flow was broken as ΓG/L was over 0.4. The lower limit of ΓG/S
may vary with the change of the nature of particles and types
of frother or collector. So, it may not be applicable in other sys-
tems used to remove other pollutants. However, the upper limit
of ΓG/L should be independent from the nature of pollutants. It
should be applicable in other ECF systems as long as the ECF
reactor is a closed system.