Conversion of snail shells (Achatina achatina) acclimatized in Benin to calcium phosphate for medical and engineering use

Most methods for producing calcium phosphates involve synthetic calcium and phosphates sources. However, it has recently been proposed that calcium phosphate can be produced with bio-based calcium sources such as nacre, coral, and cuttlefish bones. One specific source of bio-based calcium is found in the Achatina snail shell, which becomes a waste product after flesh consumption. The present work aimed to assess the effectiveness of Achatina snail shells and to study the conversion kinetics in both acid and alkaline environment rich in phosphate ions. It was observed that in acidic conditions, the calcium released by the dissolution of the aragonite precipitates with the phosphate ions of reaction medium induces brushite formation which is rapidly converted into monetite. In alkaline conditions, calcium released from aragonite reacts with surrounding phosphates and carbonate ions and induces carbonated apatite precipitation. Regardless of the source of calcium used in the presence of phosphate, the conversion is carried out according to complex phenomena that involve topotactic transformation or dissolution-precipitation mechanisms