A　calcined　and　hydrothermally　annealed　material　for　phosphate　removal　was　prepared　in　a　hollow　cylindrical　shape　from　fumed　silica　generated　by　a　ferroalloy　factory,　and　pulverized　oyster　shell.　Phosphorus　removal　from　wastewater　by　this　material　calcined　at　a　range　of　temperatures　(700-900　degrees　C)　and　hydrothermally　annealed　at　temperatures　from　130　to　180　degrees　C.　for　8-16　h,　was　investigated　and　the　most　suitable　physicochemical　conditions　were　determined.　XRD,　SEM,　EDS.　and　XRF　techniques　were　used　to　characterize　the　microstructures　and　compositions　of　the　materials　produced,　and　UV-Vis　spectrophotometry　using　the　ammonium　phosphomolybdate　blue　method　was　used　to　determine　the　phosphate　concentration　in　the　wastewater.　The　results　indicate　that　calcium　carbonate　in　oyster　shell　reacted　with　SiO2　in　fumed　silica　and　formed　hydrated　calcium　silicate　after　hydrothermal　treatment,　and　the　hydrated　calcium　silicate　reacted　with　phosphate　ions　in　wastewaters　to　form　hydroxyapatite　precipitate.　The　optimal　conditions　for　material　production　were　calcination　at　800　degrees　C,　and　hydrothermal　annealing　at　150　degrees　C　for　12　h.　Materials　made　under　these　conditions　showed　74%　or　92%　phosphate　removal　after　2　or　4　h,　respectively.　(C)　2010　Elsevier　Inc.　All　rights　reserved.