Valorization of Arbacia tripneustes Shell Waste into Calcium Oxide via a Simple Calcination Process

Abstract The valorization of marine biowaste into functional ceramic precursors offers a sustainable and low-cost alternative to conventional mineral-derived materials. In this study, Arbacia tripneustes shell waste from Wakatobi, Indonesia, was converted into calcium oxide (CaO) through calcination at 1000 °C for 6 h. X-ray fluorescence (XRF) analysis confirmed calcium as the dominant element, accompanied by Mg, Sr, and Si as minor components, while phosphorus became detectable after calcination. X-ray diffraction analysis (XRD) results showed the complete transformation of CaCO 3 (calcite) into crystalline CaO, and fourier transform infrared (FTIR) spectra verified this conversion through the disappearance of carbonate bands and the emergence of Ca-O vibrations. XRD analysis confirmed the near-complete phase transformation, with semi-quantitative analysis showing 93–95% CaO crystallinity in the calcined product. Scanning electron microscope (SEM) observations revealed morphological refinement with an average particle size of 7.11 ± 2.16 μm, while Energy Dispersive X-ray Spectroscopy (EDS) confirmed Ca and O as the major elements, with Mg retained in smaller amounts. Elemental mapping further demonstrated the homogeneous distribution of Ca, O, and Mg throughout the calcined sample. These findings highlight that A. tripneustes shells can be efficiently and cost-effectively converted into reactive CaO with uniform elemental distribution, supporting their potential as sustainable precursors for ceramics, adsorbents, and biomaterials.