Novel and green hydroxyperylene imide based fluorescent polymer for calcium sulfate scale inhibition

A new green scale inhibitor, hydroxyperylene imide (PBI-OH)-poly (malic acid) graft polymer (PBI-PMA), was synthesized by PBI-OH and malic acid (MA). The structure of PBI-PMA was discussed by infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (¹H NMR) and gel permeation chromatography (GPC). The scale inhibition property of calcium sulfate was researched by static scale inhibition method. When PBI-OH content in MA was 0.1%, the scale inhibition efficiency of PBI-PMA was the highest. The observation showed that the dosage of PBI-PMA had an effect on the inhibition of CaSO₄. It can be concluded that the scale inhibition rate reached 96% when the dosage of PBI-PMA-0.1% was 25 mg/L. Fluorescence spectra proved that there was a perfect linear relationship among the fluorescence intensity and concentration of PBI-PMA. The correlation coefficient R² of PBI-PMA was 0.9977. Moreover, the effects of pH and temperature on fluorescence intensity were also discussed. In a certain range, pH and temperature had little effect on fluorescence intensity. The results of scanning electron microscope (SEM), X-ray diffraction (XRD) and molecular simulation (MD) showed that PBI-PMA-0.1% can overcome the steric hindrance effect and prevent the growth of calcium sulfate scale by adsorption on the crystal surface.