Greg,
The other down side to the peroxide approach, aside from the consumption
volume difference and stability of the peroxide itself, is that if you
overdose the system with peroxide, large amounts of chlorine gas will be
evolved...a dangerous proposition.
The balanced reaction is:
H2O2 + 2HCL + Cu --> CuCl2 + 2H2O
Excess peroxide will react with free HCl acid to create water and free
chlorine gas: (1:2 mole ratio)
(H2O2 + 2HCl --> 2H2O +Cl2)
So an excess peroxide reaction is:
2H2O2 + 4HCl + Cu --> CuCl2 + 4H2O + Cl2
Sorry about the font layout...I can't do subscripts in Eudora.
At 02:05 PM 12/5/01 -0600, you wrote:
Hey Greg, long time no talk to. The
most common oversight in comparing
peroxide and chlorate is understanding consumption and by-products
generated from the reaction. The reaction using peroxide generates 1
mole
of water for 1 mole of cupric chloride regenerated, the reaction
using
sodium chlorate generates 1 mole of water for 2 moles of cupric
chloride,
half as much water. Also, 1 mole of peroxide consumes 1 mole of
copper
whereas 1 mole of sodium chlorate consumes 3 moles of copper. The
volume
consumption of 50%by weight Hydrogen Peroxide is 3 times that of CuOx,
e.g.
if a process consumes 100 gallons of peroxide per day, when switching
to
chlorate they will only use app. 33 gallons of chlorate in the same
conditions. Given the other dilution and stabilization issues with
peroxide
it is common for the consumption difference to be closer to 4 times that
of
sodium chlorate.
Salt is a by-product generated in the chlorate reaction, which my of us
add
over the side to increase etch rate.
Alot of water is generated in the peroxide reaction, which somtimes
makes
it difficult to maintain Cu loading. Hope this helps,
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