A selective flotation-spectrophotometric method for the determination of nickel using dimethylglyoxime

Abstract

Um método simples e seletivo para a separação e pré-concentração de níquel foi desenvolvido. O método é baseado na flotação de um complexo de Ni e dimetilglioxima (DMG) na interface de uma solução aquosa com n-hexano. O complexo Ni-DMG foi separado e determinado por espectrofotometria. A flotação quantitativa do complexo foi possível no intervalo de pH de 9-12. O método é simples e livre da interferência de todos os cátions e ânions e apresenta um grande intervalo linear. O procedimento foi aplicado com sucesso na determinação de traços de níquel em águas de poços e águas residuais de um processo de eletrodeposição. A exatidão do método foi avaliada usando material de referência certificado (NIST 864) e enriquecendo as amostras com diferentes quantidades de Ni 2+ .A simple and selective method for separation and preconcentration of nickel has been developed. The method is based on the flotation of a complex of Ni and dimethylglyoxime (DMG) at the aqueous solution-n-hexane interface. The complex was separated and Ni determined spectrophotometrically by DMG after addition of oxidizing agent. The quantitative flotation of the complex was possible in the pH range of 9-12. The method is simple and free from the interference of all cations and anions and has a wide linear range. The procedure was successfully applied to the determination of trace amounts of nickel in well water and waste water in coating plant. The method's accuracy was investigated by using standard reference materials alloys (NIST 864) and by spiking the samples with different amounts of Ni 2+ . Keywords: flotation, spectrophotometry, dimethylglyoxime, nickel IntroductionNickel is an important constituent of several steel alloys. Its determination is required to control both raw material and industrial products. 1 In addition it is readily encountered in the environment, which enters from land-based resources, such as oxidic and sulfide ores or industrial sources, such as spent catalysts, alloy scrap, sludge, dust, and wastewater. 2 Dimethylglyoxime (DMG) is widely used and for the spectrophotometric determination of nickel 3,4 it has also been used for separation and preconcentration of Ni by liquid-liquid extraction 5 or solid phase extraction 6-8 but all of these separation methods suffer from lack of selectivity. For example, metal ions such as Ni(II), Pb(II), Mn(II), Bi(III), Co(II), Cd(II), Zn(II), and Fe(II) could interfere at concentrations higher than 5 mg L -1 in solid phase extraction of Ni 2+ using DMG as a complexing agent. 8 This paper deals with a selective and simple method for separation and preconcentration of Ni with DMG.Flotation spectrophotometry allows one to preconcentrate the trace elements in various materials. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Primary investigations showed that the none of two usual complexes of Ni and DMG could not float completely in interface of liquid and organic phase due to solubility in water and organic phase of Ni(Dm) 3 2-and Ni(HDm) 2 , respectively. Thus a different ...