Modification of activated carbon via grafting polyethyleneimine to remove amaranth from water

A new adsorbent was fabricated via grafting polyethyleneimine (PEI) on activated carbon (AC) to remove anionic amaranth from water. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used to characterize the grafting process of PEI. The adsorption behavior of the anionic amaranth (AM) on the modified AC is further evaluated by adjusting pH, the modified AC dosage, contact time and the initial AM concentration. AM adsorption was dramatically dependent of solution pH and the optimum pH is 1.08. The adsorption rate was very high within 20 min and equilibrium was achieved at 180 min. The maximum adsorption amount of AM on the modified AC is 72.68 mg/g at pH 1.08. Compared with the unmodified AC, the adsorption efficiency on the modified AC was dramatically increased from 29.9 to 97%. An electrostatic interaction mechanism was proposed in the acidic solution. The adsorption isotherms were consistent with the Langmuir model and the obtained kinetic data were in accordance with a pseudo-second order adsorption behavior for the modified AC.