Amidoamine calix[4]resorcinarene-based oligomers and polymers as efficient sorbents of azo dyes from water.

The sorption behaviour of three kinds of macrocyclic sorbents – amidoamine tetradodecyloxyphenylencalix[4]resorcinarene1and tetramethyloxyphenylencalix[4]-resorcinarene2; composition of calix[4]resorcinarene1+2, and novelP.1andP.2polymers with amidoamine calix[4]resorcinarene units towards three water-soluble azo dyes – methyl orange (MO), acid orange (AO5) and Congo red (CR) was studied. All sorbents form supramolecular complexes with the aforesaid dyes. The best sorbent forMOwas shown to be polymerP.1, for theAO5– composition1+2and for theCR– macrocycle 2, with high sorption capacities (373, 497 and 625 mg/g, respectively). The main factor in the binding of dyes by all studied sorbents proved to be surface electrostatic interactions. In addition to the Coulomb interactions, the most important factor for the polymers appeared to be the ‘net’ structure of the polymer with a high concentration of binding sites, providing electrostatic, hydrogen, dipole–dipole and hydrophobic interaction. Hydrophobic substituents in the sorbents exert a significant influence on the dye sorption. The increase of the sorbents' hydrophobicity leads to a lower sorption capacity forMOandCRand a higher sorption capacity forAO5. It was shown that sorption efficiency of the sorbent depends on the ‘dye–sorbent’ structure conformity. [ABSTRACT FROM AUTHOR]