant. Cr(III) was favorably partitioned to the electrolyte-rich phase (ERP) of the ABS, whereas the Cr(VI) was preferentially concentrated in the macromolecule-rich phase (MRP) in most analyzed ABS. The fluorescence spectroscopy data revealed that the Cr(III) and Cr(VI) separation process is governed by specific interactions between the ethylene oxide segments in the macromolecules and the Cr(VI) species, which do not occur for Cr(III) species. The extraction percentage (%E) of chromium species from the ERP to the MRP was affected by pH, tie-line length (TLL), electrolyte nature, and macromolecule hydrophobicity. For the ABS comprising of PEO1500 + Na2SO4 + H2O, TLL = 50.89% (m/m), 25 °C and pH 2.0, the %E values for Cr(III) and Cr(VI) were 0.0100 and 99.9%, respectively. The speciation of Cr(III) and Cr(VI) that was achieved in this ABS resulted in an excellent separation factor (SCr(VI),Cr(III)) of 1.00 × 10 8.Item Thermodynamics and optimization of norbixin transfer processes in aqueous biphasic systems formed by polymers and organic salts(Separation and Purification Technology, 2012-09-19) Mageste, Aparecida Barbosa; Senra, Tonimar Domiciano Arrighi; Silva, M. Carmo Hespanhol da; Bonomo, Renata Cristina Ferreira; Silva, Luis Henrique Mendes daPartitioning of the natural dye norbixin has been studied in aqueous two-phase system (ATPS) that are formed by mixing aqueous solutions of a polymer (or copolymer) and an organic salt (sodium tartrate or succinate). In this work, the norbixin partition coefficient (KN) was optimized, taking into account the variables of polymer concentration, salt concentration and pH. It was found that KN is highly dependent on the electrolyte nature, system hydrophobicity and TLL values. Testing produced KN values between 8 and 130, indicating the great potential of ATPS as a method for norbixin pre-concentration/purification. Thermodynamic transfer parameters (ΔtrG, ΔtrH, ΔtrS) indicate that the preferential concentration of norbixin in the top phase is favored by enthalpic and entropic contributions.Item Separation of Cd and Ni from Ni–Cd batteries by an environmentally safe methodology employing aqueous two-phase systems(Journal of Power Sources, 2009-09-05) Lacerda, Vânia Gonçalves; Mageste, Aparecida Barbosa; Santos, Igor José Boggione; Silva, Luis Henrique Mendes da; Silva, Maria do Carmo Hespanhol daThe separation of Cd and Ni from Ni–Cd batteries using an aqueous two-phase system (ATPS) composed of copolymer L35, Li2SO4 and water is investigated. The extraction behavior of these metals from the bottom phase (BP) to the upper phase (UP) of the ATPS is affected by the amount of added extractant (potassium iodide), tie-line length (TLL), mass ratio between the phases of the ATPS, leaching and dilution factor of the battery samples. Maximum extraction of Cd (99.2 ± 3.1)% and Ni (10.6 ± 0.4)% is obtained when the batteries are leached with HCl, under the following conditions: 62.53% (w/w) TLL, concentration of KI equal to 50.00 mmol kg−1, mass ratio of the phases equal to 0.5 and a dilution factor of battery samples of 35. This novel methodology is efficient to separate the metals in question, with the advantage of being environmentally safe, since water is the main constituent of the ATPS, which is prepared with recyclable and biodegradable compounds.Item A green and sensitive method to determine phenols in water and wastewater samples using an aqueous two-phase system(Talanta, 2009-09-04) Rodrigues, Guilherme Dias; Lemos, Leandro Rodrigues de; Silva, Luis Henrique Mendes da; Silva, Maria do Carmo Hespanhol da; Minim, Luis Antonio; Coimbra, Jane Sélia dos ReisA greener and more sensitive spectrophotometric procedure has been developed for the determination of phenol and o-cresol that exploits an aqueous two-phase system (ATPS) using a liquid–liquid extraction technique. An ATPS is formed mostly by water and does not require organic solvent. Other ATPS components used in this study were the polymer, polyethylene oxide, and some salts (i.e., Li2SO4, Na2SO4 or K2HPO4 + KOH). The method is based on the reaction between phenol, sodium nitroprusside (NPS) and hydroxylamine hydrochloride (HL) in an alkaline medium (pH 12.0), producing the complex anion [Fe2(CN)10]^10− that spontaneously concentrates in the top phase of the system. The linear range was 1.50–500 μg kg^−1 (R ≥ 0.9997; n = 8) with coefficients of variation equal to 0.38% for phenol and 0.30% for o-cresol (n = 5). The method yielded limits of detection (LODs) of 1.27 and 1.88 μg kg^−1 and limits of quantification (LOQs) of 4.22 and 6.28 μg kg^−1 for phenol and o-cresol, respectively. Recoveries between 95.7% and 107% were obtained for the determination of phenol in natural water and wastewater samples. In addition, excellent agreement was observed between this new ATPS method and the standard 4-aminoantipyrine (4-AAP) method.Item Aqueous two-phase systems: An efficient, environmentally safe and economically viable method for purification of natural dye carmine(Tecnologia de Alimentos, 2009-11-09) Mageste, Aparecida Barbosa; Lemos, Leandro Rodrigues de; Ferreira, Guilherme Max Dias; Silva, Maria do Carmo Hespanhol da; Silva, Luis Henrique Mendes da; Bonomo, Renata Cristina Ferreira; Minim, Luis AntonioPartition of the natural dye carmine has been studied in aqueous two-phase systems prepared by mixing aqueous solutions of polymer or copolymer with aqueous salt solutions (Na2SO4 and Li2SO4). The carmine dye partition coefficient was investigated as a function of system pH, polymer molar mass, hydrophobicity, system tie-line length and nature of the electrolyte. It has been observed that the carmine partition coefficient is highly dependent on the electrolyte nature and pH of the system, reaching values as high as 300, indicating the high potential of the two-phase extraction with ATPS in the purification of carmine dye. The partition relative order was Li2SO4 ≫ Na2SO4. Carmine molecules were concentrated in the polymer-rich phase, indicating an enthalpic specific interaction between carmine and the pseudopolycation, which is formed by cation adsorption along the macromolecule chain. When the enthalpic carmine–pseudopolycation interaction decreases, entropic forces dominate the natural dye-transfer process, and the carmine partitioning coefficient decreases. The optimization of the extraction process was obtained by a central composite face-centered (CCF) design. The CCF design was used to evaluate the influence of Li2SO4 and PEO 1500 concentration and of the pH on the partition coefficient of carmine. The conditions that maximize the partition of carmine into the top phase were determined to be high concentrations of PEO and Li2SO4 and low pH values within the ranges studied.Item Green recovery of mercury from domestic and industrial waste(Journal of Hazardous Materials, 2015-11-10) Cunha, Roselaine C. da; Patrício, Pamela R.; Vargas, Silvia J. Rodriguez; Silva, Luis Henrique Mendes da; Silva, Maria C. Hespanhol daRecovery of mercury from effluents is fundamental for environmental preservation. A new, green method was developed for separation of mercury from effluent containing different metals. The extraction/separation of Hg(II) was studied using aqueous two-phase system (ATPS) comprising by polyethylene oxide (PEO1500) or triblock copolymers (L64 or L35), electrolyte (sodium citrate or sodium sulfate) and water in the presence or absence of chloride ions. The extraction behavior of the Hg(II) for the macromolecule-rich phase is affected by the following parameters: amount of added extractant, pH, and the nature of the electrolyte and macromolecule of the ATPS. The APTS of PEO1500 + sodium citrate + H2O (pH 1.00 and 0.225 mol kg−1 KCl) produced the highest Hg(II) %E = (92.3 ± 5.2)%. Under the same conditions, excellent separation factors (1.54 × 102 − 3.21 × 1010) for recovery of mercury in the presence of co-existing metals were obtained. Efficient and selective extraction of Hg(II) from domestic and industrial synthetic effluents was achieved using this ATPS.Item Copper recovery from ore by liquid–liquid extraction using aqueous two-phase system(Journal of Hazardous Materials, 2012-08-14) Lemos, Leandro Rodrigues de; Santos, Igor José Boggione; Rodrigues, Guilherme Dias; Silva, Luis Henrique Mendes da; Silva, Maria C. Hespanhol daWe investigated the extraction behavior of Cu(II) in the aqueous two-phase system (ATPS) formed by (L35 + MgSO4 + H2O) or (L35 + (NH4)2SO4 + H2O) in the presence of the extracting agent 1-(2-pyridylazo)-2-naphthol (PAN). At pH = 3 and a PAN concentration of 0.285 mmol kg−1, both ATPS lead to the effective separation of Cu(II) from other metallic ions (Zn(II), Co(II), Ni(II) and Fe(III)). High separation factors range between 1000 and 10,000 were obtained for the extraction of Cu(II) and concomitant metallic ions. This ATPS was used for the extraction of Cu(II) from a leached ore concentrate with a extraction percentage of 90.4 ± 1.1%; other metals were mainly located in the bottom phase.Item Sistema aquoso bifásico: uma alternativa eficiente para extração de íons(Química Nova, 2006-07-06) Silva, Maria do Carmo Hespanhol da; Silva, Luis Henrique Mendes da; Paggioli, Fernanda Jürgensen; Coimbra, Jane Sélia Reis; Minim, Luis AntonioSolvent extraction has been successfully applied to metal ion preconcentration and often meant the use of toxic organic diluents. However, regulatory pressure is increasingly focusing on the use and disposal of organic solvents, and thus the development of nonhazardous alternatives is important. In this review, we examine the application of aqueous biphasic systems (ABS) to extraction of ions, analyzing their potential and limitations and suggest that ABSs could be an efficient substitute for oil/water biphasic systems. ABSs are formed by mixing certain inorganic salts and water-soluble polymers, or by mixing two water-soluble polymers.