Efficient adsorption of bisphenol A from aqueous solutions using low-cost activated carbons produced from natural and synthetic carbonaceous materials

Milk-vetch (MV) and compact discs (CDs) wastes, as natural and synthetic carbonaceous precursors, were used to produce low-cost activated carbons. The efficiency of adsorption of these adsorbents was compared with commercial activated carbon (CAC) for the adsorption of bisphenol A (BPA) from aqueous solutions. The activated carbon prepared from MV (MVAC) had a higher adsorption capacity, 33.19 mg g –1 , than that of both CD wastes (CDAC), 12.15 mg g –1 , and CAC, 29.22 mg g –1 . These adsorbents were characterized using X-ray diffraction, scanning electron microscope, Brunauer–Emmett–Teller method, pH zpc and Fourier transform-infrared spectra techniques. The effect of operating parameters on the adsorption of BPA such as the pH, contact time, adsorbent dosages, initial BPA concentra-tions, temperature, and ionic strength were studied. The optimal removal of the BPA was achieved at neutral pH (pH 7) by three adsorbents. Equilibrium contact times of 90 min were achieved for all the investigated activated carbons. Based on the obtained results, the pseudo-second-order kinetic model and Langmuir isotherm fitted the experimental finding better than other isotherms and kinetics. Furthermore, thermodynamic parameters were calculated and ΔG, ΔH and ΔS indicate that the reac-tion is spontaneous and endothermic, and physisorption mechanism was the dominant mechanism in terms of adsorption of BPA onto the three adsorbents.