Effect of Activated Carbon Pore Structure on the Adsorption of Pb(II) from Aqueous Solution

Pb(II) adsorption by three activated carbons (ACs) with similar surface chemistry but different pore distributions was investigated by isothermal adsorption experiments. The ACs were characterized by scanning electron microscopy (SEM) and N-2 adsorption at 77 K, while the micropore and mesopore size distributions were obtained from the density functional theory (DFT) and the Barrett-Joyner-Halenda (BJH) method, respectively. The specific surface area and total volume were ranked in order of AC1, AC2, and AC3. The AC2 sample had a uniform distribution of open pores on the surface and the highest saturating adsorption capacity, while the capacity of AC3, which had more aggregated pores, was similar to that of AC1, Which had a concentrated distribution of open pores on the surface. A correlation analysis of pore structure and adsorption capacity indicated that pores with diameters in the range of 0.4-0.6 nm were favorable for Pb(II) adsorption, whereas pores with diameters in the ranges of 10.5-20.6 nm, 20.6-55.6 rim, and 5.2-10.5 nm had an adverse effect.