Activated carbon derived from cigarette butts (CI-AC), corn cobs (CO-AC), and luffa sponge (LU-AC) was evaluated for adsorbing iron and manganese from aqueous solutions. Each material was carbonized at 300℃ for 2 hours, followed by chemical activation with HCl (carbonaceous material/HCl ratio of 1:5). Fourier transform infrared spectroscopy characterized the adsorbents. The effects of pH, adsorbent dosage, initial Fe and Mn concentrations, and contact time on Fe(II) and Mn(II) adsorption were investigated using response surface methodology (RSM) based on a Box–Behnken design. Optimal conditions for CI-AC were: pH 8, 50 minutes contact time, 2g adsorbent dose, and 3.32 mg/l initial Fe and Mn concentration, resulting in 70.33% Fe and 65.12% Mn removal. Optimal conditions for CO-AC were: pH 6.34, 37.8 minutes contact time, 1.25g adsorbent dose, and 3.52 mg/l initial Fe and Mn concentration, resulting in 88.53% Fe and 79.75% Mn removal. Optimal conditions for LU-AC were: pH 6.49, 50 minutes contact time, 1.67g adsorbent dose, and 0.5 mg/l initial Fe and Mn concentration, resulting in 79% Fe and 86.37% Mn removal.