The sorption of ionizable benzotriazole(BTA) to corncob biochars pyrolyzed at different temperature(i.e., 300oC, 500oC and 800oC) 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 oC and 800 oC, respectively. Solution p H affected speciation of BTA and surface charge properties of biochars. For BTA~0, 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 oC) showed the highest sorption affinity for BTA. Ca~(2+) in solution enhanced BTA~- and BTA~0 sorption through cation-bridge and surface complexation.