Sciencemadness Discussion Board

Conditions for hypochlorite formation

Zandins - 1-7-2016 at 21:59

Greetings Sciencemadness community,
I am planning to do a production run for NaClO by unseparated electrolysis of NaCl solution.
NaCl +H2O -> NaClO + H2
My prelimintary tests show carbon anodes erode excessively, so I have ordered a 1×2 inch platinized titanium anode. I am trying to find the right set of conditions to maximize hypochlorite production while minimizing oxygen evolution and chlorate production.
To summarize my current findings:
1)The solution must be kept concentrated to prevent O2 production at the anode. Since saturated solution is 26% NaCl by mass, I will be trying to keep the concentration above 20%;
2)There are different sources for temperature which favors chlorate production.I've come across figures ranging from 40 to 70°C.
3) The pH must be kept above 7; therefore a base must be added. Would NaCO3 be sufficient or NaOH is necessary?
4)By adjusting the separation of electrodes, the cell can draw up to 10A at 12V. This equals 120W of Joule heating. Therefore, an Ice-bath must be used.
Does anyone on the community have experiance with this? In that case, is there any information on the precise condictions of the setup?

NEMO-Chemistry - 2-7-2016 at 01:51

Would a solution of sodium hydroxide and a chlorine generator be better? bubble the chlorine into the sodium hydroxide and use the change in weight to calc the strength?

Zandins - 2-7-2016 at 02:26

A chlorine generator would require NaClO,which is the same chemical I am trying to produce, accoriding to the reaction:
NaClO+HCl->Cl2+NaOH
Besides, the electrochemical approach has a series of advantages, such as requiring only mundane substances(salt) and being able to work unattended. I have previously made NaClO in the process I described, I am looking for ways to improve the poor efficiency.

NEMO-Chemistry - 2-7-2016 at 07:29

Quote: Originally posted by Zandins  
A chlorine generator would require NaClO,which is the same chemical I am trying to produce, accoriding to the reaction:
NaClO+HCl->Cl2+NaOH
Besides, the electrochemical approach has a series of advantages, such as requiring only mundane substances(salt) and being able to work unattended. I have previously made NaClO in the process I described, I am looking for ways to improve the poor efficiency.


My bad sorry,

Firmware21 - 10-7-2016 at 03:09

You can still produce Cl2 with TCCA and conc. HCl. I intended to use Nemo's method this summer to produce a little sodium Hypochlorite.
There must be threads on SM for this way of doing it, use the search engine.

If you don't have access to TCCA, then you don't have other options.

hyfalcon - 10-7-2016 at 03:25

Try a different way of searching the site. This topic has been covered quite a bit. Try this string in Google.
Code:
site:sciencemadness.org sodium hypochlorite


https://www.google.com/search?q=site%3Asciencemadness.org+so...



[Edited on 10-7-2016 by hyfalcon]

hissingnoise - 10-7-2016 at 03:42

Quote:
By adjusting the separation of electrodes, the cell can draw up to 10A at 12V. This equals 120W of Joule heating. Therefore, an Ice-bath must be used.

12V is too high and will quickly corrode graphite ─ no more than 5V should be used!

If you want chlorine, HCl oxidation by KMNO4 is a convenient method...

As to pH, alkaline drift in electrolysis is troublesome and is remedied by drip additions of HCl!

yobbo II - 10-7-2016 at 13:01


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hyfalcon - 11-7-2016 at 01:40

It looks like laserred has more MMO for sale. Come and get it boys!

http://www.ebay.com/itm/MMO-coated-expanded-titanium-mesh-an...

Zandins - 11-7-2016 at 03:35

Definitely looks like a bargain, will order one today!

On a slightly unrelated note - would a MMO mesh fail if it were sawed into a series of smaller electrodes ?(6 x 10 inch is probably too much for one cell)

hyfalcon - 11-7-2016 at 05:12

Nope. Their is people that take these and shear them into 1 inch strips and resell them for a markup.

As long as you don't run these in a low chloride condition they should last quit a while. By the way, give these a good muratic acid soak before putting them to use. I don't know exactly what process they have been in but there is usually a brown deposit on them that will come off in your cell if you don't presoak them in acid first.

[Edited on 11-7-2016 by hyfalcon]