Activated carbon granules present in our household filters used in water purification are significant waste. Activated carbon waste (ACW) was ground to a fine powder, then impregnation of SnO 2 on ACW was performed under mild conditions followed by calcination of SnO 2 -ACW at 700 °C for 2 h, producing a SnO 2 -ACW hybrid composite. This hybrid composite material was used in the preparation of electrodes for supercapacitor and capacitive deionization applications. The electrochemical performance of the electrodes was investigated by using cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. Calcination and addition of SnO 2 contributed to an obtained electrode with a high specific capacitance of 30.46 F g –1 in a solution of 1 M Na 2 SO 4 compared to the original ACW (0.122 F g –1 ) and calcined-ACW (1.42 F g –1 ) at an actual current of 1 mA. This electrode was also investigated for water desalination through the capacitive deionization technique and exhibited an electrosorption capacity of 6.44 mg/g compared to the commercial AC (8.9 mg/g) so it is a highly promising and economic electrode.