DEAR SANSOX

GREETINGS

The attached content is presumed to be helpful for you. iT IS NOT DIRECT TO ISSUE BUT CAN PROVIDE SOME USEFUL CLUES TO EXECUTE YOUR WORK.Kindly go through.

GOOD LUCK.

Thank you, Singh! These methods are indeed, curious. However, in the situation of my company I wonder if any of the following processes can treat well the wastewater in relation to soluble Zinc:

- oxygenation and aeration (for example there is a method of iron removal by oxidation);

- cavitation;

- flotation;

-membrane ultrafiltration;

-centrifugal separation

Do you have any thoughts or perhaps, have encountered with corresponding researches?

With regards,

Liu

Have your solution any other metal or only zinc?, what is the main concentration?, the answers may change a lot the kind of solution you need.

During my PhD I was working on zinc recovery from the spent pickling baths coming from the hot dip galvanizing industries. However, an electrochemical reactor was used to deposit zinc in order to reintroduce it to the process. If you have a high concentration of zinc I suggest you to use this method as zinc has a great added value.

Thank you for the reply, Jordi!

So far, what I know about the situation:

There is a plant producing stainless steel from recycled material. Three FeCr ovens, with gas detergents, the zinc from ore is transferred from gas to water.

Water is shaken with clarifiers and sand filters, cooled down in concrete pools.

Total volume of water basins is about 150,000 m3, water consumption is about 2000 m3 / h, recycling rate 90-95%.

The solids content of the water after the scrubber varies from hundreds to thousands of mg / l.

One of the problems here is that the particle size of Zn is very small, below the micrometer class, which does not fall into the clarifiers. Thus, the solids content of the excess is about 50 mg / l.

The pH of water varies between 7-9 according to the state of the process. Low pH increases the amount of soluble zinc.

Flocculants are added to the clarifier, but it's difficult to estimate the amount needed, hence, the overdose blocks the sand filters.

The total zinc in the water is about 1000 kg / d, most of which ends up in gaseous form.

The discharge zinc limit is 4 kg / d.

As for presence of other elements in the wastewater, I guess they are being dealt with.

Do you have any ideas, Jordi, how to treat properly those particularly fine particles of Zinc as well as the form which is left as soluble?

With regards, Liu.

Hello Liu,

I think that is a real problem that needs a previous study. First of all, in order to have a better effluent characterization and, in this way, study the different possibilities to treat it.

As a brainstorming I can give you some alternatives:

- Increasing the pH you could achieve the complete precipitation of all the metals present in the effluent. For zinc precipitation you need pH>10. The problem is what to do with the generated sludge.

- Microfiltration or UF to remove the zinc particles may be an interesting alternative. However you will need another treatment coupled to eliminate the solved zinc. In this case you might use electrodialysis and concentrate the zinc solution, followed by zinc electroylsis or apply this technique directly without the concentration step. The metallic zinc recovered can be perfectly sold.

Maybe you can find more information in this article:

http://www.sciencedirect.com/science/article/B6TGF-4XY4K4B-6/2/3bd33e263140537d32e637e567762522

Have your bosses though about to ask for help in the University?. This may be an interesting project to solve.

I'd agree with you that distantly, 1 person with no Chemistry background won't have much of a chance to solve such. As for bosses, they won't apply to a Uni with this problem because all they aim for is utilizing their products while not being able to afford any real research.

Do you know, Jordi, under what circumstances Zinc precipitates via use of oxygenation or flotation techniques? An answer to this would at least shrink my search a lot.

Appreciating your help!

Liu.

Hello Liu,

I have to add that I don't think that a chemistry background can bring you the solution to the problem, it may help to find useful information.

Regarding your bosses decision it is sad to hear about it because it would be a source of an interesting research and, maybe, funds.

Unfortunately, I don't have knowledge enough about your question to bring you a correct answer.

I've worked with an air sparkling electrochemical reactor (to remove chloride from solution) but I have see no zinc precipitation nor pH increase, but my solutions were to acid (pH of 1 or below).

About the flotation techniques I have no experience, but I don't know how zinc can precipitate with it.

I'm sorry Liu

Best regards!!

And again, I agree with you, Jordi! Thank you very much for your time, your help was useful, in fact!

With regards, Liu.