| Popis: |
Layered hexaniobate K 4 Nb 6 O 17 was intercalated with two cationic surfactants, dodecylammonium (C 12 N) and dioctadecyldimethylammonium (2C 18 2MeN) ions, and the obtained intercalation compounds were utilized as adsorbents for phenols dissolved in water. Competitive adsorption of phenol, 2-chlorophenol (2-CP) and 2,4-dichlorophenol (2,4-DCP), in binary- and ternary-solute systems was investigated. Both the adsorbents showed high adsorption selectivity for 2,4-DCP. The uptake of each solute was reduced by the presence of the other species, and the reduction in the multi-solute systems depended on the hydrophobicity of the adsorbates coexisted in the solution. For the adsorbent modified with 2C 18 2MeN, however, uptakes of the solutes were enhanced by the presence of each other at low equilibrium concentrations in comparison with the single-solute solutions, because of cooperative adsorption. Adsorption isotherms of phenols in single-solute systems plotted against the equilibrium concentrations normalized with the solubility in water suggested that solute portioning was the main adsorption mechanism. Freundlich adsorption model succeeded in fitting the adsorption isotherms of phenols on the niobate modified with C 12 N cations in single-solute systems, and prediction of the competitive adsorption behavior of phenols with the Freundlich-based Sheindorf–Rebuhn–Sheintuch (SRS) model gave acceptable results. |
Full Text from ScienceDirect