Efficient Adsorption of Food Colorants onto Activated Carbon Derived from Haematococcus pluvialis Residue: Performance and Mechanism

• • HPR-AC achieved maximum adsorption capacities of 67.12 mg·g−1 for Sunset Yellow, 79.72 mg·g−1 for Ponceau 4R, and 72.75 mg·g−1 for Tartrazine at pH 5 and 55 °C, demonstrating high efficacy for azo dye removal from industrial wastewater. • • The adsorption process followed Langmuir isotherm and pseudo-second-order kinetics, indicating monolayer chemisorption with an endothermic nature, which is critical for designing energy-efficient treatment systems. • • Characterization via BET, FTIR, XRD, and XPS confirmed high specific surface area and abundant mesoporous structure, enabling rapid dye diffusion and enhanced adsorption capacity, essential for scalable water treatment applications. • • Statistical physics modeling revealed a multilayer physical adsorption mechanism dominated by pore filling, electrostatic interactions, hydrogen bonding, π-π stacking, and charge transfer, providing a mechanistic basis for optimizing adsorbent regeneration and process conditions.