Synthesis of Hydroxyapatites via Wet Mechanochemical Process for Enhanced Catalytic Decomposition of Volatile Organic Compounds

In present study, calcium hydroxide (Ca(OH)(2)) and calcium hydrogen phosphate dihydrate (DCPD) were subjected to a wet mechanochemical reaction for the first time to synthesize hydroxyapatite (HAp), as a noble-metal-free catalyst, towards efficient oxidative decomposition of volatile organic compounds (VOCs). The crystallinity, size and morphology, chemical composition and surface properties of the HAps synthesized using different mechanochemical conditions were investigated schematically. These properties were investigated using powder X-ray diffraction, scanning electron microscopy, inductively coupled plasma atomic emission spectroscopy, and adsorption isotherms of acidic/basic gases. Moreover, the synthesis mechanism was clarified via detailed investigation of the elution dynamics of DCPD and Ca(OH)(2) via the mechanochemical treatment. Consequently, the mechanism of mechanochemical reaction was found to involve a reaction between the DCPD activated by mechanochemical treatment and the Ca ions eluted from Ca(OH)(2). In addition, the synthesized HAps were tested for oxidative decomposition of VOCs. The results suggest that the HAp synthesized via mechanochemical treatment exhibits enhanced catalytic performance compared to HAp prepared via conventional liquid-phase precipitation, and the catalytic activity significantly depends on the chemical structure determined by the mechanochemical condition. The details related to the synthesis mechanism and catalytic properties presented herein provide new insights in designing and developing novel catalyst materials.