Extraction Kinetics of Ni(II) in the Ni2+- SO42--Ac-(Na+, H+)-Cyanex 272 (H2A2)-Kerosene-3% (v/v) Octan-1-ol System Using Single Drop Technique

摘要

The kinetics of extraction of Ni(II) in the Ni2+-SO4 2_AC- (Na+, H+)-Cyanex 272 (H2A2)-kerosene-3% (v/v) octan-1-ol system using the single falling drop technique have been reported. The flux of Ni2+ transfer (F) at 303 K in presence of 3% (v/v) octan-1-ol (de-emulsifier) can be represented as:.Depending on reaction parameters, the activation energy (Ea) and enthalpy change in activation (DH±) varies within 17 - 58 kJ/mol and 17 - 67 kJ/mol, respectively. Entropy change in activation (DS±) is always negative. Based on the empirical flux equation, Ea and DS± values, mechanisms of extractions in different parametric conditions are proposed. At low and [Ac-], and pH, the chemical controlled step is: Ni2+ + A- → NiA+; and this reaction occurs via an SN2 mechanism. But in most parametric conditions, the process is under intermediate control; and at high SO42- and [Ac-], and pH, the extraction process is under diffusion control.