From: REMOVE_THISdwilkins@means.net (Don Wilkins)
Newsgroups: sci.chem
Subject: Re: D2O from H2O
Date: Fri, 11 Dec 1998 04:04:08 GMT

On Thu, 10 Dec 1998 22:42:36 GMT, jvinson@cyberSPAMLESShighway.net
(John Vinson) wrote:

>On 10 Dec 1998 21:11:35 GMT, The Runos <asmjruno@worldnet.att.net>
>wrote:
>
>>Hello-
>>    If I wanted to get D2O from H2O how would I go about doing it? You
>>couldn't just keep running "normal" water through "seperatory flasks"
>>could you? How would you seperate out the H2O after letting some of it
>>evaporate (since it's lighter then D2O it should float right?)?

Not quite that easy.

>You're not too far from right, but just gravity isn't enough to get a
>useful separation.  D2O boils at a slightly higher temperature than
>H2O; sequential fractional distillation will carry off the lighter H2O
>and enrich D2O in the pot.

Yes but commercially this is only used in the final stage.

>Canada has been a major commercial source of D2O over the years; they
>came up with the CANDU atomic reactor which uses heavy water, so they
>built several plants to separate D2O from H2O.  I don't know if they
>still use distillation or if some sort of membrane diffusion process
>is now used.

The first several stages use the H2S-H2O-HDS-HDO equilibrium. They
have towers which contain tons of H2S (under high pressure) flowing up
and H2O flowing down (a simplification) with a temperature
differential in the tower. The deuterium is concentrated in each stage
and finally finished by distillation.

Now that is a simplification of a complex process in a huuuuuge tower
complex.

To the best of my knowledge the process was first reduced to a
commercial process by duPont at Savannah River. I spent several months
sorting out problems at the Port Hawkesbury Plant (Nova Scotia) when
it was managed by a US company for the Canadian government. Once the
damned thing started working as designed the whole deal was sold to
the Canadian government and I was off the project.

Incidentally I returned on a vacation trip many years later and the
plant was still operational.

I believe Canada built a plant on the coast (Nova Scotia) to make D2O
from sea water. There are some advantages but that project ended up in
one huge pile of rust. Sea water is vicious stuff at high temperature
with H2S in steel containers.

Canada did build at least two other successful plants on Lake Huron
later and may have built more.