Ag-doped carbon aerogels for removing halide ions in water treatment

The objective of this study was to analyze the efficiency of silver(Ag)-doped carbon aerogels for the removal of bromide (Br-) and iodide (I-) from drinking waters. Textural characterization of Ag-doped aerogels showed that an increase in the Ag dose added during the preparation process produced: (i) a reduction in the surface area (S-BET) and (ii) an increase in mesopore (V-2) and macropore (V-3) volumes. Chemical characterization of the materials revealed an acidic surface (pH of point of zero charge, pH(PZC) = 4.5, O-surface = 20%). The oxidation state of Ag was +1 and the surface concentration of this element ranged from 4% to 10%. The adsorption capacity (X-m) and affinity of adsorbent (BXm) increased with a reduction in the radius of the halogenide. Furthermore, an increase in the adsorption capacity was observed with higher Ag concentrations on the aerogel surface. The high adsorption capacity of the aerogel may be due to the presence of Ag(I) on its surface, with the formation of the corresponding Ag halides. Our observations indicate that the halogenides adsorption on commercial activated carbon (Sorbo-Norit) is much lower than that of the Ag-doped carbon aerogels. The presence of chloride and natural organic matter (NOM) in the medium reduced the adsorption capacity of Br- and I- on Ag carbon aerogels. (C) 2006 Elsevier Ltd. All rights reserved.