Discussion by R. Cabridence, France
The development of a cheap and efficient procedure for the removing of hexavalent chromium
from wastes is interesting because hexavalent chromium is toxic towards the freshwater fauna and
flora.
What may be the effects on the process of traces of organic matter or of inorganic compounds
(except fluroides)? Is it possible to compare the cost of this new method with the cost of the currently
used techniques?
V. Bernard, France
Have the authors examined the fate of the sludges containing Cr^I by for instance, tests of the
rate of description by natural waters?
Reply
If the organic matter is colloidal or in a suspended state, the presence of hydrous ferric oxide will
help to flocculate and to remove the organic matter from the waste water. Inorganic compounds will
effect the adsorption of chromates, depending on the charge of their ions: anions can be competitive.
It is almost impossible to compare costs in a general way. Our technique will be advantageous when
the chromate wastes are very alkaline and one has also a waste water flow containing ferro and ferric
ions.
Tests where a hydrous ferric oxide sludge containing Cr^I was diluted with distilled water, have
shown a desorption of the C r ^ , so that the disposal of the sludge must be carried out with some
precautions.
625
The development of a cheap and efficient procedure for the removing of hexavalent chromium
from wastes is interesting because hexavalent chromium is toxic towards the freshwater fauna and
flora.
What may be the effects on the process of traces of organic matter or of inorganic compounds
(except fluroides)? Is it possible to compare the cost of this new method with the cost of the currently
used techniques?
V. Bernard, France
Have the authors examined the fate of the sludges containing Cr^I by for instance, tests of the
rate of description by natural waters?
Reply
If the organic matter is colloidal or in a suspended state, the presence of hydrous ferric oxide will
help to flocculate and to remove the organic matter from the waste water. Inorganic compounds will
effect the adsorption of chromates, depending on the charge of their ions: anions can be competitive.
It is almost impossible to compare costs in a general way. Our technique will be advantageous when
the chromate wastes are very alkaline and one has also a waste water flow containing ferro and ferric
ions.
Tests where a hydrous ferric oxide sludge containing Cr^I was diluted with distilled water, have
shown a desorption of the C r ^ , so that the disposal of the sludge must be carried out with some
precautions.
625