Selenium containing clays minerals as additive for the discoloration of glass

While selenium is applied as decolorizing agent for flint container glass or tableware glass, the retention of selenium in glass however is very low. Generally more than 75% of the total selenium input sublimes from the glass melt and leaves the clay minerals due to the high volatility of SeO2. Therefore, alternative selenium containing raw materials, which might offer a better retention of added selenium and therefore substantially reduce the emission of selenium, are needed. One possible option is to intercalate suitable ionic compounds containing selenium into clay minerals and using the intercalated compounds as a carrier for the selenium into the glass melt. The intercalation of saponite with a specially synthesized selenonium compound (triphenylselenonium) is described and their performance in the glass melt is partially characterized. Compared to glass batches with ZnSeO3 the release of selenium could be reduced by about 75% if the selenonium intercalates are used.