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topic 303

How to make Sodium hypochlorite for cyanide destruction


(1996)

Hi,

How can I make sodium hypochlorite for waste water treatment. Thanks for your help

Lawrence [last name deleted for privacy by Editor]
Hong Kong


(1996)

Hi, Lawrence. There are a couple of 'cyanide treatment systems' that consist of simply putting a small electrolytic device into a drum of waste solution with salt. I believe they function by electrolytically converting salt water (NaCl plus H2O) to NaOCl plus H, something like this:

NaCl + H2O --> NaOCl + H2^, although there are probably additional side reactions.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


Conversion to On-Site Sodium Hypochlorite Generation

(1996)

I seem to recall seeing a unit called a "Brinecell" advertised in Metal Finishing Magazine a few years ago. As I recall, it was marketed to produce bleach for public water treatment, the pulp and paper industry, as well as a method for destroying cyanide, the latter being what sparked my interest. I seem to think that they touted that you could produce bleach for ten cents a gallon or something to that effect. I don't recall their address, only that I believe they were located in Utah, although that could be wrong. Also, Ludwig Hartinger's "Handbook of Effluent Treatment & Recycling for the Metal Finishing Industry" [link is to product info at Amazon] has a good overview of the process.

Hope this helps,

Brooke W [last name deleted for privacy by Editor]
(1996)

I cannot tell from your notes what you are looking for in the way of producing sodium hypochlorite for - what purpose? Oxidation or disinfection?

There are a number of methods available. If you advise your end result required, I will attempt to point you in the right direction. It has been done for almost 25 years in the swimming pool industry

Regards,

Dennis Ashworth
- Toronto, Ontario - Canada


Thanks, Dennis,

Cyanide is used in many electroplating shops and the cyanide in the waste water is destroyed by alkaline chlorination. Lawrence appears to be referring to chlorine cells that are appropriate for treating cyanide-bearing waste water.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(1996)

PLEASE NOTE THAT DRINKING WATER SHOULD BE TREATED WITH GREAT CARE. TO USE CHLORINE TO DISINFECT DRINKING WATER MAY CAUSE OTHER TOXIC COMPOUNDS. BEFORE DISINFECTING DRINKING WATER ON A SMALL VOLUME BASIS A NUMBER OF THINGS MUST BE CHECKED. SOURCE WATER - IF IT IS SURFACE WATER FROM A LAKE OR RIVER COULD CONTAIN CRYTOSPORIDIUM. EVEN THE EXPERTS HAVE HAD THEIR PROBLEMS. 400,000 PEOPLE SICK IN MILWAUKEE. THERE IS A REFERENCE BOOK ON CHLORINE "HANDBOOK OF CHLORINATION AND ALTERNATIVE DISINFECTANTS" [link is to product info at Amazon], GEORGE CLIFFORD WHITE.

WELL WATER WILL PRODUCE OTHER PROBLEMS IF IT CONTAINS IRON. YOU SHOULDN'T TAKE RAW WATER AND PUT CHLORINE IN IT AND THEN DRINK IT. FILTRATION, OXIDATION WITH SOMETHING LIKE WAPOTEC FROM AUSTRIA (CHLORINE DIOXIDE) THEN SOME FORM OF DISINFECTANT.

ADDING CHLORINE TO WATER AND THEN DRINKING IT IS DANGEROUS ON A LONG TERM BASIS - THE POSSIBILITY OF TRIHALOMETHANES IS REAL DEPENDING ON YOUR SOURCE WATER. ALWAYS GO BACK TO THE BASICS - YOU ARE NOT TREATING THE WATER YOU ARE TREATING WHAT IS IN THE WATER. THE TOXIC MATERIALS ARE USING THE WATER AS THE CARRIER. YOU ARE ATTEMPTING TO WORK ON SOMETHING YOU CANNOT SEE.

IF YOU ARE GOING TO DRINK IT AND LOTS OF IT. BE AWARE.

Dennis Ashworth
- Toronto, Ontario - Canada


(2000)

We just returned from SMAQUA 2000 in Zaragoza, Spain. Lots of new ideas and the production of sodium hypochlorite is front and center. When any chlorine product is added to seawater, bromine is produced from the sodium bromide in the sea water. If the produced product is then going to be used for disinfecting drinking water it is very important to keep in mind that it is possible you will produce bromoform or 'bromate' which is toxic. Just as chloroform is produced when chlorine is added to waters containing waste from surface waters (lakes, rivers) or swimming pools, whirlpools, spas (recreational waters). The simple process of adding chlorine or bromine to water will not produce (potable) drinkable water and in fact may be producing something which is harmful to the consumer.

Dennis Ashworth
- Toronto, Ontario Canada


(2004)

Instead of using chlorine or sodium hypochlorite whatever you want to call it, has anyone ever tried to use chlorine dioxide? It is generated using sodium chlorite and R.O. Water. It is similar to Ozone but less toxic.

Nick Kaufman
- Indiana


(2004)

I saw an electrolysis device's wiring diagram in a website for making sodium hypochlorite, though it is in Chinese. It's really simple: it has a 60 minute auto stop timer, uses about 6 v, and the part you put into the salt water is made from stainless steel to prevent corrosion by the bleach.

Philip Wong
- NYC, New York


(2005)

Forget chlorine dioxide, aka ClO2. It's very corrosive and toxic to the point of being lethal in a high enough concentration.

Kane Sheldon
- Flagstaff, Arizona


March 1, 2011

I want to produce a 15% strength Sodium Hypochlorite for water disinfection. How much salt must I add to 200 liters of water? At what amps must the process being run and for what time period?

Albert van Vuuren
- South Africa

March 3, 2011

Hi, Albert.

I don't think it's nearly as simple as that :-)

While a small amount of chlorine ion can be generated in situ with a simple cell, high concentration sodium hypochlorite is made by different processes and requires stabilization with sodium hydroxide, and possibly other chemicals. Making it is a whole industrial science, not a trite matter of applying some electricity to an electrode in saltwater. You might review the history of its manufacture at pubs.acs.org/subscribe/archive/tcaw/11/i04/html/04chemistry.html, and then see if Dow Chemical has made any further information publicly available. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



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