Where the
world gathers for metal finishing
Q&As since 1989


-----

Metals and Anions Precipitation

 

Is there a product that can bind metal ions and anions(chlorides,sulphates,nitrates,etc.), like a polymer or a combination of anionic and cationic polymers that can be used in our reactor clarifier?

Jesus Quinonez
- Riverbank, California, USA

Polymers help to agglomerate precipitated materials by neutralizing electrical charges and by forming a bigger particle for faster settling. Anions like chlorides, sulphates, and nitrates are highly soluble; they are dissolved rather than being precipitates, so polymers won't do anything for them.

You might study disposable ion exchange materials like insoluble starch xanthates, or one of the proprietary materials that are blends of activated carbon and disposable ion exchange resin.

As an aside: On some faraway planet they may do industrial treatment and disposal of salt water via treatment methods designed for dealing with salt water, and then discharge the salt water to their seas. But here on earth that concept would be labeled "ocean dumping" by the morally gifted, so it can't be done. Instead of discharging salt water to the oceans they have decided it is wiser to remove the salts and store them (until the liners wear out) in landfills above our freshwater aquifers :-)

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

---

 

I'm not aware of any chemical products that can bind your metals (cations) with anions, as they exist naturally in that state up until they are dissolved in liquid together. That ionic balance that results in the process is a natural occurrance. Its hard to reverse nature - and not cheap!

Anions are particularly tough to remove from waste streams - and unless you go to the source and try to recycle your concentrates, your only alternatives are to try to concentrate and dispose of in some manner. The unfortunate thing about them is that they usually stay in solution at very high concentrations - which complicates the removal process.

An ion exchange or a reverse osmosis will remove them, but you will be left with a volume of concentrated solution that requires further processing. You are probably being surcharged or worse for TDS in your effluent being in the area you are, so your best course of action would be to look at ways to minimize waste generation from your rinses and especially, look at methods to re-purify and return your process baths to operation without dumping them. They can be highly cost effective if applied correctly.

Tom Baker
wastewater treatment specialist - Warminster, Pennsylvania