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"Technique for recycling Caustic Soda"

February 11, 2010

Dear Sir / Madam

we use etching bath prior to anodization process for aluminum substrates and we face a difficulty to treat the wastes of basics and acids in the treatment plant, inefficient pH adjustment results a sludge in the whole steps of treatment results of spending this waste to drain without treatment.

Please any body can suggest a suitable technique for recycling soda to save cost and to avoid environmental hazard.

This could lead to serious issues so kindly so I will be grateful for sooner response.

Thank you in advance.

Dina Ghanim
Anodizing plant employee - Great Cairo, Egypt

February 12, 2010

There are ways to recycle the caustic soda and someone else may comment on it further, but I think the cheapest and easiest thing to do is to upgrade your treatment system to handle the waste properly. Are you having problems with just the rinsewater or are you talking about periodic dumps of the etch bath? Either way, you need to measure and adjust the pH of your effluent, clarify and filter. If you are trying to treat the etch bath dumps, then the sludge volumes can be astonishing, so you need to size your clarification and filter press accordingly. It can be done automatically for continuous flow or in batches. If your etch bath has additives other than caustic soda (like a gluconate), then further treatment may be necessary to precipitate other metallic contaminants such as copper.

Jon Barrows
Jon Barrows, MSF, EHSSC
Independence, Missouri

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