Sorption rate of uranyl ions by Hyphan cellulose exchangers and by hydrated titanium dioxide

Summary Sorption of uranyl ions by the cellulose exchanger Hyphan proceeds rather fast. Two steps are observed with half-times of the order of 10 s and 2 min. The majority of the uranyl ions is bound in 1 min. Sorption of uranyl ions by titanium dioxide is a very slow process. For particle sizes between 0,1 and 0.5 mm the half-time is about 3 h and equilibrium is attained in about 1 day. The effect of stirring suspensions of inorganic sorbents like titanium dioxide in solution is investigated in detail. Sorption of uranyl ions by titanium dioxide and change in pH in solution are measured simultaneously as a function of time.Alexander von Humboldt fellow     

Reinigen mit Licht und Regen

After the discovery of the lotus‐effect in the 1970s the attention concerning the field of self‐cleaning surfaces increased rapidly. Besides hydrophobic surfaces which are designed following the example of the lotus flower, superhydrophilic and photocatalytic active coatings play an important role. These coatings are using sunlight to oxidize pollutants and remove residues by rinsing with water. Coatings based on the lotus‐effect suffer from their weak mechanical durability, but are able to work without light. On the other hand, photocatalytic layers are mechanically stable, but they need to be illuminated to become self‐cleaning.