Thermally treated biomass of pine (Pinus kesiya) leaves for effective removal of organic dyes from aqueous solutions.

BACKGROUND: Methyl orange (MO) and methylene blue (MB) from aqueous solutions were effectively removed using thermally treated pine (Pinus kesiya) leaves. The influences of solution pH (2–10), contact time (10–240 min) and initial dye concentration (100–500 mg L−1) were found to be significant in the process of dye removal. The experimental data were fitted with four isotherm models (Langmuir, Freundlich, Sips and Temkin) and four kinetic models (Elovich, pseudo‐first‐order, pseudo‐second‐order and intraparticle diffusion). Some mechanisms of the MO and MB adsorption onto the adsorbent material were proposed and discussed. Results: Among the four isotherm models examined, the experimental data gave the best fit with the Langmuir model. The maximum Langmuir adsorption capacities were 136.99 mg g−1 for MO and 140.85 mg g−1 for MB. Kinetic studies illustrated that the biosorption of both dyes onto pine leaves aligns with Elovich, pseudo‐first‐order, pseudo‐second‐order and intraparticle diffusion models. Thermodynamic studies showed that the uptake of the two dyes was regulated by physisorption, and it was spontaneous and endothermic in nature. Electrostatic interactions, as well as other noncovalent forces such as π–π interactions and hydrogen bonds, were mechanisms of dye adsorption on heat‐treated pine leaf biomass. Conclusion: The present study suggests that pine leaves could be a potential biosorbent for wastewater treatment due to their high availability and production, resulting in several environmental advantages. © 2023 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]