Fig. 4

Calcium carbonate precipitated using oyster shell-derived calcium ions by AK13. a FE-SEM image of calcium carbonate precipitated by AK13 growth in B4O medium. b, c EDX and XRD analysis of calcium carbonate precipitated in B4O medium. d Comparison of the amount of calcium carbonate precipitated by AK13 with the calcium ions separated from the same mass of calcium lactate and oyster shell powder