Hydrophobic effect on the partitioning of [Fe(CN)5(NO)]2− and [Fe(CN)6]3− anions in aqueous two-phase systems formed by triblock copolymers and phosphate salts

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.

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).