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Complexation-adsorption Studies of Bis(Salicylidene) Ethylenediamine Fe(II) Metal Chelate Extraction Model Using Response Surface Methodology

Nworie FS, Nwabue FI, Akpa SO and Igidi OJ

A new method on solvent extraction combined with response surface methodology (RSM) modeling and optimization has been developed for the preparation and extraction of Fe(II) metal chelate based on the complexation of Fe(II) with bis(salicylidene)ethylenediamine(Salen). The RSM method based on a three level and five variable Box-behnken design (BBD) was employed to obtain the optimal combination of extraction conditions. Summarily, Fe(II)metal chelate was optimally prepared and extracted with 0.42% Salen concentration, 20 μg metal ion concentration, a temperature of 20°C, extraction time of 8.19 minutes, acid concentration of 10-4 M and one cycle extraction. The 3D response surface plot and the contour plot derived from the mathematical models were applied to determine the optimal conditions. Under the optimized conditions, the experimental value of 81% complex extracted was in close agreement with the value predicted (81.75%) by the model. Dynamic adsorption data were applied to pseudo-first–order and pseudo–second order rate equations. The time series data fitted well to pseudo-second order kinetic model. According to the correlation coefficients, the complexation adsorption of Fe(II) and Salen correlated well with Langmuir and Freundlich models. GC-MS, FT-IR and UV-vis data of the ligand and the complex were recorded and the data showed complexation between the ligand and the Fe(II) ion.