Preparation of activated carbons from pecan nutshell and their application in the antagonistic adsorption of heavy metal ions

Activated carbons have been synthetized using the pecan nutshell (Carya illinoinensis) biomass for the adsorption of heavy metal ions. Adsorbents with different surface and ion exchange properties were obtained using physical and chemical activation routes with different reagents. These activated carbons have been assessed and compared in the removal of heavy metal ions Zn2+, Cd2+, Ni2+ and Cu2+ given a special emphasis on the analysis of competitive adsorption of these pollutants in binary systems. Adsorption behavior of tested adsorbents was correlated with some of their physicochemical properties and a removal mechanism has been proposed. Results showed that a synthesis route combining physical and chemical activation improved substantially the adsorption properties of these adsorbents. The chemical activation may improve the metal adsorption using these adsorbents up to 1214 % where adsorption capacities ranged from 0.011 to 0.368 mmol/g. However, the tailoring of activated carbons for the effective multi-component adsorption of heavy metals is still a challenge. This study highlights the impact and relevance of surface chemistry and ion exchange capacity of pecan nutshell - based adsorbents in the antagonistic adsorption of heavy metal ions.