Partitioning of mercury in aqueous biphasic systems and on ABEC resins

Evolution of Environmentally Friendly Strategies for Metal Extraction

The demand for the recovery of valuable metals and the need to understand the impact of heavy metals in the environment on human and aquatic life has led to the development of new methods for the extraction, recovery, and analysis of metal ions. With special emphasis on environmentally friendly approaches, efforts have been made to consider strategies that minimize the use of organic solvents, apply micromethodology, limit waste, reduce costs, are safe, and utilize benign or reusable materials. This review discusses recent developments in liquid- and solid-phase extraction techniques. Liquid-based methods include advances in the application of aqueous two- and three-phase systems, liquid membranes, and cloud point extraction. Recent progress in exploiting new sorbent materials for solid-phase extraction (SPE), solid-phase microextraction (SPME), and bulk extractions will also be discussed.

Determination of Heavy Metal Ions and Organic Pollutants in Water Samples Using Ionic Liquids and Ionic Liquid-Modified Sorbents

Water pollution, especially by inorganic and organic substances, is considered as a critical problem worldwide. Several governmental agencies are listing an increasing number of compounds as serious problems in water because of their toxicity, bioaccumulation, and persistence. In recent decades, there has been considerable research on developing analytical methods of heavy metal ions and organic pollutants from water. Ionic liquids, as the environment-friendly solvents, have been applied in the analytical process owing to their unique physicochemical properties. This review summarizes the applications of ionic liquids in the determination of heavy metal ions and organic pollutants in water samples. In addition, some sorbents that were modified physically or chemically by ionic liquids were applied in the adsorption of pollutants. According to the results in all references, the application of new designed ionic liquids and related sorbents is expected to increase in the future.

Aqueous two-phase system (ATPS): an overview and advances in its applications

Aqueous two-phase system (ATPS) is a liquid-liquid fractionation technique and has gained an interest because of great potential for the extraction, separation, purification and enrichment of proteins, membranes, viruses, enzymes, nucleic acids and other biomolecules both in industry and academia. Although, the partition behavior involved in the method is complex and difficult to predict. Current research shows that it has also been successfully used in the detection of veterinary drug residues in food, separation of precious metals, sewage treatment and a variety of other purposes. The ATPS is able to give high recovery yield and is easily to scale up. It is also very economic and environment friendly method. The aim of this review is to overview the basics of ATPS, optimization and its applications.

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.

Cd(II) extraction in PEG-based two-phase aqueous systems in the presence of iodide ions. Analysis of PEG-rich solid phases

Cd(II) plus iodide species were extracted into PEG-rich phases in the aqueous PEG(1550)-(NH4)2SO4 system at pH 2.05–7.12. IR spectra show that increasing (NH4)2SO4 solution acidity does not protonate PEG ether oxygen atoms, but decreases water content in the PEG-rich phases. Metallic species’ extraction into the PEG predominantly alters how water molecules bind to polymer chains; the changes in their absorption bands depend on pH. Microscopy shows that “fixation” of the extracted metal in the PEG-rich phase occurs by specific interactions which depend on the species. These also determine changes in the polymer chains’ conformation.

The extraction of Zn(II) in aqueous PEG (1550)-(NH4)2SO4 two-phase system using Cl- ions as extracting agent

The extraction of Zn(II) in an aqueous PEG (1550) - (NH4)2SO4 two-phase system as a function of several experimental parameters was studied. PEG-based aqueous two-phase systems are composed of two immiscible phases: a polymer-rich phase and a salt-rich phase, which can be used for extraction experiments. In the absence of a suitable extracting agent, for the system consisting of a mixture of equal volumes of 40 mass% PEG and 40 mass% (NH4)2SO4 aqueous solutions, Zn(II) remained predominantly in the salt-rich phase. Variation of the pH of the salt stock solution did not change very much the extraction efficiency. By adding chloride ions, an enhancement of the Zn(II) extraction was observed. The Zn(II) extraction efficiency in presence of Cl- depends on the acidity of the salt stock solution and on the concentration of chloride ions added into the system.

Functionalized imidazolium salts for task-specific ionic liquids and their applications

Recent developments in task specifically functionalized imidazolium salts, which can be used for specific tasks ranging from catalysts recycling, supports for organic synthesis, catalysis, separation of specific metal ions from aqueous solution, and construction of nanostructures and ion conductive materials, have been reviewed.

Hg (II) extraction in a PEG-based aqueous two-phase system in the presence of halide ions. I. Liquid phase analysis

The partition behaviour of Hg (II) was studied in an aqueous polyethylene glycol (PEG) — (NH4)2SO4 two-phase system as a function of halide, halide concentration, and pH. For a system prepared by mixing equal volumes of 40 % (w/w) PEG (1550) with 40 % (w/w) (NH4)2SO4, Hg(II) remains almost exclusively in the salt-rich phase. The addition of NaX (X = Cl−, Br−, I−) enhances Hg (II) partition into the PEG-rich phase due to the formation of halide complexes. The efficiency of halide extractants increases in the order: Cl− < Br− < I−. Mercury extraction is improved at lower halide ion concentration by higher stock salt solution acidity. From the distribution coefficients determined as a function of halide ion concentration, the extracted species were identified. The Hg (II) extractability is determined by the type and stability of the Hg (II) halide species, and depends on the stock salt solution acidity. The observed behaviour is discussed and a possible extraction mechanism is proposed.

Unified Markov thermodynamics based on stochastic forms to classify drugs considering molecular structure, partition system, and biological species:

To date, molecular descriptors do not commonly account for important information beyond chemical structure. The present work, attempts to extend, in this sense, the stochastic molecular descriptors, incorporating information about the specific biphasic partition system, the biological species, and chemical structure inside the molecular descriptors. Consequently, MARCH-INSIDE molecular descriptors may be identified with time-dependent thermodynamic parameters (entropy and mean free energy) of partition process. A classification function was developed to classify data of 423 drugs and up to 14 different partition systems at the same time. The model has shown a high overall accuracy of 92.1% (293 out of 318 cases) in training series and 90% (36 out of 40 cases) in predicting ones. Finally, we illustrate the use of the model by predicting a high probability (%) for G1 (a novel antibacterial drug) to undergo partition on different biotic systems (rat organs): liver (97.7), spleen (97.5), lung (97.4), and adipose tissue (97.6). These theoretical results coincide with herein reported steady state plasma concentrations (c) and partition coefficients (P) in liver (c=42.25+/-7.86/P=4.75), spleen (11.47+/-4.43/P=1.29), lung (17.04+/-3.58/P=1.91), and adipose tissue (28.19+/-11.82/P=3.17). All values were relative to (14)C-labeled-radioactive-G1 in plasma (c=8.9+/-3.05) after 3h of oral administration. In closing, the present stochastic forms derive average thermodynamic parameters fitting on a more clearly physicochemical framework with respect to classic vector-matrix-vector forms, which include, as particular cases, quadratic forms such as Wiener index, Randic invariants, Zagreb descriptors, Harary index, Balaban index, and Marrero-Ponce quadratic molecular indices.

Electroanalytical Determination of Trace Chloride in Room-Temperature Ionic Liquids

The electroanalytical quantification of chloride in [C4mim][BF4], [C4mim][NTf2], and [C4mim][PF6] ionic liquids has been explored using linear sweep and square wave voltammetry. Cathodic stripping voltammetry at a silver disk electrode is found to be the most sensitive. The methodology is based on first holding the potential of the electrode at +2.0 V (vs Ag wire), to accumulate silver chloride at the electrode. On applying a cathodic scan, a stripping wave is observed corresponding to the reduction of the silver chloride. This stripping protocol was found to detect ppb levels of chloride in [C4mim][BF4], [C4mim][NTf2], and [C4mim][PF6]. Although other methods for chloride have been reported for [BF4](-)- and [PF6](-)-based ionic liquids, no methods have been reported for [NTf2](-) ionic liquids.

Model for the partition of metal ions in aqueous two-phase systems

A model for the partition of metal ions in aqueous two-phase systems (ATPS) has been developed. The partition coefficient of a metal ion D(M), is a function of several variables of the ion (size, charge and electronegativity), characteristics of the ATPS such as type of salt, salt concentration and PEG concentration and additional inorganic salt present in the ATPS. The model has been tested for complex anions of BiX4- (BiCl4-, BiBr4- and BiI4-) and cations from groups I and II (Na+, Cs+, Ca2+, Sr2+ and Ba2+) giving a good correlation in both systems. It was found that for these systems partition coefficient increases with ion size and the variables Y which is a characteristic of the ATPS and Z which is a characteristic of the additional salt present in the system. The partition coefficient of BiX4- increases with the variable X which is a characteristic of the electrical interactions of the metal ion. The cations from groups II and I exhibit the opposite behavior, which is attributable to the ion charge.

Partitioning and concentrating biomaterials in aqueous phase systems

Aqueous phase separation is a general phenomenon which occurs when structurally distinct water-soluble macromolecules are dissolved, above certain concentrations, in water. The number of aqueous phases obtained depends on the number of such distinct macromolecular species used. Aqueous two-phase systems, primarily those containing poly(ethylene glycol) and dextran, have been widely used for the separation of biomaterials (macromolecules, membranes, organelles, cells) by partitioning. The polymer and salt compositions and concentrations chosen greatly affect the physical properties of the phases. These, in turn, interact with the physical properties of biomaterials included in the phases and affect their partitioning. Specific extractions of biomaterials can be effected by including affinity ligands in the systems. The phase systems can also be used to obtain information on the surface properties of materials partitioned in them; to study interactions between biomaterials; and to concentrate such materials.