Removal of Cu(II), Pb(II), and Ni(II) by adsorption onto activated carbon cloths

The adsorption of three metal ions, Cu(II), Ni(II), and Pb(II), is performed by activated carbon cloths (ACC). Two adsorbents, CS 1501 (with more than 96% of micropore volume) and RS 1301 (with 32% of mesopore volume), are studied. Batch experiments are carried out to assess kinetic and equilibrium parameters. They allow kinetic data, transfer coefficients, and maximum adsorption capacities to be computed. These parameters show the fast external film transfer of metal ions on fibers, because of their low diameter (10 mum). Intraparticular diffusion coefficients are lower than those obtained with a granular activated carbon, but maximum adsorption capacities agree with literature values for GAC. They show the dependency of adsorption on metal ion size and ACC porosity, the largest cation Pb(II) being more adsorbed by the mesoporous cloth. The pH effect is studied, and pH adsorption edges are determined. They are short, only 2 pH units, and located below the precipitation edges. A decrease of equilibrium pH with an increase of metal ion concentration, coupled with a regeneration study of saturated ACC by HCl, lead us to propose an adsorption mechanism by ion-exchange between metal cations and H+ ions at the ACC surface. Carboxylic groups seem especially involved in this mechanism, and precipitation between metal ions could happen.