Page 135 - Industrial Wastewater Treatment, Recycling and Reuse

Advanced Physico-chemical Methods of Treatment for Industrial Wastewaters 109

(Neumann and Fatula, 2009). In the plating industry, ion exchange processes
are widely employed for removal of chromium and for water recycling and
reuse. Ammonia removal from wastewaters using ion exchange has also been
explored and has been found effective (Jorgensen and Weatherley, 2003).
In recent years, new resins that are more selective for specific ions have
been developed. They have shorter diffusion paths and better exchange
rates. Ion exchange provides a good separation technology for dilute systems
requiring less frequent regeneration.
The need to recover or remove contaminants from dilute solutions will
increase in the future due to stringent regulations applying to waste streams
(Adler et al., 2000). Today, the requirement of clean water for the growing
population has already reached a demanding stage. Many problems associ-
ated with the application of ion exchange in wastewater treatment need
to be addressed. The most prominent among the issues include the cost
of ion exchange that linearly scales with column size and the cost and dif-
ficulties in the regeneration of materials. Highly selective ion exchange
materials pose serious difficulty in regeneration: The more favorable the
loading, the more difficult the unloading is the operating rule. The capacity,
selectivity, and specificity of existing ion exchange material issues are major
impeding factors to improved efficiencies in treating dilute solutions of
wastewaters, be they from the chemical or biochemical industry. A new
approach for devising more robust, high-capacity, high-selectivity
exchangers with ease of operation needs to be found. It is a recognized fact
that the solution to environmental problems will require very inexpensive
ion exchange materials, some that can even be used once and discarded
(Adler et al., 2000). This aspect is driving research in the area of ion
exchange materials derived from biomass, such as chemical modification
of bagasse. Developing a highly selective material at low cost is therefore
a serious challenge for the future.

2.3.6 Case Study: Adsorption/Ion Exchange for Acid Removal

Organic acids are major commercial chemicals, and their recovery/separa-
tion from reaction mixtures, fermentation broths, and wastewaters has been
a challenging problem for over four decades. Wastewater streams containing
low concentrations of acids are inevitably encountered in acid manufactur-
ing plants, industries where acids are used as raw material or as catalyst,
fermentation processes, the metal plating industry, and others (Table 2.3).
Wastewater usually contains a single acid or mixture of acids from 0.5%