The use of dialdehyde starch derivatives in the phytoremediation of soils contaminated with heavy metals.

Products of the reaction between dialdehyde starch and Y-NH2 compounds (e.g. semicarbazide or hydrazine) are effective ligands for metal ions. The usefulness of these derivatives was tested in the experiment, both in terms of the immobilization of heavy metal ions in soil and the potential application in phytoextraction processes. The experimental model comprised maize and the ions of such metals as: Zn(II), Pb(II), Cu(II), Cd(II), and Ni(II). The amount of maize yield, as well as heavy metal content and uptake by the aboveground parts and roots of maize, were studied during a three-year pot experiment. The results of the study indicate the significant impact of heavy metals on reduced yield and increased heavy metal content in maize. Soil-applied dialdehyde starch derivatives resulted in lower yields, particularly disemicarbazone (DASS), but in heavy metal-contaminated soils they largely limited the negative impact of these metals both on yielding and heavy metal content in plants, particularly dihydrazone (DASH). It was demonstrated that the application of dihydrazone (DASH) to a soil polluted with heavy metals boosted the uptake of Zn, Pb, Cu, and Cd from the soil, hence there is a possibility to use this compound in the phytoextraction of these metals from the soil. Decreased Ni uptake was also determined, hence the possibility of using this compound in the immobilization of this metal. The study showed that dialdehyde starch disemicarbazone was ineffective in the discussed processes.

Formation of nanometal particles in the dialdehyde starch matrix.

Environmentally friendly method of the preparation of dialdehyde starch (DAS) based composites containing nanosilver (DAS/Ag) and nanogold (DAS/Au) as reducing and protecting agents was developed. UV-vis spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD) confirmed formation of about 10nm ball shaped Ag and Au nanoparticles situated within the polysaccharide template. Thermal properties of the composites were characterized involving differential scanning calorimetry (DSC), whereas molecular weights of polysaccharide chains of the matrix were estimated with the size exclusion chromatography coupled with multiangle laser light scattering and refractometric detectors (HPSEC-MALLS-RI). Formation of nanosilver and nanogold containing composites led to induction of the polymerization and/or crosslinking reactions of DAS molecules, resulting in a significant rise of molecular weight of polysaccharide chains constituting DAS/Ag and DAS/Au composite templates.