Performance of Pb(II) Removal By an Activated Carbon Supported Nanoscale Zero-Valent Iron Composite at Ultralow Iron Content

Activated carbon (AC) is commonly used as a kind of versatile material for drinking water purification. However, its application is limited by low efficiency and capacity of heavy metals. In addition, it is also concerned that secondary release of adsorbed heavy metals. Therefore, modification of AC is indispensable. In present work, AC supported nanoscale zero-valent iron composite (NZVI/AC) at ultralow iron content was synthesized and used to remove Pb(II) from aqueous solution. The technical characterization demonstrated that the loaded amorphous NZVI nanoparticles had a chain-like shape in or close to pores and were found as individual nanospheres with size of approximately 10 nm on the outer surface. The adsorption capacity of Pb(II) by NZVI/AC was 59.35 mg g^-1 at 298.15K with a pH of 6.00, which was 8.2 times than that of AC support only. The NZVI/AC with the iron content of only 1.57% showed a highly efficient Pb(II) removal performance with 95% of Pb(II) eliminated within 5 min. The monitoring of iron release indicated no iron was released at a pH above 4.02. The Pb(II) removal by NZVI/AC was well-represented by a pseudo-second-order kinetics model and showed the behavior of an exothermic process. Essentially, Pb(II) was converted to insoluble forms such as Pb⁰, PbCO₃, Pb(OH)₂, PbO or white lead ([2PbCO₃·Pb(OH)₂]). To sum up, these results indicate the first fabrication of NZVI/AC composites with such low iron loading that still present an outstanding Pb(II) removal performance in drinking water purification absence of any potential risk.