Great　importance　has　been　attached　to　the　utilization　of　low-cost,　accessible,　and　high-pollution　waste　materials,　particularly　industrial　solid　wastes　(i.e.,　steel　slag)　and　hazardous　solid　wastes　(i.e.,　spent　adsorbents/catalysts).　Herein,　the　transformation　of　Ca-containing　whewellite　precipitation　originated　from　steel　slag　leaching　solution　into　hydroxyapatite　(Hap)　nanorods　is　realized.　Fe(III)-bearing　Hap　(xFe-Hap,　x　represents　initial　concentration　of　Fe3+　ions,　mg/L)　is　then　prepared　via　cation　exchange　between　Fe3+　in　solution　and　Ca2+　in　Hap.　The　preferred　60Fe-Hap　shows　large　specific　surface　area　of　132.59　m2/g　and　100%　Cr(VI)　photoreduction　(60　mL,　40　mg/L　Cr(VI))　with　the　assistance　of　oxalic　acid　(0.5　g/L)　based　on　intramolecular　charge　transfer　from　oxalic　acid　to　Fe(III)　in　[FeIII(C2O4)n]3-2n　complex　under　visible　light　irradiation.　This　work　thus　offers　a　novel　strategy　for　a　high-efficient　utilization　of　waste　materials　which　may　shift　the　waste　materials　into　things　of　value　in　wastewater　purification　applications.　©　2023　Elsevier　B.V.