Leandro Rodrigues de Lemos

Application of hydrophobic extractant in aqueous two-phase systems for selective extraction of cobalt, nickel and cadmium.

This work developed a new and efficient method of extracting and separating Co(II), Ni(II) and Cd(II) in aqueous two-phase systems (ATPS) composed of triblock copolymer (L64)+Na(2)C(4)H(4)O(6)+water and L64+Li(2)SO(4)+water using the hydrophobic extractant 1-nitroso-2-naphtol, which complexes the metal ions and partitions in the triblock copolymer micelles in the ATPS top phase. Metal extraction from the salt-rich phase to the copolymer - rich phase is strongly affected by the fine-tuning of the following parameters: amount of added extractant, type of electrolyte, pH, and tie-line length. Excellent separation factors (S(i,j)) between the metals were obtained at pH=3.00 (S(Co,Cd)=1550 and S(Ni,Cd)=16,700) and pH=1.00 (S(Co,Ni)=826). In the interference study, Co(II) was selectivity extracted in the top phase in the presence of Ni(II) and Cd(II) in a concentration of up to 20 times the cobalt level in the system.

Copper recovery from ore by liquid-liquid extraction using aqueous two-phase system.

We investigated the extraction behavior of Cu(II) in the aqueous two-phase system (ATPS) formed by (L35+MgSO(4)+H(2)O) or (L35+(NH(4))(2)SO(4)+H(2)O) 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.

A green and sensitive method to determine phenols in water and wastewater samples using an aqueous two-phase system

A 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., Li(2)SO(4), Na(2)SO(4) or K(2)HPO(4)+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 [Fe(2)(CN)(10)](10-) that spontaneously concentrates in the top phase of the system. The linear range was 1.50-500microgkg(-1) (R>or=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 1.88microgkg(-1) and limits of quantification (LOQs) of 4.22 and 6.28microgkg(-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.

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.

Application of a macromolecular micellar system formed by the P123 triblock copolymer for determination of copper concentrations

This work proposes a method for determination Cu(II) concentrations, based on the formation of a copper-1-nitroso-2-naphthol complex, in the presence of micelles; formed by a triblock copolymer, made up of two blocks of polyethylene oxide (PEO), and one block of polypropylene oxide (PPO). The insoluble copper complexes, are concentrated inside the hydrophobic micelle core; formed by the PPO block. For a solution containing 0.200 mg L−1 Cu(II), the proposed method had a relative standard deviation of 2.0% (n = 3); an absolute error from 0.11 to 0.39 mg L−1; and a linear calibration range, from 0.200 to 0.800 mg L−1. Detection and quantification limits, were 43.1 mg L−1 and 144 mg L−1, respectively. We show that there is excellent agreement, between the results obtained using our novel method; and those obtained using flame atomic absorption spectrometry: In the determination of Cu(II) concentrations, in Brazilian sugar-cane spirits. The proposed method, is the first to apply macromolecular micelle systems, to the determination of copper concentrations; and improves upon the results obtained using molecular surfactants. This method is environmentally friendly (since it does not use any organic solvents for extraction), and the triblock copolymer is biodegradable and non-toxic.