Analysis of Syneresis of HPAm/Cr(II) and HPAm/Cr(III) Acetate Gels Through1H Nuclear Magnetic Resonance, Bottle Testing, and UV-vis Spectroscopy

Polymer solutions with 7500 mg/L of partly hydrolyzed polyacrylamide were crosslinked with Cr(III) acetate 50% active, Cr(III) acetate hydroxide, and Cr(II) acetate respectively. A syneresis-inducing polymer to crosslinker weight ratio of 5/1 was employed. An empirical correlation was found between 1H NMR data and gel syneresis. Chromium speciation indicated that at the experimental conditions used aging the gels did not favor the oxidation of Cr(II) or Cr(III) to Cr(VI). The polymer solution crosslinked with Cr(III) acetate 50% active behaved similar to that cross-linked with Cr(III) acetate hydroxide.