Prediction of BaSO4 precipitation in the presence and absence of a polymeric inhibitor: Phosphino-polycarboxylic acid

The induction periods of BaSO4 nucleation from supersaturated solutions hav e been measured over a wide range of conditions in the presence and absence of phosphino-polycarboxylic acid (PPCA). The inhibition of Barite nucleati on in the presence of PPCA was correlated to the solution chemistry over a wide range of conditions. Only the dissociated fraction and the metal-compl exed fraction of PPCA are effective to inhibit BaSO4 nucleation, while the protonated fraction has a poor inhibitory effect toward Barite nucleation. Ca2+ enhances the overall efficiency of PPCA through forming Ca-PPCA comple xes and decreasing the fraction of protonated PPCA. Temperature does not st rongly affect the Barite nucleation inhibition by PPCA. A set of equations has been proposed to model Barite nucleation time in the presence and absen ce of PPCA.