Effects of Al₂O₃ Nanoparticles on the Crystallization of Calcium Carbonate in Aqueous Solution

The effects of Al₂O₃ nanoparticles on the precipitation behavior of CaCO₃ and on the anti-scale performance of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) in CaCO₃ growth solution were studied by means of solution analysis, gravimetric methods, scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The results illustrate that Al₂O₃ nanoparticles had little effect on the concentration of calcium ions in the test solution without PBTCA, but significantly changed the form and morphology of calcium carbonate crystals, which were transformed from calcite to aragonite. As a commonly used and effective scale inhibitor, PBTCA showed good Ca²⁺ retention ability in the test solution, distorting the calcite crystal lattice and promoting the formation of vaterite. When Al₂O₃ nanoparticles co-existed with PBTCA in the test solution, calcium carbonate was more likely to precipitate, and the Ca²⁺ retention ability of PBTCA reduced. A newly designed gravimetric method was used to evaluate the scale inhibition performance of Al₂O₃ nanoparticles on the heat exchange surface. When the concentration of Al₂O₃ nanoparticles reached 1 g/L, the surface scale inhibition efficiency of Al₂O₃ nanoparticles exceeded 80%.