Process modeling and structural reconstruction mechanisms of coal gasification fine slag via alkali leaching for enhanced phenol adsorption

In order to realize the high-value utilization of coal gasification fine slag (CGFS) and efficiently treat phenol wastewater, the Box-Behnken Design (BBD) response surface method was used to optimize the alkali leaching activation process of CGFS. The NaOH concentration, alkali leaching time, and solid-liquid ratio were used as influencing factors, and the leaching rate of metal oxides was the response value. Combined with SEM, FTIR, Raman spectroscopy, BET and other characterization methods, the influence mechanism of alkali leaching on the physical and chemical properties and adsorption properties of CGFS was systematically explored, and its treatment effect on simulated phenol wastewater was verified by static adsorption experiments. The results showed that the optimal alkali leaching process was as follows: NaOH concentration 1 mol/L, reaction time 15 min, solid-liquid ratio 1: 20, temperature 25 °C. After alkali leaching, the agglomeration of CGFS was reduced, the pore patency was improved, the number of surface hydroxyl groups (Si-OH / Al-OH) and carbon defects was significantly increased (I D / I G ratio increased from 2.67 to 4.40), and the material obtained better specific surface area and pore size distribution. The removal rate of phenol by NaOH-CGFS prepared under this condition increased from 88.47% of the original CGFS to 96.11%. After modification, the adsorption capacity of the material increased from 17.69 mg / g to 19.22 mg / g. The enhancement of adsorption performance was due to the synergistic effect of hydrogen bonding and π-π stacking. In this study, the structural modification and performance improvement of CGFS were realized by alkali leaching activation, which provided a new idea for the resource utilization of industrial solid waste.