Simultaneous removal of cationic heavy metals and arsenic from drinking water by an activated carbon supported nanoscale zero-valent iron and nanosilver composite

Cationic heavy metals (Pb 2+ , Cu 2+ , Zn 2+ , Cd 2+ ) and arsenic contamination are generally found in water. Therefore, the development of a versatile method of removing cationic heavy metals and arsenic from water is indispensable. Herein, an activated carbon-supported nanoscale zero-valent iron and nanosilver composite (nAg/nZVI/AC) at ultralow content (1.539 ± 0.039 % of Fe and 0.162 ± 0.004 % of Ag) was synthesized, followed by characterization of its properties by several techniques, such as XRD , SEM–EDS, HRTEM , Raman spectroscopy , nitrogen adsorption-desorption isotherm experiments and XPS. Its reactivity was evaluated by removing cationic heavy metals and arsenic from water and then analyzing the interfacial behavior and mechanisms. The results showed that crystalline nanosilver (20–30 nm) and amorphous nZVI (10–20 nm) were uniformly immobilized on AC. The surfaces of nZVI and nAg in the fresh composite were mainly composed of γ-FeOOH and AgO, respectively. The nAg/nZVI/AC displayed synergetic adsorption behavior between AC and supported nAg/nZVI and simultaneously enhanced the efficiency of the removal of cationic heavy metals and arsenic. The composite was stable and durable. Most Cu 2+ , Pb 2+ , Cd 2+ , and Zn 2+ transformed into Cu 0 , CuO , Pb 0 , CdCO 3 , and ZnO by means of adsorption, precipitation, and reduction at the cathode (nAg), while Ag 2 O. AsO 4 3– and AsO 3 3– were reduced to As 0 and As 3+ at the anode (nZVI), where Fe 0 , Fe 2+ (i.e., FeO), and Fe 3+ (i.e., FeOOH, Fe 2 O 3 ) were also present. No obvious competition between multiple-component heavy metals was observed. nAg/nZVI/AC has much potential to be used in the purification of water contaminated with cationic heavy metals and arsenic.