Effect of calcination conditions of pork bone sludge on behaviour of hydroxyapatite in simulated body fluid

Abstract

The paper presents in vitro (in SBF) behaviour of hydroxyapatite (HAp) obtained from pork bone sludge from meat plant via two essentially different calcination methods using a stationary, electrically heated chamber oven and enlarged laboratory scale rotary kiln designed by the authors, heated by gas combustion methods enabling application of different set of physical parameters such as temperature, holding time-differing according to type of the kiln. HAp ceramic discs, after 62-days of incubation in SBF at 37 °C, characterized by X-ray diffraction (XRD), FTIR, SEM and EDS methods, underwent changes recorded by: (i) a reduction in Ca/P molar ratio in all the investigated materials resulting from modification in phase composition and (ii) weight increase in the investigated disc-samples, resulting from a precipitation of newly formed phase as an admixture of primary HPO $_{{4}}^{{2-}}$ -free HAp. They were: secondary (with HPO $_{{4}}^{{2-}}$ incorporated) HAp and chlorapatite in all the samples, while in addition to the listed above, β -tricalcium phosphate was formed on the discs made of HAp from stationary chamber oven, but not from rotary kiln. The new phases were formed in agglomerates on the surface of the investigated ceramic discs and in their pores. The results obtained proved that calcination conditions of pork bone sludge (temperature 750–950 °C, time and type of the applied kiln) under which hydroxyapatite (HAp) powders were obtained had an impact on its different behaviour in SBF, nevertheless, indicating a potential ability of the material to form a new biologically relevant interface with hard tissue and suitability for further investigations intended for medical grafting.