Recycling of coal gasification fine slag as ultra-high capacity adsorbents for the removal of Rhodamine B dye: Graded synthesis method, kinetics and adsorption mechanism

Maximizing the utilization of elements in coal gasification fine slag (CGFS) and converting them into high-value-added materials is of great significance for the resource utilization and harmless disposal of CGFS. In this study, SBA-15 and hierarchical X-type zeolite/carbon composite were prepared from CGFS by a graded synthesis method, and their pore structures were modulated by 1,3,5-trimethylbenzene and CO2 pre-activation, respectively, and then the materials were then amino-modified. Both materials have a regular structure and large specific surface area (586.32 m2/g and 460.97 m2/g). The adsorption efficiency of the material increases due to the increased mass transfer capacity in the pores, while the surface amine group functionalization can further improve the adsorption performance of the material. The Langmuir model and the Pseudo-second-order kinetic model provided an accurate description of the adsorption behavior of the materials, which showed a good adsorption capacity of 147.93 mg/g and 157.98 mg/g, respectively. The XPS and FT-IR results demonstrate that hydrogen bonding and electrostatic attraction play a key role in the adsorption process. The results proved the CGFS can be converted into high performance adsorption materials for efficient dye removal, which achieves the “waste to treat waste” effect.