Dihydrazone of dialdehyde starch and its metal complexes

Dialdehyde starch (32%) from periodate oxidized potato starch was converted into its dihydrazone (DASHZ). It was considered as a potential trap of heavy metals from sewage and in soil. The dihydrazone (DASHZ) coordinated to Ca, Cd, Co (II), Cu (II), Fe (II), Mg, Mn (II), Ni (II), Pb (II), and Zn ions. The nitrogen atoms of the C=N moiety in dihydrazone as well as the oxygen atom of the former pyranose ring were the coordination sites. Metal ions were chelated to a different extent. One mole of a metal ion could coordinate with 3 [Cu(II)] to 50 [Mn(II)] mole of the DASHZ units. Similarly, as DASHZ, the metal complexes decomposed thermally in four steps but the rates of decomposition of the ligand and chelates in relevant steps were different. Except the complex with Mg, these rates for complexes were lower. (C) 2004 Elsevier Ltd. All rights reserved.