Adsorbent-adsorbate interactions in the adsorption of organic and inorganic species on ozonized activated carbons: a short review

摘要

This objective of this work was to summarize the main results obtained in previous papers related to the adsorbent-adsorbate interactions involved in the adsorption of naphthalenesulphonic acids and heavy metals (Cd(II) or Hg(II)) by modified activated carbons. The adsorption of organic compounds (1-naphthalenesulphonic acid, 1,5-naphthalenedisulphonic acid and 1,3,6-naphthalenetri-sulphonic acid) and inorganic species (Cd(II) and Hg(II)) was studied on a series of ozonized activated carbon in aqueous phase. Commercial activated carbon (Filtrasorb 400) was treated with different ozone doses to study the effect of ozone treatment on its surface properties and investigate the behavior of the treated carbon samples in the above adsorption processes. After ozonation, carbonyl- and carboxyl-type groups were generated on the carbon surface. The action of ozone also affected the textural characteristics of the carbon; thus, the surface area diminished due both to the ozone attack and to the increase in oxygenated groups, which prevented the diffusion of nitrogen by obstructing micropore entrances. The capacity of activated carbon to adsorb naphthalenesulphonic acids sharply decreased with a greater number of sulphonic groups in the aromatic rings of these acids. As the concentration of oxygenated electron-withdrawing groups on the carbon surface increased, a significant reduction in adsorption capacity was observed. In all cases, the adsorption uptake decreased with higher solution pH. The adsorption of metallic ions, Cd(II) and Hg(II), by this series of ozonized activated carbons was also studied. In the case of Cd(II), the adsorption capacity and affinity of the adsorbents increased with a higher concentration ofacid oxygenated groups on the activated carbon surface. In the case of Hg(II), the adsorption diminished with an increase in the degree of oxidation of the activated carbon. The adsorption of 1,3,6-naphthalenetrisulphonic acid on the ozonized carbons was also studied in the presence of Cd(II) and Hg(II). The presence of Cd(II)) in the medium enhanced the sulphonic acid uptake, mainly for the most ozonized activated carbon sample, whereas the presence of Hg(II) had no significant effect on the adsorption.