Abstract This study investigates the adsorption performance of activated carbon prepared from spent coffee grounds (SCG) through pyrolysis and subsequent CO₂-assisted physical activation for the removal of Methylene Blue (MB) dye from aqueous solutions. SCG was pyrolyzed at 400 °C, 500 °C, and 600 °C, and the resulting biochars were activated at 900 °C under CO₂ flow. The obtained materials were characterized using FTIR, SEM, BET, and elemental analyses to evaluate structural, morphological, and chemical properties. Among the samples, the activated carbon derived from 600 °C pyrolysis exhibited the highest surface area (44.59 m 2 /g) and was selected for detailed adsorption studies. Batch experiments were conducted to investigate the influence of pH (4–9), adsorbent dosage (2.5–15 g/L), initial dye concentration (15–50 mg/L), temperature (10–40 °C), and contact time (0–120 min) on MB removal efficiency. The maximum removal efficiency (99.15%) was obtained at 15 g/L and 45 min, while comparable performance (> 98.9%) was achieved even at lower dosages, indicating high adsorption capacity and economic feasibility. Kinetic analysis revealed that the adsorption process followed the pseudo-second-order model (R 2 > 0.94). The Freundlich isotherm (R 2 = 0.9924) provided the best fit, indicating multilayer adsorption on heterogeneous surfaces. These findings demonstrate that SCG-derived activated carbon is an effective, sustainable, and low-cost adsorbent with strong potential for dye removal and wastewater purification. The study also highlights the environmental value of coffee waste valorization within a circular economy framework, contributing to resource recovery and sustainable material development.
Ciner et al. (Mon,) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: