Pamela R. Patrício

Application of aqueous two-phase systems for the development of a new method of cobalt(II), iron(III) and nickel(II) extraction: A green chemistry approach

We have investigated the extraction behavior of the metallic ions Co(II), Fe(III) and Ni(II) as a function of the amount of potassium thiocyanate used as an extracting agent, using the following aqueous two-phase systems (ATPS): PEO + (NH(4))(2)SO(4) + H(2)O, PEO + Li(2)SO(4) + H(2)O, L35 + (NH(4))(2)SO(4) + H(2)O and L35 + (Li)(2)SO(4)+H(2)O. Metal extraction from the salt-rich phase to the polymer-rich phase is affected by the following parameters: amount of added extractant, pH, and the nature of the electrolyte and polymer that forms the ATPS. Maximal extraction percentages were obtained for Co(II) (99.8%), Fe(III) (12.7%) and Ni(II) (3.17%) when the ATPS was composed of PEO1500 + (NH(4))(2)SO(4) + H(2)O containing 1.4 mmol of KSCN at pH 4.0, providing separation factors as high as S(Co, Fe) = 3440 and S(Co, Ni) = 15,300. However, when the same ATPS was used at pH 2.0, the maximal extraction percentages for iron and nickel were 99.5% and 4.34%, respectively, with S(Fe, Ni) equal to 4380. The proposed technique was shown to be efficient in the extraction of Co(II) and Fe(III), with large viability for the selective separation of Co(II) and Fe(III) ions in the presence of Ni(II).

Aqueous two-phase systems: A new approach for the determination of p-aminophenol

A new method has been developed for the spectrophotometric determination of p-aminophenol (PAP) in water, paracetamol formulations and human urine samples with a recovery rate between 94.9 and 101%. This method exploits an aqueous two-phase system (ATPS) liquid-liquid extraction technique with the reaction of PAP, sodium nitroprusside and hydroxylamine hydrochloride in pH 12.0, which produces the [Fe(2)(CN)(10)](10-) anion complex that spontaneously concentrates in the top phase of the ATPS ([Formula in text]). The ATPS does not require an organic solvent, which is a safer and cleaner liquid-liquid extraction technique for the determination of PAP. The linear range of detection was from 5.00 to 500 μg kg(-1) (R ≥ 0.9990; n=8) with a coefficient of variation of 2.11% (n=5). The method exhibited a detection limit of 2.40 μg kg(-1) and a quantification limit of 8.00 μg kg(-1). The ATPS method showed a recovery that ranged between 96.4 and 103% for the determination of PAP in natural water and wastewater samples, which was in excellent agreement with the results of the standard 4-aminoantipyrine method that was performed on the same samples.

Green recovery of mercury from domestic and industrial waste.

Recovery 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 (1.54×10(2)-3.21×10(10)) 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.

Green speciation of iron using aqueous two-phase system

Fe(II) and Fe(III) have distinct chemical and biological functions. Consequently, it is more important to determine the fraction of both oxidation state that knowing the total iron concentration in a sample. However, green methods for iron speciation are still limited. This work uses aqueous two-phase system, a safe alternative to liquid-liquid extraction, to perform the chemical speciation of iron. This method is based on the reaction of Fe(II) with 1,10-phenanthroline extractant, forming a complex of Fe(II)-phenanthroline that concentrates in the top phase of the system. The Fe(III) specie concentrated in the bottom phase of the system. Iron speciation was affected by the electrolyte nature, macromolecule type, quantity of phenanthroline added, and pH. The system formed by PEO1500 + Na3C6H5O7 + H2O at pH 6.00, containing 5.00 mmol kg-1 of phenanthroline, was successfully used to separate the iron species before determination by flame atomic absorption spectrometry. Under these optimal conditions, a separation factor of 233 was obtained between Fe(II) and Fe(III) with extraction percentages of (95.1 ± 1.0)% and (7.68 ± 0.50)%, respectively The proposed method was successfully applied for iron speciation in water samples, and provided recovery percentages ranging between 90 and 106%.