Syngenetic effects in co-activation of willow wood with homogenous biochar facilitate pore generation in activation

Abstract

Mixing feedstocks of varied aromatic/aliphatic content is a simple method for tailoring pore structures of activated carbon (AC) in activation. Herein, willow wood and homogenous biochar produced at 300 or 500°C, which have distinct content of aliphatic component, were co-activated with K2C2O4, at 800°C for changing pore characteristics of resulting AC. The results indicated that co-activation of willow and biochar diminished production of AC and impacted evolution of organics and gases through intensive volatiles-char interactions. The AC from the co-activation of willow with either biochar-300 or biochar-500 exhibited higher specific surface area than that from direct activation of willow (1409.7 or 1297.0 m2 g−1 versus 1243.6 m2 g−1), which was also higher than calculated average of that from feedstock (ca. 1160 m2 g−1). This resulted from intensified gasification of the biochar with H2O/CO2 derived from willow, creating additional macropores and micropores of enlarged pore sizes. The enhanced gasification also reduced crystallinity of graphitic carbon, lowered O content via accelerated deoxygenation and diminished CO on nascent AC. Volatiles-char interactions also minimized pore filling from carbonaceous deposit generated from secondary condensation of primary volatiles. Additionally, direct activation of aliphatic-rich willow tended to form more micropores, while more mesopores were formed from aromatic-rich biochar.