Structure design of spherical activated carbon from waste ultrafine green coke powder and its adsorption behavior for cationic and anion dyes

Waste ultrafine green coke powder is a by-product generated during the spheroidization process of artificial carbon anodes (needle coke) used in lithium-ion batteries. The ultrafine particle size (D50 = 6.40 μm) significantly affects its processability, resulting in resource wastage. Therefore, the high-value-added utilization of waste ultrafine green coke powder is essential for enhancing the economic efficiency of lithium-ion battery carbon anode enterprises. In this study, spherical activated carbon (CSAC) was synthesized through the steam activation of green coke powder-based spherical carbon (CS). Specifically, green coke powder-based spherical carbon (CS) was prepared using a granulation method, with ultrafine green coke powder as the raw material and medium-temperature coal pitch (MTP) as the binder. The adsorption capacity of the as-prepared CSAC for removing anionic dye methyl orange (MO) and cationic dye methylene blue (MB) from printing and dyeing wastewater was also investigated. The CSAC was optimized in terms of its microstructure, mechanical properties, and adsorption performance. Factors influencing the adsorption performance of CSAC were systematically investigated, and the adsorption mechanism as well as its recyclability were examined in detail. The results indicate that CS prepared with 25 % MTP addition exhibits optimal mechanical properties and microstructure. After activation, the resulting CSAC achieves a maximum specific surface area of 608.07 m2/g, with adsorption capacities of 149.70 mg/g for MO and 194.57 mg/g for MB, respectively. After five adsorption–desorption cycles with thermal regeneration, the regeneration efficiency of CSAC for MO remained at 78.24 %. The adsorption mechanism of CSAC for MO and MB is attributed to its unique structural characteristics, π-π interactions, electrostatic interactions, and the synergistic effect of hydrogen bonding. This study offers theoretical support for the clean and high-value-added utilization of green coke powder, as well as the effective treatment of printing and dyeing wastewater.