Waste Biomass-Derived Carbon with Ultrahigh Adsorption Capacity for Anionic and Cationic Dyes and Antibiotics in a Wide pH Range

Herein, a novel two-step ZnCl2–KOH activation process was developed to produce wheat bran-derived biocarbon (WBZ5K9) with an ultrahigh specific surface area of 3200.8 m2 g–1, a porous structure mainly containing micropores (0.5–2 nm) and mesopores (2.0–2.17 nm), a high graphitization degree (ID/IG = 0.9), and a good production yield of 21.4%. After further N-doping treatment, the obtained WBZ5K9-N had a similar textural structure but a high N content of 3.5 atom %. Owing to the well-developed pore structure and abundant active adsorption sites (i.e., graphitic carbon and nitrogen), both adsorbents showed ultrahigh adsorption capacities toward various pollutants without pH adjustment. Particularly, WBZ5K9-N presented adsorption capacities of 558.7–1965.3 mg/g toward 6 anionic dyes, 3 cationic dyes, and 4 antibiotics, ranking the top level among the known adsorbents. Finally, the synergistic chemisorption mechanism of electrostatic interaction, π–π stacking interaction, H-bonding, and N interaction was revealed. Such an activation method can be extended to prepare other waste biomass-derived carbons.