Coupling recycled K₂CO₃ from first-round activation with Ca(OH)₂ for facilitating development of mesopores for...

Activation with K₂C₂O₄ generates K₂CO₃ that could be recycled for second-round activation. However, activation with either K₂C₂O₄ or K₂CO₃ produces activated carbon (AC) with mainly micropores. Herein, recycled K₂CO₃ reacted with Ca(OH)₂ to generate KOH, CaO and CO₂ for activation of poplar, cellulose and lignin. The results indicated that K₂CO₃ + Ca(OH)₂ showed superior cracking capability, generating AC from poplar with higher S_BET (1822.1 versus 1179.4 m²/g with K₂CO₃ or 1255.6 m²/g with K₂C₂O₄) and higher meso-porosity (43.3 % versus 10.0 % with recycled K₂CO₃ and 3.1 % with K₂C₂O₄). This was due to strengthened activity for cracking with KOH and CaO, CO₂ for gasification, and CaO as a hard template. The in-situ DRIFTS characterization showed that K₂CO₃ + Ca(OH)₂ interrupted dehydration of -OH, dehydrogenation of -C-H and even aromatization via cracking. The AC activated with Ca(OH)₂/K₂CO₃ showed the highest capability for tetracycline adsorption via monolayer mode, and membrane diffusion was the key rate-determining step.