Calcium phosphate bioceramics synthesized from eggshell powders through a solid state reaction

摘要

Everyday millions of tons of eggshells are produced as biowaste around the world. Most of this waste is disposed of in landfills without any pretreatment. Eggshells in landfills produce odors and promote microbial growth as they biodegrade. The present invention provides an environmentally beneficial and cost-effective method of producing calcium phosphate bioceramics (hydroxyapatite or tricalcium phosphate) from eggshell waste. In this investigation, heat treatment produced solid state reactions between eggshell powders and dicalcium phosphate dihydrate (CaHPO_4 ? 2H_2O, DCPD) or calcium pyrophosphate (Ca_2P_2O_7). When eggshell powders (CaO) and DCPD were heat treated at 1150℃ for 3 h, only a single hydroxyapatite (HA) phase was found;no diffraction peaks of starting materials and no β-TCP were observed. The XRD patterns of the product fabricated from raw eggshell powders (CaCO_3) and Ca_2P_2O_7 heat treated at 1100℃ for 3 h showed that almost only pure β-TCP remained with a trace amount of HA. The calcium phosphate ceramic synthesized from eggshell powders contains several important trace elements such as Na, Mg and Sr.