A calcinated hierarchical porous composite, for removal of phosphate in wastewater, comprises a carrying component and a layered double hydroxide component. The carrying component includes a carbon-source material and a bio-carrier material. The carbon-source material is selected from the group consisting of graphene oxide, reduced graphene oxide, and a combination thereof. The bio-carrier material is configured for carrying the carbon-source material and includes biflavonoid and triterpenoid. The layered double hydroxide component is grown on the carrying component, and includes a layered double hydroxide having phosphate-specific active sites. |