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 deriva tives on the surface of silica gel is described. The new silica gel ph ases were synthesized by a very simple and rapid route which can be de fined as a one-step reaction. The phases were proved to show an excell ent 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 s haking times. The process of selective extraction of iron (III), in pr esence of an interfering ion, by these phases was also studied by both column and batch equilibrium techniques in order to identify the poss ible type of interference of each metal ion in this process. Three div alent metal ions (Mg, Ca and Mn) exhibited a minimum interference in i ron (III) extraction. A group of six divalent metal ions (Co, Ni, Cu, Zn, Cd and Pb) were found to be interfering in the selective extractio n of iron (III) via the arylazo-moiety of the silica phase, while Cr(I II) was found to show a specific interference type based on the affini ty of Cr(III) for binding to the chelation centers of the salicylic ac id moiety of the silica phase. (C) 1997 Elsevier Science B.V.