No abstract

The recently synthesized ionic liquid (IL) 2-butylthiolonium bis(trifluoromethanesulfonyl)amide, [mimSBu][NTf(2)], has been used for the extraction of copper(II) from aqueous solution. The pH of the aqueous phase decreases upon addition of [mimSBu](+), which is attributed to partial release of the hydrogen attached to the N(3) nitrogen atom of the imidazolium ring. The presence of sparingly soluble water in [mimSBu][NTf(2)] also is required in solvent extraction studies to promote the incorporation of Cu(II) into the [mimSBu][NTf(2)] ionic liquid phase. The labile copper(II) system formed by interacting with both the water and the IL cation component has been characterized by cyclic voltammetry as well as UV-vis, Raman, and (1)H, (13)C, and (15)N NMR spectroscopies. The extraction process does not require the addition of a complexing agent or pH control of the aqueous phase. [mimSBu][NTf(2)] can be recovered from the labile copper-water-IL interacting system by washing with a strong acid. High selectivity of copper(II) extraction is achieved relative to that of other divalent cobalt(II), iron(II), and nickel(II) transition-metal cations. The course of microextraction of Cu(2+) from aqueous media into the [mimSBu][NTf(2)] IL phase was monitored in situ by cyclic voltammetry using a well-defined process in which specific interaction with copper is believed to switch from the ionic liquid cation component, [mimSBu], to the [NTf(2)] anion during the course of electrochemical reduction from Cu(II) to Cu(I). The microextraction-voltammetry technique provides a fast and convenient method to determine whether an IL is able to extract electroactive metal ions from an aqueous solution.

Electrochemical studies on the Fc + e(-) <==> Fc(+) (Fc = ferrocene) process have been undertaken via the oxidation of Fc and reduction of Fc(+) as the hexafluorophosphate (PF(6)(-)) or tetrafluoroborate (BF(4)(-)) salts and their mixtures in three ionic liquids (ILs) (1-butyl-1-methylpyrrolidinium bis[(trifluoromethyl)sulfonyl]imide, 1-butyl-3-methylimidazolium tetrafluoroborate, and 1-butyl-3-methylimidazolium hexafluorophosphate). Data obtained at macro- and microdisk electrodes using conventional dc and Fourier-transformed large-amplitude ac (FT-ac) voltammetry reveal that diffusion coefficients for Fc and Fc(+) differ significantly and are a function of the Fc and Fc(+) concentration, in contrast to findings in molecular solvents with 0.1 M added supporting electrolyte media. Thus, the faradaic currents associated with the oxidation of Fc (Fc(0/+)) and reduction of FcPF(6) or FcBF(4) (Fc(+/0)) when both Fc and Fc(+) are simultaneously present in the ILs differ from values obtained when individual Fc and Fc(+) solutions are used. The voltammetry for both the Fc(0/+) and Fc(+/0) processes exhibited near-Nernstian behavior at a glassy carbon macrodisk electrode and a platinum microdisk electrode, when each process was studied individually in the ILs. As expected, the reversible formal potentials (E(o)') and diffusion coefficients (D) at 23 +/- 1 degrees C were independent of the electrode material and concentration. However, when Fc and FcPF(6) or FcBF(4) were both present, alterations to the mass transport process occurred and apparent D values calculated for Fc and Fc(+) were found to be about 25-39% and 32-42% larger, respectively, than those determined from individual solutions. The apparent value of the double layer capacitance determined by FT-ac voltammetry from individual and mixed Fc and Fc(+) conditions at the GC electrode was also a function of concentration. Double layer capacitance values increased significantly with the concentration of Fc and FcPF(6) or FcBF(4) when species were studied individually or simultaneously, but had a larger magnitude under conditions where both species were present. Variation in the structure of the ILs and hence mobilities of the ionic species, when Fc and FcPF(6) or FcBF(4) are simultaneously present, is considered to be the origin of the nonadditivity of the faradaic currents and variation in capacitance.

Different global events such as industrial development and the population increment have triggered the presence and persistence of several organic and inorganic contaminants, representing a risk for the environment and human health. Consequently, the search and application of novel technologies for alleviating the challenge of environmental pollution are urgent. Nanotechnology is an emerging science that could be employed in different fields. In particular, Nanoremediation is a promising strategy defined as the engineered materials employed to clean up the environment, is an effective, rapid, and efficient technology to deal with persistent compounds such as pesticides, chlorinated solvents, halogenated chemicals, or heavy metals. Furthermore, nanoremediation is a sustainable alternative to eliminate emerging pollutants such as pharmaceutics or personal care products. Due to the variety of nanomaterials and their versatility, they could be employed in water, soil, or air media. This review provides an overview of the application of nanomaterials for media remediation. It analyzes the state of the art of different nanomaterials such as metal, carbon, polymer, and silica employed for water, soil, and air remediation.