Hexafunctional Poly(propylene glycol) Based Hydrogels for the Removal of Heavy Metal Ions

摘要

Two types of degradable poly(propylene glycol) (PPG) hydrogels that are suitable for the absorption of heavy metals have been presented. The PPG-O-P(O)Cl_2 fragments obtained by treating hexafunctional PPG with phosphorous oxychloride (POCl_3) react with 1,3-propanediamine (PDA; Gel-1) or PDA together with 1,2-ethanedithiol (Gel-2), to yield cross-linked and water-swellable hydrogels in a one-pot method. This protocol for the fabrication of PPG hydrogels exhibits promising advantages over prior methods including a short reaction time, mass-production, easy separation, and high yield. A series of heavy metal ions were employed to test the adsorptive properties of the hydrogels. Gel-2 shows better adsorption capacity than Gel-1 for all the metal ions and the metal ions adsorption efficiency of the two types of hydrogels is in the order of Fe(III)>Pb(II)>Cd(II)>Zn(II)>Cu(II)>Ni(II)>Co(II)>Hg(II). The amounts of metal ions adsorbed increases with metal ion concentration and hydrogel dosage, but decreases with temperature.