Selective Salt Recovery from Reverse Osmosis Brine - University of ...

Ions are eluted from an exhausted column through one of two processes.
Regeneration is done by flowing a concentrated acid, base, or salt solution through the
column to drive all ions into the solution phase and out of the column. This process is
used when the ions in the column are not intended for recovery. Elution is the process of
removing ions of interest from the column [3]. A variety of solutions can be used to
achieve this end, but they all are based on the process of exchanging ions in the solution
phase for one or more ions in the resin phase. This can either be done with a
concentrated solution or with a solution containing ions that are more highly selective
than those on the resin. Figure 4 shows the loading and regeneration of ion exchange
column. Note the ion banding effect and the displacement of the lower selectivity ions, A
and B, by ion C.
Figure 4: Loading and Regeneration of an Ion Exchange Column
1.214 Modeling of Column Processes
The modeling of ion exchange processes in a column is a complex problem. In
1962, Helfferich [6] thought a rigorous solution to be hardly feasible. Over the
intervening years, however, many column models have emerged. Column models can be
divided into two main categories: equilibrium models and rate based models.
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