Cucurbituril for water treatment. Part II: Ozonation and oxidative regeneration of cucurbituril.

In Part I it was shown, that cucurbituril has high sorption capacities for the removal of reactive dyes from textile wastewater; despite the partial dissolution of this sorbent. Ozonation has been suggested as a regeneration step for loaded cucurbituril. Ozonation of loaded and pure cucurbituril was therefore evaluated. Dissolved cucurbituril reacts with ozone forming oxidation products like nitrite, nitrate, formate, acetate and oxalate. Oxidation is enhanced at alkaline pH. Dye-loaded cucurbituril suspended in water can be decolorized by ozone, but the ozone consumption is tip to seven times higher than for ozonation of the dissolved dyes without cucurbituril. Loaded columns can be regenerated by ozone gas, but dissolution of cucurbituril results in a higher DOC content than the initial one to be removed. Therefore oxidative regeneration does not seem to be a feasible approach in this case.