Congo red (CR) is a stable anionic diazo dye that causes allergic reactions with carcinogenic properties. The rapid removal of CR using cation-incorporated nanohydroxyapatite (pristine HAp: X (X = Fe, Ni, Zn, Co, and Ag)) was investigated. pristine cation ion-doped HAp adsorbents were coprecipitated subjected to hydrothermal ultrasound treatments subsequent microwave drying. dopant ions signifi...