The detail process of citric acid purification in chemical plant

The pharmaceutical company Roche provides a PDF document on their
website that describes the industrial production of citric acid.  It
has the following description of the purification process:

"SEPARATION
Filtration removes all physical impurities from the biological acid
that contains the citric acid.  Then, the citric acid is separated as
calcium citrate from the liquid by applying lime.  [..] The calcium
citrate is dissolved by a strong acid into citric acid.

PURIFICATION
The purification of crude citric acid is now continued by an exchange
of ions and decolourizing.  After this, the remaining water is
evaporated and the citric acid crystallized.  Different
crystallization temperatures result in different product forms. 
Additional drying of the crystals turns them into marketable
products."

You can view more details on this process by downloading
http://www.roche.com/vitamins/pdf/ca_prod_e.pdf to your computer.  You
need Acrobat Reader (http://www.adobe.com/products/acrobat/readstep2.html)
to view the document.

This should answer your question; if not, please request an answer
clarification.

Search terms used on Google:
"citric acid" manufacturing OR manufacture OR production OR synthesis
purification

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Request for Answer Clarification by ke_lkh-ga on 20 Sep 2002 05:10 PDT

Sorry, the answear i need is need the deatil of purification operation 
condition such as temperature, pH.........etc
can you help me search again?

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Clarification of Answer by blazius-ga on 20 Sep 2002 05:53 PDT

I am sorry, but I have not been able to find the requested information
on the web.  I have sent an email to Roche's public relations office,
they probably won't reply until after the weekend.

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Clarification of Answer by blazius-ga on 25 Sep 2002 16:29 PDT

I have not got any response from Roche so far, and I will soon be away
on vacation for some time.  If you do not think that the answer you
got was satisfactory (with regards to the question asked and the
listed price), you could request a refund and give another researcher
a try on the question.