Molecular Simulation Comparison of Two Ultrafine Coal-Based Activated Carbons for the Removal of Methylene Blue from Water

Abstract

Coal-based activated carbons (CACs) have excellent valuable applications, and have been industrially produced. However, ultra-fine coal-based activated carbons (UCACs) and their removal of methylene blue (MB) have rarely been reported in the present literature. Two kinds of UCACs were obtained in this paper and the adsorption test of MB was carried out. The adsorption performance of MB on UCAC was simulated by Grand Canonical Monte Carlo (GC-MC) method. The experimental results were validated by molecular simulation, and the adsorption mechanism was investigated. The adsorption amount of MB, the d50, and specific surface area values of the UCACnew (obtained by the new method) and UCACcm (obtained by the conventional chemical method) were 746.95 mg/g, 12.54 μm, 1225.36 m2/g and 652.77 mg/g, 12.10 μm, 713.76 m2/g, respectively. The results of the molecular simulation calculations were consistent with the pattern of magnitude of the experimental results. The peak of the adsorption concentration occurred near 6 Å on the pore surface. The interaction energy of MB molecules with carboxyl groups was much larger than with hydroxyl groups. Van der Waals forces dominated the adsorption process, with a contribution of >60% in both cases.