Sustainable synthesis of ettringite from phosphogypsum and aluminum foil waste: Characterization and Rietveld refinement analysis

Phosphate fertilizers are essential for maintaining global agricultural productivity and ensuring food security for a growing population. However, their production generates substantial quantities of phosphogypsum, a byproduct that presents significant environmental challenges. This study addresses the pressing need for effective phosphogypsum waste management by exploring its conversion into ettringite, a valuable material with wide raging applications in cement chemistry and environmental remediation. The primary objective of this research was to develop a cost-effective synthesis pathway to transform phosphogypsum into ettringite through a controlled coprecipitation process. The dissolution of phosphogypsum was systematically optimized by adjusting key parameters, including the concentration of hydrochloric acid and temperature. The most effective condition was found to be 2 M HCl at 60 °C, which ensured high solubility and process efficiency. Under this condition, a fixed mass of 2.5 g of phosphogypsum was used along with 0.2 g of aluminum waste to maintain a Ca/Al molar ratio of 2, enabling controlled precipitation of ettringite. The synthesized material was thoroughly characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and energy-dispersive X-Ray (EDX), confirmed the phase composition, high crystallinity and characteristic morphology. Additionally, Rietveld refinement was performed to quantitatively analyze the crystalline structure and phase purity, ensuring the formation of a well-defined trigonal ettringite structure. This innovative approach effectively transformed phosphogypsum into a valuable material, demonstrating its potential for scalable and sustainable applications in waste valorization and industrial use. This approach not only reduces waste problems, but also contributes to the sustainable use of resources and circular economy practices.