The adsorption properties and mechanisms of magnetic carbon–silicon composites in situ prepared from coal gasification fine slag

Abstract

A novel magnetic carbon–silicon composite (Fe-HH-CGFS) was prepared from solid waste coal gasification fine slag (CGFS) by a two-step acid leaching and one-step chemical co-precipitation process, which was optimized using a 3-factor, 3-level Box–Behnken design and then analyzed for correlation. Fe-HH-CGFS was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), thermal gravimetric analysis (TGA), and vibrating sample magnetometer (VSM) measurements. The results demonstrated that Fe-HH-CGFS had a reverse spinel structure with an average particle size of 5.14 nm, exhibiting a microporous/mesoporous structure with a specific surface area (SSA) of 196.84 m² g⁻¹ and pore volume of 0.346 cm³ g⁻¹. Furthermore, Fe-HH-CGFS could achieve 97.59% removal efficiency of rhodamine B (RhB) under the optimal conditions: an initial concentration of RhB of 100 mg L⁻¹, an adsorption time of 60 min, and a dosage of Fe-HH-CGFS of 1.0 g L⁻¹. The pseudo-second-order model and the Langmuir isotherm satisfactorily described the adsorption behavior. The results indicated that the RhB removal process was a single-molecule layer endothermic adsorption, which is dominated by chemical adsorption reactions. This work is expected to provide an alternative route for the high-value utilization of CGFS and offer a valuable insight for the recycling of other solid wastes, aligning with the green development concept of “treating wastes with wastes”.