Efficient adsorption of bisphenol A using magnetically recyclable nanocomposites with Box Behnken optimization

The study focused on evaluating the adsorption potential of Fe₃O₄/ZIF-8 (MFZ) for Bisphenol A (BPA) removal from aqueous environments. Different physicochemical factors, encompassing pH, Fe₃O₄/ZIF-8 dose, mixing time and temperature exerted an impact on the adsorption process. The adsorbent was characterized by Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometry (VSM), Thermogravimetric Analysis (TGA), Brunauer–Emmett–Teller (BET) analysis, X-ray Photoelectron Spectroscopy (XPS), Fourier-Transform Infrared Spectroscopy (FT-IR), and X-ray Diffraction (XRD). Using Response Surface Methodology (RSM), experimental data underwent optimization through a Box–Behnken Design (BBD) with 29 trials. The quadratic model, with a maximum R² (0.995), emerged as the best fit, delineating a suitable relationship between the variables and the response. The optimum conditions for BPA removal by MFZ, determined by the model, were detected to be a pH of 6.2, an adsorbent dose of 0.75 g/L, a mixing time of 72 min, and a temperature of 315 K, yielding an anticipated percentage removal of 99.1. Experimental validation under these conditions showed a percentage removal of 98.9%, deviating only 0.2% from the predicted value. In the presence of NaCl, Na₂SO₄, Na₂CO₃, NaNO₃, varying degrees of inhibition are observed in the adsorption effectiveness of MFZ on BPA. Across the five regeneration cycles, the percentage removal of MFZ for BPA experienced a slight decrease. The results suggest that the removal of BPA ions is notably influenced by the adsorption conditions.