Cucurbituril for water treatment. Part I: Solubility of cucurbituril and sorption of reactive dyes.

Cucurbituril was investigated regarding its potential as a sorbent for the removal of reactive dyes from model solutions and authentic wastewaters. The solubility of cucurbituril is low in pure water but increases in the presence of salts. When dyes sorbing onto cucurbituril are present, solubility is drastically decreased compared to dye-free media. Sorption efficiency depends on salt concentration and salt species. Moderate salt concentrations favor sorption, high concentrations lead to cucurbituril dissolution. Divalent ions have a stronger effect than monovalent ions and larger ions more than smaller ones. In tests with authentic wastewaters cucurbituril was partially (20-100%) dissolved and contaminant removal was inefficient. Because of its solubility, cucurbituril is not feasible as a sorbent in wastewater treatment unless it could be covalently fixed onto a suitable support material.