Synthesis, Characterization and Metal Sorption Studies of Isatin and Ninhydrin Reagents Immobilized on Silica Gel Amine Surface

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Abstract
Silica gel immobilized aliphatic mono and polyamine sorbents (I–IV) were further modified by Schiffs base reaction with the carbonyl-containing compounds isatin and ninhydrin to produce the corresponding eight newly synthesized sorbents (V–XII). The capability of these sorbents (V–XII) for the extraction of Fe(III) and the divalent metal ions Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(III), along with Fe(III) extraction by the parent sorbents (I–IV), from aqueous solutions, are determined in various buffer solutions by using the batch equilibrium method. The results obtained are discussed in terms of molecular structure of the immobilized chelates and indicated that the incorporated hard oxygen donor ligands significantly improve the uptake of Fe(III), known to act as a hard acid. Moreover, TGA revealed that there is an appreciable increase in thermal stability of two representative new sorbents, isatin (VI) and ninhydrin (X) as compared to their parent ethylenediamine silica gel sorbent (II).