The Calculation of the Stability Constant of Nickel Fulvate, using an Average Molecular Weight of Active Associate of Fulvic Acids at pH = 8

Abstract

Fulvic acids play an important role in complicated formation processes and determine how heavy metals migrate in natural waterways. Despite investigation, experimental data on the stability constants of complex fulvic acid-heavy metal complexes (including nickel) is heterogeneous and differs in various ways from one another. One of the sources of this problem is the failure to consider the average molecular weight of fulvic acid partners, which leads to incorrect results. The solubility method was used to investigate the complex formation process between Ni (II) and fulvic acids at pH=8.0. The suspension of Ni(OH)2 was used as a solid phase. The adsorption–chromatographic approach was used to separate fulvic acids from Paravani Lake. The active charcoal was used as a sorbent. In this chapter is shown that, during complex formation process every 0,29 part of an associate of fulvic acids(Mw=6260), inculcates into nickel’s inner coordination sphere as an integral ligand, so it may assume, that the average molecular weight of the associate of fulvic acids which takes part in complex formation process equals to 1815. This component of the fulvic acid association was previously referred to as a "active associate.".The average molecular weight of the “active associate” was used for determination the composition of nickel dyhydroxo fulvate complex (1:1), the concentration of free ligand and average stability constant, which equals to \(\beta\) = 7,95x105; lg \(\beta\)=5,90