FTIR studies on photocatalytic activity of Ti(IV)-doped calcium hydroxyapatite particles

Hydroxyapatite-based composites: Excellent materials for environmental remediation and biomedical applications

Given their unique characteristics and properties, Hydroxyapatite (HAp) nanomaterials and nanocomposites have been used in diverse advanced catalytic technologies and in the field of biomedicine, such as drug and protein carriers. This paper examines the structure and properties of the manufactured HAp as well as a variety of synthesis methods, including hydrothermal, microwave-assisted, co-precipitation, sol-gel, and solid-state approaches. Additionally, the benefits and drawbacks of various synthesis techniques and ways to get around them to spur more research are also covered. This literature discusses the various applications, including photocatalytic degradation, adsorptions, and protein and drug carriers. The photocatalytic activity is mainly focused on single-phase, doped-phase, and multi-phase HAp, while the adsorption of dyes, heavy metals, and emerging pollutants by HAp are discussed in the manuscript. Furthermore, the use of HAp in treating bone disorders, drug carriers, and protein carriers is also conferred. In light of this, the development of HAp-based nanocomposites will inspire the next generation of chemists to improve upon and create stable nanoparticles and nanocomposites capable of successfully addressing major environmental concerns. This overview's conclusion offers potential directions for future study into HAp synthesis and its numerous applications.

Calcium hydroxyapatite-based photocatalysts for environment remediation: Characteristics, performances and future perspectives

Calcium hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ (HAp) is a material widely used in biomedicine, for bone implants manufacture, due to its biocompatibility. HAp has also application for environmental remediation, as it can be employed as metal removal; moreover, it has the capability of effectively adsorbing organic molecules its surface. In recent years, the photocatalytic properties of HAp have been investigated; indeed several studies report of HAp used as photocatalyst, either on its own or combined with other photocatalytic materials. Although in the majority of cases the activity was induced by UV light, some reports of visible light-activated materials were reported. Here we present a critical review of the latest developments for HAp-based photocatalysts; the materials discussed are undoped single phase HAp, doped HAp and HAp-containing composites. For undoped single phase HAp, the possible surface treatment and lattice defects which can lead to a photoactive material are discussed. Considering doped HAp, the use of Ti⁴⁺ (the most common dopant) is described, with particular attention to the effects that this metal have on the characteristics of the material (i.e. crystallinity) and on its photocatalytic behaviour. The use of other dopants is also discussed. For the multiphasic materials, the combination of HAp with other photocatalysts is discussed, mainly but not only with titanium dioxide TiO₂. Overall, HAp is a compound with high potential as photocatalyst; this property, combined with its capability for heavy metal removal, makes it a multifunctional material for environmental remediation. As future perspectives, further studies, based on the results obtained until present, should be performed, to improve the performance of the materials and/or shift the band gap into the visible. The use of other dopants and/or the combination with other photocatalysts, for instance, are features which is worth exploring.