Adsorptive removal of Pb(II) by magnetic activated carbon incorporated with amino groups from aqueous solutions

A novel adsorbent (AC/Fe 3 O 4 @SiO 2 –NH 2 ) was synthesized via a co-condensation process for the enhanced removal of Pb(II) from aqueous solutions. Characterization analyses including SEM, TEM, BET and XRD confirmed the successful integration of magnetic nanoparticles and amino groups with carbon matrix. Results demonstrated that AC/Fe 3 O 4 @SiO 2 –NH 2 (mass ratio of AC to Fe 3 O 4 was 1:0.25) with specific surface area (48.9   m 2 /g) showed higher adsorption capacity for Pb(II) as compared to other mass ratios. Kinetics study revealed that the adsorption reach equilibrium within 20   h and the maximum adsorption capacity of 104.2   mg/g was achieved with increasing the initial concentration from 20 to 250   mg/L using AC/Fe 3 O 4 @SiO 2 –NH 2 . Maximum removal efficiency was recorded at pH 5.2 and the removal capacities toward four divalent metal ions calculated by the Langmuir model were found to be in the order of Pb(II) > Cu(II) > Ni(II) > Cd(II). Furthermore, Δ G 0 decreased from –1.6 to −3.1   kJ/mol with increase in temperature from 293 to 333   K illustrating that the adsorption was spontaneous and an endothermic process. Complexation adsorption mechanism was found prominent in FTIR and XPS analyses between Pb(II) and AC/Fe 3 O 4 @SiO 2 –NH 2 due to the presence of amino groups.