The Naked Scientists

The Naked Scientists Forum

Author Topic: what electrodes and how do you make chlorine from electrolysis  (Read 5598 times)

Offline RodneyBeadon

  • First timers
  • *
  • Posts: 3
    • View Profile
I am new to this form so trust I am posting my question in the correct forum. I am an electrician by profession and live in Zimbabwe a country plagued with many problems, one being suitable water. I have to buy 5000 ltrs of water at US$60.00 a week which is VERY expensive.

I have built a grey water reclaiming pit which has been a on going project for several years. I think I have this almost right.

I would like to introduce chlorine produced via electrolysis run from Solar power. I have searched the internet and successfully managed to totally confuse myself.

Would someone be kind enough to point me in the right direction. I need to know the solution and the electrodes. The water is not for consumption.

Many thanks

Rodney


 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
Do you really need to treat the water for non-potable use?  Perhaps use a sand filter?

A good fine mesh filter, and perhaps a carbon filter, and you may be able to get most of the contaminants out of your water.  Perhaps boil your drinking water.

Many people use chlorine bleach (sodium hypochlorite) for water treatment.  Look up on the internet for instructions.  I'm seeing recommendations of 5 ounces liquid bleach (3-8%) per 1000 gallons of water treated.  Much less if you get it in a powdered concentrate.  Oh, it looks like the powdered form is often calcium hypochlorite, but it should still work.  Look at swimming pool supplies.

If you try electrolysis of salt water, you should get a mix of chlorine gas, hydrogen gas, and oxygen gas.  If you separate your cathode and anode, you may get some gas separation.

If you melt pure salt, then try electrolysis, you should produce pure sodium metal, as well as pure chlorine gas.  Both are potentially dangerous.

I'm not sure about electrodes.  For simple water electrolysis, perhaps a stainless steel mesh depending on your design to separate the gases. 

Earlier someone was talking about carbon electrodes, perhaps you could scavenge the electrodes out of large alkaline lantern batteries.
« Last Edit: 19/04/2014 09:35:17 by CliffordK »
 

Offline RodneyBeadon

  • First timers
  • *
  • Posts: 3
    • View Profile
Thank you very much for the comprehensive reply. Part of the experiment is the need to know I can produce the chlorine. The more practical aspect is that Grey water develops a very bad smell if stagnant. I want to use it by pumping the grey water back into the cisterns of the toilets to use again. Chlorine should kill the bacteria and help with the smell.

I know I can put pool chlorine in or bleach the big thing here is being able to produce it.  Is chlorine only a gas or can it be converted into a granule or liquid.

Many thanks

Rodney
 

Offline chiralSPO

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 1875
  • Thanked: 143 times
    • View Profile
Electrolysis of a solution of chloride at high pH (>10) will produce hypochlorite (bleach) while electrolysis at low pH (<4) will produce chlorine gas. I don't know which product you prefer. I believe that titanium electrodes are best for this application because of corrosion resistance. Steel or nickel electrodes will give only very small quantities of active chlorine species, as they react to form iron and nickel chloride salts.
 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
I would encourage for you to look for new waste water or greywater treatment that does not involve the production and addition of chemicals.  Even your septic system will be happier if you're not dumping tons of chlorine and bleach into it.

if you generate enough greywater on a daily basis, then there would be no need for longterm storage of the water, which would reduce the impact of bacteria growth in stagnant water. 

I'm not quite sure what to do with your toilet tank.  I think commercial toilet systems (at least in the USA) are sealed which might be a benefit. 
 

Offline RodneyBeadon

  • First timers
  • *
  • Posts: 3
    • View Profile
Thank you for all your assistance. After talking to several people and with reading a bit more I realise I am looking for an ioniser rather than a chlorinator. I got a very simple explanation using 2 copper electrodes and placing them into the water alternating between the anode and cathode. I will try this out and report back.

Thanks for the help

Best wishes

Rodney
 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
What does it mean to ionize water?

I can't say that bacteria would like to be exposed to AC power.  But, it isn't really ionizing the water, at least not in a permanent sense.  You may end up making a mix of hydrogen and oxygen.
 

Offline chiralSPO

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 1875
  • Thanked: 143 times
    • View Profile
If the plates are far enough from each other, and DC voltage is applied, one can generate a pretty strong pH gradient between the two electrodes (cathode consumes H+ ions while anode produces them)
 

Offline gadaadhoon

  • First timers
  • *
  • Posts: 1
    • View Profile
I have done this with graphite electrodes, and they seem to hold up although I don't know how they would do over years.  If you don't use graphite you need a non-reactive metal such as platinum, which as you know is expensive.
 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
How much space do you have?  Rain? 

You might also consider some kind of a biofilter.  Maybe a small open pond with lots of living stuff in it.  Are mosquitoes a problem?  Perhaps you can get enough living stuff in the pond to help reduce the mosquitoes. 

Most of the greywater should actually be pretty fertile.
 

The Naked Scientists Forum


 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums