A Process for the Production of Carbonated Nano-Hydroxyapatite (C-nHAp) from Fish Scale Waste Using Carbonation-Assisted Thermal Shock Calcination

Abstract

The present invention relates to a process for producing carbonated nanohydroxyapatite (C-nHAp) from fish-scale waste through sequential pretreatment, defatting, alkali deproteinization, carbonation, aging, thermal-shock calcination, and size reduction. Fish scales are cleaned, dried, defatted with n-hexane, deproteinized using 0.5% NaOH, carbonated with 1.0 M sodium bicarbonate, aged for 24 hours, and calcined at 800°C through three thermal-shock cycles before grinding into a nanostructured powder. The process yields 34.55% CHA with 99.01% ash, negligible moisture, and no detectable protein or fat. FTIR, XRD, WD-XRF, and SEM analyses confirm the formation of crystalline carbonated nano-hydroxyapatite with nanoscale particles (36.4–83.9 nm). The combined carbonation and repeated thermal-shock treatment distinguish the process from conventional methods, providing an efficient waste-valorization approach for producing a high-value calcium-phosphate biomaterial from fish-processing waste. Reaction involved: