The CO2 adsorption capacity of CaO sorbents with different MgO wt% (calcination temperature 800 °C, carbonation at 650 °C with 100% CO2, and de-carbonation at 800 °C in 100% N2).

Hydroxyapatite (HA) has drawn great attention to biomedical applications due to their bone mineral similarity, strong bioactivity, biocompatibility and osteoconductive. Despite the fact that HA has many advantages, several properties are still lacking, emphasising the crucial need for ion doping/substitution. Many attempts have been made to incorporate ions into HA structure to increase their physical, chemical, and biological properties. With such a diverse range of methods available for the synthesis of doped HA, this article discussed the importance of doping for HA and summarizes four common techniques used to prepare doped hydroxyapatites which include precipitation, hydrothermal, sol-gel and mechanochemical method.

Ca(OH)(2) nano-pods were synthesized through a precipitation method. Solvents such as ethanol/deionized water (DIW) and dimethylformamide (DMF)/deionized water (DIW) were used at different volume ratios to synthesize the samples. Various characterization techniques such as X-ray diffraction (XRD), filed emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and BET surface area analysis were employed to investigate the role of solvent on the crystallinity, morphology and surface area of Ca(OH)(2). The solvent mixtures with a high volume of organic solvent (ethanol or DMF) acted as good capping agents to suppress the growth of Ca(OH)(2) in the (1010) direction and induce anisotropic growth along the (0001) direction. A uniform pod like morphology was observed for the Ca(OH)(2) sorbent synthesized using ethanol/ DIW with a volume ratio of 78 ml/02 ml. Besides, the sorbents synthesized using ethanol/ DIW showed good CO2 adsorption capacity and high surface area when compared to that of DMF/DIW.