Adsorption of lead ions onto activated carbon prepared from bio-plant stems activation with H3PO4

Key words: 
• activated carbon /
• H3PO4 activation /
• adsorption

Abstract: Low-cost activated carbons were prepared from cotton stalk and Spartina alterniflora by phosphoric acid activation. Adsorption capacities for lead on the prepared carbons were measured by conducting a series of batch adsorption experiments. The results showed that the carbon prepared from cotton stalk activated at 500 ℃ for 2 h has 1.43 mmol/g acidic surface groups and 1 570 m2/g BET surface area. The activated carbon prepared from Spartina alterniflora under the conditions has 1.27 mmol/g acidic surface groups and 856 m2/g BET surface area. The maximum adsorption capacity for lead onto the two activated carbons calculated from Langmuir isotherm is 119 mg/g and 111 mg/g at 25℃ respectively. The optimum pH for the removal of lead was found to be 4.3, and the Freundlich isotherm model was found to best describe the equilibrium experimental data. It was also found that the ion-exchange mechanism was involved and played an important role in the adsorption.