Abstract: Non-ferrous smelter flue gas is a major anthropogenic source of arsenic emissions in China. Because the composition of non-ferrous smelter flue gas is complicated, efficient removal of gaseous arsenic remains a significant challenge. Biomass charcoal usually contains abundant functional groups on its surface, which have a strong affinity for arsenic. Therefore, a modified biomass charcoal adsorbent was synthesized by a hydrothermal method from Camellia oleifera shells. The analysis and characterization results of the adsorbent confirmed that the prepared biomass charcoal had a porous and spherical structure with a large specific surface area (532.441 m²/g) and a well-developed microporous structure (0.647 cm³/g). FTIR confirmed that the prepared biomass charcoal contained a large number of oxygen-containing functional groups such as C—O and C=O. Gaseous arsenic adsorption experiments revealed that the optimal adsorption temperature of the biomass charcoal for arsenic was 400 ℃, and its maximum arsenic adsorption capacity reached 16.14 mg/g, which was superior to that of traditional mineral adsorbents. The adsorption capacity of biomass charcoal adsorbent at the concentrations of 8 g/kg SO₂, 10 g/kg HCl, and 16% CO₂ maintained an adsorption capacity above 10 mg/g, demonstrating a strong resistance to acid gas poisoning. Furthermore, the presence of O₂ in smelting flue gas enhances arsenic removal, whereas H₂O has a slight inhibitory effect. The final arsenic adsorption product was characterized using X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma-high performance liquid chromatography (ICP-HPLC). The dominant arsenic species in the adsorption product was As⁵⁺, which accounted for 62.7% of total arsenic at 250 ℃ and under a pure N₂ atmosphere. Upon increasing the adsorption temperature to 400 ℃ and O₂ volume concentration to 6%, the proportion of As⁵⁺ increased to almost 100%, indicating that arsenic oxidation plays a crucial role in arsenic removal. The proposed arsenic removal mechanism involves the physical adsorption of gaseous arsenic trioxide on the biomass charcoal surface, followed by oxidation to stable diarsenic pentoxide by the oxygen-containing functional groups, ultimately leading to arsenic purification. The spent biomass charcoal was regenerated by alkaline boiling. After 10 regeneration cycles, the arsenic removal efficiency of biomass charcoal decreased by only 30%, demonstrating that the biomass charcoal from Camellia oleifera shells exhibited good regeneration potential. These results demonstrate the excellent industrial application potential of the biomass charcoal for arsenic pollution control.