Adsorption behavior and mechanism of modified <i>Abies marocana</i> Trab. needles for the efficient removal of methylene blue dye

ABSTRACT The study aimed to explore the effectiveness of Abies marocana needles as a cost-efficient adsorbent for water purification, focusing on the adsorption of methylene blue (MB) dye. Chemical treatment with sulfuric acid (H2SO4) was applied to the needles, followed by a thorough analysis of surface characteristics and functional groups using various techniques. Experimental parameters such as adsorbent quantity, pH, contact duration, initial dye concentration, and temperature were investigated to determine their influence on adsorption capacity, revealing that under optimal conditions, the biosorbent AMNS displayed significant MB dye removal efficiency of 96.527 ± 0.017%. The study found that the pseudo-second-order model better explained the adsorption of MB dye on AMNS compared with the pseudo-first-order model, while the Freundlich mathematical model effectively described the adsorption isotherms. Thermodynamic analyses indicated that the adsorption process is both exothermic and spontaneous, with various interactions such as electrostatic attractions, H-bonding, π–π interactions, and pore-filling contributing to the adsorption mechanism. Furthermore, the investigation highlighted the reusability of AMNS when desorbing with 1 M sulfuric acid, emphasizing the significant role of A. marocana needles in environmental protection, especially in treating industrial effluents.