Enhanced surface properties of coralline hydroxyapatite from natural resources of Depapre Coast, Papua

Hydroxyapatite (HAp) is gaining significant attention because of the structural similarity to bone mineral and versatile applications in both biomedical and environmental fields. Therefore, this study aimed to synthesize coralline HAp from dead coral collected along the Depapre coast, Papua, through calcination of coral powder and precipitation, followed by surface modification using potassium hydroxide (KOH) at two concentrations (0.5 M and 2.5 M). The structural and physicochemical properties of the materials were characterized by XRD, FTIR, SEM-EDS, and BET analyses. The results showed that CaCO 3 was successfully transformed into crystalline HAp with characteristic phosphate and hydroxyl groups, while SEM-EDS had porous morphologies and Ca/P ratios consistent with HAp. BET analysis showed that Depapre-derived coralline HAp had an exceptionally high surface area (>500 m²/g), significantly greater than typical values reported for synthetic HAp. Mild KOH activation (0.5 M) further enhanced porosity and adsorption-relevant surface properties, while concentrated treatment (2.5 M) led to partial re-carbonation and decreased surface area. These results showed that coral-derived HAp from Depapre provided a sustainable and highly porous material with promising potential for heavy metal adsorption and other environmental applications.