Abstract: Based on the concept of waste control by waste, agroforestry waste oil-tea cake was used to remove azo dye Reactive Red 15 (RR15) via biosorption from aqueous solution. To optimize the biosorption condition, a Box-Behnken Design with a response surface methodology was carried out. Three independent variables-pH, initial RR15 concentration and biosorption temperature-were studied, and biosorption capacity and removal efficiency were set as the response values. Statistical analysis showed that pH was highly significant for both biosorption capacity and removal efficiency (P<0.0001); the optimal biosorption condition was pH 1.0, initial RR15 concentration 300 mg/L and biosorption temperature 20 ℃. The Temkin isotherm model was more applicable for describing the biosorption equilibrium data in the whole initial RR15 concentration range than the Freundlich or Langmuir isotherm model. Q0 gained from Langmuir isotherm model at 20 ℃ was 74.63 mg/g. The kinetic study showed that the experimental data were well fitted by the pseudo-second-order model (R2>0.9997), which indicated that the dominant biosorption belonged to the chemisorptive nature. Both intra-particle diffusion and boundary layer diffusion might affect the biosorption rate. Thermodynamic study demonstrated that the biosorption was a spontaneous and exothermic process. To understand the mechanical behavior of RR15 biosorption process, SEM, EDS and FTIR were employed to characterize the oil-tea cake pre- and post-biosorption. The FTIR analysis indicated that functional groups (e.g., amine, hydroxyl) on the oil-tea cake biosorbent were the active binding sites for the RR15 biosorption. These results showed that oil-tea cake is a promising biosorbent, which could effectively remove RR15 from dye wastewater.