Transforming seafood waste: Green mussel shell-derived hydroxyapatite as a catalyst for spirooxindole synthesis

Utilizing bioresources and renewable materials represents a sustainable approach in chemical reactions. This study aims to harness seafood waste from green mussel shells as a raw material to produce hydroxyapatite (HAp) and employ it as a heterogeneous catalyst for synthesizing spirooxindole compounds. The green mussel shells underwent varying temperature calcination to yield CaO, subsequently utilized in HAp synthesis. XRD analysis exhibited the characteristic peak pattern of HAp and revealed a reduction in crystal sizes with increased calcination temperatures for CaO formation. Additionally, FTIR analysis identified the constituent functional groups of HAp in the sample. SEM analysis revealed irregularly shaped HAp particles, with average sizes of 268.42 nm (HAp-800), 212.46 nm (HAp-900), and 184.6 nm (HAp-1000). Using HAp as a catalyst in synthesizing spirooxindole yielded a 64 % product yield and demonstrated reusability. Utilizing mussel shell-derived hydroxyapatite as a catalyst offers a cost-effective and environmentally friendly approach to achieving higher product yields.