A Review on Sustainable Ways to Make Hydroxyapatite for Wastewater Purification

In this review, hydroxyapatite (HAp) as a promising sustainable adsorbent for wastewater treatment was considered by synthesizing the HAp from bio-waste material sources such as eggshells and fish bones. Of all these different methods, co-precipitation route is easy and amenable to scale up while the sol-gel synthesis route gives high purity and homogeneity of the particles. The metal and metal oxide supported HAp composites (i.e. Fe-HAp-TiO2-HAp) are reported to exhibit excellent heavy metal and dye impurity removal owing to high surface reactivity and photocatalysis. Nevertheless, the small and small wastewater operating conditions show the prevalence of degradation efficiency with the pH dependency, co-occurring ions, low recyclability. Future research direction should be dominated on low temperature green synthesis, regeneration and multi-cycle stability, and the properties should be evaluated from the techno economic view to determine the commercial sustainability. To achieve this, the proper design of these pathways will help to move from hydroxyapatite from a promising laboratory reagent to a feasible, eco-friendly adsorbent to support circular economy wastewater treatment.