The hydroxyapatite is the main constituent of vertebrates¿ hard tissue and could be found in the Earth¿s cortex participating in the phosphorous cycle. Hydroxyapatite has eco-friendly methods of synthesis, also could be obtained from natural resources, and possesses high biocompatibility and low toxicity. Due to its eco-material profile and its chemical, physical, and structural properties, the hydroxyapatite has been investigated for multiple applications. The aim of this chapter is to explore the applications of hydroxyapatite nanoparticles and nanocomposites like suitable materials for wastewater treatment, specifically in the removal of organic compounds by adsorption mechanism, elimination of heavy metals and other ionic pollutants by ionic interchange, and photocatalytic elimination of traditional and emerging pollutants. Compositional, morphological, structural, and physicochemical properties of the hydroxyapatite will be also discussed and related to its performance in the mentioned applications.
