Synthesis and Characterization of Calcium Oxide Nanoparticles (CaO NPS) from Snail Shells Using Hydrothermal Method

Abstract

Calcium oxide (CaO) holds significant importance as a catalyst and effective chemisorbent for hazardous gases. This study presents the synthesis of CaO nanoparticles (NPs) using the hydrothermal technique with snail shells' calcium carbonate (CaCO3) as the starting material. The hydrothermal method offers several advantages over alternative approaches for producing metal oxide NPs, including its simplicity, cost-effectiveness, and ability to operate at low temperatures and pressures. By utilizing waste materials like snail shells as a precursor, the entire process becomes more economical, environmentally friendly, and sustainable. The synthesized NPs were analyzed using various techniques, including Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), the Barrett-Joyner-Halenda (BJH) model for pore structure quantification, Brunauer-Emmett-Teller (BET) for surface area calculation, and thermo gravimetric analysis (TGA/DTA-DSC). XRD analysis confirmed that the size of the synthesized CaO NPs was 43.14 nm, determined using the Debye-Scherrer equation. The transmission electron microscopy (TEM) image provided valuable insight into the morphology of the nano-catalyst. The analysis revealed that the nano-catalyst displayed a spherical shape, with an average particle size measuring 50 nanometers. The FTIR and XRD results unequivocally demonstrated the successful conversion of calcium carbonate (CaCO3) derived from snail shells into calcium oxide (CaO). TGA exhibited a significant weight loss peak at 700 °C, indicating the transformation of CaCO3 into CaO. The DTA-DSC curve exhibited sharp endothermic peaks at 700 °C, suggesting a decomposition reaction and the formation of a new compound. SEM images displayed porous, rough, and fragile surfaces that became agglomerated at higher temperatures. In other words, the FE-SEM images of NPs illustrated that the particles were predominantly spherical in morphology. Hence, waste snail shells hold promise as a valuable source of calcium for various applications in different fields.