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 ZnCl 2 and H 3 PO 4 , or activators in sequence (activation firstly with ZnCl 2 or H 3 PO 4 at 350 °C and the other activator subsequently at 550 °C) were conducted. The results showed that the H 3 PO 4 →ZnCl 2 sequential activation (activating first with H 3 PO 4 then with ZnCl 2 ) destructed P-O-C bonds and created additional micropores, forming H 3 PO 4 →ZnCl 2 -AC of 1344.7 m 2 /g with superior capability for adsorption of phenol from phosphorus doping. Nonetheless, The ZnCl 2 →H 3 PO 4 sequential activation did not enhance pore development (998.5 vs. 991.8 m 2 /g for H 3 PO 4 -AC) and reduced AC yield to 27.8 %, due to deficient aliphatics for second-round activation with H 3 PO 4 . Co-activation with ZnCl 2 +H 3 PO 4 only enhanced percentage of micropore but not S BET . Activation with ZnCl 2 but not H 3 PO 4 transformed fibers into densified bulky particles. However, activator selected in first-round activation determined final morphology of ACs in sequential activation.