Removal of cadmium using acid-treated activated carbon in the presence of nonionic and/or anionic surfactants

The adsorption of cadmium ions on granular activated carbon treated with nitric acid (NGAC), and untreated regular granulated activated carbon (RGAC) is reported in the absence and presence of mixtures of anionic (sodium dodecyl sulfate, SDS) and nonionic (Triton X-100, TX100) surfactants. In the absence of surfactants, NGAC adsorbed 8.7 times more Cd (0.165 mmol/g) than did RGAC (0.019 mmol/g). In RGAC suspensions, the amount of Cd sorbed increased significantly with increasing dose of SDS, to a maximum of 0.112 mmol/g. This increase was due to increased binding of Cd with sorbed SDS. However, in NGAC suspension, the amount of Cd sorbed was not increased further by the addition of SDS. It suggested that addition of SDS blocked the availability of surface functional groups in the microporous structure of NGAC. (C) 2009 Elsevier B.V. All rights reserved.