Hard Water Softening

[kudzi]

Hi
I am a chemical engineer and have been tasked to condition shaft water which is required for use in a nickel tankhouse for electrowinning purposes.
This water is high in sulphates as well as nickel and sulphates and thse salts present problems in the electowining circuit, as they form salt crystals which reduce the current efficiency. Please view attachment for full assays.

Currently trials are underway to treat the water with soda ash, lime and aluminium sulphate. my question is, "Is it possible to treat this kind of water via an anion exchange resin or are there better ways available for use?''
Your feedback will be greatly appreciated.

Best Regards
Kudzi

 

[bimr]

Treating this process water with soda ash, lime and aluminium sulphate is not going to do anything for you. It is not possible to precipitate the sulfates to a level less than what you currently have.

Anion exchange alone will not work either as you must remove the cations as well as the anions. Removing the anions only will leave you with a high hardness water that has a high pH and that will quickly cause scaling problems.

You need to speak to a firm that has experience with using RO for wastewater. There is a a RO process that uses RO to recycle the nickel.

The blowdown from your plating process has a high TDS and will probably have to be evaporated if you are unable to dilute the TDS in some manner.

 

[chief]

You could also use a vapor compressor distillation plant, to give you very pure water. But of course, there is a capital cost for this equipment. Check out Aqua-chem or Meco for details. Vapor compression in my experience is far more user friendly than RO.

Offshore Engineering&Design

 

[bimr]

Various nickel recovery schemes:

http://www.p2pays.org/ref\02/01187.pdf

http://www.epa.state.oh.us/ocapp/p2/mercury_pbt/fact97.pdf

http://www.eco-tec.com/techpapers/TP 145 Nickel Salt Recovery.pdf

http://www.pprc.org/pprc/rpd/fedfund/epa/epastd/wattsnic.html

http://www.nmfrc.org/bluebook/sec371.htm

http://www.desline.com/articoli/5752.pdf

 

[Finlandia]

Nice article about hard water problems from Ezinearticles

Dangerous Hardness Ions
By <a href=

http://ezinearticles.com/?expert=Idalia_Luczak>Idalia

Luczak</a>

Water is everywhere. Nothing can happen without it and nothing can live. We commonly say about pure water and impure one. This recording to the possibility of drinking it or not. But except the rain there is no such thing as clean water. There is one important class of impurity: hardness.

Hard water is the type in which we have dissolved minerals of magnesium and calcium. And water that comes to our houses probably always has it. It's kind of a natural process: rain is falling and getting into the rivers and finally to our houses. But while it sleeps trough the ground it is slightly possible that it picks up minerals from the rocks like limestone, chalk. And that is the reason of hard water at home.

As it may seem natural to have that kind of water at home it may cause different problems. For example when you are wondering why your bills for heating increased the limescale might be the answer. The minerals, during the heating process, form a visible scale in pipes. As a result, the scale is clogging them and the efficiency of heat that it is needed to make water hot is increasing. That is why bills may get much higher. Whole process may also damage other appliances which are using heated water as for example kettles and dishwashers, and shorten their lives. Not speaking about smaller issues caused by hard water as sticky hair or harsh clothes.

We have two categories of hard water - temporary hard and permanent. The first one is water which hardness can be removed by boiling it. It's caused by combination of ions and bicarbonate ions in the water. And boiling promotes the formation of carbonate from the bicarbonate and precipitates calcium carbonate out of solution, leaving water that is softer upon cooling. Second type is much harder to soft and this is the one which deposits limescale and causes all the bad effects that were described above. To make permanent hard water soft you can't boil it. Heating permanent hard water increasing the problem. You need a good <a href=

http://www.scalewatcher.co.uk/pages/hard_water_issues.asp>water

treatment</a>.

The most popular solution is using water softener. It
might be one that works by replacing the calcium and magnesium in the water with sodium. Or an electronic limescale remover, that may remove lime scale problem. The truth is that all are less expensive than ignoring the problem. Prevention might be much cheaper than removing the effects. In that case the only thing left is to think about the best solution for you to deactivate dangerous 'hardness ions'.

Article Source:

http://EzineArticles.com/?expert=Idalia_Luczak

http://EzineArticles.com/?Dangerous-Hardness-Ions&id=877359

 

[Finlandia]

Nice article about hard water problems from Ezinearticles

Dangerous Hardness Ions
By <a href=

http://ezinearticles.com/?expert=Idalia_Luczak>Idalia

Luczak</a>

Water is everywhere. Nothing can happen without it and nothing can live. We commonly say about pure water and impure one. This recording to the possibility of drinking it or not. But except the rain there is no such thing as clean water. There is one important class of impurity: hardness.

Hard water is the type in which we have dissolved minerals of magnesium and calcium. And water that comes to our houses probably always has it. It's kind of a natural process: rain is falling and getting into the rivers and finally to our houses. But while it sleeps trough the ground it is slightly possible that it picks up minerals from the rocks like limestone, chalk. And that is the reason of hard water at home.

As it may seem natural to have that kind of water at home it may cause different problems. For example when you are wondering why your bills for heating increased the limescale might be the answer. The minerals, during the heating process, form a visible scale in pipes. As a result, the scale is clogging them and the efficiency of heat that it is needed to make water hot is increasing. That is why bills may get much higher. Whole process may also damage other appliances which are using heated water as for example kettles and dishwashers, and shorten their lives. Not speaking about smaller issues caused by hard water as sticky hair or harsh clothes.

We have two categories of hard water - temporary hard and permanent. The first one is water which hardness can be removed by boiling it. It's caused by combination of ions and bicarbonate ions in the water. And boiling promotes the formation of carbonate from the bicarbonate and precipitates calcium carbonate out of solution, leaving water that is softer upon cooling. Second type is much harder to soft and this is the one which deposits limescale and causes all the bad effects that were described above. To make permanent hard water soft you can't boil it. Heating permanent hard water increasing the problem. You need a good <a href=

http://www.scalewatcher.co.uk/pages/hard_water_issues.asp>water

treatment</a>.

The most popular solution is using water softener. It
might be one that works by replacing the calcium and magnesium in the water with sodium. Or an electronic limescale remover, that may remove lime scale problem. The truth is that all are less expensive than ignoring the problem. Prevention might be much cheaper than removing the effects. In that case the only thing left is to think about the best solution for you to deactivate dangerous 'hardness ions'.

Article Source:

http://EzineArticles.com/?expert=Idalia_Luczak

http://EzineArticles.com/?Dangerous-Hardness-Ions&id=877359

 

[GarySCWSVI]

None of us can be of much help without knowing what the analysis of the water to be treat is and what is required for a resulting water quality. Ion exchange is a good answer but will require the water analysis and what resulting water quality is wanted. By the way, what your application sounds like is not "Hard Water Softening". Demineralization or Deionization are the terms used when removing those contaminants. Either or is fine. They both are the same process.

Gary Schreiber, CWS VI
The Purolite Co.