Optimization of activated carbon as adsorbent using response surface methodology and its application for cadmium removal from wastewater

Cadmium contamination in water remains a critical environmental and health concern due to its persistence, bioaccumulative nature, and toxicity even at trace levels. In this study, commercial activated carbon (AC) was optimized as an adsorbent for Cd(II) removal using response surface methodology (RSM) based on a central composite design (CCD). The effects of adsorbent mass (0.2–1.0 g), contact time (15–75 min), and initial Cd(II) concentration (1–9 ppm) on removal efficiency were evaluated. The quadratic model demonstrated strong statistical significance ( p < 0.0001) with a high coefficient of determination (R 2 = 0.9957). The optimized conditions was 0.8 g AC, 60 min contact time, and 3 ppm initial concentration which yielded a predicted removal efficiency of 95 %. Experimental validation using optimum condition and point prediction using real sample produced an average removal of 98.19 % and RSE below 5 %, confirming the model’s reliability. FTIR analyses indicated that surface functional groups contribute to Cd(II) adsorption. The findings confirm that RSM is an effective optimization tool and that AC is a promising low-cost, high-efficiency adsorbent for Cd(II) removal.