Abstract:
This study focuses on the adsorption of Malachite Green (MG) and Basic Fuchsin (BF) dyes from aqueous solutions using cedar cone powder (CP) as a natural, readily available, and low-cost adsorbent. Experimental investigations enabled the determination of optimal process conditions: maximum adsorption capacity was achieved with an adsorbent mass of 0.1 g, at 30 °C, an agitation speed of 300 rpm, and an optimal pH of 4.42 for MG and 4 for BF. The presence of salt (NaCl) did not significantly affect the performance of the system.
Adsorption isotherm modeling revealed an L-type behavior (Langmuir model) for both dyes, indicating a strong affinity between the adsorbent and the dyes. The experimental equilibrium data were better described by the Langmuir model than by the Freundlich model, while the Temkin model suggested an exothermic process.
The kinetic study, based on the Elovich, pseudo-first-order, and pseudo-second-order models, showed that the pseudo-second-order model provided the best fit. The Boyd and Weber–Morris models indicated that external diffusion is the main rate-limiting step, although intraparticle diffusion also plays a role.
Finally, the thermodynamic study confirmed that the adsorption of MG and BF onto cedar cone powder is a physicochemical, spontaneous, and exothermic process.
