No Subject

[ttweed@wildrockies.org (Tony Tweedale)]

for anyone fighting the ClO2 battle:

On Fri, 13 Dec 1996, Tony Tweedale wrote:

> the new _responZe_ issue from sodra-cell gives the explanation of
> why ClO2 use leads to Cl2, and therefore greater dioxins & total aox (total
> adsorbable halogens).  this is *very relevant to stone/msla* not just
> because current ClO2 use is carried out in *acidic* environment (according
> to the bleach sequence description in epa/8's chemical safety audit for the
> mill), but because they are favoring a switch to a ClO2 only bleach
> sequence, and it's likely their favorite proposed sequence (oxy delig w/ a
> ClO2 polishing stage at end) will also be acidic.

> formation of Cl2 gas from ClO2:
>
> 1.  ClO2  +  lignin  -->  HClO  +  baseline amount of dioxins & aox
>
> HClO (hypochlorous acid) is in a pH dependent equilibrium with chlorine gas:
>
> 2.  HClO  +  H+  +  Cl-  <--->  Cl2  +  H2O
>
> in other words, an acidic environment [by definition, an abundance of H
> protons; that's what the H in pH stands for (pH is just the negative log of
> the H+ concentration; it's negative only so that it can be expressed in
> terms > than 1)] drives the Rx to the right, producing ever more Cl2 gas,
> which leads to more dioxins and more total aox!
>
> [if you look at Rx 2. you'll see it's likely the water is formed from the
> lone H+ and the H and the O from HClO, leaving behind a chloride anion
> (Cl-) to react with the other Cl- (possibly genearated in n repeat of this
> reaction, or direct from ClO2 in Rx 1.) to form the Cl2 gas.]
>
>( stone/msla may actually be adding hypochlorous acid in its antiquated
> bleaching seqquence, i can't recall right now).
>
> tony