Removal of Methylene Blue from water using nitric acid modified corn cob derived activated carbon: synthesis, characterization, kinetics, and isotherm study

This study utilized corn cob as the raw material and HNO ₃ as the activator to prepare carbon materials through high-temperature carbonization and activation processes. An orthogonal experimental design was employed to optimize the preparation conditions for corn cob based activated carbon, examining the effects of solid-liquid ratio, activation time, activation temperature, and carbonization temperature on the properties of the resultant porous carbon materials. The optimal preparation conditions were determined based on the adsorption performance of the carbon materials for methylene blue in simulated wastewater. The results indicated that a solid-liquid ratio of 1, an activation temperature of 1123 K, an activation time of 90 min, a carbonization temperature of 723 K yielded the best adsorption performance for methylene blue, with an adsorption capacity of 40.78 mg/g, The yield of activated carbon is about 29.53%. Furthermore, the activated carbon prepared under these optimal conditions was analyzed using SEM, BET, XRD, and FTIR. The surface exhibited a rich pore structure,, with a Langmuir specific surface area of 510.0303 m ² /g and a significant presence of oxygen-containing functional groups, which are critical for the exceptional adsorption performance of this carbon material. The adsorption properties of activated carbon for Methylene Blue(MB)were investigated, focusing on the effects of adsorption time and temperature on adsorption efficiency. The kinetic study revealed the characteristics of the adsorption process, indicating that the quasi-second order kinetic model more accurately describes the adsorption behavior. The adsorption thermodynamic analysis confirmed that the adsorption process of MB onto corn cob-based activated carbon in simulated wastewater is endothermic, accompanied by an increase in entropy and a decrease in Gibbs free energy, suggesting that the process is spontaneous under isothermal and isobaric conditions. This study holds both theoretical and practical significance for the application and development of corn cob activated carbon in treating industrial wastewater containing organic dyes.