Fabrication of cotton textile waste-based magnetic activated carbon using FeCl₃ activation by the Box-Behnken design:...

Cotton textile waste-based magnetic activated carbon was prepared via simultaneous activation-pyrolysis using FeCl₃ as a novel activating agent. The response surface methodology based on the Box-Behnken design method was applied to optimize the preparation parameters and predict the specific surface area of the samples. The optimal activated carbon was obtained at a mass ratio of FeCl₃/CTW, activation time and activation temperature of 1.62 : 1, 1 h and 700 °C, respectively. The experimental maximum yield and iodine adsorptive value (32.66% and 714.55 mg g^-1) of the resultant carbon were close to that of the predicated response values (34.85% and 783.75 mg g^-1), respectively. SEM, N₂ adsorption-desorption isotherms, XRD, PPMS, FTIR and pH_pzc measurements were conducted to analyze the physicochemical characteristics of the optimal sample. The results showed that the carbon matrix had a high specific surface area of 837.39 m² g^-1 with abundant micropores and acidic surface functional groups, and the saturation magnetization (Ms) was 5.2 emu g^-1 due to the formation of Fe₃O₄. The maximum adsorption of Cr(vi) by the carbon reached 212.77 mg g^-1. Furthermore, the addition of FeCl₃ lowered the pyrolytic carbonization temperature and inhibited the generation of volatiles in the activation-pyrolysis process. Meanwhile, the formation of Fe₂O₃ and Fe₃O₄ derived from FeCl₃ was beneficial for the development of vast micropores.