Page 134 - Industrial Wastewater Treatment, Recycling and Reuse

108 Industrial Wastewater Treatment, Recycling, and Reuse

Feed
Regenerant
Breakthrough curve
Feed [HA] i

[HA] o
[HA] b o

t B Time

Product

Used regenerant
Figure 2.10 Ion exchange operation: Column and breakthrough curve analysis.

dictates the column utilization, and the sharp/rectangular form of the curve
is most desirable. However, in reality, this is rarely possible and typically dis-
persive fronts are common. The larger the dispersive front, the more unu-
tilized the resin bed is in the column, implying significant underutilization of
the resin capacity, even if the resin has a theoretical high capacity of sorption.
The nature of the breakthrough curve can be modified using different
changes in the process parameters; breakthrough curves also will depend
on the material itself. Therefore, in real applications, breakthrough capacity
or operating capacity are more important parameters than theoretical equi-
librium capacity (which is rarely achieved). Further, it is to be understood
that 100% regeneration is practically never achieved due to excessive chem-
ical requirements. Many times, capacity up to 80% is regenerated as a com-
promise between regenerant usage and capacity.

2.3.5 Ion Exchange: Advances and Applications
in Wastewater Treatment
Recently, newer synthetic polymers without functional groups have been
developed and used commercially. These have a very large surface area
and defined pore structure for better performance and regenerability. For
selective removal of heavy metals, newly developed chelating resins that
help in removal of these toxic metals from wastewaters are widely used