This study introduced the red mud as a filter of heavy metal ions in cement mortar by partial cement replacement. The raw red mud and thermally activated red mud at three different temperatures, 650, 700, and 750ºC represented as RM650, RM700, and RM750 were comprehensively analyzed to find an optimum processing temperature as a better cement replacement for metal extraction. The Atomic Adsorption Spectroscopic (AAS) process evaluated the metal extraction capacity of raw and thermally treated red mud from their respective standard solutions. The optimum processing temperature of red mud was decided by Thermogravimetric analysis (TGA), X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Field emission scanning electron microscope (FE-SEM), and pozzolanic activity. Test results show that the temperature stimulates the formation of CaO, Al₂O₃, and Fe₂O₃, which decides the pozzolanic activity of the material. Red mud calcined at 700ºC (RM700) was found as an optimum calcination temperature with reactive, crystalline compounds. RM700 showed the maximum pozzolanic activity and better heavy metal ion extraction capacity. The extraction ability of all red mud samples was in the sequence of Cr>Cd>Pb>Cu. The experimental results of metal extraction capacity and the pozzolanic activity were analyzed and validated by establishing linear regression models to predict a statistically significant mathematical model.