Abstract: Because nitrified aerobic granular sludge exhibits high porosity, large surface area and decent separation capacity, aerobic granular sludge can be utilized as a biological adsorbent. In this study, nitrified aerobic granular sludge was used to remove Pb²⁺ from aqueous solution. Different initial pH values, initial Pb²⁺ concentrations, adsorbent doses and temperatures on Pb²⁺ adsorption were evaluated as well. Three types of adsorption isotherms (i.e., by Langmuir, Freundlich and Redlich-Peterson models) were investigated. The results indicated that the equilibrium was well described by the Langmuir isotherm, predicting that the adsorption of Pb²⁺ on nitrified aerobic granules was a monolayer adsorption. The R² was 0.9901, and the maximum adsorption capacity was 79.58 mg/g at 25 ℃. Moreover, the equilibrium kinetic adsorption data were fitted to the pseudo-second-order kinetic equation with R² values of 1.0000,1.0000 and 0.9999 respectively. The relation coefficients (RC), which were 30.706%, 28.019% and 24.188%, were all under 50%, showing that the sorption of Pb²⁺was controlled primarily by intraparticle diffusion. Fourier transform infrared spectroscopy (FTIR) results indicated that the active groups including O—H, N—H, CO, CC, C—OH and C—O—C were involved in Pb²⁺ adsorption. Zeta potential analysis and pH_ZCP rose from 2.5 to 3.1, demonstrating that inner-sphere adsorption happened for Pb²⁺ adsorption on nitrified aerobic granules. The nitrified aerobic particles were well fitted by the good adsorption function on Pb²⁺; the adsorption mechanisms mainly included inorganic micro precipitation, surface complexation, inner-sphere complexation reaction and ion exchange.