Enhancing mass yield and adsorption performance of activated carbon via pyrolysis-condensation pretreatment coupled with activation of biomass by K2C2O4

Pre-carbonization plus activation is commonly used for activation of biomass. Nonetheless, pre-carbonization via pyrolysis removes a significant portion of aliphatic structures, diminishing mass yield of resulting activated carbon (AC) from activation. In this study, pyrolysis-condensation (pyro-condensation) was proposed as a method for pre-carbonization prior to activation of peach, cellulose, and lignin with K 2 C 2 O 4 , which could achieve recycled polymerization of volatiles to maximize mass yield of biochar and correspondingly AC. The results confirmed double or even triple of biochar yields with peach or cellulose via pyro-condensation, attributed to volatile recycling and carbon retention via aliphatic polymerization. The mass yields of AC from subsequent activation were also tripled with cellulose and doubled with lignin when compared with the pyrolysis-activation route. Moreover, pyro-condensation plus activation enhanced specific surface area of AC (i.e. 1243.6 versus 1048.1 m 2 g −1 from pyrolysis-activation route with peach), abundance of mesoporous structures (12.8% versus 3.2% with cellulose) and enlarged pore size (1.9 versus 1.6 nm with cellulose). The in-situ IR characterization confirmed abundant aliphatic structures in form of −C- H, –OH, C O and C-O- C in the biochar from pyro-condensation, which were formed from re-polymerization of volatiles and filled voids of biochar, rendering smooth surface. The AC from pyro-condensation pretreatment exhibited superior phenol adsorption performance (maximum capacity: 426.3 mg/g, 49.5% higher than the counterpart with pyrolysis pretreatment) and excellent reusability. The abundant aliphatic components induced more intense cracking in the followed activation, forming AC of more developed pores, higher thermal stability, higher degree of aromatization and lower overall impacts on environment.