Effect of swelling agent on pore properties of mesoporous carbonated hydroxyapatite

Abstract

Mesoporous carbonated hydroxyapatite (CHA) has been seen to be suitable as an adsorbent material due to the proven biocompatibility, bioactivity and chemical stability. However, obtaining the high surface area and desired pore size for mesoporous materials become the main challenge in producing good quality adsorbent materials. Thus, this study aims to investigate the effect of addition of swelling agents on pore properties of mesoporous CHA. Mesoporous CHA was synthesised by precipitation method. Triblock co-polymer, P123 surfactant was used as a soft template to introduce pores within the CHA particles and 1-dodecanethiol as a swelling agent. Two different mixing temperature (60°C and 80°C) were used during the mixing process of P123-calcium solution and 1-dodecanethiol. The effect of different mixing temperature (60°C and 80°C) and various concentration of swelling agent on the phase, morphology and pore characteristics of mesoporous CHA were investigated using various material characterization techniques. Mixing temperature 60°C, produced mesoporous CHA with much higher surface area (92.8 m2/g), larger pore size (22.9 nm) and higher pore volume (0.502 cm2/g) than those produce at 80°C (surface area = 62.7 m2/g, pore size = 2.6 nm and pore volume = 0.105 cm2/g). The highest surface area (146.9 m2/g) of mesoporous CHA was obtained when there was no swelling agent added. However, the pore size of the sample was very small. Therefore, the optimum pore characteristics (surface area = 104.5 m2/g, pore size = 24.4 nm and pore volume = 0.530 cm2/g) of mesoporous CHA was obtained when the swelling agent concentration is 0.6 M and the mixing temperature is 60°C. Both mixing temperature and swelling agent concentration have profound effect on the pore characteristics of mesoporous carbonated hydroxyapatite (CHA).