Applications of Bipolar Membrane Electrodialysis Eurodia Industrie
and its main shareholder Tokuyama Corporation have designed, built,
and started up several bipolar membrane electrodialysis plants for
the production of various specialty chemicals (many are confidential
ar our customers request). In addition, several key employees of
Ameridia are experienced with the design and operation of bipolar
membrane electrodialysis systems thanks to their involvement with
Aqualytics, one of the first companies to commercialize the technology
(now closed down). - Production of specialty inorganic and organic
acids: several operating plants
- pH adjustment in chemical processing
- Recovery of NaOH/H2SO4 from waste sodium sulfate
- Production
of HCl & NaOH for IX resins
- Conversion of salts of KOH, NaOH, NH4OH, etc.
Conventional Production
If the acid is produced by fermentation, selected microorganisms
are used to convert the carbohydrate feedstock. Most of these microorganisms
cannot work efficiently in acidic conditions and a base is added
to the fermenter to maintain the desired high pH. In these cases,
the acid is produced as the salt and must be converted to the acid
outside of the fermenter. Conventionally, the conversion of the
organic salt into the acid is handled by either acidification/ crystallization
or ion exchange resins. In either case, a strong mineral acid, such
as sulfuric acid, must be used, with safety and corrosion issues
and at a cost. Even more, the acidification results in a by-product
salt such as CaSO4 or Na2SO4 that must be either precipitated or
crystallized, filtered and for which an outlet has to be found.
Additionally, organic acid yields can be low as there can be significant
losses of product in the precipitation step or in the ion exchange
columns. After the by-product separation, the organic acid has to
be processed through extensive purification steps to remove residual
impurities from the fermentation. The acid products can also be
contaminated with the anion from the strong acid.
These conventional methods generate wastes or unwanted byproducts.
By bipolar membrane electrodialysis, the acidification of organic
acids can be clean, without a salt waste, and in some cases, can
simultaneously concentrate and purify the organic acid.
Advantages of Bipolar Membrane Electrodialysis
Bipolar membrane electrodialysis can be used to directly acidify
the organic salt without the addition of chloride or sulfate anions,
thus eliminating the formation of the unwanted salt byproduct and
all the handling and disposal problems. Instead, the H+ ions generated
from the water splitting occurring in the bipolar membranes cleanly
acidifies the organic salt solution. At the same time, the salt
cations, either potassium, sodium or ammonium, are converted in
the base that is valuable to the fermentation process. Additionally,
in some cases, product concentration and purification may take place,
decreasing the demand for the downstream purification.
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