ACTIVATION AND DETOXIFICATION OF UICC CROCIDOLITE - THE EFFECT OF CONVERSION OF OXIDATION-STATE OF IRON ON THE TOXICITY OF THE FIBERS

Detoxification of crocidolite, an asbestiform riebeckite with a coatin g of ferric salt, converted some of the ferrous ions into ferric ions and therefore decreased the activity of the fibres to catalyse the red uction of oxygen and hydrogen peroxide. The H-2-activation of crocidol ite fibres on the other hand, changed some of the ferric ions into fer rous ions and therefore increased the capacity of the fibres to cataly se these two reactions. Mossbauer spectroscopy (MS) combined with wet chemical analysis, X-ray diffraction, X-ray fluorescence, and neutron activation analysis enabled us to determine the site occupancies of ir on and magnesium in UICC (Union Internationale Contre le Cancer) croci dolite and the ratio of the recoil-free fractions f(Fe 2+)/f(Fe 3 +) = 0.86 +/- 0.07. These results and further MS studies with detoxified an d activated fibres explained the effect of the two processes on the ac tivity of iron in the fibres.