Effect of Surface Modification with TiO2 Coating on Improving Filtration Efficiency of Whisker-Hydroxyapatite (HAp) Membrane

Whisker-like hydroxyapatite (HAp) particles were prepared by controlling particle growth via hydrothermal synthesis. The surface modification for the hydrothermally synthesized HAp whiskers was accomplished by TiO2 coating. After the TiO2 modification, the zeta potential of the HAp whiskers was significantly improved from +8.6 to +21 mV at pH = 8.5. A free-standing membrane (diameter of ~4.5 cm and thickness of ~0.2 mm) was fabricated by using the TiO2-coated HAp whiskers and was used to separate the Au nanoparticles (size = 5 nm and zeta potential = −38.6 mV at pH = 8.5) at a significantly high filtration efficiency of ~100%. The achieved high filtration efficiency was considered to be the result of effectively utilizing the electrostatic interaction between the positively-charged TiO2-coated HAp whiskers and negatively-charged Au nanoparticles. The excellently biocompatible and highly effective TiO2-coated HAp membrane would be potentially applied as biological and artificial separators in biotechnology processes for the biomedicine field.