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topic 5582

Removing Aluminum from Sulfuric Acid Anodizing Solutions


Q. I have clients searching for a good method of removing aluminum from both conventional and hard anodizing solutions. Their present technique is "dumping once a year". The other alternative we have used is to remove 10% of the solution when it gets too high in aluminum content. This solution is replaced with fresh sulfuric acid. There is a "sorption" process available commercially but apparently, first cost is very high.

Bert J. Sherwood
- Los Angeles, California, USA


A. An effect method for removing and maintaining the Aluminum concentration at a constant level is by using a Diffusion Dialysis System. My company manufactures this type of system for Acid Recovery and is suited to your application. A majority of the aluminum can be removed and the operation of the bath can be maintained more consistently by removing aluminum as it builds up.

Tony D'Amato
- Chicopee, Massachusetts


A. We do anodizing & hardcoating & have a system for removing aluminum from a company called ECO-TEC - It works great. We purchased it from Chris Ebbrecht at Eastern Anodic.

David A. Kraft
- Long Island City, New York


A. Aluminum can be selectively removed using a so called "ACID RETARDATION PROCESS". It is a relatively simple process and although there is an initial investment it pays back within a year.

Ruud Gerritsen
- Simpelveld, Netherlands


Q. Ruud,

Can you explain me what is the 'acid retardation process'?

Which companies can I contact in europe for this technique?

Thank you and best regards.

Francesco Cicchetti
Francesco Cicchetti
- Sulmona, Italy


Francesco, Acid retardation is an ion-exchange process where the aluminium contaminated sulfuric acid is passed through a resin. After loading the resin it is eluted with water, resulting in a sulfuric acid stream with low Al and aN aluminium sulfate solution with low sulfuric acid. A larger number of European companies provide this system.

Ruud Gerritsen
- Simpelveld, Netherlands

February 18, 2014

Q. What is the advantage of sulfuric acid recovery system? I have recently asked for quotation of the same, but it seems it's too costly. My anodizing tank size is 21' x 3' x 3' (L x B x H). H2SO4 concentration is 165-175 gm / liter. Please help me to know the size of recovery system required? The cost of such system? And the most important thing is the ROI (return on investment) on such system. Is it feasible to buy such a system? What is the maintenance required for such system? How regularly do we have to use this system for removing the aluminum dissolved in the anodizing tank? Please explain mathematically the advantage of using such system to get the advantage in the form of reduced electricity bill.

Please guide.

Rahul Mogal
- Nashik, Maharashtra, India

February 18, 2014

A. I used to run our acid recovery unit 3 days a week, about 6 hours at a time.

The advantage is that you can control Al without doing periodic batch dumps of electrolyte. That requires neutralization, with the generation of massive amounts of Al(OH)3 sludge which must be dewatered, and disposed of. The costs and labor associated with this is why the unit is worth the money, not the cost of the acid.

dave wichern
Dave Wichern
Consultant - The Bronx, New York

February 20, 2014

Q. Can anybody please tell me what is adsorption process, diffusion dialysis, and acid retardation process. Which one is more effective and involves less investment (less costly).

Rahul Mogal [returning]
- Nashik, Maharashtra, India

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