Removal of cephalexin from aqueous solutions by original and Cu(II)/Fe(III) impregnated activated carbons developed from lotus stalks Kinetics and equilibrium studies.

Lotus stalk activated carbon (AC) was produced by ultrasound digestion of lotus stalks in H(3)PO(4). Copper nitrate and iron nitrate were used to impregnate AC, producing Cu(II)-impregnated AC (AC-Cu) and Fe(III)-impregnated AC (AC-Fe). The modified ACs were characterized by N(2) adsorption-desorption isotherms, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The adsorption kinetics and isotherms of cephalexin (CEX) in aqueous solution were studied for AC, AC-Cu and AC-Fe. The kinetics and equilibrium data agreed well with the pseudo-second-order kinetics model and Freundlich isotherm model for all three adsorbents. The results also showed that the adsorption capacities of AC-Cu and AC-Fe were larger than the capacity of AC and AC-Fe was found to be the most effective at the removal of CEX in solution. Furthermore, batch experiments were conducted to study the effects of pH (2.5-10.5), initial concentration of CEX (4-16 mg/L), ionic strength (10-1000 mM) on CEX removal.