Blue coke-based activated carbon adsorbents: Insights into the efficiency and mechanism of methyl blue removal

In this study, a systematic analysis was conducted to investigate the efficiency and mechanism of methylene blue (MB) removal from water using blue coke-based activated carbon (AC) as an adsorbent. The investigation encompassed several critical parameters, including adsorbent dosage, contact time, pH, temperature, initial MB concentration, and the regeneration capacity of the adsorbent. The adsorption mechanism of MB by AC was elucidated through instrumental analysis and theoretical models such as adsorption kinetics, isotherm models, and thermodynamic analysis. The experimental results demonstrated several key findings: the removal efficiency of MB increased with the adsorbent dosage, although the unit adsorption capacity decreased; the removal rate of MB rose rapidly with increasing contact time and reached equilibrium after 90 min; the highest removal efficiency was achieved at pH 6; the adsorption capacity increased with higher initial MB concentrations. The adsorption kinetics conformed to the pseudo-second-order model, indicating that chemical adsorption was the predominant control step. The adsorption process was identified as a spontaneous reaction, with the Langmuir model suggesting a maximum adsorption capacity of 2040.696 mg/g at 318 K. Furthermore, AC exhibited an abundant mesoporous structure and surface functional groups, contributing to the efficient removal of MB. The adsorption mechanism involved pore-filling, hydrogen bonding, π-π interactions, and electrostatic attraction. Additionally, AC demonstrated excellent regeneration performance. These findings suggest that AC prepared from blue coke holds significant potential for industrial applications in MB removal, owing to its high removal efficiency, low cost, and good regenerative properties, making it highly valuable for practical use.