Characterization of adsorbent materials prepared from avocado kernel seeds: Natural, activated and carbonized forms

The development, characterization and application of adsorbents prepared from avocado kernel seeds are described. The preparation comprises physical activation at temperatures up to 1000 °C and chemical activation with and without H3PO4, with and without carbonization. The resultant adsorbents have high oxygen content and the main inorganic components are silicon and potassium. After carbonization the surface retains acidic groups, mainly phenolic moieties. Characterization by adsorption of methylene blue revealed that the initial sorbent exhibited low surface area. After carbonization and activation the specific surface increased up to 1500 m2 g−1. The adsorption capacity was evaluated against basic blue 41. The results indicated a mayor adsorption capacity of the non-carbonized adsorbent in comparison with carbonized samples, due to the greater amount of surface acidic groups. The adsorption of basic violet 16 and basic blue 9 was controlled by the interaction with the acidic groups. For the dyes acid blue 74 and acid green 25, the magnitude of the specific surface area played a mayor role.