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α-Fe 2 O 3 modified biochar (Fe 2 O 3 /BC) was prepared to remove Cu(II), Pb(II) and As(V). By adjusting the calcination temperature, the morphology and exposed crystal facets of α-Fe 2 O 3 on the biochar were changed which further affected the adsorption performance. The kinetics and isotherms were investigated systematically to reveal adsorption effect of the adsorbent on Cu(II), Pb(II) and As(V). The results indicated that chemisorption process was the dominant adsorption mechanism. Fe 2 O 3 /BC-350 exhibited superior adsorption capacity for Cu(II) (258.22 mg/g) and Pb(II) (390.60 mg/g), and Fe 2 O 3 /BC-250 showed relatively good adsorption capacity for As(V) (5.78 mg/g). By adsorption mechanism analysis, electrostatic adsorption, ion exchange, precipitation and complexation were coexisted in the process of removing metal ions by Fe 2 O 3 /BC. The repeatability test and the effect of ion strength exhibited the strong stability of Fe 2 O 3 /BC. Meanwhile, density functional theory (DFT) calculations manifested that the (202) facet of α-Fe 2 O 3 on Fe 2 O 3 /BC-350 possessed the lowest adsorption energies of Cu(II) and Pb(II). While for As(V), it was the (104) facet of α-Fe 2 O 3 on Fe 2 O 3 /BC-250 that exhibited the lowest adsorption energy. DFT results revealed that different Fe 2 O 3 /BC had different adsorption affinities to various heavy metals. In general, this work not only prepared a promising adsorbent via a simple procedure, but also served as a reference for researchers in designing absorbents with specific active facet for efficient heavy metals remediation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)