Pengaruh pH terhadap Derajat Kristalinitas Hasil Sintesis Hidroksiapatit dari Cangkang Kerang Kepah (Polymesoda erosa) dengan Metode Pengendapan Basah

Abstract

Kepah shell waste (Polymesoda erosa) contains a high calcium oxide (CaO) content of approximately 96.06%, making it a promising calcium source for hydroxyapatite (HAp) synthesis. This study aims to analyze the effect of pH variation on the degree of crystallinity of HAp synthesized via the wet precipitation method. The calcined shell powder at 900 °C was reacted with (NH₄)₂HPO₄ solution at 90 °C under pH conditions of 8, 10, and 12, adjusted using NH₄OH. FTIR characterization confirmed the presence of PO₄³⁻ and OH⁻ functional groups characteristic of HAp, with no CO₃²⁻ absorption observed, indicating the formation of pure HAp. XRD analysis revealed diffraction patterns consistent with the JCPDS 09-0432 standard, where increasing pH enhanced crystallinity from 60% to 79%. Higher alkalinity accelerated the nucleation process, producing finer and more ordered crystals. SEM micrographs at pH 12 displayed homogeneous and smooth particles with an average size of around ±438 nm, while EDX analysis yielded a Ca/P ratio of 1.71, close to the ideal stoichiometric value of 1.67. Therefore, pH 12 is identified as the optimum condition that produces HAp with high crystallinity, and good phase purity, making it a promising candidate for the development of environmentally friendly bioceramic and bone implant materials.