Synthesis of a mesoporous carbon from peach stones for adsorption of basic dyes from wastewater: kinetics, modeling, and thermodynamic studies

The objective of this work was to evaluate the efficiency of a synthesized activated carbon for the removal of methylene blue from aqueous solution. Activated carbons synthesized from agricultural wastes precursors are an interesting alternative for their use as adsorbents and catalyst supports in the wastewater treatment field, and represent an important ecological benefit. In this work, mainly, mesoporous-activated carbon was synthesized from peach stones by chemical activation. The textural, morphological, and chemical characterizations of the material were carried out, revealing the acidic nature of the solid. The effects of different experimental conditions on the adsorption capacity, initial methylene blue concentration, pH solution, adsorbent dosage, and temperature have been investigated. The kinetic experimental data followed the pseudo-second-order model. Intra-particle diffusion model indicated that the adsorption process is controlled by intra-particle diffusion stage. Adsorption isotherms were conducted at several operation temperatures, obtaining the largest methylene blue adsorption capacity value, 444.3 mg g⁻¹, at the highest temperature, 333 K. The equilibrium adsorption data were tested by four isotherm models, i.e., Langmuir, Freundlich, Tóth, and Redlich–Peterson. It was found that the adsorption data fitted better to Tóth and Redlich–Peterson isotherm models. The calculated thermodynamic parameters suggested that an endothermic and spontaneous process is occurring.