The sorption of ionizable benzotriazole (BTA) to corncob biochars pyrolyzed at different temperature (i.e., 300 ℃, 500 ℃ and 800 ℃) was investigated in this study. Biochars produced at higher temperature showed higher surface area, micropore volume and aromaticity. Consequently, the sorption of BTA changed from absorption to adsorption for biochars pyrolyzed at 300 ℃ and 800 ℃, respectively. Solution pH affected speciation of BTA and surface charge properties of biochars. For BTA⁰, H-bond, partition and micropore filling are dominant sorption mechanisms. For BTA^-, it is suggested that negative charge-assisted H-bond plays an important role in sorption. Corncob biochar pyrolyzed at high temperature (e.g., 800 ℃) showed the highest sorption affinity for BTA. Ca²⁺ in solution enhanced BTA^- and BTA⁰ sorption through cation-bridge and surface complexation.