Effect of Alkaline Treatment on Characteristics of Bio-Calcium and Hydroxyapatite Powders Derived from Salmon Bone

Abstract

Alkaline treatment has been extensively implemented in the extraction process of hydroxyapatite (HAp) extraction from various kinds of bio-materials, such as animal bone and scales. The main purpose of such treatment is to remove proteinaceous substances from raw materials. The influence of the alkaline treatment that could alter not only the organic contents but also chemical composition—specifically the Ca/P mole ratios of bio-calcium, HAp, and the biphasic apatite powders derived from salmon bone, a by-product from the salmon industry—was investigated. Both HAp and biphasic apatite powders were obtained from the calcination of bio-calcium powders with and without alkaline treatment, respectively. An X-ray diffraction analysis confirmed the presence of hydroxyapatite and β-tricalcium phosphate (β-TCP) in the calcined bone powder without alkaline treatment while only a single phase of hydroxyapatite was observed in the alkaline-treated sample. Calcium and phosphorus contents were measured by an inductively coupled plasma optical emission spectrometer (ICP-OES). A variation of Ca/P ratios was observed among all samples, depending on the chemical and heat treatment conditions. Organic molecules, such as protein, fat, hydroxyproline, and TBARS, were significantly lowered in bio-calcium powders with the alkaline treatment. This work represents important research on chemical treatment prior to the raw material conversion process, which significantly influences chemical and phase compositions of the bio-calcium and hydroxyapatite powder derived from salmon bone waste.