Calcium phosphate nano powder biosynthesis from sea urchin shells: a response surface approach

In this experimental study, calcium phos phate Ca3(PO4)2 nanopowders, in the form of nano hydroxyapatite (n-HA), were successfully synthesized from sea urchin shells (Diadema setosum, Leske, 1778) via a process involving precipitation and heat treatment method at various calcination tempera tures (800 to 1200 °C). The optimal conditions for producing n-HA with maximum free CaO content were determined using response surface methodology (RSM) through a Box–Behnken Design. Key findings demonstrated that calcination temperature, calcina tion time, and ball-milling time significantly influ enced the free CaO content. The study identified that a calcination temperature of 1100.73 °C for 2.78 h for CaO derived from sea urchin shells, combined with a ball-milling time of 66.37 h, resulted in the highest purity of n-HA. The biosynthesized n-HA exhibited desirable characteristics for bone and dental restora tion applications, as confirmed by comprehensive analyses of functional group vibrations, chemical structure/composition, molecular interactions, sur face morphology, and particle size distribution. These f indings underscore the potential of using invasive sea urchin shells as a sustainable and effective source for n-HA production in biomedical applications.