Optimization of pyrolysis conditions using Design of Experiments for the preparation of an adsorbent from traditionally fried fish bones

Fish waste from traditional processing and frying activities represents a hybrid source of inorganic and organic substances. Their valorization as precursors for high value-added materials, particularly adsorbents, offers a sustainable solution to growing environmental challenges. In this study, an adsorbent was developed from this waste by pyrolysis in the absence of air. The main objective is to optimize operating conditions by evaluating the effect of four key parameters, namely temperature, pressure, treatment time, and initial waste mass. To do this, a statistical approach based on experimental designs was implemented to analyze the individual and combined influence of these factors on the yield and quality of the adsorbent. All four pyrolysis parameters significantly affected adsorbent performance. Under optimal conditions (450 °C, −0.1 bar, 15 g, 2.76 h), the predicted adsorption capacity of 219 ± 5 mg/g was experimentally validated. Preliminary kinetic tests with methylene blue and naphthol green B confirmed high removal efficiencies, while ICP analysis showed negligible leaching of Ca 2+ and phosphate indicating chemical stability. Physicochemical characterization revealed a porous structure rich in minerals groups, suitable for adsorption. This process provides an environmentally friendly and economically viable method for valorizing fried fish waste into an effective adsorbent for wastewater treatment.