Stability of sodium polyphosphate dispersants in mineral processing applications

Polyphosphates are commonly used industrially to provide electrostatic stabilisation to mineral and material suspensions. Polyphosphate solutions however have shown instability under processing conditions such as high temperature and acidic pH which may lead to a reduction in dispersion properties when added to mineral or material suspensions. In this study the influence of pH, temperature and divalent cation concentration pre-treatment on polyphosphate dispersion properties is reported. Dispersion properties are determined using rheological suspension analysis. The suspensions investigated are material-based model systems of titania pigment and high purity boehmite. Infrared spectroscopy studies of polyphosphate solutions were undertaken to directly investigate the polyphosphate structure after pre-treatment. The rheological measurements show reduced polyphosphate dispersion properties with reduced pH, increased temperature and at high calcium concentrations which correlate with directly measured and reported changes in the polyphosphate structure. When pH, temperature and high divalent cation concentrations are combined, the synergistic effect on reduced polyphosphate dispersion performance is particularly prominent