Factors affecting the complexation of polyacrylic acid with uranyl ions in aqueous solutions:: A luminescence study

A study was carried out in aqueous solutions using luminescence technique to investigate the effects of pH, salt concentration, and temperature on the polyacrylic acid/uranyl ion (PAA/UO22+) complex formation as well as competitive phenomena of enhancement and quenching effects on photoexcited state of uranyl ions. It was found that excess of H+ and OH- is not favorable for complexation between uranyl ions and polymer. Added nitrate salts of Na+ and K+ had significant enhancement effect on emission spectra of PAA/UO22+ complex. These results indicated that the metal ion/polymer chain complex collapsed by addition of salts and then complex became more compact with consequent phase separation. No significant effect of temperature on the PAA/UO22+ complex stability has been observed between 25-50 degrees C. The quenching rate constants obtained from Stern-Volmer plots were found to be in the order of k(q)(H+) >> k(q)(K+) > k(q)(Na+). (c) 2005 Wiley Periodicals, Inc.