Study of the Nickel Complex Formation with Citric Acid in A Mixture Alkyl Polyglycoside10 (APG10) Surfactant/Water System
Abstract
The stability constants of complexes formed by metal cations Ni(II) and citric acid in water and in APG10 surfactant/water medium are determined by the pH titration method combined with using Hyss 2009 simulation software. Under experimental conditions, the Ni(II) complexes with citric acid ligand were determined consisting of [NiCit]- , [NiHCit], [NiCit2] 4- and [NiHCit2] 3- . The logβ values of the stability constants of the complex species are linearly dependent and decreases with increasing concentration of APG10. The influence of APG10 surfactant on the decrease of stability constants maybe explained by the interation of the surfactant micelles with the complex species. In 0.5% APG10/water solution, the decrease in stability constant value of Ni(II) - Citric complexes compared to these values in the aqueous environment are from 4.367 to 14.126 times.
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Introduction
The Complexes of metal ions with chelated agents exhibits great concern in many approaches of researches and applications, such as paper production, textiles, medicine, biology and water treatment [1-3]. The complexes of heavy metal ions as such Ni, Co, Sr, U … with chelating organic ligands in aqueous media were studied [4-7]. The formation of metal ions – chelating organic ligands in mixed surfactant compounds/water is received a great interest due to their advantage of micelles present in media to the possibility varying the complex stability constants [8-10]. In this paper, the nickel Ni(II) complex formation with citric acid in a mixed alkyl polyglycoside (APG10) was studied in detail. Alkyl polyglycoside is a biodegradable ingredient that is growing in popularity due to its favorable environmental profile, is non-ionic surfactant widely used in a variety of cosmetic, household, and industrial applications [11-12]. The raw materials to produce alkyl polyglycoside are typically starch and fat. The final products of this process are typically complex mixtures of compounds with different sugars comprising the hydrophilic end and alkyl groups of hydrophobic.
Conclusion
In the environment of APG10 surfactants/water system, the metal ions Ni(II) form complexes with citric acid in the same complex form as in the aqueous medium. However, the constituent content of citric acid, complexes and the stability constant values have changed. For citric acid, when the concentration of APG10 increased to 0.5% of the values β(H3Cit), β(H2Cit), β(HCit2- ) decreased by 2.188; 1.778; 1.318 times compared with the stability constant value in water environment. For Ni2+ complexes, this value decreases gradually for [NiCit]- , [NiCitH], [NiCit2] 4- , [NiCit2H]3- complexes, being 4.367; 5.623 ; 14.126 ; 9.550 times respectively at APG10 0.5%.