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Caustic & aluminum recovery from cleaning processes

Q. Hi, how can we take out aluminium from used caustic soda [affil links] after die cleaning after extrusion process as it is loss of all the extruder?

Akhilesh Gupta
- Mumbai India
February 21, 2023
privately respond to this RFQ ^
Ed. note: As always, gentle readers: technical replies in public and commercial replies in private please (huh? why?)

A. Hi Akhilesh,
The basic problem is that aluminum removal and caustic recovery is possible but it is so expensive that it is prohibitive for a lot of applications :-(

But in the case of, for example, caustic etching of aluminum, it has been found to be affordable despite the expense. We appended your inquiry to a bunch of others on your same topic, but to learn more details regarding the situations where it has been found practical, please see topic 5582, "Remove aluminum from etching & anodizing baths".
Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

⇩ Closely related postings, oldest first ⇩

Q. I'm writing to see if anyone has experience with recovery of caustic solutions used to clean dies from the aluminum extrusion process. It seems that chemical/physical treatment prior to sewer discharge is the most common handling method. I have a few specific questions:

What chemicals are typically used in the treatment process?

Has anyone looked at treatment of the caustic solution w/ultrafiltration, RO, electrodialysis, or ion exchange?

Judy Adler
- Georgia
1999

A. Hi Judy. Most of we readers on this site are from the metal finishing field, and metal finishers probably have different effluent limitations & guidelines than extruders, but metal finishers such as anodizers neutralize the pH, and the metal content is precipitated out and is filtered, and the solid waste landfilled.

But something to be aware of is that even though aluminum is often an unregulated waste, the alloying metals like copper and zinc can be sufficient to require treatment lest the wastewater exceed allowances.
Luck & Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Q. Greetings,

We are an institute of environment research in Republic of Korea. We have developed the new mass-production process of organic acids by continuous fermentation equipped with cell-recycling system, and evaluated the productivity of organic acids using organic by-products as raw feedstocks.

The economically competitive process can be achieved by recovery of amount of caustic soda [affil links] in waste water from organic acid fermentation, so we are now looking for some new technology and further information for the separation and the recovery of caustic soda.

Pil-Ki Hwang, Ph.D. student,
Kwandnong Univ. - Republic of Korea
2000

RFQ: I am interested in hearing of caustic recovery using membranes. I am currently working in this field and already have results. I would like cost estimates of full scale membrane installations. Suppliers welcome as well.

Sugen Chetty
- Durban, South Africa
2000

Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)

Electroplating of aluminum from caustic waste stream

Q. I have a waste stream containing high concentration of Aluminate in 2% NaOH. I would like to know if it is possible to recover the aluminum from this stream by electroplating technology. Is it possible to do in such aqueous stream? Is it necessary to adjust the pH? What type of additives are necessary? What equipment shall I buy for such process and where?

Anna Alyoshin
biotechnology - Rehovot, Israel
2001

A. Sorry, that one is not going to work, Anna.

Aluminum is an active metal which cannot be electrolytically reduced from a water solution (water separates into hydrogen and oxygen first). Further, aluminum salts are of very low value since aluminum oxide is as common as dirt. Precipitate it, dry it, landfill it unless the caustic is high enough in volume to be affordable to recover/purify.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Caustic Recovery

Q. I am currently researching various methods of recovering caustic soda [affil links] used to clean dies from the aluminum extrusion process.

I am after information on
- the functioning of systems such as membranes, ion exchange or RO in the extrusion industry
- their effectiveness in terms of cutting overall costs in die cleaning
- A ball-park cost in setting up a membrane system for 2 x 1000L caustic tanks

Thank you

Jim Pejoski
- Canning Vale, Western Australia.

A. I presume that when you say you want to recover this caustic, that that is roughly equivalent to saying that you want to remove oil & grease and dissolved aluminum from the caustic soda so that you can keep using it rather than dumping it? If so, topic 5582, "Remove aluminum from etching & anodizing baths" will probably interest you.
Good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

RFQ: Greetings,

I am eager to learn about processes/technologies that are currently available for Sodium Hydroxide/Caustic recovery. Suppliers are also welcome.

Kind regards,

Segran Pillay
- Durban, Natal, South Africa
2002

RFQ: At the company where I am working, they are using an evaporation plant to concentrate the product and it's very costly. I have heard about the caustic recovery using membranes. I would like to obtain information concerning the functioning of this system. In addition to that, I would like to get an idea of its cost estimates of full scale membrane installation.

Natacha leung hong kwai
textile mill - Mauritius
2002

A. Dear Sir,

It is possible to the following operation with ceramic membranes for caustic recovery. Caustic solution can be filtered with 0.14 micron or 300KD membranes clearing all suspended solids, particles, microorganism etc. It is NOT possible to concentrate caustic with membranes to our knowledge.

Do let us know if you need any further clarifications.

Best Regards,

Hiren Shah
- Mumbai, MH, India
2005

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