Study of the selective extraction of iron (III) by silica-immobilized 5-formyl-3-arylazo-salicylic acid derivatives

A method for immobilization of 5-formyl-3-arylazosalicylic acid derivatives on the surface of silica gel is described. The new silica gel phases were synthesized by a very simple and rapid route which can be defined as a one-step reaction. The phases were proved to show an excellent improvement in the iron (III) extraction and the determined mmol g(-1) values are in the range of 1.24-1.32. The metal-uptake properties of eleven metal ions were also evaluated at different pH values and shaking times. The process of selective extraction of iron (III), in presence of an interfering ion, by these phases was also studied by both column and batch equilibrium techniques in order to identify the possible type of interference of each metal ion in this process. Three divalent metal ions (Mg, Ca and Mn) exhibited a minimum interference in iron (III) extraction. A group of six divalent metal ions (Co, Ni, Cu, Zn, Cd and Pb) were found to be interfering in the selective extraction of iron (III) via the arylazo-moiety of the silica phase, while Cr(III) was found to show a specific interference type based on the affinity of Cr(III) for binding to the chelation centers of the salicylic acid moiety of the silica phase. (C) 1997 Elsevier Science B.V.