Study of stability constant and complexing capacity of humic acid extracted fromSahara soil with Ni(II), Zn(II) and Cd(II) by quenching of fluorescence

Abstract

Humic substances play a role in the dissolution, transport and deposition of charged positively inorganic ions such as heavy metals. The complexation of these ions by humic substances is widely studied because it plays a very important role on the chemical speciation of these elements, and therefore their reactivity in an ecosystem1-5.The objective of this study is to determine the complexing capacity of humic acid extracted from Sahara soil (Tamanrasset: THA) with Ni(II), Zn(II) and Cd(II) and the stability constants of formed complexes byquenching of fluorescence, and to compare the results with other methods. This work allows a preliminary study to highlight a biosensor of heavy metals using Algerian humic acid.The calculated complexing capacity indicates that the degree of association of metal ion with Tamanrasset humic acid is higher than other humic acids found in the literature5. For the examined humic acid, the stability constants (logKML) of M-THA formed complexes follow the order: Ni(II)>Zn(II)>Cd (II).Basing on these results, THA may play a role of biocaptor of polluting metals.