Abstract: Hydroxylapatite/bagasse biochar composite adsorbent(HBA) was prepared from sugarcane bagasse by using the hydrothermal synthesis method.The adsorption capacity for As(V) on HBA was measured through a series of batch adsorption experiments.The adsorption mechanism of As(V) from aqueous solution onto HBA was investigated using Fourier transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS).The results showed that the specific surface area of HBA was 89.52 m²/g, and the point of zero charge values of HBA was 7.2.The molecular formula of hydroxylapatite in HBA was Ca₁₀(PO₄) ₆(OH) ₂.The pH range for the optimal As(V) adsorption was between 5.0 and 9.0.The As(V) adsorption isotherm could be well fitted with the Langmuir model.The maximum As(V) adsorption capacity for HBA was 6.76 mg/g at 25℃, which is 23 times that of the bagasse biochar.FTIR analysis indicated that oxygen-containing functional groups presented abundantly on the external and internal surfaces of HBA, which provided numerous chemical sorption sites and thereby increased the adsorption capacity of HBA.XPS analysis showed that the oxygen-containing functional groups, carboxyl oxygen─O─C＝O, 532.2 eV and hydroxyl-OH, 530.6 eV, were involved in adsorption.Hydroxylapatite in HBA played the key role in the As(V) adsorption process.The As(V) adsorbed on the HBA surface existed mainly as AsO₄^3- and HAsO₄^2-.