Role of the pericarp of Carya illinoinensis as biosorbent and as precursor of activated carbon for the removal of lead and acid blue 25 in aqueous solutions

The pecan nuts are widely cultivated in states of north of Mexico and the residues generated during nut processing are abundant and not reused. In the present study, the pericarp of pecan (PP) was physicochemically characterized and their use as low cost biosorbent of lead and acid blue 25 was studied in batch systems at different experimental conditions. Also, the PP was used as precursor of activated carbon and a natural modifier agent extracted from egg shells was used in the synthesis of the carbons. Results suggest that the pericarp of pecan (PP) has an acidic character due to the presence of phenolic and carboxylic groups, which play an important role in the adsorption of lead, obtaining a maximum adsorption capacity of 6 mg g−1 at pH 5. But this adsorption performance was higher in the activated carbon (79 mg g−1). This behavior was similar for the adsorption of AB25, indicating that carbons are more effectives in the removal of lead and AB25 than PP. The equilibrium data were fitted to Langmuir, Redlich–Peterson and Freundlich isotherm models and the Redlich–Peterson model gave a better fit for modeling our adsorption isotherms.