Sequential activation of willow wood with ZnCl2 and H3PO4 drastically impacts pore structure of activated carbon

Dual activators can be used together or in sequence to intensify pore development in activation of biomass. If used in sequence, arrangement of an activator in first- and second-round activation dictates overall reaction network in activation and pore characteristics of activated carbon (AC). Herein, activation of willow wood with single, mixed ZnCl2 2 and H3PO4, 3 PO 4 , or activators in sequence (activation firstly with ZnCl2 2 or H3PO4 3 PO 4 at 350 degrees C and the other activator subsequently at 550 degrees C) were conducted. The results showed that the H3PO4-*ZnCl2 3 PO 4-*ZnCl 2 sequential activation (activating first with H3PO4 3 PO 4 then with ZnCl2) 2 ) destructed P-O-C bonds and created additional micropores, forming H3PO4-*ZnCl2-AC 3 PO 4-*ZnCl 2-AC of 1344.7 m2/g 2 /g with superior capability for adsorption of phenol from phosphorus doping. Nonetheless, The ZnCl2-*H3PO4 2-*H 3 PO 4 sequential activation did not enhance pore development (998.5 vs. 991.8 m2/g 2 /g for H3PO4-AC) 3 PO 4-AC) and reduced AC yield to 27.8%, due to deficient aliphatics for second-round activation with H3PO4. 3 PO 4 . Co-activation with ZnCl2+H3PO4 2 +H 3 PO 4 only enhanced percentage of micropore but not S BET . Activation with ZnCl2 2 but not H3PO4 3 PO 4 transformed fibers into densified bulky particles. However, activator selected in first-round activation determined final morphology of ACs in sequential activation.