Ultrasound-Assisted Synthesis of Mesoporous Zirconia-Hydroxyapatite Nanocomposites and Their Dual Surface Affinity for Cr³⁺/Cr₂O₇^2– Ions

Abstract

Zirconia-hydroxyapatite nanocomposites were prepared by sol-gel deposition of zirconium oxide from a zirconium alkoxide in the presence of apatite colloidal suspension under ultrasonication. The material porosity evolves from mainly microporous zirconia to mesoporous hydroxyapatite, with decreasing surface area and increasing pore volume. XRD studies indicate that the apatite phase is well-preserved within the composite materials. The homogeneous dispersion of apatite colloids within the zirconia network was supported by TEM observations and nitrogen sorption measurements. (31)P solid-state NMR studies suggest that partial dissolution of apatite may have occurred during the preparation, leading to the adsorption of phosphate species on zirconia particles. This is confirmed by XRD studies of nanocomposites after thermal treatment that demonstrate the preferred formation of tetragonal over monoclinic ZrO(2) in the presence of hydroxyapatite. In order to investigate the surface properties of these novel materials, the adsorption of Pb(2+), Cr(3+), and Cr(2)O(7)(2-) was evaluated. Metal cations were preferentially adsorbed on apatite-rich composites, whereas Cr(2)O(7)(2-) shows a good affinity for the zirconia-rich phases. Zirconia-apatite materials showed the most promising performance in terms of recyclability. These nanocomposites that combine microporosity, mesoporosity and dual sorption properties for these species appear as interesting materials for metal ion remediation and may also find applications as biomaterials.

Magnetically recoverable iron oxide–hydroxyapatite nanocomposites for lead removal

“…FeH x isotherms have a similar shape to that of HAp materials and can be classified as type IV isotherms with a type H3 hysteresis (Singh et al 1985). This can be attributed to the platelet-like shape of HAp nanoparticles, as already observed in zirconia-HAp nanocomposites (Achelhi et al 2011). In the high-p/p 0 pressure domain, the HAp and FeH x isotherms do not exhibit a well-defined plateau, reflecting the absence of a closed mesoporosity.…”

“…Although several studies have indicated that apatitebased materials can be useful for the sorption of organic molecules (Bahdod et al 2009;Bouyarmane et al 2010), they have been mostly studied for heavy metal ion removal due to the strong affinity of their surface for cationic species (Baillez et al 2007;Dybowska et al 2009). Most recent trends in apatite application to water remediation include the use of natural phosphate minerals as sorbents (Cao et al 2004;El Asri et al 2010), the surface modification of apatite by organic ligands that can enhance the material affinity for metal species (da Silva et al 2006;Saoiabi et al 2012) and the formation of apatite-based composites with improved sorption properties (Jang et al 2008;Achelhi et al 2011).…”

Adsorption kinetic study: Effect of adsorbent pore size distribution on the rate of Cr (VI) uptake

“…Due to the different toxicities of Cr (VI) and Cr (III) analytical measurements should involve speciation rather than total Cr concentration to best evaluate the potential physiology and toxicological effects of exposure [4,5]. For this reason Cr (VI) concentrations have been determined in liquid and soil samples [6][7][8]. However, Cieślak-Golonka et al [9] concluded that the speciation of Cr (VI) in the liquid phase is still a poorly understood field compared to its behavior in the gas and solid states where Cr generally exists with a co-ordination number of 4.…”

Zinc oxide-hydroxyapatite nanocomposite photocatalysts for the degradation of ciprofloxacin and ofloxacin antibiotics

“…Among sorbing phases that may be advantageously associated with ZnO, hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) appears particularly interesting due to its high capacity for metal ions retention and good sorption properties towards certain organic pollutants, including antibiotics [21][22][23][24][25][26]. The 4 co-precipitation of hydroxyapatite-based nanocomposites with other inorganic phases, such as ZrO 2 , Fe 3 O 4 or TiO 2 , for remediation purpose has already been described [27][28][29]. In particular, Ti-doped hydroxyapatites have shown very promising properties as photocatalysts [30][31][32][33].…”