2.4. Adsorption Kinetics

All adsorption experiments were performed at 25 ± 0.5 °C. Typically, 2.5 g samples were placed into a 500 mL beaker containing 0.01 M NaNO₃ and 500 µL of an As(III) solution with a concentration of 100 mg L⁻¹. The resulting suspensions were magnetically stirred, and samples withdrawn every 1 min for 12 h and analyzed by atomic fluorescence spectrometry (AFS-9760, Beijing Haiguang Instrument Co., Ltd., Beijing, China) after dilution according to the adsorption capacity of FMCBCs.

BC, FMCBC₁, FMCBC₂, and FMCBC3 samples (0.04, 0.08, 0.12, 0.16, and 0.2 g) were placed into a 50 mL brown bottle and treated with a solution of As(III) (20 mL, 20 mg L^–1) in 0.01 M NaNO₃. The effect of pH on adsorption was investigated by adjusting the pH in the range 3–7 using 0.10 M NaOH and HNO₃ solutions. The effect of solution concentration on adsorption was investigated by using 0.001, 0.01, and 0.1 M NaNO₃. The obtained suspensions were shaken for 6 h and filtered through Whatman No. 42 filter paper, and the concentrations of As(III) in the resulting filtrates were determined by atomic fluorescence spectrometry. All experiments were performed in triplicate.