Hydrophobic Modification of the a-Hemihydrate Phosphogypsum (a-HH) Surface by Myristic Acid

Phosphogypsum is widely used as a filler. However, gypsum fillers exhibit poor water resistance, compromising the performance of subsequent products. To address this issue, we modified a-hemihydrate phosphogypsum (a-HH) with myristic acid (Ma), a low surface energy material used to prepare super hydrophobic (SHP) surfaces. The MA concentration, temperature, and modification time were optimized using a Box-Behnken experimental design method. The surface properties, microstructure, and thermal stability of the modified powders were characterized using contact angle measurements, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Raman spectrum, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), and thermal gravimetry-differential scanning calorimetry (TG-DSC). Additionally, we discussed the hydrophobic modification mechanism of the modified a-HH. The modified a-HH/MA prepared with 11.0x10(-4) mol L-1 MA at 60 ? for 60 min exhibited high hydrophobicity. During modification, MA bound to the calcium ions on the surface of a-HH to form calcium myristate, thereby forming a hydrophobic film. The thermal stability of a-HH was improved by MA modification. The modified powder maintained high hydrophobicity even at 250 ?.