Development of activated carbons for removal of heavy metal ions from wastewater

M. C. BASSO; E. G. CERRELLA; A. L. CUKIERMAN

SANTA FE, ARGENTINA

Congreso; Third Mercosur Congress on Process Systems Engineering. First Mercosur Congress on Chemical Engineering; 2001

Activated carbons (ACs) from Arundo canes are developed to obtain low cost adsorbents with highly specific effectiveness for heavy metal ions removal using this rapidly renewable bio-source as a precursor. H3PO4 acid activation at mild operating conditions under either an oxygen self-generated atmosphere or flowing air is applied. The ability of the resulting ACs to sequester Cd (II) ions from dilute aqueous solutions as a model, is comparatively examined, from adsorption experiments conducted at pre-established equilibrium conditions for different carbon dosage, in terms of the developed pore networks and surface oxygen functional groups of the samples. Large differences in metal adsorption on the carbons are found. ACs obtained under flowing air exhibit a considerably higher removal effectiveness (> 90%), attributable mainly to the larger content of oxygen functional groups developed on the carbons? surface as a consequence of the stronger oxidation atmosphere. Cd (II) ion adsorption on these ACs results even superior to that determined for a commercial carbon used for comparison. Adsorption kinetic data and equilibrium isotherms are determined for ACs derived under flowing air. A pseudosecond order rate expression and the Langmuir model isotherm describe properly the experimental results, respectively. The influence of the solution pH on metal adsorption is also investigated, optimum adsorption taking place above pH 4. Furthermore, desorption experiments reveal a recovery of Cd (II) ions higher than 85 %, and that the spent carbon can be regenerated and reused, its adsorption capability remaining similar to that determined prior to metal uptake