| Abstract [eng] |
Due to growing air pollution and other global issues, environmental protection and waste reduction have become increasingly important. The efficient and intelligent use of available resources is one of the key factors ensuring sustainable development across nations. Such practices not only enhance a country's international reputation but also contribute to a safer and more sustainable future. A relevant example in Lithuania is the phosphogypsum waste generated during phosphoric acid production by the company "Lifosa", located in Kėdainiai, which has the potential to become a valuable secondary raw material. This study presents a comprehensive characterization of phosphogypsum waste using TG-DSC, XRD, FTIR, SEM, BET, EDX, XRF, and AAS analytical techniques. The aim of the research was to assess the feasibility of using this waste as a raw material for the synthesis of calcium hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, CHA) via the dissolution–precipitation method. The obtained results in this study revealed that the most effective formation of CHA occurs when using untreated or low-temperature (100–150 °C) dried phosphogypsum in combination with Na₂HPO₄ or Na₂HPO₄/NaH₂PO₄/NaHCO₃ mixtures, with reaction durations of 144 and 192 hours. The synthesized products exhibited mesoporous structure, high specific surface area, and well-defined crystalline microstructure. XRD and EDX analyses confirmed the formation of hydroxyapatite-specific phases and Ca/P ratios close to the theoretical value. SEM and BET analyses indicated that the morphology and porosity of the materials depended on the reagents used, with the best results obtained when using Na₂HPO₄ alone. The findings demonstrate that phosphogypsum is a suitable and sustainable raw material for CHA synthesis, with potential applications in the medical field, such as the production of artificial bone implants. |
