PERFORMANCE OF ANIONIC POLYMERS AS PRECIPITATION INHIBITORS FOR CALCIUM PHOSPHONATES: THE INFLUENCE OF CATIONIC POLYELECTROLYTES

摘要

This paper addresses the precipitation of calcium salts of phosphonates (i.e., hydroxyethylidine 1,1-diphosphonic acid, HEDP; aminotri(methylene phosphonic acid), AMP; 2-phosphono-butane 1,2,4-tricarboxylic acid, PBTC) at pH 8.50 and 50°C. The aim of the study was to investigate the role of cationic polyelectrolytes (i.e., poly(diallyldimethyl ammonium chloride), Poly-E and poly(acrylamide:2-(acrolyloxy)ethyltrimethyl ammonium chloride), Poly-F) on the performance of several anionic calcium phosphonate inhibiting polymers. The anionic polymers studied include: acrylic acid/maleic acid-based homo-, co-, and terpolymers; fulvic acid (FA) and tannic acid (TA). The inhibiting data on several anionic polymers indicate that the performance of polymers depends on the type of the functional groups present in the polymer. It has been found that addition of low concentrations (from 0.25 to 1.0 parts per million) of Poly-E and Poly-F adversely impacts the performance of calcium phosphonate inhibiting polymers. The results also indicate that under similar experimental conditions Poly-F exhibits a stronger antagonistic affect than Poly-E.